Different forms of focal dystonias
What are the other forms of focal dystonias?
Blepharospasm, either isolated (11%) or combined with oromandibular dystonia (23%), is the second most common form of focal dystonia.
It is defined as an involuntary, bilateral eye closure produced by dystonic contractions of the orbicularis oculi muscles.
Blepharospasm is three times more common in women than men.
Onset is usually gradual. Often, before the onset of sustained eyelid closure, patients experience excessive blinking triggered by bright light, wind, and stress. With progression, most patients develop dystonia involving other facial muscles as well as the masticatory and cervical musculature.
Sensory tricks (alleviating maneuvers) that help to maintain the eyes open include pulling on the upper eyelids, talking, and yawning.
Up to 15% of patients with blepharospasm become legally blind because of an inability to keep their eyes open.
Dystonic writer’s cramp is a form of task-specific dystonia associated with handwriting.
Although able to use their hands for performing daily chores, after a few seconds or minutes of writing patients develop dystonic, usually painful, spasms of the forearm musculature, which prevent them from writing further.
With progression of disease, the dystonia becomes less task specific, occurs during other activities, and may spread to involve more proximal muscles.
Approximately 50% of patients develop similar symptoms contralaterally.
Other task-specific dystonias occur among musicians (piano player’s cramp, guitar player’s cramp) and others whose recreational or occupational activities require fine motor coordination.
The actual prevalence of these task-specific dystonias is unknown because only a few patients seek medical attention.