A reappraisal of long-latency abdominal muscle reflexes in patients with propriospinal myoclonus.

Background: We report 3 patients with typical clinical and electrophysiological characteristics of propriospinal myoclonus propagating from a thoracic spine generator.
Methods: In these patients, the pattern of recruitment of long-latency electromyographic reflexes in abdominal muscles was studied in response to various stimuli.
Results: Abdominal reflex latency varied from 60 to 140 ms depending on stimulus location. Latency increased from magnetic stimulation of the thoracic spine to electrical stimulation of the supraorbital nerve, electrical stimulation of the median nerve, and magnetic stimulation of the motor cortex.
Conclusions: Long-latency abdominal reflex jerks are probably controlled by the brain stem to propriospinal system projections in patients with propriospinal myoclonus. The stereotyped pattern of recruitment of these reflexes could be of clinical utility to differentiate organic propriospinal myoclonus from psychogenic or mimicked jerks.
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