Absolute and relative contraindications to IV rt-PA for acute ischemic stroke [6].
Abstract
Stroke imaging/Cerebral Venous sinus thrombosis/Arterial dissecting disease in Head and Neck regions/Neurocomplication of anticoagulation therapy. Nowsday, anticoagulant drugs are common drugs used in daily practice for patients in neurology clinic. Anticoagulant treatment used for treated symptomatic patients as well as for prophylaxis therapy in asymptomatic patients. The purpose of this chapter based on the review of essential neuroimaging in the most common neurological conditions that benefit from treatment with anticoagulant drugs such as ischemic stroke, cerebral venous sinus thrombosis, and arterial dissecting disease of head and neck arteries and will be enclosed with neuroimaging in case of neurocomplication by anticoagulant therapy.
Keywords
- stroke
- intracerebral hemorrhage
- cerebral infarction
- CT
- MRI
- CTA
- CTV
- CTP
- MRA
- MRV
- angiography
- cerebral venous thrombosis
- arterial dissection
- neurocomplication
- anticoagulation
1. Introduction
Stroke is a neurovascular disease with a high incidence throughout the world; according to the global stroke fact sheet 2019 by World Stroke Organization, stroke is the second leading cause of death and the third leading cause of disability. As up to 13.7 million new cases of stroke each year, globally one in four people over age 25 will have a stroke in his or her lifetime. About 5.5 million people die from stroke annually, and 39% of all who die from stroke are under 70 years old [1]. The burden of stroke is due to widely prevalent risk factors such as hypertension, diabetes, smoking, metabolic syndrome, and behavioral factors. Modification risk factors and administration preventive therapy are the keys to decrease stroke burden. Besides of the systemic disease such as hypertension can cause stroke, a number of cardiac diseases and vascular diseases affected intracranial arteries such as non-valvular atrial fibrillation, prosthetic heart valve, dilated cardiomyopathy, atrial appendage thrombus and atrial myxoma, atherosclerosis disease of aortic arch, neck arteries and intracranial arteries, arterial dissection etc. are the common causes of stroke [2, 3, 4]. Those conditions are prone to cause an embolic stroke (cardioembolic or artery to artery embolism). Antithrombotic agents such as antiplatelet drugs and anticoagulants are the drugs that are efficient in the prevention of embolic stroke. Thus, a majority of patients who have high risk factors in the group of stroke experience and inexperience stroke might have a regular anticoagulant administration. Regular monitoring of prothrombin time and International normalized ratio (INR) to predict the bleeding complications. Because ischemic and hemorrhagic strokes have different causes and effects on the body, both require different treatments. The accurate diagnosis types of strokes as ischemic stroke or hemorrhagic stroke is important. Neuroimaging is the investigate procedure to make a correct diagnosis type of stroke and extension of stroke lesion that take part in triage stroke 2patients for further proper management.
Guideline recommendation for stroke prevention (ischemic stroke/TIA) [5]:
To evaluate the cause of ischemic stroke.
Getting rid of all risk factors is important for secondary stroke prevention such as well-controlled DM/hypertension, pause of smoking, and decreased lipid level.
Changing patients to a healthy diet (low salt, low cholesterol rich diet) and promoting physical activity such as exercise.
The administration of antithrombolytic therapy in the patients who have no contraindication to antiplatelet or anticoagulant treatment such as combination of antiplatelets and anticoagulation or dual antiplatelet therapy is not recommended in long term treatment. For the short term treatment, dual antiplatelet therapy is recommended in specific patients such as early arriving minor stroke, high risk transient ischemic stroke or severe sympatimatic intracranial stenosis etc.
Atrial fibrillation remains a common and high-risk condition for second ischemic stroke. Anticoagulation is usually recommended if the patient has no contraindications. Heart rhythm monitoring for occult atrial fibrillation is usually recommended if no other cause of stroke is discovered.
Extracranial carotid artery disease is an important and treatable cause of stroke. Patients with severe stenosis ipsilateral to a nondisabling stroke or transient ischemic attack who are candidates for intervention should have the stenosis fixed, likely relatively early after their ischemic stroke. The choice between carotid endarterectomy and carotid artery stenting should be driven by specific patient comorbidities and features of their vascular anatomy.
Patients with severe intracranial stenosis in the vascular territory of ischemic stroke or transient ischemic attack should not receive angioplasty and stenting as first-line therapy for preventing recurrence. Aggressive medical management of risk factors and short-term dual antiplatelet therapy is preferred.
Patients with embolic stroke of the uncertain source should not be treated empirically with anticoagulants or ticagrelor because it was found to be of no benefit.
Stroke has three major subtypes:
Ischemic stroke
Hemorrhagic stroke
Stroke mimic conditions
Neuroimaging modalities as noninvasive techniques for the diagnosis of stroke are mainly based on computed tomography (CT) or magnetic resonance imaging (MRI) studies such as noncontrast CT study, CT angiography (single-phase or multiphase CTA), CT perfusion (CTP), CT venography (CTV) and dual-energy CT (DECT) or MRI, MR angiography, MR perfusion, etc. invasive study such as digital subtraction catheterized angiography (DSA) is usually preserved for further treatment by endovascular options such as mechanical thrombectomy, coiling aneurysm, etc. Imaging plays a key role in current guidelines for thrombolysis. The knowledge of typical early ischemic signs in nonenhanced computed tomography (CT) is necessary.
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Usually no visible intraluminal clot density
Increased sharpness (well-demarcated area) of hypodensity of the infarcted area
Increased mass effect from cytotoxic edema
Potential to hemorrhagic transformation (looking for hyperdensity lesion among the infarcted area)
Decreased degree of brain edema.
Hypodensity of the infarction is equal to CSF density.
Signs of brain volume loss at old infarcted area such as ex vacuo dilatation of adjacent ventricle, widening of adjacent subarachnoid spaces, such as sulci, folia, and fissure dilatation.
Retrograde Wallerian degeneration along the corticospinal tract may occur at the level of cerebral peduncle and pons.
The basic principle of MR machine comprises a magnet embedded within the MRI scanner imaging use of radiofrequency (RF) wave to the brain and activate proton in all different tissues in the area scanned to spin, after that the proton is returning to its original state known as precession with release RF wave to the receiver coil. The different tissue types within the brain return at different rates and it allows us to visualize and differentiate tissues in the brain. MRI is superior to CT in terms of lack of radiation, excellent tissue contrast resolution in spatial and temporal resolution between different normal tissues in the brain, and also well discriminate between normal tissue and the abnormalities. Nevertheless, some disadvantages of the MRI study are it is a long duration scan, it needs the cooperation of the patient, it needs close monitoring, it is high cost, and it is not widely available in all hospitals.
Diffusion weighted image (DWI) is a very important pulse sequence for diagnosing acute ischemic stroke, DWI can early detect acute ischemic stroke 80–90% of cases. Restrictive diffusion lesion in DWI is the area of cytotoxic edema that will be bright (hypersignal) and typically together with a low ADC value in the ADC map image (hyposignal) (Figures 11 and 12). The pattern of DWI will differentiate large vessel occlusion, small vessel infarction or cardiac emboli, or border zone infarction.
T2WSE is for stroke mimic condition.
T2W_FLAIR looks for the nonmatched area (T2W_FLAIR-DWI) in the acute stage, which probably represents an area of penumbra, evaluates white matter leukoaraiosis, and some time will help in the diagnosis of subarachnoid hemorrhage by MRI study.
SWI (susceptibility weighted image) uses for the detection whether hemorrhagic transformation in area of infarction and also provides detection of cerebral hemorrhage prior to treatment or follow up after IV thrombosis treatment and also detect cerebral microbleeds (CMBs). The paramagnetic substances in hemorrhage display blooming of hyposignal (dark signal, signal void) lesion which is in contrast to CT scan hemorrhage is hyperdensity (white color).
On the subacute stage of infarction, there is no longer visualization of the hypersignal restrictive diffusion but hypersignal in T2W_FLAIR and T2WSE are well-delineated (Figure 13) in the early stage of subacute infarction, degree of mass effect from brain edema is still present.
Chronic stage of infarction, the infarcted brain tissue will be phagocytosis by macrophage with fluid replaced as old CSF lesion in the brain, therefore, chronic or old infarction will have a signal intensity similar to CSF, hyposignal T2W_FLAIR and hypersignal in T2WSE (Figure 13).
Similar to the evaluation of hyperdense clot sign in acute ischemic stroke, before interpretation of the hyperdensity lesion such as acute thrombus, a complete evaluation of intracranial vascular system density is needed to get rid of the false sign of hyperconcentration blood.
The brain parenchyma changes (Figures 16A and B) such as brain swelling, vasogenic brain edema related to the site of venous occlusion. Intracranial hemorrhage can occur in the brain parenchyma as hemorrhagic venous infarction, or in the extra-axial locations such as subarachnoid hemorrhage, subdural hemorrhage usually relates to the site of venous occlusion.
After administration of contrast medium, T1W contrast enhances study, there is nonopacification segment of thrombosed sinuses, and veins cause filling defect of those venous structures (Figure 17) such as an empty delta sign.
MRV (MR Venography) (Figure 17): It is an MRI technique for demonstration of cerebral venous structures. This technique can be performed either by noncontrast enhanced such as time-of-flight (TOF), phase contrast MRV or contrast enhanced study. Usually, we performed with noncontrast technique and normal cerebral venous sinuses will have normal hypersignal of flow along the course of cerebral venous sinuses includes dural venous sinuses, cortical veins, and deep cerebral venous system. If CVT occurs, there is no flow, no MRV hypersignal in the thrombosed venous structures. However, the limitation of noncontrast enhanced study is the flow artifact. To avoid this limitation, the contrast enhanced MRV may be beneficial. Contrast medium signal opacification entirely of the patency cerebral veins.
CVT can result in death or permanent disability, it generally has a favorable prognosis if diagnosed and treated early. CVT is treatable and curable by medical treatment, and the mainstay is prompt anticoagulation with parenteral heparinization.
The causes of arterial dissection are traumatic and spontaneous in origin. Head and neck trauma or minor trauma as cervical manipulation can trigger in patients with underlying arteriopathy. Connective tissue diseases, such as fibromuscular dysplasia, Ehlers-Danlos syndrome type IV, Marfan syndrome, autosomal dominant polycystic kidney disease, and osteogenesis imperfect are the underlying cause of arteriopathies. When a primary tear occurs in the intima of the arterial wall, the blood stream can penetrate into the depth of the arterial wall, such as tunica media and extends cranially according to the direction of blood stream, then intramural hematoma develops and compression to the arterial lumen. If dissection toward adventitia, it will form dissecting pseudoaneurysm and thromboembolic phenomenon can occur.
Common locations of dissection is the extracranial segment in the cervical level, spontaneous dissection particularly internal carotid artery (ICA) tends to occur at distal to carotid bulb and extends not beyond ICA entry to the petrous bone. For the extracranial vertebral artery (VA) dissection, the most common locations are at V2 segment (foramen transversarium segment) and V3 segment (extravertebral segment). The reason of high incidence in the extracranial arteries dissection is those neck arteries can mobility than intracranial arteries and also trauma against to adjacent bony structures such as styloid process or cervical spines. The most frequent clinical manifestation of carotid territory ischemia (49%–82.5%), whereas dissections without luminal narrowing cause more local signs and symptoms. A completed stroke usually occurs during the first 7 days after the onset of symptoms but can occur up to 1 month later. Local signs and symptoms include head, facial, or neck pain, Horner syndrome, pulsatile tinnitus, and cranial nerve palsy. Headache is frequently the earliest symptom (47%) of patients. The clinical manifestation from vertebral artery dissection is headache or neck pain accompanied or followed by posterior circulation ischemia (57%–84%). Treatment of craniocervical dissection is by medical therapy, anticoagulant drugs are used to prevent thrombosis and embolism caused by extracranial dissection. Endovascular treatment is for the patient who remains symptomatic due to thromboembolic events or subarachnoid hemorrhage from dissecting pseudoaneurysm intracranial location.
Imaging: Even though Digital Subtraction Angiography (DSA) is the gold standard in the diagnosis craniocervical dissection, but noninvasive imaging technique CT Angiography or MR Angiography is widely accepted and used in clinical practice.
CT Angiography (CTA) (Figure 18): CTA study in diagnosis craniocervical artery dissection may study from aortic arch up to cervical and intracranial levels continuously. Normal CTA is complete contrast medium opacification of the arterial lumen from origin to the whole course of arteries. Based on pathophysiology, eccentric narrowing of the arterial lumen with mural wall thickening cause “target sign” in axial CTA scan. Other signs such as short segment arterial stenosis, total occlusion, dissecting aneurysm, filling defect, intimal flap, focal stenosis and dilatation (string and pearl sign), and tapering stenosis (flame sign) may be detected. Please note that intimal flap is a rare finding for craniocervical arterial dissection and is common in carotid dissection. The sensitivity of CTA in the diagnosis of cervical artery dissection is 74%-98% and specificity is 84%-100%.
MRI and MR Angiography (MRA) (Figure 19): Similar to the CTA study, the MRA study may study in the whole axis from the aortic arch to the intracranial level. Whenever suspicious of extracranial arterial dissection, MRI with fat-suppressed T1 weighted image is a recommended pulse sequence in detection intramural thrombus. If intramural thrombus is in the subacute stage (3 days up to 2 months duration of blood clot), the hematoma will give hypersignal in T1W; therefore, the mural thrombus might be demonstrated for diagnosis of arterial dissection. Luminal stenosis, eccentric shaped lumen (mural wall thickening with the displacement of arterial lumen off midline and external diameter enlargement from the summation of mural hematoma are all possible findings that assist in the diagnosis of arterial dissection. MRI and MRA are excellent imaging methods in diagnosis of carotid artery dissecting artery with sensitivity 87%-99% compare to DSA whereas sensitivity is about 60% for vertebral artery (VA) dissection. The detection in vertebral artery dissection is quite lower than in carotid artery are due to small size of vertebral artery and flow related enhancement of paravertebral veins make the diagnosis is difficult. In clinical practice, when equivocal finding in diagnosis VA dissection, CTA is recommended.
Recommendation, when clinical suspicious of carotid artery dissection, we can use either CTA or MRA with similar results, whenever, suspicious of VA dissection, CTA may be superior to MRA.
2. Neurological complication of anticoagulation therapy
The most common intracranial complication during regular treatment by anticoagulant drugs is intracerebral hemorrhage (ICH) [22, 23, 24, 25]. Basically, the cause of ICH is classified into two groups as primary cause due to spontaneous rupture of small vessels or amyloid angiopathy as a majority of the patients about 78%-88% and secondary cause associated with tumor, impaired coagulopathy as a minority group. Even though small in number but significant risk factors with ICH such as hemophilia or acute leukemia with thrombocytopenia or patient during treatment by anticoagulant drugs, massive intracranial hemorrhage is often cause of death.
2.1 Cause of intracranial hemorrhage (ICH)
ACQUIRED:
Iatrogenic coagulopathy
ICH related to aspirin
ICH related to anticoagulation, heparin, and Coumadin
ICH related to thrombolytic treatment
Neoplastic coagulopathy
ICH related to leukemia
SDH in cancer patient
Rare cause of ICH
Drug-induced thrombocytopenia
Uremia
Alcohol
Liver transplantation
CONGENITAL:
Hemophilia
2.2 Physiology of hemostasis
Two important mechanisms against bleeding are blood coagulation and platelet-mediated hemostasis. The coagulation cascade is triggered as soon as blood contacts the injured endothelial lining. The combination of both coagulation cascade and active formation of the platelet plug is effective autoregulation mechanisms in occlusion of a vascular lesion. Coagulation cascade mechanism have its own two main pathways: 1) intrinsic pathway by physical-chemical activation which its role is not well understanding and 2) extrinsic pathway activated by tissue factor released from the damaged cell.
Extrinsic Pathway: When blood vessel wall injuries exposed plasma to tissue factor, then, Factor VII is a plasma protein bind to tissue factor and activated to factor VIIa, this complex will activate factor IX, X to factor IXa, Xa. Factor Xa and its cofactor Va form a phospholipid-bound complex called the prothrombinase complex, which is highly activated on the surface of platelets and cleaves prothrombin (factor II) to thrombin (factor IIa). Thrombin cleaves fibrinogen (factor I) to fibrin (factor Ia), which is covalently cross-linked by factor XIIIa into fibrin strands. Factor VIII binds to vWF (an adhesive protein important for the generation of the initial platelet plug). Thrombin feedback is important to the entire system. Thrombin, one generated is powerful procoagulant further conversion factor V, VIII to factor Va, VIIIa and covert more prothrombin to thrombin. Thrombin will further accelerate the entire cascade in the formation of a large amount of fibrin.
Regulatory mechanism of the coagulation cascade, such as tissue factor pathway inhibitor, antithrombin III, activated protein C and protein S, thrombomodulin, and fibrinolytic system, is to limit the amount of fibrin clot avoiding tissue ischemia and to prevent widespread thrombosis.
2.3 Pathophysiology of bleeding disorders
Coagulopathies leading to intracranial hemorrhage mostly from acquired caused. Iatrogenic coagulopathy from aspirin, anticoagulants, and thrombolytic agent treatment.
Warfarin is an oral anticoagulant that interfere with vitamin K metabolism in the liver and cause impairment synthesis functional coagulation factors II, VII, IX, X and protein C, protein S. Therefore, Warfarin administration can prolong prothrombin time (PT), INR.
Heparin is administered parenterally and inhibits action of antithrombin III cause prolong of the partial.
Thromboplastin time (PTT).
Enoxaparin, low molecular weight heparin, similar action to heparin with a longer half-life time (4.5 hrs.)
Anticoagulant therapy related ICH is about 10%-20% and ICH is the most dreaded and least treatable complication. The mortality rate is about 46%-68%. The distribution of intracranial hemorrhage related to anticoagulant therapy is in the brain parenchyma, intracerebral hemorrhage (ICH) about 70% followed by subdural hemorrhage (SDH). There is no specific predilection in the brain. Risk factors such as hypertension, increasing age, and previous cerebral infarction. The mechanism of spontaneous ICH developing during anticoagulants is not clearly understood. Postulate that patients with underlying hypertension with hemorrhage derived from small vessel vasculopathy, usually have normal hemostatic mechanisms but fail when anticoagulant.
Absolute and relative contraindications to IV rt-PA for acute ischemic stroke.
Acute ICH including hemorrhagic infarction.
History of ICH (microbleed is not contraindicated).
BP>185mmHg, BPs>110mmHg.
Serious head trauma or stroke < 3months.
Thrombocytopenia (platelet <100,000/mm3) and coagulopathy (PT>15, INR>1.7).
LMWH within 24 hr (38% risk of sICH, 29% risk of death, 33% favorable outcomes, od 0.84 for sICH, od5.3 for death).
DTIs (TT is sensitive to the presence of DITs).
Factor Xa inhibitor.
Severe hypoglycemia(<50mg/dl) and hyperglycemia(>400mg/dl) may be permitted for IVT.
Early radiographic ischemic changes (>1/3 MCA).
Advanced age (>80yrs.)
Mild or improving stroke (NIHSS<5)
Severe stroke (IVT should be cautiously administered in NIHSS>25 at 3–4.5 hrs.)
Major surgery within 2 weeks (some 3 months)
Arterial puncture of noncompressible site
Recent GI bleeding or GU bleeding
Seizure at onset
Recent MI within 3 months
Intracranial structure abnormality (axial tumor, AVM, aneurysm)
Dementia
3. Summary
Neuroimaging is a noninvasive investigation tool that is essential not only to confirm the diagnosis of emergency neurological diseases such as stroke but also to play a role in triage patients into receiving proper medical treatment, surgical treatment, or intervention treatment. Basic interpretation of CT brain and MRI brain in stroke, CVT, dissection, hemorrhage warrants the understanding of density (CT) or signal intensity (MRI) changes of affected brain tissue in stroke and intraluminal thrombus in each stage of the disease. Further using of advanced neuroimaging investigation such as CTA, multiphase CTA, CTV, and CTP aimed for more specific conditions of the artery disease such as arterial thrombosis, arterial dissection, venous disease such as venous sinus thrombosis, yet, also reduced the need for more invasive investigation such as digital subtraction angiography.
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