Cranial Nerve Disorders - Spasmodic Torticollis (ST)
Spasmodic torticollis (ST), also known as cervical dystonia, is characterized by involuntary movements of the head as a result of muscle spasms in the neck and shoulders. These spasms can cause the head to turn, jerk, or pull to one side (rotational), towards the shoulder (laterocollis), forward (anterocollis), or backward (retrocollis). The movements can be sustained (tonic), intermittent and jerky (clonic), or a combination. ST can also cause pain in the neck or shoulders.

ST usually begins spontaneously, although it is sometimes preceded by injury or trauma to the neck. The severity and frequency of spasms may vary amongst sufferers, but they generally intensify over time. The disease is unlikely to go away on its own, especially once present for more than five years.

Activity, stress, and anxiety may aggravate the spasms, whereas relaxation partially relieves symptoms; sleep usually provides total relief. Spasmodic movements may be partially relieved by gentle touch to specific parts of the face, such as a finger placed on the chin. These maneuvers are called gestes antagonistiques.

ST can lead to uneven shoulders, enlarged muscles, arthritis in the neck, and headaches. There is no effect upon cognition, strength, sensation, or other nerve function. However, this disorder can become physically, emotionally, and socially debilitating.

Diagnosis of primary ST is based on clinical findings, or information from the affected individual. There are no specific tests to confirm the diagnosis. However, various investigations may be used to exclude other causes of abnormal position.

The cause or causes of ST are not well understood. Some believe ST is caused by dysfunction of the basal ganglia, which are centres deep in the brain that control coordination of movements. Some cases of ST appear related to traumatic injury of the spinal accessory nerve (cranial nerve XI). Vascular compression of this cranial nerve (XI) has also been suggested as a primary cause of ST.

Overiew of Treatments

The goal of treatment is to reduce the symptoms of spasmodic torticollis (ST), while minimizing the risks of the interventions. There is little consensus about the best management strategy. Three general categories of treatment are available and include non-medical, medical, and surgical aid.

Non-medical therapies include physiotherapy, stress management and relaxation therapies, biofeedback, and hypnosis. These modalities are generally ineffective in reducing ST when applied on their own, but may be complementary to other treatment approaches.

Medical therapy involves the use of drugs to relieve symptoms. Oral medications to treat ST include anticholinergics, dopaminergics, and benzodiazepines. A special type of medical therapy consists of injecting botulinum toxin (Botox®) into the affected muscles. Botox® often produces relief of symptoms for months at a time. Repeated injections may provide long-term control of ST. 

Neurosurgery is usually considered when all other treatments have failed. Many types of surgery exist, but they can be divided into two categories: (1) destructive and (2) non-destructive. Microvascular decompression (MVD) surgery is a non-destructive procedure in which blood vessels that compress and irritate certain nerves are moved without injury to the vessels or brain structures. Destructive procedures aim to produce controlled injuries to the nerves and/or muscles. These include thalamotomy, pallidotomy, myotomy, and selective peripheral denervation.

Decisions regarding the use of medications, the timing of surgery, and the specific surgical procedure may be complex and should be based upon a good understanding of all of the treatment options. It is also important that the medical team has experience and expertise in providing the treatments selected.

Medications

A variety of medications have been tried in the treatment of spasmodic torticollis (ST). These include anticholinergics, dopaminergics, and benzodiazepines.

Drugs in the anticholinergic group include trihexyphenidyl (Artane), biperiden (Akineton), cycrimine (Pagitane), and benztropine (Cogentin). They are usually required in large doses for effective relief of spasms. About half of ST sufferers cannot tolerate the side effects of these medications.

Dopaminergic drugs include levodopa (Sinemet or Madopar), bromocriptine (Parlodel), and amantadine (Symmetrel). They are effective only in certain cases. The benzodiazepine group includes diazepam (Valium) and flunitrazepam (Rohypnol, Somnubene, or Somnibel)..

Medications are usually the first line of treatment, because they are the most convenient for the patient: they are easily administered and are the least invasive. Unfortunately, most patients do not find satisfying long-term relief with these drugs, and other forms of treatment are considered.

Botox® Injections

Botulinum Toxin (Botox®) is a purified neurotoxin derived from the bacterium Clostridium botulinum, which temporarily weakens or paralyzes human muscle. The neurotoxin consists of molecules that bind to nerve endings and prevent the release of stimulating neurotransmitters. This means the nerve signal is blocked from reaching the muscle, and hence the muscles no longer contract. This treatment does not change the abnormal brain signal that causes ST, but it temporarily reduces the symptoms of muscle spasms.

Botox® is injected directly into the affected muscles. The resulting muscle relaxation reaches its peak about two to four weeks following injection, and lasts between two and three months. Re-injections are then required to maintain relief of symptoms.

Botox® injections for ST are usually safe and effective. However, the toxin can travel into neighboring muscles and cause temporary side effects, like swallowing difficulty and weakness. Over time patients may develop a resistance to the botulinum toxin as they produce antibodies that render the toxin ineffective. Two types of the toxin are currently manufactured, Types A and B. Type A is the most common form used, while people who develop a resistance to it may respond favourably to Type B.

While Botox® injections are initially helpful in reducing the severity of ST muscle contractions, the disease often progresses and becomes more disabling. Ultimately, patients may become dissatisfied with the repeated injections and prefer to consider other treatment options.

Microvascuar Dcompression (MVD) Surgery

Vascular compression of the spinal accessory nerve (cranial nerve XI) by the vertebral artery or other vessels has been proposed as a cause of ST. The neurovascular compression is thought to irritate the brainstem and spinal cord centers that control neck movement. The resultant hyperexcitability of these nerves leads to the neck spasms of ST. Microvascular decompression (MVD) surgery aims to alleviate the neurovascular compression and thereby target the cause of the disorder. The procedure does not injure the nerve roots, brain stem, or the spinal cord. Few results have been published, although surgical cure rates of over 50% are reported.

The surgery is performed through a posterior incision and exposure of the lower brain stem and upper spinal cord. Vessels that are abnormally contacting the affected nerves are moved to new positions and held with small shredded Teflon® felt implants. ST symptoms may start to disappear immediately after MVD surgery, or may begin to fade away gradually over a few months or even up to two years. Complications related to this surgery are rare at centres with expertise in MVD surgery.

Rhizotomies

Destructive procedures for ST aim to interrupt the neural pathways thought to be responsible for the neck spasms. Some believe that hyperactivity of the basal ganglia causes ST; therefore they focus the conrolled injury proedures on the thalamus (thalamotomy) or globus pallidus (pallidotomy). Alternatively, surgical attention may be directed at the individual muscles, either by severing or removing them (myotomy), or by cutting their nerve supply.

The nerve injury procedures include rhizotomies of the upper anterior nerve roots or accessory nerve rootlets, as well as selective peripheral denervation. The latter procedure aims only to interrupt nerve branches to affected neck muscles, while preserving normal muscle activity. 

These procedures have shown moderate to very good success rates, but because of the invasive and permanent nature of these destructive procedures, ST patients usually resort to them only when their symptoms have become severe and unresponsive to other therapies. Risk of complications must also be considered, including the loss of muscle control, muscle atrophy and neck deformity, instability, the continued presence of pain, and the possible spread of ST to different muscles.

Unfortunately, no treatment approach is effective for all patients with ST. Therefore, careful consultation with experienced neurologists and neurosurgeons is important in formulating a management plan.

National Spasmodic Torticollis Association – Information on symptoms, different forms, causes, and treatments of ST.

Dystonia Medical Research Foundation – An informative resource, including research updates and multi-media presentations, to learn more about dystonias, such as Cervical Dystonia (ST).