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Cervical Dystonia
Cervical dystonia (CD) is the most common focal dystonia.1 It results in the sustained contraction of the cervical musculature, leading to abnormal posturing of the neck, head, and shoulder. The injection of botulinum neurotoxin (BoNT) into the overactive muscles of CD patients can effectively treat the abnormal neck movements and pain caused by this disorder. The abnormal movements of the neck and head can result in twisting (torticollis), tilting (laterocollis), flexion (anterocollis), or extension (retrocollis). Additional movements are shoulder elevation and lateral movement of the head/neck with relation to the chest wall.
Epidemiology
The incidence of CD is 9 to 30 per 100,000 people in the United States, and the prevalence may vary among ethnic groups.1,2 Studies have shown a higher incidence among women, with an approximate 2:1 female-to-male ratio.3 In greater than 70% of cases, the disease begins between the fourth and sixth decades of life, with a peak incidence in the fifth decade.4 A family history of dystonia is seen in 12%. Progression of dystonia to other anatomic areas is seen in up to one third of cases.3
Symptoms typically worsen over the course of the first 5 years before stabilizing. Spontaneous remission is seen in 10 to 20% of individuals lasting days to years, although these are temporary and most patients eventually relapse.3,5 Employment status is significantly affected by CD, with over 30% requiring reduced work hours or reduced responsibilities and 19% resulting in loss of employment.6
Pathophysiology
As in all dystonia, the pathophysiology of idiopathic CD is not well understood, although it is generally thought to be an abnormality in central motor processing. There is a genetic component to the development of dystonia, but trauma and drug exposure can also be a precedent to focal dystonia.7 Currently, the main theories are decreased central inhibition, sensory deficit with sensorimotor mismatch, aberrant neuroplasticity, and abnormal basal ganglia discharge.8–13 Although any muscle in the neck may be involved, Table 7.1 lists the common muscles with the associated head/neck movements. There may be multiple muscles involved with co-contraction of agonist and antagonist muscles.
Table 7.1 Typical Muscles Involved in Cervical Dystonia
Movement | Muscles Involved |
Rotational torticollis | • Ipsilateral splenius capitis • Contralateral sternocleidomastoid |
Laterocollis | • Ipsilateral sternocleidomastoid • Ipsilateral splenius capitis • Ipsilateral scalene complex • Ipsilateral levator scapulae • Ipsilateral trapezius |
Shoulder elevation | • Ipsilateral levator scapulae • Ipsilateral trapezius |
Retrocollis | • Bilateral splenius capitis* • Bilateral upper trapezius* |
Anterocollis | • Bilateral sternocleidomastoid* • Bilateral scalene complex* • Bilateral submental complex* |
(Adapted from Brashear A, The botulinum toxins in the treatment of cervical dystonia. Semin Neurol, 2001;21(1) 85–90; Benecke R, Dressler D. Botulinum toxin treatment of axial and cervical dystonia. Disabil Rehabil 2007;29:1769–1777; and Deuschl G, Heinen F, Kleedorfer B, Wagner M, Lucking CH, Poewe W, Clinical and polymyographic investigation of spasmodic torticallis. J Neurol. 1992 Jan. 239(1) 9–15.)
Clinical Manifestation
Idiopathic CD usually begins with abnormal head/neck movements before progressing to other areas. Head tremor and neck spasms are cardinal features of CD, and the majority of affected patients complain of pain.
Approximately half of patients are able to identify a sensory trick, or geste antagonistique, to help control their abnormal neck spasms.14 Typically this trick constitutes placing the hand on the side of the face or neck, and this contact reduces the muscle spasm without actually mechanically opposing the spasm. Some patients can even imagine the sensory trick to diminish symptomatic spasms.15 The pathophysiology of the sensory trick is unknown. Although early in the course of disease these tricks are helpful in most patients, they tend to lose effectiveness as the disease progresses.
Additional palliative factors include relaxation, alcoholic beverages, and “morning benefit,” in which symptoms are less intense just after waking. CD is exacerbated by activity, stress, and fatigue.
Table 7.2 Differential Diagnosis of Torticollis
• Cervical spine fracture or disease • Peritonsillar or retropharyngeal abscess • Drug reaction (tardive dystonia) ○ Neuroleptics: droperidol, haloperidol, pimozide, Thorazine, Compazine ○ Dopamine receptor antagonists: metoclopramide • Wilson’s disease • Klippel-Feil syndrome • Sandifer syndrome • Bobble-head doll syndrome (with third ventricle cyst) • Progressive supranuclear palsy • Posterior fossa tumor • Spinal cord tumor or syrinx • Multiple sclerosis • Systemic lupus erythematosus • Huntington’s disease • Psychogenic dystonia |
On physical examination, muscles should be palpated for hypertrophy, activity, and contracture/fibrosis, although it may be difficult to differentiate among these conditions. Areas of pain should be noted. By convention, the direction of the rotation is defined by the chin, so right-turning torticollis means that the chin deviates to the patient’s right. Abnormal head and neck postures can occur in multiple planes. Rotational torticollis occurs around the longitudinal axis, laterocollis rotates the head in the coronal plane tilting the ear to the shoulder, and anterocollis and retrocollis rotate the head in the sagittal plane; additionally, there may be sagittal or lateral deviation of the base of neck from the midline. Deviations in only one plane are seen in less than one third of patients.5
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