Levodopa-Responsive Primary Slow Orthostatic Tremor: A Premotor Sign of Parkinson’s Disease?

Abstract

We present a case of primary orthostatic tremor (OT) responsive to dopaminergic medication. The patient was a 62-year-old woman, who had leg tremor on standing for 2 years. No parkinsonian or other neurological signs were observed. Surface electromyography of the quadriceps muscles showed regular 5-6 Hz muscle discharges. [ 123 I]-FP-CIT DAT-SPECT imaging revealed decreased specific binding ratio values in the striatum compared with age-matched controls. Her leg tremor almost completely disappeared following administration of levodopa 200 mg and pramipexole 0.75 mg. Since her OT with low-frequency discharge was responsive to dopaminergic medication, we speculate that it may be a premotor sign of Parkinson's disease.

Parkinsonism and tremor syndromes

“…While OT is often isolated, in one series of 41 patients, 4 patients also had PD [150]. Orthostatic tremor (particularly if under 13 Hz) may be associated with other neurologic disorders [151], including ET [150,[152][153][154] and PD [149]. Leg tremor in patients with ET or PD should be differentiated from OT [50].…”

“…Orthostatic tremor (OT) describes a predominantly lower extremity tremor that starts upon standing and improves with sitting, leaning, or walking [149]. Instead of tremor, patients may describe a sense of unsteadiness or leg vibration, and the tremor may not be even visible, although it may be palpable or audible (with stethoscope) because of its high-frequency (13)(14)(15)(16)(17)(18) [50].…”