Electrophysiological aids to the diagnosis of psychogenic jerks, spasms, and tremor

Abstract

Retrospective surveys of specialist movement disorder clinics suggest that 2.1% to 3.3% of patients have psychogenic movement disorders. Some movement disorders are more likely to be psychogenic than others. Around 60% of nonfamilial, idiopathic paroxysmal dyskinesias are psychogenic, whereas less than 0.5% of cases of parkinsonism and chorea attending specialist movement disorder clinics are psychogenic. Within the setting of a specialist clinic, tremor, jerks, or abnormal limb postures comprise the majority of psychogenic movement disorders. In our experience, as in that of others, up to 10% of tremor and myoclonus cases have a psychogenic aetiology. Fifty percent of patients with a psychogenic movement disorder (PMD) improve to a degree. Only onethird resolve. These patients tend to have a shorter duration of movement disorder, suggesting that early diagnosis and treatment may be important. At the same time, erroneous diagnoses of PMD may lead to important delays in the treatment of nonpsychogenic diseases, as was the case for the dystonias in the past. It also is important to note that 25–30% of patients with PMD have a coexisting nonpsychogenic movement disorder or other neurological disease.