[Dystonia as a common status against a common belief]

Primary dystonia is believed to be rare, and its estimated prevalence is roughly around 10-20 per 100,000 in the general population. In middle-aged or elderly people, the prevalence is much higher, reported to be over 700 per 100,000. Dystonia also occurs secondarily in various conditions, as drug-induced (acute or tardive) dystonia or in association with neurological disorders. Reported prevalence values may be underestimate. The diagnosis of dystonia tends to be delayed for several years after the onset of symptoms, or the symptoms may be left unrecognized or misinterpreted. "Dry eye" is common in the modern society and is a frequent misdiagnosis of blepharospasm. "Stiff sensation of the neck", a ubiquitous symptom among Japanese, may actually be a phenotype of cervical dystonia. A subset of "essential tremor" and tremor in SWEDDs (Scans Without Evidence of Dopaminergic Deficits) reportedly have similar pathophysiology to dystonia. Occupational dystonia is common within a specific population. About 1% of musicians may suffer from musician's dystonia, and about one-third of professional or highly skilled golfers may have "yips", possibly a representation of dystonia. Dystonia is common against a general belief, and should be included among the differential diagnosis in patients with muscular hyperactivity and impaired voluntary movements.