Cervical dystonia is a neurological movement disorder characterized by involuntary, sustained, or intermittent muscle contractions in the neck region. Also known as spasmodic torticollis, this focal dystonia forces the head and neck into abnormal postures or repetitive, twisting movements. The involuntary nature of these contractions means a person cannot consciously control the movements. This disorder is localized to a specific part of the body, creating discomfort and pain for those affected.
Understanding Cervical Dystonia and Associated Tremor
Cervical dystonia (CD) physically manifests through a variety of patterned movements, including the head twisting toward the shoulder (torticollis) or tilting sideways (laterocollis). The head may also be pulled forward (anterocollis) or backward (retrocollis) due to the sustained contraction of neck muscles like the sternocleidomastoid, trapezius, and splenius. These movements are often accompanied by severe, chronic neck and shoulder pain, which is frequently cited as the most burdensome symptom.
A significant feature of CD is the presence of an associated head tremor, which affects a large proportion of patients. This dystonic tremor is distinct from conditions like essential tremor because it occurs in the body part affected by the dystonia, often appearing as a jerky or irregular shaking. The tremor frequently worsens when a person attempts to hold the head still or move it against the direction of the dystonic pull. A unique clinical sign is the “sensory trick” or geste antagoniste, where lightly touching the chin or back of the head can temporarily alleviate the abnormal posture or movement.
The involuntary movements and postures severely impact daily life, making simple tasks like driving, reading, or maintaining eye contact difficult. Symptoms often increase under stress or during walking, but they disappear entirely during sleep. The constant tension and abnormal positioning can eventually lead to secondary issues, such as muscle hypertrophy and spinal changes.
Potential Origins of the Condition
The precise cause of cervical dystonia remains unknown in most patients, classifying the majority of cases as idiopathic. Scientific understanding points to a malfunction within the basal ganglia, deep brain structures responsible for regulating motor control. This dysfunction involves an imbalance in the neurotransmitters that control muscle movement and inhibition.
Impaired integration of sensory and motor information within the brain’s circuits leads to a loss of inhibition, causing the simultaneous, excessive contraction of both opposing and primary neck muscles. While most cases are sporadic, a small percentage can be linked to genetic factors, with identified mutations in genes such as THAP1 and GNAL causing specific forms of dystonia.
Secondary causes, though less common, can include head or neck trauma, certain neurodegenerative diseases, or exposure to specific medications, particularly dopamine-blocking drugs. These secondary forms are usually easier to identify due to a clear history of an inciting event or associated condition. Regardless of the trigger, the underlying issue is a failure of the brain’s motor system to coordinate normal, smooth muscle action.
Confirming the Diagnosis
Diagnosis of cervical dystonia is a clinical process requiring a detailed patient history and a physical examination by a movement disorder specialist. The physician observes the characteristic, patterned nature of the involuntary muscle contractions and head movements. The presence of the sensory trick, where a light touch temporarily reduces the dystonia, is a strong indicator of the condition.
There are currently no laboratory tests or specific imaging scans that can definitively confirm a diagnosis of CD. Imaging techniques, such as Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans, are utilized to rule out other potential causes of neck twisting or tremor. These tests help ensure that the symptoms are not caused by structural issues like stroke, tumor, or degenerative spine disease, which can sometimes mimic dystonia. Genetic testing may be pursued if there is a strong family history or an early age of onset.
Managing Symptoms Through Treatment
Treatment for cervical dystonia focuses on managing symptoms. The first-line and most effective treatment is the injection of Botulinum toxin (BoNT), commonly known by brand names such as Botox, Dysport, or Xeomin. This neurotoxin is injected directly into the overactive neck muscles identified as causing the abnormal posture.
Botulinum toxin works by blocking the release of the neurotransmitter acetylcholine at the neuromuscular junction, weakening the targeted muscles. This reduction in muscle activity alleviates the involuntary pulling, decreases pain, and often reduces the associated dystonic tremor. The effects are temporary, typically lasting three to four months, requiring patients to return for repeat injections to maintain symptom relief.
Oral medications are used for patients who cannot tolerate injections, though they are less effective. Medications like anticholinergics (e.g., trihexyphenidyl) and muscle relaxants (e.g., baclofen) may help by influencing neurotransmitter activity to reduce muscle spasms. Their use is limited by potential side effects, such as dry mouth, drowsiness, or cognitive changes, and they provide less profound relief for motor symptoms.
Physical Therapy and Surgical Options
Physical therapy plays a supportive role, focusing on improving range of motion, strength, and posture to counteract the effects of muscle imbalance. For patients with severe, treatment-refractory dystonia, surgical options may be considered.
Deep Brain Stimulation (DBS)
Deep Brain Stimulation (DBS), which involves implanting electrodes in the globus pallidus internus (GPi) area of the brain to modulate abnormal electrical signals, is a procedure that offers significant symptom improvement in select patients.
Selective Peripheral Denervation
Alternatively, selective peripheral denervation surgically cuts the nerves supplying the most affected muscles. This procedure may be used to provide long-term relief.