Dystonia and Peripheral Nerve Surgery in the Cervical Area

Cervical dystonia is the most common form of focal dystonia (Dashtipour et al., 2007). It is characterized by involuntary movement of the neck resulting in abnormal neck posture (Brin & Benabou, 1999; Dent, 2002). Cervicalgia and headache sometimes occur in patients suffering from the disease (Albanese, 2005; Brashear, 2004, Schim, 2006). A critical long-term sequelae of this kind of movement disorder is premature cervical spinal degenerative disease (Chawda et al., 2000) which possibly progresses to cervical spondylotic myelopathy (Hagenah et al., 2001; Jameson et al., 2010; Konrad et al., 2004; Krauss et al., 2002; Spitz et al., 2006; Tonomura et al., 2007; Waterston et al., 1989).

Conventional treatment of cervical dystonia consists of oral medication, botulinum toxin injection, and physical therapy. For patients who do not respond to such therapies or are refractory cases, surgical treatment is an appropriate option (Nunta-aree & Sitthinamsuwan, 2009;Nunta-aree et al. 2010aNunta-aree et al. , 2010b. Surgical therapy for cervical dystonia has been continuously developed for a significant period to improve outcome and diminish complication. Some operations have been abandoned because of their potential complications while some of them have been used increasingly and are currently popular on account of their effectiveness and safe (Albanese, 2005;Albanese et al., 2006;Brin & Benabou, 1999;Feely, 2003). Overview of surgical treatment for cervical dystonia is described in the following.

b) Intradural posterior cervical rhizotomy
The formerly common procedure was bilateral C1-C4 posterior rhizotomy (Vogel et al., 2010) which was ultimately proved ineffective in the treatment of cervical dystonia. It sometimes caused respiratory insufficiency as a result of diaphragmatic dysfunction (Fraioli et al., 1977). Nowadays, posterior rhizotomy in the cervical level are performed only on C5 to T1 posterior nerve spinal roots and it aims to treat bilateral upper limb spasticity (Benedetti et al, 1977;Bertelli et al., 2000Bertelli et al., , 2003Heimburger 1973;Hsin et al., 2004, Laitinen et al., 1983.

c) Intradural accessory nerve denervation
This abandoned method was resection of the accessory nerve situated in the posterior cranial fossa (Adams, 1984;Hernesniemi & Keränen, 1990). It affected not only motor fibers to the sternocleidomastoid but also those to the trapezius. Postoperative trapezius atrophy and shoulder instability inevitably occurred (Bronte-Stewart, 2003;Sorensen & Hamby 1965).

e) Microvascular decompression of the accessory nerve
This rarely used operation primarily aims to rectify dystonia of the sternocleidomastoid and trapezius in patients with torticollis (Sun et al, 2009). Nevertheless, the hypothesis of accessory nerve decompression cannot explain improvement of cervical dystonia in the individuals who have no dystonia of both the muscles (Albanese et al., 2006;Brin & Benabou, 1999;Bronte-Stewart, 2003;Taira, 2009).

f) Selective peripheral denervation
This relatively safe and popularly used procedure is an ablative surgery specific on peripheral motor nerves innervating dystonic neck muscles whereas motor branches supplying normal muscles and sensory nerves will be entirely preserved (Bertrand, 1987(Bertrand, , 1993Braun & Richter, 1994). Good to excellent outcome is often achieved by the operation, so it has become a common surgical treatment for cervical dystonia (Albanese, 2005;Albanese et al., 2006;Krauss, 2010). This type of surgery is the central idea of the present chapter and its content will be stated in detail.

g) Myotomy or myectomy
Resection of dystonic muscles is occasionally combined with selective peripheral denervation (Albanese et al., 2006;Bronte-Stewart, 2003;Chen et al., 2000;Huh et al., 2005;Krauss, 2010;Münchau et al., 2001a;Xingkang, 1981). In the authors view, muscle section is an adjunctive procedure for cervical dystonia and should be considered in cases with longstanding dystonia which exhibit evidence of soft tissue stiffness or muscle shortening. Furthermore, it may be performed on muscles which are difficult to denervate (Ondo & Krauss, 2004), such as the scalene muscles.

h) Pallidal deep brain stimulation
High-frequency stimulation of the globus pallidus internus often yields outstanding result in dystonic individuals, including patients with cervical dystonia (Albanese et al., 2006;Bittar et al., 2005;Cacciola et al., 2010;Hung et al., 2007;Krauss et al., 1999Krauss et al., , 2004Krauss, 2007;Parkins et al., 2001;Vercueil, 2003;Volkmann & Benecke, 2002;Yianni et al., 2003). However, among our patients with uncomplicated or simple cervical dystonia, we did not encounter substantial difference of outcome between the patients who underwent pallidal deep brain stimulation and those who underwent peripheral denervation. Therefore, we always chose peripheral nerve resection as the primary surgical therapy in the uncomplicated cases. On the other hand, we consider the deep brain stimulation as the prerequisite treatment of complex cervical dystonia, such as mobile cervical dystonia, segmental dystonia, head tremor, anterocollis, severe retrocollis, in the patients who have significant extracervical symptoms, or who have never been improved by botulinum toxin injection (primary botulinum toxin non-responder). Such complicated cases are always difficult to deal with through selective peripheral denervation (Albanese et al., 2006;Krauss, 2010;Nunta-aree & Sitthinamsuwan, 2009;Nunta-aree et al., 2010aNunta-aree et al., , 2010b.

i) Intrathecal baclofen therapy
Implantation of this kind of intraspinal drug delivery system is more suitable for generalized dystonia or multifocal dystonia than focal dystonia at the neck (Albright et al., 2001;Dykstra et al., 2005).

j) Spinal cord stimulation
Dorsal column stimulation of the spinal cord gave inconstant outcome and there was no continuous study in dystonic patients since 1990s (Fahn, 1985;Taira & Hori, 2007;Taira, 2009). However, currently, it appears to be a good surgical option in various pain disorders, particularly in neuropathic pain and pain of ischemic origin (Forouzanfar et al., 2004;Kunnumpurath et al., 2009). This chapter focuses on peripheral nerve surgery in the cervical region for cervical dystonia which refers to selective peripheral denervation in terms of patient selection, preoperative evaluation, operative procedures with relevant surgical anatomy, and surgical outcome.

Patient selection
Selective peripheral denervation is chiefly indicated in patients with failed botulinum toxin injection, including those who have never responded to the injection (primary botulinum toxin non-responder) or who have a change from significant previous response to poor recent response (secondary botulinum toxin non-responder) (Albanese et al., 2006;Brin & Benabou, www.intechopen.com 1999;Bronte-Stewart, 2003;Feely, 2003;Taira, 2009;). Good surgical candidates for the operation include those who meet the following parameters (Braun et al., 1995;Brin & Benabou, 1999;Chen et al., 2000;Dashtipour et al., 2007;Feely, 2003. a. Patients who are botulinum toxin responder or even secondary non-responder b. Dystonic symptoms have been stable or not progressed at least 1 year c. Dystonic disorder mainly confines in the neck region d. Pure torticollis with slight laterocollis or retrocollis e. Preoperative electromyography and imaging of the cervical muscles are concordant with clinical manifestation Furthermore, selective peripheral denervation is sometimes considered as a major alternative to botulinum toxin injection in the treatment of cervical dystonia. For example, for patients who do not require multiple repeated injections or who cannot afford the cost of the toxin, the operation is meaningful for them (Taira, 2009). Nevertheless, some kinds of cervical dystonia are not suitable for the procedure, including head tremors, anterocollis, complex cervical dystonia or cervical dystonia with marked phasic movement. In such kinds of dystonia, pallidal deep brain stimulation should be considered first (Albanese et al, 2006;Nunta-aree et al., 2010b).

Preoperative evaluation
In the surgical point of view, consideration before decision of the denervating procedure should cover the following.

Identification of dystonic muscles
Basically, dystonic muscles must be always defined by using clinical observation and physical examination. Visualization of abnormal posture of the neck, palpable deviant muscle tone and tension usually give valuable preliminary information about the group of involved muscles. Electromyography or video-electromyography is an important tool to define the specific group of dystonic muscles (Brin & Benabou, 1999;Dressler, 2000;Feely, 2003;Krauss et al., 1997;Münchau et al., 2001a;Ostergaard et al., 1996), for which it is very helpful in operative planning. Recently, FDG PET-CT was introduced in localization of dystonic muscles in the neck region (Sung et al., 2007).

Prior response to botulinum toxin injection
As mentioned above, patients with good prior response to the toxin have tendency to achieve good outcome following the operation, whereas the primary non-responders may not (Braun et al., 1995). The information about injected muscles which accomplish good outcomes is very critical for operative planning.

Fixed bony deformity
This secondary change should be investigated, especially in patients who have long-lasting cervical dystonia. It can be simply revealed by noting passive range of motion of the neck and plain radiographic studies of the cervical spine. Limitation of passive neck motion implies probable fixed deformity which often impairs surgical outcome, particularly in terms of postoperative neck posture.

Measure of cervical dystonia
The commonly used measures of cervical dystonia severity and its impacts are The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and Tsui score (Cano et al., 2004;Ceballos-Baumann, 2001;Comella et al., 2003;Taira, 2009;Tsui et al., 1986). The TWSTRS (Comella et al., 1997) (Table 1) is comprised of three main sections, including torticollis severity scale, disability scale, and pain scale. The Tsui score (Moore & Blumhardt, 1991;Tsui et al., 1986) (Table 2) is a composite score calculated by a formula. By both the methods, a higher level of score indicates increased severity of cervical dystonia (Comella et al., 1997;Moore & Blumhardt, 1991). The score can be used for comparison between before and after a treatment or between among various alternatives of treatment. Unlimited ability to read in normal seated position but bothered by torticollis 2 Unlimited ability to read in normal seated position but requires use of tricks to control torticollis 3 Unlimited ability to read but requires extensive measures to control torticollis or is able to read only in nonseated position (e.g., lying down) 4 Limited ability to read because of torticollis despite tricks 5 Unable to read more than a few sentences because of torticollis E. Television Unlimited ability to watch television in normal seated position but bothered by torticollis 2 Unlimited ability to watch television in normal seated position but requires use of tricks to control torticollis 3 Unlimited ability to watch television but requires extensive measures to control torticollis or is able to view only in nonseated position (e.g., lying down) 4 5 Limited ability to watch television because of torticollis Unable to watch television more than a few minutes because of torticollis F. Activities outside the home (e.g., shopping, walking about, movies, dining, and other recreational activities) 0 No difficulty 1 Unlimited activities but bothered by torticollis 2 Unlimited activities but requires simple tricks to accomplish 3 Accomplishes activities only when accompanied by others because of torticollis 4 Limited activities outside the home; certain activities impossible or given up because of torticollis 5 Rarely if ever engages in activities outside the home 3. Pain scale (maximum = 20) A. Severity of pain Rate the severity of neck pain due to spasmodic torticollis during the last week on a scale of 0 -10 where a score of 0 represents no pain and 10 represents the most excruciating pain imaginable. Score calculated as: [worst + best + (2 x usual)]/4 Best ____ Worst ____ Usual ____ Score____  limitation or interference from pain  1 Pain is quite bothersome but not a source of disability   2 Pain definitely interferes with some tasks but is not a major contributor to disability 3 Pain accounts for some (less than half) but not all of disability 4 Pain is a major source of difficulty with activities; separate from this, head pulling is also a source of some (less than half) disability 5 Pain is the major source of disability; without it most impaired activities could be performed quite satisfactorily despite the head pulling   (Tsui et al., 1986)

Operative procedures and relevant surgical anatomy
Selective peripheral denervation consists of several surgical procedures. One well-known operation is the Bertrand procedure which originally included section of peripheral branches of the cervical spinal nerve and selective denervation of the sternocleidomastoid nerve. Taira's method is a modification of the classic procedure of Bertrand aiming to overcome some drawbacks of the original method. Cutting of peripheral branches supplying the sternocleidomastoid or levator scapulae endeavors to reduce their dystonia resulting in improved neck posture and function. The authors simply divide the denervating procedures into three main themes, including denervation of the posterior cervical paraspinal, sternocleidomastoid, and levator scapulae muscles. In order to understand these operations, each of them will be preceded by exposition of its relevant surgical anatomy. In addition, identification of nerves by using intraoperative electrical nerve stimulator, conclusion of nerve supply to the neck muscles, options in selective denervation, and combined operations will be discussed consecutively.

Surgical anatomy of the posterior cervical paraspinal muscles and related nerve supply
In all patterns of cervical dystonia except for anterocollis, the posterior cervical paraspinal muscles have the key role in occurrence of dystonic postures. They are abnormal on the same side of rotating or tilting head in torticollis or laterocollis, respectively (Anderson et al., 2008;Krauss et al., 1997). This group of muscles are found to be dystonic bilaterally in retrocollis (Taira, 2009). The commonly involved muscles include the splenius capitis, semispinalis capitis, semispinalis cervicis, multifidus, suboccipital muscles (rectus capitis posterior major and minor, obliquus capitis superior and inferior), and upper trapezius (Taira, 2009) (Fig.3).
Aside from the trapezius, all of them are innervated by the posterior rami of the C1 to C8 spinal nerves while the upper twig of the accessory nerve directly supplies the trapezius. The most influent muscles are controlled by the C1 to C6 posterior rami. Consequently, a common procedure of posterior neck muscle denervation is C1-C6 posterior ramisectomy (Krauss et al., 1997).
The C1 dorsal root and its ganglion are usually absent (Tubbs et al., 2007), so the C1 spinal nerve mostly originates from the C1 ventral nerve root which contains pure motor fibers. The C1 segmental nerve emerges from the atlanto-occipital space located superior to the atlas, then it abruptly branches into the anterior and posterior rami. Unlike the C2 to C6 posterior rami, the C1 posterior ramus does not ramify into medial and lateral branches ( Fig.4A) while those of the C2-C6 spinal nerves do (Clemente, 1985;Kahle & Frotscher, 2003;Kayalioglu, 2009;Roman, 1981). The posterior ramus of the C2 spinal nerve always bifurcates into medial and lateral branches. The medial branch mainly contains sensory fibers which it terminates as the greater occipital nerve supplying the posterior scalp up to the vertex (the C2 dermatome). The lateral branch is composed of motor fibers supplying the upper portion of the posterior cervical group (Fig.4B). The C3-C6 posterior rami often divide into medial and lateral branches innervating the corresponding skin as well as paraspinal muscles of the neck (Clemente, 1985;Kayalioglu, 2009;Roman, 1981) (Fig.4C).

Denervation of the posterior cervical paraspinal muscles
The two main strategic options in selective denervation of the posterior neck muscles are posterior cervical ramisectomy in the Bertrand procedure and Taira's modified method. The details of both alternatives are described as the follows.

Posterior cervical ramisectomy in Bertrand procedure
Classically, peripheral denervation for torticollis in the Bertrand procedure is comprised of selective peripheral denervation of the posterior cervical muscles ipsilateral to the rotating head and selective denervation of the contralateral sternocleidomastoid muscle (Anderson et al., 2008;Bertrand, 1993;Braun & Richter, 1994;Feely, 2003;Krauss, 2010;Sitthinamsuwan et al., 2010b;Taira, 2009). This genuine extraspinal procedure provides good surgical outcome and is currently a widely used operation for cervical dystonia (Bronte-Stewart, 2003;Krauss, 2010;Taira, 2009). Denervating procedure on peripheral nerves supplying the posterior cervical group is typically performed on those arising from the C1 to C6 spinal cord segment (Brin & Benabou, 1999;Dashtipour et al., 2007;Krauss, 2010;) through a midline posterior cervical incision (Fig.5). Original Bertrand's denervation of the posterior cervical muscles is comprised of extraspinal resection of C1-C2 spinal nerve roots (extraspinal C1-C2 rhizotomy) with section of C3-C6 posterior rami (C3-C6 posterior ramisectomy) (Bertrand, 1993;Huh et al., 2005Huh et al., , 2010. Alternatively, C1-C2 posterior ramisectomy can be used instead of C1-C2 extradural rhizotomy (Brin & Benabou, 1999;Münchau et al., 2001a;Ondo & Krauss, 2004). In the authors' practice deriving from C1-C2 operation, we preferred posterior ramisectomy rather than extraspinal rhizotomy. Therefore, C1-C6 posterior ramisectomy was always performed in our denervation. During dissection, muscular branches emerging from the C1-C6 posterior rami are identified by using an electrical stimulator and prepared for ramisectomy. The ablation is done just before the peripheral nerves penetrating the targeted muscles (Fig.6).  A common pitfall of posterior cervical ramisectomy is inadequate denervation of the semispinalis capitis resulting in residual or recurrent cervical dystonia. The pitfall may occur as a result of complex innervation of this muscle comprised of two entities. The first one is motor branches originating from the medial branches of the posterior cervical rami. They intervene in the plain between the semispinalis capitis and semispinalis cervicis and then enter into the deep surface of the semispinalis capitis (Fig.7A). In the same manner, the other entity is muscular branches coming from the lateral branches of the posterior cervical rami which they are situated in the plain between the semispinalis capitis and splenius capitis, then supply the semispinalis capitis through its superficial aspect (Taira, 2009) (Fig.7B). Hence, to accomplish complete denervation of the semispinalis capitis, exploration and resection of the motor nerves in both the plains are mandatory.
In patients suffering from retrocollis, bilateral posterior cervical muscle denervation is required. With caution, bilateral section of the C6 posterior rami should be avoided, particularly in elderly females who have thin neck muscles. Following bilateral C6 posterior ramisectomy, such patients probably develop difficulty in their neck extension and swallowing (Bertrand, 1988;Taira 2009). In our experience of bilateral posterior cervical denervation for intractable retrocollis, we always performed C1-C6 posterior cervical ramisectomy on a more severe side and cut from the C1 posterior ramus caudally to the C4 or C5 posterior ramus with total preservation of the C6 one on the contralateral side.
A major sequelae of Bertrand procedure is dysesthesia over the skin innervated by the C2 spinal nerve. The sensory disturbance of the C2 dermatome is inevitable in almost all cases who undergo this procedure. It always occurs in the early postoperative period as a result of resection of the proximal C2 dorsal ramus containing both motor and sensory nerve fibers (Albanese et al., 2006;Braun & Richter, 1994;Feely, 2003;Münchau et al., 2001a;Fig. 7. Innervation of the semispinalis capitis muscle (SM SP CAP). A and B are the muscular branches arising from the medial branch (MB) and lateral branch (LB) of the posterior cervical rami (PR), respectively. They supply the semispinalis capitis through its opposite surfaces. AR, anterior cervical rami; SM SP CV, semispinalis cervicis; SPL CAP, splenius capitis.
Resection of the C1 and C2 anterior spinal nerve roots (C1-C2 anterior rhizotomy) can entirely preserve sensory function of the C2 posterior spinal nerve root, so C2 dysesthesia does not occur. Furthermore, the unilateral C1-C2 procedure does not bring about swallowing trouble. Although the efficacy of Taira's modified method in the treatment of cervical dystonia was not significantly different from that of the Bertrand procedure, the C2 sensory disturbance, www.intechopen.com operative time, and intraoperative blood loss were appreciably minimized by Taira's operation (Taira & Hori, 2001;Taira et al., 2002;. Potential complications of intradural C1-C2 operation may have occurred, such as cerebrospinal fluid leak, meningitis, spinal cord injury, and spinal cord ischemia. However, all of them are preventable and avoidable. Fig. 8. A, B and C, A comparison between Bertrand procedure and Taira's method. A, C1-C2 denervation in Bertrand procedure. The C1-C2 nerves can be cut on either the spinal roots (extraspinal rhizotomy) presented by red dashed lines or posterior rami (PR) displayed by green dashed lines. B, Intradural C1-C2 anterior rhizotomy in Taira's method. The resection will be performed on the C1 and C2 anterior spinal nerve roots (red dash lines), while the C2 posterior spinal nerve root will be entirely preserved. For A and B, The C1 posterior spinal nerve root and its dorsal root ganglion are usually absent in the majority of humans. Therefore, they are presented in a dashed appearance. C, C3-C6 posterior ramisectomy is identical in both the operations.

Surgical anatomy of the accessory nerve and its peripheral branches
The accessory nerve originates from its cranial and spinal roots. After the nerve exits the posterior cranial fossa through the jugular foramen, it runs underneath the sternocleidomastoid muscle where it gives motor branches to the muscle and appears in the posterior triangle of the neck after that (Aramrattana et al., 2005;Clemente, 1985;Frank 1997;Roman 1981). In the triangle, it emerges from the posterior border of the www.intechopen.com sternocleidomastoid at the punctum nervosum (Erb's point) (Anderson et al., 2008;Aramrattana et al., 2005). There are several nerves arising from this point, including the great auricular, lesser occipital, transverse cervical, and supraclavicular nerves (Anderson et al., 2008;Aramrattana et al., 2005;Dailiana et al., 2001). From the punctum nervosum, the accessory nerve courses inferolaterally, then ramifies into numerous branches supplying the trapezius (Aramrattana et al., 2005;Clemente, 1985;Dailiana et al., 2001;Kierner et al., 2000;Roman 1981;Shiozaki et al., 2000) (Fig.9). In addition to the accessory nerve, motor branches of the cervical plexus derived from the C2-C3 anterior rami participate in innervation of the sternocleidomastoid and trapezius muscles (Aramrattana et al., 2005;Bertrand, 2004;Clemente, 1985;Dailiana et al., 2001;Pu et al., 2008;Roman 1981;Stacey et al., 1995;Zhao et al., 2006). Among the entire phalanx of nerves to both the muscles, multiple variations can be encountered during surgical exploration (Brennan et al., 2002;Brown et al., 1988;Caliot et al., 1984Caliot et al., , 1989Latarjet, 1948;Stacey et al., 1995;Taira, 2009) (Fig.10 and Fig.11). Knowledge of the variations is essential in accessory nerve denervation. Incomplete denervation of the sternocleidomastoid usually occurs in individuals who have hidden extra nerve supply from the cervical plexus. Failure of improvement or recurrent dystonia is occasionally due to this aberration. Furthermore, ignorance of diversity of trapezius innervation perhaps gives rise to injured trapezius nerves resulting in shoulder dysfunction.
www.intechopen.com  Caliot et al., 1984]. Fig. 11. Variation of the nerve to the trapezius (TPZ). A, The nerve originates from a connecting branch between the accessory nerve (AN) and anterior ramus of the C2 spinal nerve (C2). A direct branch from the C2 anterior rami (dotted line) may participate in the supply. B, The accessory nerve gives a direct branch to supply the trapezius. An additional twig perhaps comes from the C2 anterior ramus to join the main supply (dotted line). C, The trapezius is innervated by the nerve arising from the junction between the C2 anterior ramus and a connecting branch from the accessory nerve. D, The nerve emerges from the union of the connecting branches of the accessory nerve, C2, and C3 anterior rami (C3). E, A connection between C2 and C3 anterior rami gives the nerve supplying the trapezius muscle. SCM, sternocleidomastoid. [Modified from Latarjet, 1948].

Selective denervation of the sternocleidomastoid muscle
Selective resection of nerve to the sternocleidomastoid with sparing of the trapezius nerve is commonly used in the treatment of torticollis and laterocollis. It is one of two main parts of Bertrand procedure. In our viewpoint, we considered sternocleidomastoid denervation on the contralateral side of posterior cervical muscle denervation in all patients with torticollis. In addition, we used the ipsilateral procedure in some laterocollic cases, particularly in patients with absence of shoulder elevation, which probably indicated hyperactivity of the sternocleidomastoid rather than that of the levator scapulae. The denervation can be done through a small incision along the posterior boundary of the sternocleidomastoid muscle (Fig.12A). Medial retraction of the sternocleidomastoid is helpful in visualization of the nerve. The nerve is often seen underneath the retracted muscle (Fig.12B). Electrical stimulation of the correct nerve absolutely reveals contraction of the sternocleidomastoid without movement of the trapezius. On the other hand, isolated trapezius contraction indicates stimulation of the trapezius nerve which is inaccurate. If contraction occurs on both the muscles, that is a too proximal position. Besides, the additional nerve supply from the cervical plexus should be investigated and then sectioned. The potential complications are injury of nerve to the trapezius (Albanese et al., 2006;Braun & Richter, 1994, 2002Taira, 2009) and numbness in the retro-auricular area caused by injury or excessive retraction of the great auricular nerve during the operation (Braun & Richter, 1994).

Anatomy of the levator scapulae and its nerve supply
The levator scapulae is the key muscle in emergence of laterocollis (Anderson et al., 2008;, particularly when the lateral neck deviation is accompanied by elevation of the ipsilateral scapula. It extends from transverse processes of the 1st to 4th cervical www.intechopen.com vertebrae to insert at the medial aspect of the upper scapular border superior to the scapular spine (Roman, 1981) (Fig.13A). Contraction of the muscle brings about lateral inclination of the ipsilateral head and neck in the coronal plane together with upheaval of the shoulder on the same side (Clemente, 1985;Roman, 1981; (Fig.13B). Its major nerve supply originates from C3, C4, and C5 anterior rami. The twigs from C3-C4 nerve roots pass underneath the sternocleidomastoid and then enter the anteromedial aspect of the levator muscle. The dorsal scapular nerve arising from the C5 anterior ramus also participates in the innervation of the levator muscle through its inferomedial surface (Anderson et al., 2008;Clemente, 1985;Roman, 1981;Taira, 2009).

Levator scapulae muscle denervation
The operation is mainly indicated in laterocollic patients (Anderson et al., 2008) with marked shoulder elevation and minimal head rotation (Taira, 2009). The ascending shoulder points to the hyperactive levator muscle (Hernesniemi & Keränen, 1990;Taira & Hori, 2001;Taira, 2009). Importantly, noting palpable tense levator scapulae in the posterior cervical triangle is helpful in the diagnosis (Taira, 2009). The surgical incision is identical to that of the sternocleidomastoid denervation. The C3-C4 muscular branches can be encountered by using electrical nerve stimulator and then cutting on the anteromedial surface of the levator muscle (Fig.14). The further supply coming from the dorsal scapular nerve should be explored and eventually ablated. Care should be taken to preserve the adjacent phrenic nerve  and upper part of the brachial plexus. Nerve to the levator muscle can be identified on the anterior aspect of the innervated muscle.

Intraoperative electrical nerve stimulation
Aside from knowledge in the surgical anatomy, identification of accurate nerves by using intraoperative electrical nerve stimulator is very crucial in selective peripheral denervation for cervical dystonia. Intraoperative nerve stimulation has many benefits. It assists in exploration of nerves in the operative field (Brin & Benabou, 1999), in discrimination between motor and sensory nerves, and, importantly, defines muscle topography supplied by electrically stimulated nerve. Sensory nerve must be distinguished from motor nerve. The former has to be routinely preserved as much as possible to avoid neuropathic pain caused by injured or sectioned sensory nerve. Stimulation of motor nerve absolutely elicits contraction of the corresponding muscle (Ondo & Krauss, 2004) whereas there is nothing which occurs when sensory nerve is stimulated. Determination of innervation topography is valuable in selective nerve section. It can tell us which ones should be cut and left (Brin & Benabou, 1999;Sitthinamsuwan et al., 2010c). This strategy always results in the absence of adverse events caused by wrong nerve resection and unnecessary denervation (Sitthinamsuwan et al., 2010c). In utilization of the intraoperative electrical stimulator, shortacting muscle relaxants can be administered only for induction of general anesthesia and must be prohibited after that (Ondo & Krauss, 2004;Taira, 2009).
In posterior cervical muscle denervation, stimulation on each posterior cervical ramus gives rise to segmental contraction of the corresponding muscle. For instance, stimulation of the C2 posterior branch leads to vigorous contraction of the upper fibers of the splenius capitis, while movement of its lower portion is always elicited by electrical stimulation of the C5 or C6 posterior ramus. As discussed in denervation of the sternocleidomastoid, too proximal stimulation of the accessory nerve brings about concurrent contraction of both muscles innervated by the nerve. Isolated movement of either the sternocleidomastoid or trapezius indicates separated stimulation on the sternocleidomastoid or trapezius nerve, respectively. Furthermore, direct stimulation of nerve to the levator scapulae simply reveals contraction www.intechopen.com of the muscle. If movement of the diaphragm also appears, that means we are very close to the phrenic nerve. In the same manner, if the levator scapulae and rotator cuffs of the shoulder or pectoral muscles contract simultaneously during stimulation of the dorsal scapular nerve, this phenomenon indicates that the present location is too closely adjacent to the C5 spinal root or upper trunk of the brachial plexus.

Alternatives in selective peripheral denervation
In selective peripheral denervation, the procedure should be tailored according to the presenting dystonic forms . Surgical options for cervical dystonia are listed in Table 4 (Bertrand, 1993;Braun & Richter, 2002;Brin & Benabou, 1999;Chen et al., 2000;Huh et al., 2005Huh et al., , 2010Münchau et al., 2001a;. Selective peripheral denervation is not a good alternative for anterocollis because extensive bilateral denervation of both superficial and deep anterior cervical muscles can lead to significant disabling anterior neck muscle paresis and swallowing dysfunction. Furthermore, the operation is usually not effective in the treatment of anterocollis and complex cervical dystonia. Therefore, pallidal deep brain stimulation should be considered as the primary surgical therapy for such kinds of cervical dystonia.

Combined operative procedures
Our treatment of complex cervical dystonia and idiopathic generalized dystonia by using bilateral pallidal deep brain stimulation indicates that all of them dramatically respond to the operation. However, a few cases still had some residual cervical dystonia even though we attempted to adjust their implanted neurostimulators optimally. In such patients, we decided to add selective peripheral denervation to the muscles which have residual hypertonia. Postoperative improvement was encountered in all our cases who underwent the combined procedures. In summary, if the satisfactory outcome cannot be fulfilled by deep brain stimulation alone, selective peripheral denervation (or even selective muscle resection) is a good further surgical option in the treatment of refractory complex cervical dystonia. A demonstration of a case on whom we operated by using the combined procedures is presented in Fig.15.

Surgical outcome
By collecting surgical outcomes of selective denervation for cervical dystonia, the numerous studies revealed satisfactory results with minimal complications. Nonetheless, various methods in measure of outcome were utilized. Some of them were unvalidated and employed subjective methods whereas the remaining studies used widely accepted and validated measure tools, such as the TWSTRS or Tsui score. Overall therapeutic outcomes of selective peripheral denervation are displayed in Table 5 (Bertrand, 1993;Braun et al., 2002;Chen et al., 2000;Cohen-Gadol et al., 2003;Huh et al., 2005Huh et al., , 2010Jang et al., 2005;Meyer, 2001;Münchau et al., 2001a;Nunta-aree et al., 2010a;Sitthinamsuwan et al., 2010b;. Fig. 15. A female patient with idiopathic generalized dystonia who underwent combined pallidal deep brain stimulation and selective peripheral denervation. A, Preoperative image reveals severe disabling generalized dystonia including mobile cervical dystonia. B, After the deep brain stimulation, her generalized and complex cervical dystonia was markedly improved. She could return to sitting and walking again. However, residual complex cervical dystonia (mobile left torticollis and retrocollis) was persistent even though we adjusted the implanted neurostimulator to achieve maximal benefit. Hence, we decided to denervate the remaining dystonic muscles. C, After multifocal selective denervation of the cervical muscles (left C1 -C6 and right C1 -C4 posterior ramisectomy, right sternocleidomastoid, and bilateral upper trapezius denervation), the residual dystonia was dramatically improved without complication.  Table 5. Therapeutic outcome of selective peripheral denervation in the treatment of cervical dystonia

Conclusion
Various surgical procedures should be considered in cervically dystonic individuals who do not respond to the conventional treatment. Among them, selective peripheral denervation usually yields a satisfactory result and has been one of the most popularly used operations for the disorder. It is mainly indicated in almost types of cervical dystonia, excluding www.intechopen.com anterocollis and complex patterns. The surgical planning and tailored resection of the nerve should be relied on the individual dystonic pattern. Good candidate selection, knowledge of the relevant anatomy, surgical skills in nerve exploration and precise identification are very significant in the operation through which they will lead to an excellent therapeutic outcome and avoidance of potential adverse effects. Dystonia has many facets, and among those, this book commences with the increasingly associated genes identified, including a construct on how biology interacts with the dystonia genesis. The clinical phenomenology of dystonia as approached in the book is interesting because, not only were the cervical, oromandibular/lingual/laryngeal, task-specific and secondary dystonias dealt with individually, but that the associated features such as parkinsonism, tremors and spasticity were also separately presented. Advances in dystonia management followed, and they ranged from dopaminergic therapy, chemodenervation, surgical approaches and rehabilitation, effectively complementing the approach in dystonia at the clinics. A timely critical pathophysiologic review, including the muscle spindle involvement in dystonia, is highlighted at the book's end.