Cervical dystonia (CD), also known as spasmodic torticollis, is a neurological movement disorder characterized by involuntary contractions of the neck muscles. These contractions force the head into abnormal and often painful postures and movements, such as sustained tilting or turning. As the most frequently occurring type of focal dystonia, the condition affects only the muscles in a single, localized body region.
Understanding the Symptoms of Cervical Dystonia
The physical manifestations of cervical dystonia result from the uncontrolled co-contraction of opposing neck muscles, leading to specific types of head posturing. The most common posture is torticollis, where the chin is pulled toward the shoulder in a rotational movement.
Other abnormal positions include laterocollis (ear pulled toward the shoulder), anterocollis (head flexed forward), and retrocollis (head extended backward). Many individuals experience a combination of these movements, often accompanied by a jerking or oscillating motion known as a head tremor. The continuous, painful muscle spasms can radiate into the shoulders.
A unique feature experienced by many with CD is the geste antagoniste, or sensory trick, where lightly touching the chin, cheek, or the back of the head can temporarily alleviate the spasms. Symptoms often worsen with stress, fatigue, or excitement, but they may temporarily improve when the person is completely relaxed. Symptoms usually begin gradually in mid-life and may stabilize after a period of progression.
The Role of Inherited Factors
Whether cervical dystonia is hereditary is complex, as the condition involves both genetic and non-genetic origins. The vast majority of cases are sporadic, occurring without a clear family history. However, approximately 10% to 15% of CD cases are familial, suggesting a genetic contribution in a minority of patients.
Genetic forms of dystonia are often inherited in an autosomal dominant pattern, meaning only one copy of the altered gene is needed to potentially develop the disorder. CD can manifest as a symptom within a broader, inherited dystonia syndrome, rather than being a neck-specific genetic condition. For instance, the TOR1A gene (previously DYT1) is associated with generalized dystonia but can also present as focal CD.
A defining characteristic of these genetic forms is reduced penetrance, meaning carrying the gene mutation does not guarantee the development of the disorder. For the TOR1A mutation, penetrance is estimated to be only about 30%. This highlights that other genetic variants or external factors must interact with the primary mutation for the condition to become clinically apparent. Mutations in other genes, such as THAP1 (DYT6), are also associated with familial dystonia involving the cranio-cervical region.
Non-Genetic Factors and Sporadic Cases
Most individuals diagnosed with cervical dystonia have the idiopathic form, meaning the cause remains unknown after a clinical investigation. These sporadic cases, which constitute the majority, are not clearly linked to a hereditary pattern. Research suggests that even in idiopathic CD, subtle, unidentified genetic predispositions may combine with external factors to trigger the onset of symptoms.
Non-genetic factors are implicated in secondary, or acquired, cervical dystonia, where a specific cause can be identified. Physical trauma to the head, neck, or shoulder is a recognized trigger that may precede the onset of symptoms. Exposure to certain medications, particularly dopamine-receptor blocking agents, can also induce a form of secondary dystonia that typically resolves after the causative medication is discontinued.
CD can also be a symptom of an underlying neurological disease, such as Parkinson’s disease or Wilson’s disease, classifying it as symptomatic dystonia. The interplay between a person’s genetic makeup and these environmental or acquired triggers explains why some individuals develop the condition while others do not.
Clinical Diagnosis and Treatment Approaches
The diagnosis of cervical dystonia is primarily clinical, relying on a detailed neurological examination and observation of the characteristic involuntary movements and postures. The specialist must distinguish CD from other conditions, such as orthopedic problems or functional movement disorders, that can mimic its presentation. Imaging studies, such as magnetic resonance imaging (MRI), are performed to rule out structural causes, like tumors or spinal cord abnormalities, which would classify the condition as secondary.
Botulinum Toxin Injections
The mainstay of management for cervical dystonia is the targeted use of Botulinum Toxin (BoNT) injections. BoNT is injected directly into the overactive neck muscles to temporarily weaken them, reducing spasms and abnormal posturing. This approach is the gold standard treatment, providing symptomatic relief that typically lasts for about three to four months, necessitating repeat injections.
Adjunctive Therapies
Adjunctive therapies are often used to complement the effects of the injections. Oral medications, including muscle relaxants and certain anti-Parkinsonian drugs, can be prescribed to help manage muscle stiffness and pain. Physical therapy is also recommended to improve neck flexibility and strength.
Surgical Options
For severe cases that do not respond sufficiently to BoNT or oral medications, deep brain stimulation (DBS) is a surgical option. DBS involves implanting electrodes to modulate abnormal brain signals.