Cervical Dystonia and Spasmodic Torticollis: Indications and Techniques

Published on 13/03/2015 by admin

Filed under Neurosurgery

Last modified 13/03/2015

Print this page

This article have been viewed 1292 times

Chapter 115 Cervical Dystonia and Spasmodic Torticollis

Indications and Techniques

John Yianni, Dipankar Nandi, Tipu Aziz

History of Dystonic Conditions

One of the earliest descriptions of dystonia was recorded by Gowers in 1888.¹ Destarac in 1901 used the term “torticollis spasmodique” to describe the twisting neck movements observed in a 17-year-old girl. Dystonic conditions were identified as distinct from other hyperkinesias by Schwalbe in 1908; however, because of the bizarre nature of the movements, dystonias were originally considered a form of “hysterical neurosis.”

The term dystonia itself was first coined by Oppenheim in 1911, who was the first to correctly identify the organic nature of dystonia.² However, focal dystonias, unlike the generalized condition, have been recognized for centuries. For example, the first recorded case of surgery for spasmodic torticollis dates back to 1641, when the German physician Minnius treated torticollis by sectioning the sternocleidomastoid muscle.¹

In 1944, the pioneering work of Herz revived the concept of dystonia being an organic disease, concluding from his frame-by-frame analysis of moving pictures showing that dystonic movements were slow, long-sustained, powerful, and nonpatterned contortions of axial and appendicular muscles. However, because of failures to identify associated brain lesions, arguments for an organic basis of the condition were not recognized until Marsden et al. studied cases of patients with hemidystonia.³ They discovered that lesions in the putamen, caudate nucleus, and posterior ventral thalamus were commonly present, contralateral to the hemidystonia. In the 1980s and 1990s, investigation into generalized dystonia, particularly among Jews of Ashkenazi descent, led to the discovery of the DYTI gene mutation at the 9q34 locus. Since then, continued research has led to the awareness of a complex array of etiologic causes underlying dystonia, giving rise to an elaborate classification system for differentiating between dystonic conditions.

Epidemiology

Dystonic conditions are not rare. Epidemiologic surveys estimate that dystonia is the third most common movement disorder after Parkinson’s disease (PD) and essential tremor,⁴ considerably more prevalent than a number of better-known neurologic conditions such as myotonic dystrophy, myasthenia gravis, and motor neuron disease. In contrast to many other conditions, however, there have been few published epidemiologic studies of dystonia. Differences in study design have further confused prevalence estimates, making it difficult to extrapolate data from certain studies to the general population. Combined estimates of around 330 per million have been made, encompassing all dystonias,⁵ with approximately one third of all cases being due to cervical dystonia (CD). One of the most comprehensive examinations of prevalence estimates currently available was provided by the Epidemiological Study of Dystonia in Europe collaborative group,⁶ which estimated CD prevalence at 57 per million. However, true prevalence is unknown, with many authors suggesting that estimates in published reports are considerably lower than the actual prevalence⁷ due to significant numbers of undiagnosed cases within the community. This has implications with regards to the provision of patient care, particularly with respect to financing medical and surgical therapies for dystonic conditions.

Classification and Etiology

The term dystonia is employed to describe a syndrome characterized by sustained muscle contractions, often causing repetitive twisting movements or abnormal postures. These involuntary movements are caused by concurrent contractions of agonist and antagonist muscles and are often exacerbated during action but improve with relaxation, sleep, or sensory tricks (geste antagoniste), such as touching the chin to improve CD. Some dystonic movements (e.g., writer’s and musician’s cramp) appear only with specific actions and are known as task-specific dystonia. Dystonic conditions are heterogeneous and comprise an array of diseases that can be described either etiologically or descriptively.

Etiologic Classification of Dystonic Conditions

An important aspect of the clinical evaluation of dystonia is the etiologic classification of the condition. This helps in formulating treatment strategies and deciding on the need for genetic counseling, and it may aid our understanding of the underlying pathophysiology of the illness. To assist the etiologic classification of dystonic conditions, a similar system for the classification of parkinsonism has been adopted by many ⁴ to include the subcategories of primary dystonia, dystonia-plus, secondary dystonia, and heredodegenerative diseases in which dystonia is the prominent feature. The molecular classification of dystonia includes several genetic loci. Currently 18 gene loci have been described,⁸ although it is likely that many more dystonia genes have yet to be discovered.

Primary Dystonia

Primary dystonia refers to those individuals in whom dystonia is the sole phenotypic manifestation, with the exception that the condition can sometimes be accompanied by tremor. There is no history of brain injury, laboratory findings to suggest a cause for dystonia, consistent associated brain pathology, or improvement following a trial of levodopa therapy. Age at onset displays a biphasic distribution, peaking at 9 years in the early-onset group and 45 years in late-onset patients.⁹ Early-onset primary dystonia tends to begin in one of the limbs and later progresses to other limbs and the trunk, most often leading to a severe generalized form of the disease. Late-onset primary dystonia usually commences in the upper body, most often the cranial–cervical region, and tends to remain focal or segmental. Early-onset primary dystonia (DYT1 dystonia) is often inherited as an autosomal dominant trait with incomplete penetrance. The genetics of late-onset primary dystonia are more complex than those of the early-onset form, although it appears that, similar to the early-onset form, inheritance occurs in an autosomal dominant fashion.^10,¹¹

Descriptive Classification of Dystonic Conditions

Age at Onset

Dystonia can be subdivided into two groups on the basis of age at onset of symptoms. When symptoms begin before 26 years of age, the term early-onset dystonia is employed; after this age, they are classified as late-onset dystonia. The earlier dystonic symptoms appear, the more likely the condition will progress to become generalized; in late-onset individuals, it is more likely to remain focal.

Distribution of Affected Body Regions

When dystonia is classified according to body distribution, it can be described as focal, segmental, multifocal, or generalized. In focal dystonia, a single body region is affected, such as the arm in writer’s cramp, the eyes in blepharospasm, the laryngeal muscles in spasmodic dysphonia, or the neck in CD.

Cervical Dystonia

CD is the most common form of focal dystonia, occurring at any age but most frequently around 50 years and more often in women compared with men.¹³ Involuntary contractions of the neck muscles lead to a variety of abnormal head movements and postures. Spasmodic torticollis is the most common form of CD, resulting from predominantly rotational head posturing. Other types include anterocollis, retrocollis, lateral flexion, lateral or sagittal shift, and shoulder elevation or more complex configurations of posturing. In some patients, the dystonic jerks may be rhythmic and produce a jerky type of tremor, which can often be confused with essential tremor. With time, the rhythmic jerking is often superimposed on or replaced by abnormal posturing. Neck pain is a commonly associated symptom and occurs in about three quarters of patients. CD spreads to become segmental in some patients, but it rarely becomes generalized. Spontaneous remissions are observed in 10% to 20% of patients but are usually not sustained.¹³

Most cases of CD are idiopathic, although a careful history may reveal a familial history of other movement disorders, including other dystonias such as writer’s cramp or tremor. Although secondary CD is relatively uncommon, a careful and thorough neurologic evaluation is necessary to look for other possible underlying etiologies (Table 115-1).

Table 115-1 Conditions Mimicking Dystonia

Psychogenic dystonia

Pseudodystonias

Congenital postural torticollis

Sandifer syndrome

Posterior fossa tumors

Chiari malformation

Syringomyelia

Stiff-person syndrome

Isaac’s syndrome

Satoyoshi syndrome

Congenital Klippel-Feil syndrome

Vestibular torticollis

Trochlear nerve palsy

Herniated cervical disc

Atlantoaxial subluxation

Infectious causes/abscess

Treatment Strategies

One of the first general considerations in approaching the treatment of a patient with dystonia is to differentiate between the primary and the secondary dystonias. In a minority of patients with secondary dystonia—for example, Wilson’s disease, drug-induced dystonia, or dopa-responsive dystonia (DRD)—benefit can be gained from specific treatments.¹⁵ For example, all patients with childhood-onset dystonias should receive a trial of l-3,4-dihydroxyphenylalanine (l-DOPA), as this brings about dramatic improvement after a short period in those with DRD. For other patients, therapy is directed at controlling the symptoms rather than the cause, with different management strategies employed for generalized as opposed to focal conditions. As a rule, in patients with generalized and multifocal disease, oral pharmacotherapy constitutes the mainstay of treatment.

Unfortunately, treatment of dystonic conditions with oral agents is generally unsatisfactory. In addition to l-DOPA, other established medications include anticholinergics, benzodiazepines, and baclofen. Except in the case of DRD, anticholinergic medications such as trihexyphenidyl are arguably the most effective pharmacotherapy for dystonia.¹⁶ Effective treatment with anticholinergics is sometimes limited by the development of side effects, including dry mouth, urinary retention, blurred vision, confusion, memory loss, and hallucinations. Although considered less effective than anticholinergics, baclofen has proved efficacious in children.¹⁷ Benzodiazepines such as clonazepam are also often employed and are particularly useful in the treatment of myoclonic dystonia.¹⁸ The dopamine-depleting drug tetrabenazine is considered effective in the treatment of some patients with tardive dystonia. Other antidopaminergics, such as haloperidol, may be effective but may also worsen symptoms or induce tardive dyskinesia and hence are not recommended. Although atypical neuroleptics such as clozapine have been suggested for the treatment of tardive dystonia, their effectiveness in treating other forms of dystonia remains questionable, and there are potentially very serious adverse effects associated with clozapine treatment, including agranulocytosis.¹⁹ Several other forms of pharmacologic therapy have been reported to be beneficial in individual cases of dystonia; however, their role in treating dystonia has yet to be fully established.

In contrast, patients with focal dystonia tend to benefit most from treatment with botulinum toxin (BTX) injection. BTX is the treatment of choice for the majority of focal dystonias, including CD, and has been the most comprehensively investigated therapy for treatment of this patient group. Injections in the most severely affected muscle groups can also be employed in association with other treatments. BTX produces chemodenervation and local muscle paralysis by inhibiting the release of acetylcholine at the neuromuscular junction. It also appears to improve reciprocal inhibition by altering sensory inflow through muscle afferent fibers.²⁰ There are several serotypes of BTX produced by different species of Clostridium botulinum, although currently only types A and B are available for use in clinical practice. The duration of effect for BTX is variable but on average lasts 2 to 3 months. Lack of response to BTX injection may occur if there is long-standing disease with contractures, insufficient dosage, or the development of antibodies. Resistance associated with neutralizing antibodies occurs after repeated injections of BTX in 5% to 10% of cases.²¹

Both BTX A and BTX B have been shown to be efficacious in placebo-controlled trials,^22,²³ with improvements of 80% to 90% observed in patients with CD.²⁴ Various injection strategies have been used to treat CD with BTX. Electromyograms (EMGs) may be useful adjuncts in some patients to guide selection of the appropriate muscle groups and determine the site of injection.²⁵ However, there is debate as to whether EMG assessment and guidance provide superior results. It is usually a safe treatment that can be performed repeatedly, with no systemic side effects. Dysphagia due to local spreading of the toxin with injections of the sternocleidomastoid and pain at the injection site are the most commonly reported side effects. However, transient dizziness, dry mouth, flu-like symptoms, and dysphonia have also been reported.²⁶

The majority of patients report satisfactory benefit from BTX treatment; however, if this and other conservative measures fail, patients should then be considered for surgical intervention.