dystonia

Dystonias are sustained involuntary muscle contractions, often distorting body posture. Dystonias can be primary or secondary, and they can be generalized, focal, or segmental. Diagnosis is clinical. Treatment of generalized dystonia is often with a combination of anticholinergic drugs, muscle relaxants, and benzodiazepines. Treatment of focal or segmental dystonias is often with botulinum toxin; more generalized or refractory cases may benefit from surgery.

Dystonia may be primary (idiopathic) or secondary to degenerative or metabolic CNS disorders (eg, Wilson’s disease, Hallervorden-Spatz disease, various lipidoses, multiple sclerosis, cerebral palsy, stroke, brain hypoxia) or drugs (most often phenothiazines, thioxanthenes, butyrophenones, and antiemetics).

Generalized dystonia (dystonia musculorum deformans): This rare dystonia is progressive and characterized by movements that result in sustained, often bizarre postures. It is often hereditary, usually as an autosomal dominant disorder with partial penetrance; asymptomatic siblings of patients often have a forme fruste of the disorder. The causative gene is usually DYT1, causing DYT1 dystonia.

Symptoms usually begin in childhood with inversion and plantar fixation of the foot while walking. The dystonia may affect only the trunk or a leg but sometimes affects the whole body. Patients with the most severe form may become twisted into grotesque fixed postures and ultimately confined to a wheelchair. Symptoms that begin during adulthood usually affect only the face or arms. Mental function is usually preserved.

Focal dystonias: These dystonias affect a single body part. They typically start in a person’s 30s or 40s and affect women more often. Initially, spasms may be periodic, occurring randomly or during stress; they are triggered by certain movements of the affected body part and disappear during rest. Over days, weeks, or many years, spasms may progress; they may be triggered by movements of unaffected body parts and may continue during rest. Eventually, the affected body part remains distorted, sometimes in a painful position, resulting in severe disability. Symptoms vary depending on the specific muscles involved.

Occupational dystonia consists of focal dystonic spasms initiated by performing skilled acts (eg, writer’s or typist’s cramp, the yips in golfers).

Spasmodic dystonia consists of a strained, hoarse, or creaky voice due to abnormal involuntary contraction of laryngeal muscles.

Torticollis begins with a pulling sensation followed by sustained torsion and deviation of the head and neck. The cause is often unknown but, in some cases, is probably genetic. In early stages, it can be voluntarily overcome. Patients may discover sensory or tactile tricks that make the spasm stop, such as touching the face on the side contralateral to the deviation. Torticollis can also be caused by dopamine

-blocking drugs (eg, haloperidol

).

Segmental dystonias: These dystonias affect ≥ 2 contiguous body parts.

Meige’s disease (blepharospasm-oromandibular dystonia) consists of involuntary blinking, jaw grinding, and grimacing, usually beginning in late middle age. It may mimic the buccal-lingual-facial movements of tardive dyskinesia.

Diagnosis

Diagnosis is clinical.

Treatment
For generalized dystonia, anticholinergics, muscle relaxants, or both
For focal dystonia, botulinum toxin

Treatment is often unsatisfactory. For generalized dystonia, a high-dose anticholinergic drug (trihexyphenidyl

2 to 10 mg po tid, benztropine

3 to 15 mg po once/day) is most
commonly used, often with a muscle relaxant (usually baclofen

), a benzodiazepine (eg,
clonazepam

), or both. Generalized dystonia that is severe or does not respond to drugs may
be treated with deep brain stimulation of the globus pallidus interna, which requires surgery.

For focal or segmental dystonias or for generalized dystonia that severely affects specific body parts, the treatment of choice is purified botulinum toxin type A

injected into the
affected muscles by an experienced practitioner. Botulinum toxin weakens muscular contractions, but it does not alter the abnormal neural stimulus. Toxin injection is particularly effective for blepharospasm and torticollis. Dosage varies greatly. Treatments must be repeated every 3 to 6 mo.

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