(See also Overview of Movement and Cerebellar Disorders.)
In cervical dystonia, contraction of the neck muscles causes the neck to turn from its usual position. Cervical dystonia is the most common dystonia.
There are two forms of cervical dystonia:
The caput form (torticaput) involves muscles that move the skull or head joints; it is further described as anterocaput, laterocaput, or retrocaput. The collis form involves muscles that control the lower cervical vertebrae and is further described as anterocollis, laterocollis, retrocollis, or torticollis. Differentiating the two forms is important because it helps clinicians identify the correct muscles to inject with botulinum toxin.
Spasmodic adult-onset torticollis is the most common form of cervical dystonia. It is usually idiopathic. A few patients have a family history, and in some of them (eg, those with dystonia-6 [DYT6], dystonia-7 [DYT7], or dystonia-25 [DYT25; associated with the GNAL gene]), a genetic cause has been identified. Some of these patients have other dystonias (eg, of the eyelids, face, jaw, or hand).
Cervical dystonia can be
Rarely, dystonia has a psychogenic cause. In this type of dystonia, pathophysiology is not well-understood; however, changes in brain function have been detected by functional neuroimaging. In many cases, an emotional stressor or an abnormal core of beliefs is identified as a trigger. In such cases, a multidisciplinary team, including a neurologist, psychiatrist, and psychologist, is necessary.
Cervical dystonia symptoms may begin at any age but usually begin between ages 20 and 60, with a peak between ages 30 and 50.
Symptoms usually begin gradually; rarely, they begin acutely and progress rapidly. Sometimes symptoms begin with a tremor that rotates the neck (in a no-no gesture).
The cardinal symptom of cervical dystonia is
Unilateral sternocleidomastoid muscle contraction causes the head to rotate to the opposite side. Rotation may involve any plane but almost always has a horizontal component. Besides rotational tilting (torticollis), the head can tilt laterally (laterocollis), forward (anterocollis), or backward (retrocollis, common when dopamine-blocking drugs are the cause). Similarly, in the caput form, the head may tilt laterally (laterocaput), forward (anterocaput), or backward (retrocaput).
Patients may discover sensory or tactile tricks that lessen the dystonic posturing or tremor (geste antagoniste). Touching the face on the side contralateral to the deviation is an example. Noting whether a sensory trick is effective can help clinicians differentiate pathophysiologic dystonia from psychogenic dystonia Such tricks typically do not lessen psychogenic tremor.
The presence of overflow or mirroring also indicates that a pathophysiologic etiology (eg, genetic, idiopathic, brain injury) is likely. Overflow refers to involuntary dystonic movement in another part of the body, distant to the primary voluntary movement. In mirroring, when patients voluntarily move the affected side of their body, they involuntarily mimic that movement with the opposite side of the body.
During sleep, muscle spasms disappear.
Spasmodic torticollis ranges from mild to severe. Usually, it progresses slowly for 1 to 5 years, then plateaus. About 10 to 20% of patients recover spontaneously within 5 years of onset (usually in milder cases with onset at a younger age). However, it may persist for life and can result in restricted movement and postural deformity.
The diagnosis of cervical dystonia is based on characteristic symptoms and signs and exclusion of alternative diagnoses, including the following:
Tardive dyskinesia can cause torticollis but can usually be distinguished by a history of chronic antipsychotic use and involuntary movements in muscles outside of the neck.
Basal ganglia disorders and occasionally central nervous system (CNS) infections can cause movement disorders but usually also involve other muscles; CNS infections are usually acute and cause other symptoms.
Neck infections or tumors are usually differentiated by features of the primary process.
Antipsychotics and other drugs can cause acute torticollis, but the symptoms usually develop in hours and resolve within days after the drug is stopped.
The collis form of dystonia (involving muscles that control the cervical spine) can usually be distinguished from the caput form (involving muscles that move the skull or head joints) based on observation of the patient. Imaging (CT bone window), in addition to clinical evaluation, is useful only for assessing rotation of the head. Lateral shift always occurs when laterocollis is present on one side and laterocaput on the other (1).
Injections of botulinum toxin type A or B into the dystonic muscles can reduce painful spasms for 1 to 4 months in about 70% of patients, restoring a more neutral position of the head. However, in a few cases, when the toxin is repeatedly injected, it becomes less effective because neutralizing antibodies against the toxin develop.
Oral drugs can usually relieve pain, but they suppress dystonic movements in only about 25 to 33% of patients. These drugs include
Anticholinergic drugs, such as trihexyphenidyl 5 mg once a day up to 10 to 15 mg orally in 2 or 3 doses (eg, 5 mg orally 2 or 3 times a day), but adverse effects possibly limiting their use
Benzodiazepines (particularly clonazepam 0.5 mg orally 2 times a day)
Baclofen 10 to 20 mg orally 3 times a day
Carbamazepine 100 to 200 mg orally 3 times a day
All drugs should be started in low doses (eg, trihexyphenidyl 2 to 2.5 mg orally once a day). Doses should be increased until symptoms are controlled or intolerable adverse effects (particularly likely in older patients) develop. In older patients, trihexyphenidyl can be started at 1 mg orally once a day.
Surgery is controversial. The most successful surgical approach selectively severs nerves to affected neck muscles, permanently weakening or paralyzing them. Results are favorable when the procedure is done at centers with extensive experience.
If hereditary generalized dystonia is severe or refractory to drugs, deep brain stimulation is the next therapeutic option. This procedure targets the area of the basal ganglia causing the dystonia.
Spasmodic torticollis is a common adult-onset cervical dystonia and is usually idiopathic.
Diagnosis is clinical and involves exclusion of tardive dyskinesia, basal ganglia disorders, CNS infections, neck infections and tumors, and drugs.
Usually, treat with physical measures, botulinum toxin injection, and/or oral drugs.