Faculty Bibliography

Orthostatic tremor (OT) is a clinically defined syndrome of leg tremor while standing. Controversy surrounds whether OT is a distinct syndrome or is an essential tremor (ET) variant. We report two patients with OT. Electrophysiological testing included polymyography, accelerometry, nerve conduction, and evoked potential studies. The effects of various maneuvers and body positions on the tremor were assessed. The findings included rapid (15-17 Hz) lower-extremity tremor burst frequency evoked by standing but not by walking or swaying; rapid upper-extremity burst pattern synchronous with lower-extremity bursts; and failure of electrical stimulation or mental concentration to 'reset' the tremor. Additionally, there was the novel finding of accelerometric recordings in the legs revealing the same rapid frequency (16-17 Hz) as the electromyographic tremor bursts. Some prior reports have suggested that OT is related to ET by emphasizing a considerable disparity and variability between the accelerometric tremor frequency and the electromyographic burst frequency. In our patients, however, the rapid (15-17 Hz) accelerometer-recorded tremor synchronous with the electromyographic bursts, and also the clinical improvement with clonazepam but not beta blockers or mysoline, and the lack of a family history of ET provide support that OT is distinct from ET

Two siblings with proximal myotonic myopathy (PROMM), a hereditary disorder, had predominantly proximal weakness, pain, and gait impairment aggravated by warm temperatures. EMG of the deltoid showed sparse abnormal spontaneous activity at room temperature and with cooling. Warming induced frequent myotonic discharges and fibrillations. Profuse myotonia recorded at room temperature in the first dorsal interosseous abated following cooling. Repetitive stimulation did not reveal a decrement recording from distal muscles, but recording from the deltoid, in the one patient tested, revealed a significant decrement that did not improve with edrophonium. Myopathic motor units were recorded only in distal musculature. The myotonia of PROMM is provoked by heat and diminished by cold and may have a different physiologic basis than traditional myotonic syndromes

Although there is evidence in experimental animals of the importance of the pedunculopontine area in locomotion, clinical lesion reports are lacking. An 83-year-old woman became unable to stand and to generate stepping movements after a hemorrhage at the pontomesencephalic junction involving the right pedunculopontine area. Her deficit resembled the gait failure present in some elderly individuals.