Background: Parkinsonism resulting from a primary psychiatric disorder has not been well characterized previously. We had been impressed that this was a rare but definite cause of parkinsonism in patients presenting to our subspecialty movement disorders clinics.
Objective: To define the clinical characteristics of "psychogenic parkinsonism" to assist in the differentiation of these patients from those with "organic" parkinsonian disorders.
Design: Retrospective chart reviews of patients seen at three large movement disorders centers.
Patients: Seven men and seven women were diagnosed as having "documented" or "clinically established" psychogenic parkinsonism after repeated assessments.
Results: Tremor (12 patients) was present at rest but continued without the usual transient dampening on taking up a posture and persisted with action. Tremor frequency and rhythmicity varied markedly. Tremor could often be entrained to the frequency of other movements or subsided with distraction. Rigidity (six patients) had features of voluntary resistance, often decreasing with distraction and/or activating synkinetic movements in opposite limbs. Arm swing was usually diminished or absent on the affected side; however, the arm could be held tightly to the side or cradled in front of the patient. Slowness of movement (all 14 patients) usually lacked the typical decrementing amplitude feature of bradykinesia. The slowness, ambulatory abnormalities, and postural instability (12 patients) often had bizarre, inconsistent, or incongruous features. Functional "give-way" weakness and nonorganic sensory disturbances were common (10 patients). Spontaneous remissions and remissions with placebo treatment or psychotherapy and response fluctuations related to unusual interventions were occasionally seen (five patients). Underlying psychological factors varied considerably. Most patients had been seen by several physicians and had undergone multiple unrevealing investigations. Fluorodopa F 18 (F-dopa) positron emission tomographic scanning yielded normal findings in three patients. Abnormal positron emission tomographic scanning results in a fourth patient, whose signs and symptoms had improved with psychotherapy and haloperidol therapy, emphasizes the possibility that prominent psychogenic features may be superimposed on organic parkinsonism in some patients.
Conclusion: Psychogenic parkinsonism occurs rarely. It is a diagnosis of exclusion that should be made only by physicians with considerable experience in the care and treatment of patients with parkinsonism.