Precipitating factors of pituitary apoplexy.
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The term “pituitary apoplexy” (PA) originating from Greek means “sudden attack” with hemorrhage and/or infarction in the pituitary tumor or, less commonly, the surrounding normal gland tissue.
The first index case was, described by Bailey, in 1898 [1], but the term pituitary apoplexy was coined by Broughamin in 1950 [2].
Pituitary tumor apoplexy is an uncommon acute clinical syndrome and one of the rare problems that is diagnostically and therapeutically challenging.
PA is frequently the onset of unknown preexisting pituitary adenoma. The clinical spectrum of presentation does vary but often reserved only for classical presentation in contrast to “Silent, subclinical or asymptomatic pituitary tumor apoplexy” even though the latter is the more frequent entity [3].
It is a potentially life-threatening complication requiring a rapid diagnosis and appropriate treatment.
The diagnosis of pituitary tumor apoplexy is based on imaging evaluations, mainly using magnetic resonance imaging.
The best approach in the acute phase is still controversial, and nowadays, PA is no longer considered as a neurosurgical emergency [4, 5].
The outcome of acute apoplexy is variable and remains difficult to predict; a regular input and follow-up from a multidisciplinary team including neurosurgeons, endocrinologists, neuro-ophthalmologists, neuroradiologists, and neurologists are mandatory.
Pituitary tumor apoplexy appears to be rare. The true incidence and prevalence of PA are difficult to establish either because the majority of the studies are retrospectives or because the diagnosis of PA is usually misdiagnosed and simply identified at surgery or during radiological investigation or pathological examination. According to the main retrospective series, an estimated prevalence of 6.2 cases per 100,000 inhabitants and [6] an incidence of 0.17 episodes per 100,000 person-years were reported [7].
In published series of surgically resected pituitary adenomas, PA can occur in 0.6–10% with a mean of 2% of all adenomas and has reached 21% in an unusual report [8]. Nonfunctioning pituitary adenomas (NFPA) appear to be at higher risk of apoplexy with an incidence of 0.2–0.6 events per 100 person-years [9]. In published series of nonfunctioning pituitary adenomas, the frequency of apoplexy can vary from 3.7 to 21% [10]. Nonsecreting pituitary adenomas represent an average of 45–70% of adenomas with apoplexy [3].
Apoplexy represents the first clinical manifestation of previously unknown pituitary adenoma in 60–80% of cases [5, 11, 12].
Pituitary tumor apoplexy can occur at all ages, but most cases are seen during the fifth or sixth decade of life. In adolescents, this event has been described by Jankoswski and cols as a very rare entity [13].
There is a discrete preponderance in males ranging from 1.1 to 2.3/1 [5, 12].
Macroadenomas, especially nonfunctioning, and prolactinomas are most susceptible to apoplexy; nevertheless, apoplexy in other tumor types such as GH-secreting or clinically silent ACTH adenomas has been reported [5].
Microadenomas may also be prone to apoplexy [14]. PA occurs in 0.6–10% of treated pituitary adenomas. In three series of macroprolactinomas, the ratio of apoplexy/therapy varied between 1.2 and 6.67% [14].
In a review, apoplexy was found to occur in 1–6% of macroprolactinomas. This average was comparable between treated and untreated adenomas [5].
Semple et al. have found that one-third of their 62 patients had only infarction [15]. Hemorrhage is more associated with macroprolactinoma and female gender [16].
The pathophysiological mechanisms of pituitary tumor apoplexy remain incompletely understood. There are various theories upon the pathophysiology of pituitary apoplexy in the current literature. It is uncertain whether the pathological process is a primary hemorrhage or whether the event is really a hemorrhagic infarction. Many pathogenic mechanisms have been proposed. Given that the risk of hemorrhage in a pituitary adenoma appears to be five times higher than in other intracranial neoplasms, intrinsic factors can be involved in the apoplectic event [12]. The rich and the complex vascular system makes the pituitary adenomas more vulnerable to bleed than any other brain tumor.
Understanding the vascularity of the pituitary gland and pituitary adenomas is crucial for etiopathogenesis of apoplexy.
As shown by the angiographic studies, the adenomas are mostly supplied by inferior pituitary artery, and its arterial flux is reduced compared with the normal pituitary [17].
The number and size of vessels are generally lesser than the normal pituitary vessels and are divided into irregular islets. Under electronic microscopy, they have incomplete maturation, poor fenestration, and ruptured and fragmented basal membranes with perivascular spaces filled with plasmatic proteins or red cells that may predispose to hemorrhage [18].
The fragility of the constitutional tumoral vascularization, can be explained by an increased expression of vascular endothelial growth factor “VEGF mRNA” in pituitary tumors; especially in nonfunctioning pituitary adenomas [14].
This expression of vascular endothelial growth factor could be explained by a tumoral overexpression of the pituitary tumor transforming and was found to correlate positively with the risk of pituitary hemorrhage. Other vascular markers were reported such as fetal liver kinase 1, nestin, etc. [5].
All the conditions associated with an acute increase in blood flow or coagulation disturbs may predispose these lesions to hemorrhage or hemorrhagic infarction [14].
This intratumoural vasculopathy, limited blood supply of the pituitary adenomas, and limited expression of angiogenic factors contrast with a high-energy requirement. As consequence, any extrinsic factor that alters the balance between tumor perfusion and tumor metabolism may cause an acute ischemia or infarction [17].
Moreover, an increased intratumoural and intrasellar pressure could concur to the reduction of tumor perfusion, further contributing to ischemia’s pathomechanisms. Tumor growth could thus contribute to ischemia which explains the size of the adenoma being a major factor. Macroadenomas are described to be at a much higher risk of apoplexy than microadenomas [10, 19, 20].
Germline AIP gene mutations may be associated with a rapid growth of the pituitary adenomas predisposing them to apoplexy [21].
PA can occur without any risk factors; however, numerous conditions have been linked to PA. Precipitating factors are identified in 10–40% of cases [3] (Table 1).
Precipitating factors of pituitary apoplexy.
The multiple factors reported as precipitating PA can be classified into three categories.
Procedures such as angiography, pneumoencephalography, myelography, lumbar puncture, and spinal anesthesia have been associated with PA. Blood pressure (BP) fluctuations or vasospasm may explain PA [22, 23]. Pituitary irradiation may induce vascular changes leading to chronic hypoperfusion of the pituitary gland and has been associated with both pituitary infarction and pituitary hemorrhage [24, 25]. Closed-head trauma which often minor may be a cause of PA, explained by acute changes in the intracranial pressure and in blood pressure [26].
PA has been described in postoperative states. Orthopedic and cardiac surgeries mainly cardiopulmonary bypass were the most incriminated [27, 28, 29]. Intra- or postoperative hypotension, anticoagulation, and microemboli leading to infarction were the proposed mechanisms. If a pituitary adenoma is known before the cardiac procedure, some authors recommend the use of off-pump technique maintaining an adequate systemic perfusion, as opposed to standard cardiopulmonary bypass [30].
Systemic hypertension leading to an increase in blood flow and diabetes mellitus has been associated with PA [31, 32]. However, this association was not confirmed by other studies [10, 33].
Severe vomiting/diarrhea with concomitant increased Valsalva pressure may also decrease blood supply to the pituitary adenoma and precipitate apoplexy, since tumoral cells are particularly sensitive to glucose deprivation [5].
Apoplexy can also occur after dynamic testing of the pituitary (insulin, TRH, GnRH, or GHRH tests and much more rarely CRH) particularly when different agents are combined. Numerous publications have documented the occurrence of apoplexy within minutes to hours after testing [10, 34, 35].
In this setting, TRH dynamic test may cause apoplexy by vasospasm induced by increased norepinephrine levels or by elevating systemic pressure.
Other tests of pituitary stimulation (especially use of GnRH) can increase the imbalance between the intratumoral metabolic demand and the poor tumor perfusion.
Reports of PA occurring after stimulation test are much rarer in the recent past. Currently, pituitary dynamic testing is not commonly used in the routine assessment of hypothalamic pituitary function.
Increased estrogen states, such as exogenous estrogen administration, pregnancy, and postpartum period, have been reported to cause PA [33, 36, 37, 38]. Treatment with GnRH agonists for prostate cancer has also been associated with PA [39, 40, 41].
The role of dopamine agonist (DAs) treatment as precipitating factor is more controversial, although many case reports suggested this hypothesis [42, 43]. In prospective studies analyzing the effects of DAs on macroprolactinomas, PA were very rarely or never observed [6, 44, 45, 46]. In a retrospective study [9], DA treatment of pituitary adenomas was not associated with PA. These results are not surprising, given that these agents decrease growth and activity of prolactinoma or other adenoma cells.
PA can occur in the setting of an acute systemic illness such as myocardial infarction or severe infection. Excessive stimulation of the pituitary gland by production of larger amount of steroids is a possible explanation [33].
PA has been observed after administration of anticoagulant drugs (vitamin K antagonist or platelet inhibitors) or thrombolytic agents, sometimes very soon after the initiation of treatment or after a prolonged period of treatment [6, 9, 47]. New classes of anticoagulant (dabigatran) [48, 49] may also be involved.
Thrombocytopenia has also been reported usually associated with hemorrhagic PA [50, 51].
The prevalence of apoplexy according to different subtypes of pituitary tumors shows a trend for nonfunctioning adenomas [3, 4, 5, 9, 22, 33, 52, 53, 54, 55] to develop apoplexy. It is believed that nonfunctioning tumors may be diagnosed at a later stage, so they grow to a larger size before diagnosis; in contrast, the functioning adenomas are generally revealed earlier by signs of hormonal secretion before bleeding/infarction occurs [5].
Other tumor types predisposing to apoplexy are prolactinomas and GH-secreting adenomas [27, 56, 57, 58, 59]. In the vast majority of cases, apoplexy complicates large macroadenomas [10]. Clinically silent ACTH adenomas may be particularly prone to necrosis, hemorrhage, and cyst transformation [5, 60]. These complications occur in 30–64% of cases, 2–14% in patients with all types of pituitary adenoma [16, 61, 62, 63].
Frequently, the PA episode is the first manifestation of undiagnosed pituitary adenoma [22, 57, 64].
It is important to consider that the pituitary apoplexy has a wide spectrum of clinical features, resulting from undergoing sudden mass enlargement. It ranges from silent asymptomatic necrotic and/or hemorrhagic adenoma to “classic” acute presentation and even death.
This is largely depending on the extent of hemorrhage, necrosis, and edema. Semple et al. suggested that the cases of pituitary tumor infarction alone had less severe clinical features and better outcome than those with hemorrhagic infarction or frank hemorrhage [15].
The clinical manifestations are summarized in Table 2.
Common clinical features of pituitary apoplexy.
Headache is the earliest and most common presenting symptom with an incidence of more than 90% [4, 65, 66].
The cephalalgia onset is often sudden and severe, namely, “thunderclap headache,” in patients presenting with pituitary apoplexy and creates an even greater degree of difficulty in the differential diagnoses. It is usually resistant to analgesics, mainly retro-orbital and sometimes bifrontal, suboccipital, or diffuse [67]. This feature can be explained by meningeal irritation due to extravasation of blood and necrotic material into subarachnoid space, enlargement of sella turcica walls, dura mater compression, or involvement of the superior division of the trigeminal nerve inside the cavernous sinus [18, 68].
Headache is commonly accompanied by signs of meningeal irritation, such as nausea and vomiting (57%), photophobia (40%), meningismus (25%), and fever (16%) [5]. The fifth cranial nerve (first branch) can be involved in PA, resulting in facial numbness [3].
Altered level of consciousness may occur in varying degrees ranging from lethargy to stupor or even coma as consequence of blood or necrotic tissue leaking into the subarachnoid space [69]. A concurrent cerebrovascular episode with a stroke has been previously described [70]. The involvement of the thalamus in a case of pituitary apoplexy with thalamic and midbrain infarction has been described [71]. In such cases, one of the following mechanisms was proposed: (1) compression of intracavernous portion of internal carotid artery due to expanding pituitary adenoma or a hemorrhage within it and (2) vasospasm caused by factors released from hemorrhagic or necrotic material [70].
Rare cases of sudden death following pituitary tumor apoplexy of fatal outcome of acute pituitary apoplexy due to massive hemorrhage were reported [72, 73].
The apoplectic pituitary adenoma can expand toward the cavernous sinus, compressing the III, IV, and/or IV cranial nerves (CN), leading to various degrees of ocular palsy (diplopia and ophthalmoplegia) in 40–70% of the patients [52, 55, 74, 75].
The third CN is the most frequently affected especially when there is an abutment without invasion of the cavernous sinuses. This was explained mainly by the location of the third nerve in the same horizontal plane as the pituitary gland; pressure from lateral growth of a pituitary tumor is relatively easily transmitted to the third cranial nerve. This leads to compression of the third cranial nerve between the tumor and the interclinoid ligament, commonly resulting in the development of the third cranial nerve palsy, occurring either alone or together with damage to the other cranial nerves [52, 76].
Isolated cranial nerve palsy III in PA with direct CN III compression outside the cavernous sinus was also reported. In these cases, the tumor had some mass effect on CN III at the level of the oculomotor trigone after erosion of the posterior clinoid [77]. Multiple CN palsies and even bilateral and asymmetric lesions have been reported [78, 79, 80]. Rarely, pituitary apoplexy may present as isolated sixth cranial nerve (abducens) palsy [81].
Compression of the necrotic intrasellar mass superiorly toward the optic nerves and optic chiasma causes visual symptoms in most (75%) patients [11, 76], including decreased visual acuity; visual field defects, especially bitemporal hemianopsia; and also complete blindness and monocular blindness.
As stated earlier, PA occurs in previously unknown history of pituitary mass in more than 80% of patients, the diagnosis can be challenging owing to its similarities with many other neurological conditions, and several other life-threatening conditions (Table 3) can lead to a delay in proper management [11].
Differential diagnoses of pituitary apoplexy.
The two most important diseases that should be considered are aneurysmal subarachnoid hemorrhage (SAH) and bacterial meningitis, subarachnoid hemorrhage [82, 83], bacterial meningitis, or parasellar abscess [84, 85].
Other differential diagnoses include subarachnoid hemorrhage, ophthalmoplegic migraine, suprasellar aneurysm, stroke and hypertensive encephalopathy, and cavernous sinus thrombosis [52, 82, 83, 85, 86, 87].
Nevertheless, a high degree of suspicion should exist in any patient presenting a severe sudden headache and visual disturbances. This aims to avoid delay in proper management.
Imaging studies are thus crucial for the diagnosis.
As most cases of pituitary apoplexy complicate pituitary macroadenoma, many of which are secretory.
Prolactinomas are the most common (20% of cases of pituitary apoplexy); this is related to the frequency of prolactinoma in the population and to their frequent hemorrhagic nature. Hyperprolactin can also result from stalk effect [88].
It was postulated that at presentation of PA in non-PRL-secreting macroadenomas, a normal or elevated serum PRL can predict the residual anterior pituitary cell viability. Inversely a very low serum PRL level at presentation is correlated with the necrosis of the normal pituitary tissue and predicts permanent hypopituitarism [89].
More rarely PA can occur in acromegaly and Cushing’s disease (too much adrenocorticotropic hormone, ACTH) in approximately 7 and 3% of cases, respectively. Co-secretion of more than one hormone may occur.
Several published series reported clinical and biochemical resolution of hormonally hyperfunctioning pituitary adenomas (including Cushing’s disease and acromegaly) following pituitary apoplexy on follow-up as a result of the infarction of the pituitary tumors [90, 91, 92, 93].
Reviewing the series of patients with PA, one or more endocrine deficiencies can be present at the onset [22, 67, 76] and the evaluation of hormonal levels is mandatory (Table 4).
Endocrine disorders in pituitary apoplexy.
The pathogenesis of hypopituitarism is complex and multifactorial.
As most episodes of PA occur in macroadenoma, the pituitary hormone deficiencies can precede the apoplectic event [22, 76].
This was explained earlier by mechanical compression of the pituitary stalk and/or the portal vessels. But more recent study suggested that it is tightly related to pressure effect of the macroadenoma, as they indicated that in patients with large pituitary adenomas, the intrasellar pressure, measured at surgery, was greater in patients who had hypopituitarism than those with intact pituitary function [94].
Moreover, the apoplexy itself can cause ischemic necrosis of the anterior pituitary secondary to a sudden rise in intrasellar pressure compressing the portal circulation, the pituitary stalk, and the pituitary gland itself [89, 95].
The most life-threatening deficit is that of adrenocorticotropic hormone (ACTH) resulting in acute central hypoadrenalism, which has been reported in more than 70% of patients [36, 52, 76]. It can result in severe hemodynamic problems. Indeed, the absence of cortisol can lead to insensitivity of the vessels to the pressor effects of endogenous or exogenous catecholamines and thus in hemodynamic instability.
Therefore, in patients with PA, empiric parental corticosteroid supplementation should be given immediately.
In the acute setting, other hormone deficiencies have less concerns. At presentation thyrotropic deficiency and gonadotropic deficiency were reported in 30–70% and 40–75% of patients, respectively [3].
Posterior pituitary involvement is not common in PA, and diabetes insipidus was reported in 3% of cases despite frequent and significant suprasellar extension in many cases [10, 96].
This may be attributable to the preservation of the posterior pituitary as a result of its different blood supply from the inferior hypophyseal artery rather than the superior hypophyseal artery that supplies the anterior pituitary and usually the tumor.
Hyponatremia is a common electrolyte disturbance reported in up to 40% of patients presenting with pituitary apoplexy [22].
In most cases, hyponatremia is mostly mild, but severe hyponatremia has been reported [96, 97, 98, 99].
It is often multifactorial and the most likely pathogenetic mechanism proposed of hyponatremia is adrenal insufficiency.
Other etiologies can include the syndrome of inappropriate ADH secretion (SIADH) resulting either from adrenal insufficiency itself or from hypothalamus irritation [99] and neurological deterioration late after initial presentation.
Hypothyroidism as common hormone deficiency in pituitary apoplexy may contribute to hyponatremia by reduction in glomerular filtration rate and elevated ADH secretion [100].
An association of a high level of atrial natriuretic peptide concomitant to a high level of ADH, a severe scenario in hyponatremic patients after pituitary apoplexy, has been demonstrated [99].
In emergency setting, most of the patients with symptoms related to PA will undergo computed tomography (CT) as it is readily available and a rapid screening test. It is likely that, in most of them, the clinical suspicion might be something other than PA.
CT is effective in visualizing pituitary heterogeneous intrasellar and/or expansive suprasellar lesions leading to sellar enlargement (up to 94% of cases) [5, 20, 25], with a coexistence of solid and hemorrhagic areas [4, 22, 76, 101].
The CT is also able to detect subarachnoid hemorrhage and cerebral ischemia, which are the most frequent complications of PA [101].
CT is most valuable in the acute phase (up to 48 h). The recent bleeding in this phase can be missed on MRI either because of infarction or because hemorrhage is still in the form of deoxyhemoglobin. In this context, CT is able to provide an improved detection of hyperdense intralesional areas [102].
Later, during the subacute or chronic phase, in line with blood degradation, hypodense intralesional areas can be present, which increases the difficulty to make the differential diagnosis of subacute hemorrhages from other necrotic or cystic lesions (aneurysms, meningiomas, Rathke cleft cysts, germinomas, and lymphoma) [101].
This makes MRI essential to differentiate between these conditions. MRI and MR angiogram techniques also help to distinguish an aneurysm from pituitary apoplexy [4, 22, 85, 103].
Nevertheless, magnetic resonance imaging (MRI) is the radiological investigation of choice. Its findings depend on the time of onset of bleeding.
It is possible to find a fluid in the intralesional level (Figure 1(C)), the lower area is constituted by red cell sediment, and the cranial corresponds to free extracellular methemoglobin.
MRI in a pregnant patient, with symptomatic pituitary apoplexy. The lesion is globally hypointense, hemorrhagic content of the pituitary mass, and the hemorrhagic area, in T1-weighted sequences ((A) coronal section, (B) sagittal section), with a high signal intensity (arrow (B)) corresponding to the cystic area. In the same patient, the coronal T2-weighted sequences (C) showing a fluid level (asterisk) inside the pituitary lesion: the upper compartment being hyperintense while the lower is isointense.
In the acute stage of pituitary apoplexy, the MRI signal is isointense or slightly hypointense on T1-weighted imaging with hypointensity on T2-weighted imaging (T2 W1). A “brushed” specific pattern of alternating subtle T1-hyperintense and T1-hypointense areas within the sellar mass may suggest apoplexy at the earlier stage [101].
Later, there is marginal signal reinforcement and the hematoma core remains isointense; in the subacute phase, the hemorrhage will appear hyperintense on T1WI as well as on T2WI. In the chronic phase, macrophages digest the clot, and the presence of hemosiderin and ferritin causes a strong hypointensity on both T1WI and T2WI [101].
In pituitary apoplexy patients, some authors reported the thickening of the sphenoid sinus mucosa related to venous engorgement in this region as an excellent sign that is present from the early stage, a reversible condition on follow-up studies that generally improves spontaneously [104]. This thickening does not indicate infectious sinusitis and thus does not rule out the surgical transsphenoidal route [103, 105].
Some published series have demonstrated the great value of special techniques as T2-weighted gradient echo to detect pituitary hemorrhage in the acute phase and chronic phase. MRI diffusion-weighted images (DWI) can be also be helpful in rare cases of ischemic pituitary necrosis without hemorrhage [105, 106, 107].
Semple et al. have demonstrated a correlation with the MRI findings and histopathology in 68% of patients with a histopathological diagnosis of hemorrhagic infarction/hemorrhage and in 82% of patients with infarction alone [103].
PA has long been considered as a neurosurgical emergency. However, nowadays, the conservative approach constitutes another therapeutic option in many situations. Untreated patients with apoplexy have higher morbidity and mortality. Altered consciousness, with all its associated complications, hypopituitarism, and intercurrent illnesses account for the increased morbidity and mortality of untreated patients. Although it is hard to estimate the relative increase in mortality associated without treatment, reports published before corticosteroid therapy were available indicating an approximate mortality rate of 50% [3].
The goals of treatment of PA are to improve symptoms, to decompress local structures especially the optic tract, and to avoid acute adrenal insufficiency. Hence, whether the treatment is surgical or conservative, glucocorticosteroid replacement is systematic.
As corticotropic deficiency is frequently associated with pituitary apoplexy, corticosteroid should be systematically given to these patients. Thus, hydrocortisone is administered at a dose of 50 mg every 6 h [3, 108] or in the form of a 100–200 mg bolus followed by 50–100 mg every 6 h intravenously (or intramuscularly) or by 2–4 mg per hour by continuous intravenous infusion [108, 109]. Corticosteroid substitution should be associated with a careful assessment of fluid and electrolyte balance and supportive measures ensuring hemodynamic stability. Once glucocorticoids are administered, clinical improvement is invariably observed, and hemodynamic stability becomes easier to maintain. The glucocorticoids are administered in supraphysiological doses to serve not only as replacement for endogenous hormone deficiency but also to help control the effect of edema on parasellar structures [3].
If surgical management is chosen, the transsphenoidal approach is almost always recommended, because it allows good decompression of the optic pathways and neuroanatomic structures in contact with the tumor and because it is associated with low postoperative morbidity and mortality [11]. Usually, necroticohemorrhagic material is evacuated as soon as the incision of the tumor capsule is made. The purpose of the surgery is the decompression of the optical pathways; the surgeon should try to identify the sellar diaphragm. In case of invasive pituitary adenoma, a maximum but incomplete resection is ensured by taking all the precautions to avoid damaging the cranial nerves or the carotids in case of invasion of the cavernous sinuses.
The timing of pituitary surgery is controversial, as no randomized trials comparing different strategies with strong evidence have been performed. However, most studies indicate that surgical treatment, usually within 7 days after the apoplectic event, leads to higher rates of visual impairment recovery [11, 110].
Occasionally, patients are clinically or biochemically hypothyroid at presentation. Unless the hypothyroidism is severe, the surgical decompression needs not be delayed, provided the anesthesiologists and the management team are aware of the patient’s condition to avoid medications and procedures that are particularly deleterious and that can potentially worsen clinical symptoms [3].
Surgical decompression normalizes visual acuity in about one-half of cases and improves it in another 6–36% of cases [52, 53]. Visual field defects normalize after surgery in 30–60% of cases and improve in another 50%. Ocular motility dysfunction can resolve spontaneously, with or without surgery [111].
Pituitary deficiencies are usually not expected to recover [19, 112]. In addition, it seems that apoplexy worsens endocrine outcome: hormonal prognosis after elective pituitary surgery is poorer in patients with PA than in patients without PA [9]. This is explained mainly by the damage to the normal gland from the initial apoplectic event. Another important point is that, in this acute setting, the operation may be performed by an on-call neurosurgeon rather than by a skilled pituitary neurosurgeon, as underlined in UK guidelines [11], and this may increase the risk of adverse events.
For tumoral outcome, complete tumor removal is reported in 48–66% of patients and subtotal resection in 23–52% of patients [95]. Tumor recurrence has been described in 6–11% of patients [112].
Surgery may also be harmful, with a risk of postoperative cerebrospinal fluid leakage, permanent diabetes insipidus caused by posterior pituitary damage, meningitis, and an increased likelihood of hypopituitarism due to removal or damage to normal pituitary tissue. Fortunately, in experienced pituitary centers, these complications are very rare [5].
Several reports have documented that spontaneous neurological recovery is possible despite unilateral ophthalmoplegia and partial visual field defects, which has suggested that nonoperative medical management of patients with PA may be appropriate in many situations. In 1995, Maccagnan et al. reported the results of a prospective study in which they treated PA with high-dose steroids (2 to 16 mg of dexamethasone daily). Only patients whose visual impairment or altered consciousness failed to improve underwent surgery. Conservative treatment was possible on 7 of 12 patients, and only 5 patients had needed surgery. Visual deficits regress in 6 of the 7 patients and improved in the remaining patients. The posttreatment prevalence of pituitary hormone deficiency and the incidence of tumor regrowth were similar in conservatively and surgically treated patients [113].
Thus, conservative therapy involved supportive therapy, continued use of supraphysiological doses of glucocorticoids for several weeks, and hormone replacement therapy. Improvement in neurological symptoms is often seen in the majority of patients treated conservatively, at times to a similar degree to that seen in surgically treated patients. However, worsening of pituitary function is usually seen in many of these patients [114]. For functioning pituitary adenomas, hormonal secretion must be also evaluated: hormonal levels could be low, be normal, or remain high after apoplexy [11]. For tumoral outcomes, additional treatment is not necessary in most cases, as tumors usually diminish and even disappear without surgical intervention [10]. It seems that a single large hypodense area within the tumor on CT might be associated with better subsequent tumor shrinkage than are several small hypodense areas [113].
PA is characterized by a highly capricious course, and randomized prospective studies with strong evidence about this syndrome are lacking, which makes optimal management of acute PA controversial. Although guidelines, as the one from the UK, proposed an algorithm for PA management, randomized trials comparing both strategies are needed for strong evidence [11, 112]. Hence, the decision of surgical treatment or conservative management should be individualized and made by experts from a multidisciplinary team including endocrinologists, neurologists, ophthalmologists, and neurosurgeon [11].
The risk-benefit ratio of conservative treatment versus surgery must be carefully evaluated, in terms of visual outcome, pituitary function and also subsequent tumor growth. On the other hand, the potentially serious complications of surgery need to be taken into consideration [115].
In spite of the methodological limits of the studies available on this subject, these data have constituted the rationale guiding the therapeutic choice of PA.
The outcome of visual acuity, field defect, or ophthalmoplegia is similar with surgery or conservative treatment. Unfortunately, visual outcome is poorer in patients with more severe disorders such as monocular or binocular blindness, irrespective of whether management is conservative or surgical [56, 116, 117]. It has been argued that conservatively treated patients may have less severe visual defects than surgically treated patients and that this might explain why the improvement is at least as good in the former as in the latter [3, 11, 118]. The number of patients with visual defects was effectively higher in the surgical groups of published series [53, 76].
For endocrine prognosis, whatever the management approach, the hormonal outcome is poor in patients with PA, who frequently suffer irreversible pituitary damage [11].
Concerning the outcome of the pituitary tumor, very few studies have compared the degree of tumor disappearance between patients receiving surgery and conservative treatment for apoplexy. The reported results were very different: the incidence of recurrence was similar between the two approaches in one study [76], higher after surgery in one other [56], and lower after surgery in two others [52]. Thus, the optimal approach for tumor control is difficult to judge. Whatever the therapeutic choice in the acute event, additional forms of therapy can be used to control residual tumor growth, depending on the type of tumor, including a dopamine agonist for documented prolactinomas or a somatostatin analogue for documented growth hormone-secreting tumors. Gamma Knife stereotactic radiosurgery can also be used on these patients and on patients with nonsecreting adenomas [3].
MRI did not predict the severity of ocular paresis or field defects. The size of the tumor on MRI is not actually a strong argument for therapeutic choice. Even when the tumor was very large, conservative management was accompanied by tumor shrinkage [76]. However, some MRI findings were found to be associated with clinical status and outcome: patients with simple infarction had less severe clinical features and better outcomes than those with hemorrhagic infarction or hemorrhage [70].
All these data from the literature have allowed deducing overall the place of, respectively, the conservative approach and the surgical treatment in the management of PA.
According to the majority of authors, surgical intervention should be considered in patients with severely reduced visual acuity, severe and persistent visual field defects, and deteriorating level of consciousness despite glucocorticoid replacement and hydroelectrolytic support [109]. Ocular paresis because of involvement of III, IV, or VI cranial nerves in the cavernous sinus is not in itself an indication for immediate surgery. Resolution will typically occur within days or weeks with conservative management [11].
The UK Guidelines for PA recommend a scoring system (Table 5), calculated using visual acuity, visual defects, cranial nerve palsies, and the Glasgow Coma Scale. The PA score ranges from 0 to 10, and surgery usually is indicated for scores ≥4 [11]. Another scoring system, from the Massachusetts General Hospital, proposes grading patients on a scale from 1 to 5: grade 1 for asymptomatic individuals, grade 2 for patients with symptoms due to endocrinopathy, grade 3 for patients with headache, grade 4 for patients with ocular paresis, and grade 5 for patients with visual deficits or a low Glasgow Coma Scale score. Patients with grade 5 should be submitted to surgery [59].
Pituitary apoplexy score (PAS).
For conservative approach, it is safe in patients with pituitary tumor apoplexy who are without any neuro-ophthalmic signs or mild and stable signs or those with evidence of early improvement after administration of glucocorticoids [76]. This would be particularly applicable in patients with prolactin-secreting adenomas, with whom dopamine agonists are very effective not only in controlling hyperprolactinemia but also in reducing the size of the adenoma [3]. “Wait-and-see” approach should be also considered in patients with significant clinical comorbidities.
If conservative treatment is chosen, then careful monitoring of visual signs and symptoms is necessary, and surgical decompression is recommended if visual disorders do not improve or if they deteriorate [5, 11, 59].
All patients with pituitary apoplexy need follow-up by endocrine and neurosurgical teams. They require repeated assessment of pituitary and visual function (visual acuity, eye movements, and visual fields), at 4–6 weeks. Thereafter, hormonal reevaluation must be performed every 6–12 months to determine whether or not the pituitary defect is permanent and the possible hypersecretory nature of the adenoma and to optimize hormonal replacement [109].
Sellar MRI should be repeated in 3–6 months, annually for 5 years, and biannually after that to monitor tumor progression/recurrence [119]. The presence of an “empty sella” is often observed [117].
Morbidity and mortality in patients with pituitary tumor apoplexy have declined in the past six decades. Four factors may have contributed to the improved survival: improved diagnostic accuracy, use of glucocorticoids, use of more sophisticated supportive therapy, and refinements in surgical techniques and postoperative care [3]. Currently, mortality in the acute setting is less than 2% [120].
PA is uncommon but a potentially life-threatening complication due to acute infarction or hemorrhage within a preexisting pituitary adenoma. Its pathophysiology, including extrinsic compression of arterial supply or intrinsic tumoral factors, is still controversial. In terms of triggering factors, the most common include major surgery. The classical presentation is highly suspected when an acute lancinating headache is combined with visual disturbance, cranial nerve palsy, and hypopituitarism. MRI is a fundamental step to evaluate the pituitary infarct and hemorrhage and to rule out other pathologies. For the management of PA, corticosteroids should be systematically administered. However, the therapeutic choice between surgery and conservative treatment is controversial and should be made by experts from a multidisciplinary team. The surgical management which used to be considered as the first-line treatment of this acute condition is now reserved for patients with severe neuro-ophthalmic signs. Improvement of the diagnostic means and the therapeutic management has allowed a better PA prognosis which is preserved in most of the cases. Reevaluation of the pituitary function and tumor mass is mandatory in the months after the acute apoplectic episode to adjust hormonal substitution, to detect the possible hypersecretory nature of the adenoma, and to initiate follow-up of a possible tumor remnant.
Consumers increasingly use online means to share their experiences and perceptions about the quality of services they use. Every day overwhelming volumes of information are produced and published online, and these seem to exert a critical influence on service choices and purchase decisions. This context is very much facilitated by the dissemination of technologies that encourage the production and sharing of user crated content. Likewise, there is a growing familiarity of customers with Internet technologies that is fueling this trend. Service providers, by their turn are keeping the pace by implementing and adhering to online tools that offer efficient ways for users to make their ideas available to vast audiences in a fast manner [1]. The importance of such form of communication, known as electronic word-of-mouth (eWOM) or word-of-mouse, has been extensively acknowledged in the literature, often being referred as a more effective means to influence customers’ consumption decisions than other tools, such as personal sales or advertising, because it can be perceived by costumers as a rather reliable source of information. Whereas customer reviews are now a common feature in many company websites, and platforms, research is still necessary to gain knowledge about how to effectively use eWOM data as a valued adding tool to inform customer decision making, as well as to guide managerial actions towards service improvement and innovation. This study proposes a contribution in this direction.
The study describes the development of a methodology to support the analysis of eWOM, in order to facilitate the systematic analysis and visualization of insights from online reviews concerning service quality. The proposed methodology is useful to both academics and managers as it proposes a concise display of the data analysis results, allowing for a quick identification and debate about priorities and concerns for quality management, while building on a frame of reference for quality attributes that is derived from service management literature. The study was developed in the particular context of the hotel industry in Portugal, as a representative business sector for the volume and reach of online consumer reviews. The development of the proposed data analysis and display method was built on a selected sample of customer reviews extracted from a prevalent online service for hotel bookings. The hotel industry offers an adequate and rich context for the nature of this study for the fact that the travel and tourism industry is known for being a pioneer for the growing trends of promotion and distribution of services over the Internet [2].
The chapter offers an approach for making sense of customer reviews, by identifying relevant service quality dimensions embedded in the voices of hotel customers, while offering a concise tool for the visualization of the results. To this end, the study employed the principles of importance-performance analysis (IPA), a marketing research technique acknowledged for offering a concise graphical representation of results, to develop a framework for identifying salient hotel service attributes from the available and uncategorized information provided by customer reviews. The study offers a timely approach for assisting managers in the task of sense making from growing volumes of user generated information from a key source of information for the identification of priorities for service improvement and innovation.
Following this introduction, this chapter offers in Section 2 an overview of the conceptual background of the study, namely addressing on the topics of service quality and service quality assessment approaches while discussing some of the key challenges in measuring service results. In Section 3 is devoted to describe the application of the importance-performance analysis (IPA) approach to the context of eWOM in hotel services, and to presented and discuss some representative results of the application of this methodology to extract meaning from user generated context. The chapter closes with a presentation of key contributions and conclusions in the last section.
The understanding of service quality and the deployment of robust and replicable methods to conduct its assessment have been in the core of the agendas of service management scholars and practitioners for many years. Despite an early consensus about the relevance of service quality for customer satisfaction, loyalty and company’s profitability [3, 4], the operationalization of methods and tools to measure service quality and inform managerial practice and consumer decision making has generated extensive debate and challenges. Many of the results of service experiences lack tangibility and for this reason many approaches for service quality assessment rely on information from customers’ “perceived” experiences [5, 6].
Many of the prevalent approaches to capture consumers quality perceptions build on the development of survey methods for data collection, consisting of multi-item scales. Such multidimensionality is aligned with the conceptualization of services as experiences that enact perceptions about multiple attributes and dimensions that affect customer value such as service responsiveness, reliability, and even elements such as the characteristics of the tangible elements such as service facilities, equipment, etc., and the performance and empathy of service professionals. In service experiences customers receive a combination of outcomes including direct process results (e.g., availability of required items in a retail store, on-time arrival to a flight destination in transportation services, etc.) along with other results related to the process experience resulting from customers’ contact and involvement in the service process (e.g., store atmosphere in retail services, comfort in a flight, etc.). Service quality is therefore conceptualized as a construct, featuring distinct dimensions that correspond to the diverse benefits that a customer can derive from a service. These dimensions of service quality are present across the prevalent service quality models and mirrored in the generalized generic scales such as SERVQUAL, SERVPERF, along with other sector specific scales where items are adapted to business particularities, such as in retail, health or hospitality and tourism services. Prevalent models account for the recognized dual nature of service quality determinants, i.e. the quality of service outputs as well as the quality of the experience with the delivery processes [4].
Overall service quality models, and the derived methods for its assessment, analysis and interpretation are built on customers’ perceptions about the performance of service delivery, rather than on objective assessments of quality items [7, 8]. Perceived service quality is defined as the customer’s evaluation of the overall excellence of a service and has been persistently distinguished from objective quality measurements, which were typically associated to the quality assessment of manufacturing products. The use of perceived service quality models is motivated by the specific nature of service outputs, which involves both tangible and intangible components and, as such, are often hard to assess and can result into very heterogeneous evaluations across customers.
Despite of the popularity of the [quantitative] multi-attribute type of measurement that has prevailed in the service quality domain along the years, several debates have highlighted the limits of such instruments. Among these are the difficulties of interpreting and using the standardized results of multi-attribute measurements. Data collected in this form offers only limited information about the richness, and the details, that contextualize customer perceptions about a service. More importantly, survey data fails from capture information about contradictions in service experiences as the respondents are forced to aggregate their quality experiences into ratings for a limited number of items. Any comprehensive listing of all quality aspects would result into lengthy questionnaires that would exceed customer’s willingness to answer and therefore hurt the validity of the information collected. A customer of an accommodation service of asked to evaluate the friendliness contact employees is forced to choose a single point on a scale despite the number of contacts and different staff met whose behavior and friendliness might vary considerably.
Overall the standard attribute-based quality and satisfaction surveys are not perfect when it comes to capturing all relevant managerial information, and for this reason other complementary approaches have been advanced, such as focus groups studies, analysis of critical incidents, among others, in order to capture richer consumer insights. In this context, word-of-mouth, i.e. the expressions about the service experiences as expressed in the words of the consumers have always been acknowledged as an important source of information, and a key determinant for consumer choice. Generally, it is referred to as an informal and personal form of communication [9] that has been acknowledged by its influence for customers ‘decisions [10], being source of trusted information [11].
In recent years, the advent of electronic-word of-mouth (eWOM) has created a rich field of data for deepening the understating about consumer experiences. Differently from traditional WOM, the its electronic version eWOM offers the advantage of being preserved, and accessible, over time in a written format that can be revisited and analyzed in detail, with distinct lenses.
The volume and reach of eWOM content have expended enormously, and are increasingly calling for the development of methods and tools that can assist consumers and managers to filter and make sense, in a timely manner of such large and rich amount of information. Consumers are expressing their opinions using multiple sources that include blogs, online reviews, and social networking websites, while interacting virtually to share information about their experiences with all sorts of goods, services, and brands [12]. eWOM has been defined as “any positive or negative statement made by potential, actual or former customers about a product or company, that is made available to a multitude of people and institutions via the internet” ([1], p. 39).
The tourism sector is a prominent example of a setting where eWOM has grown in volume and popularity, notably by means of online reviews that are the concrete examples of electronic versions of traditional WOM and result in a volume of comments from travelers about their experiences, the products, and the services they find along their journeys [13]. eWOM is available for other tourist to read and revisit, as well as for service managers to learn about their experiences. In fact many of the tourism service providers actively encourage their consumers to post reviews on their sites, social media platforms and other sources of reference [14]. The growth in eWOM is motivating increased research attention in several fronts, such as the investigation of the impacts of eWOM on sales, on consumer behavior. In tourism industry the results support that eWOM is considered credible [15], reducing consumers resistance to booking [16] and affects the sales of hotel rooms [17] and the motivations to visit some specific destinations [18]. Despite the growing number of studies that cover, the field is still far from being fully covered, and is still very much concentrated in exploring the behavioral implications of eWOM on travelers [19]. In this study we take a different approach aimed at developing approaches to make sense of the rich information contained in the reviews’ texts with the purpose of advancing in the creation of tools to support data analysis and visualization that can assist managers and consumers in extracting valuable information from eWOM sources.
Importance-performance analysis is a popular approach for interpreting customer satisfaction and for setting up priorities for upgrading service quality proposed by [20]. IPA builds on customers’ assessments concerning the importance and the performance of quality attributes in order to diagnose areas for improvement—typically using data collected by means of questionnaires employing service scales. IPA offers a plot representation for the measurements for importance-performance, declared by customers, consisting of a four quadrants matrix. The IPA matrix plots these values against two axes: a vertical axis—for the values of performance of service attributes; and an horizontal axis—for the values of attribute importance (see Figure 1).
Quad chart illustrating the breakdown of traditional importance-performance analysis approach. Desirable re-allocation of resources would go from the lower right quadrant to the upper left quadrant. Source: Adapted from Martilla and James [20].
Such concise display enables the quick visual identification of what elements demand for managerial improvement actions (i.e. attributes ranked in the quadrant for high importance vs. low performance) as well as others where the providers efforts are potentially misplaced (i.e. attributes ranked in the quadrant for low (customer) importance vs. high (provider) performance).
Subsequent studies have proposed modified approaches building on the principles of the IPA framework, extending its scope of application. For example CIPA, that stands for “Competitive Importance Performance Analysis”, is focused on the gaps of the performance of a given service company and that of its competitors, offering a tool to diagnose which competitive attributes demand for improvement. In this adaptation the horizontal axis represents the differences between a company’s performance towards the other market players.
Other formulations of IPA aim to address criticisms about its assumptions, namely the independence between the importance and performance measures and the linear relationship between the attributes and the performance. The so-called IPA with the three factor theory employs also a matrix representation for the measurements but takes into account the fact that not all service attributes are equally important for customer satisfaction [21, 22, 23]. This approach distinguishes three types of factors: (i) basic factors, i.e. minimum requirements that cause dissatisfaction if not fulfilled while not leading to customer satisfaction if fulfilled; (ii) performance factors, i.e. elements that cause satisfaction or dissatisfaction, depending on their performance level and (iii) excitement factors that can increase customer satisfaction if delivered but do not cause dissatisfaction if not delivered [24]. The modified IPA approach employs this three factor theory [25] and uses estimations of the relative importance of the quality attributes, instead of using customer declared information. The importance-performance lens of analysis therefore offers a versatile methodology for approaching the prioritization of service attributes.
This study builds on prevalent approaches of extending the applications of IPA by developing a modified version of IPA for identifying areas for service improvement building on qualitative data in the context of hotel experiences.
The main purpose of this work is to develop a flexible and concise methodology to make sense for the ever growing online customer reviews that are available for a wide diversity of service business, in an abundant and unstructured manner. Despite the volume and richness of data available, the ability of both customers and providers to summarize and interpret customer generated content is still very limited and often done ad hoc by managers, therefore hurting its utility and value for customer decision and company improvements. Yet recent research results confirm that such sources of information are increasingly accessed by customers to support purchase decisions [26]. To this end, the study focuses on customer online reviews in the context of the hotel industry for several reasons. Tourism and hospitality services are experiential in nature which makes pre-purchase quality assessments rather difficult, leading customers to search for various clues and information to support their choices. In this context the opinions of other customers assume a critical role. In addition this service industry has a pioneering record in the utilization of online means for customer service interactions (e.g. travel reservations), and for the abundance of eWOM behavior.
The study addresses a sample of customer reviews for a selected number of hotels in a medium sized tourist destination city in Portugal available in the online reservation website
Hotel | Star rating | Rooms | Location* | Available services | Average price** |
---|---|---|---|---|---|
Moliceiro | 4 | 49 | 0 | 16 | € 99 |
Aveiro palace | 4 | 49 | 0 | 13 | € 62 |
Melia Ria | 4 | 128 | 10 min | 22 | € 94 |
Américas | 4 | 70 | 5 | 16 | € 79 |
Imperial | 3 | 107 | 0 | 8 | € 63 |
Jardim | 3 | 48 | 0 | 11 | € 56 |
Afonso V | 3 | 78 | 5 | 6 | € 49 |
Veneza | 3 | 49 | 0 | 7 | € 68 |
Aveiro center | 2 | 24 | 0 | 8 | € 58 |
J. Estevão | 2 | 12 | 1 | 6 | € 57 |
Salinas | 2 | 18 | 0 | 7 | € 58 |
Characterization of the hotel sample.
Walking time to the city center (minutes).
Standard double room, average.
The first column contains the hotel name, the second column the official star rating at the time of the study, the third contains the number of rooms and the fourth the estimated walking time to the city center. The fifth and sixth columns present the number of services available at the hotel and the average price per night, respectively.
The chosen hotel reservation Website exhibits written online customer reviews, organized into groups—positive and negative reviews—as well as a rating obtained from customer scoring. In order to guarantee reliability, i.e. that the reviews resort from individual experiences, the Website only allows for reviews from customer who have effectively made a reservation.
The IPA addresses the data from the sample of extracted customer reviews. The first step in the analysis involves the identification of the most frequent terms and expressions about the hotel experience as stated by customers, for which text mining tools were employed, including a preliminary cleaning of symbols and words with no relevant meaning, and the standardization of terms, whenever synonyms are used to refer to a same hotel service element. The terms and expressions with higher frequency were retained for inclusion in the IPA analysis. A second step involves the identification of dimensions of affinity for the service quality attributes present in customers’ statements. This process leads to the identification of three dominant service quality elements, motivating the expression of (positive or negative) customer opinions: room, location and staff. Whereas a more detailed list if attributes can be retained the choice is for the use of a more aggregated level of analysis given the exploratory nature of the study.
The IPA matrix for the 11 hotels is displayed in Figure 2, where the data points for importance-performance for the three salient attributes, room, location and staff are, respectively ●, ▲ and *. In the traditional IPA the horizontal and vertical axis represent the coordinates for the values of importance, and the performance as perceived by the customers, usually resulting from structured questionnaire answers, using ordinal scales (e.g. 1–7), where customers sate their expectations (i.e. interpreted as importance) and service perceptions (i.e. experienced performance). In the current study, and given the qualitative nature of the available data—the reviews—the values for the matrix coordinates are obtained as follows.
Modified IPA graph for the hotel sample in the study.
For each service attribute (room, location and staff) the total frequency (considering all the terms and expressions associated to a given service attribute) is employed as a proxy for the importance of the attribute, therefore assuming, that customers express more opinions for items that are more relevant for their experience. As for performance, the analysis employs the ratio of the number of positive reviews towards the sum of positive and negative comments, for a given service attribute. According to this logic a hotel for which the proportion of positive comments is higher than the negatives corresponds to a positive performance. This proxy measurement for performance therefore varies between 0 (when all comments are negative) and 1 (when all comments are positive). Also, the traditional IPA usually employs a central tendency measure (e.g. mean, median) to split each axis and identify the four quadrants. In the current study the value of the mean is employed to split the plot area.
The interpretation of the IPA graph offers a number of interesting insights. Overall, for each hotel unit, the three service attributes considered in the analysis are closely positioned next to each other. This suggests that when hotel customers are pleased with a hotel, or with the particular performance of one service attribute and they engage in offering positive comments, they tend to be positive about the remaining attributes. Whereas there’s some natural dispersion in the points exhibited in Figure 2 most service attributes, for the diverse hotels, is positioned in the quadrants II and IV pointing towards urgent action and resource underutilization, respectively.
Overall the service attributes for the various hotel units are positioned very closely in the IPA map. A look at the positioning of the service attributes (room, location and staff) the one with stronger consistency in customers’ opinions is staff, as in 90% of cases appears as the most important attribute. An opposed pattern is shown for the attribute room, for which customers seem to hold more heterogeneous opinions about its importance. Overall the data suggests some inconsistency in customers’ perceptions about the importance of the service attributes. Of particular interest is the observation that there is a great variability in what regards the number of positive or negative comments. Most of the hotels exhibit a value for the performance measure (i.e. positive comments divided by the sum of positive and negative comments) not very distant from 0.5, therefore suggesting the existence of some level of service inconsistency across customers, a characteristic that is rather undesirable in service settings. The proposed analysis is susceptible of being conducted at a more fine grained level, i.e. in this case, for each hotel (see for example Figure 3).
Modified IPA displaying in detail the positioning of the three salient attributes [room, location and staff] for a single hotel unit (Hotel Afonso V).
This study, although exploratory and restricted to a small sample of service providers, from a specific service context—hotels—offers an illustrative insight of how existing managerial analytical tools can be adapted to help making sense of large volume of customer generated content. Whereas the study was applied in the context of hotel services, it is clear that the principles of the tool are applicable to any service industry, given that there is some kind of customer content to work with. Customer reviews are proliferating across service websites, platforms and social media contexts, therefore providing an ample and rich field for the development of new approaches to develop knowledge about service quality. The study illustrates that is possible to apply tools to offer a concise and structured view of the content generated by customers in their service reviews, and therefore to extract value from this abundant source of information. The extracted service attributes (room, location and staff) are particular to this study, its context and the limitations of sample selection, not meaning that they are the overall more important in the hotel industry. In order to do so, the study would have to be extended to a wider sample, and account for any conditioning variables (e.g. seasonality, weather, customer experience, etc.). As such this work suggested that there is a vast array of models and tools for assessing service quality that can be called to help make sense of the overwhelming volume of eWOM.
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