Post-Hypoxic Myoclonus and Deep Brain Stimulation. Experience from a Small Patient Cohort and Literature Review Highlighting Variable Outcomes.

Lance Adams Syndrome (LAS), or chronic post-hypoxic myoclonus (PHM), is a rare and disabling condition which occurs in the aftermath of a diffuse hypoxic brain injury, usually when patient regains consciousness. Due to its refractoriness to antiepileptics, deep brain stimulation (DBS) has been attempted over the past fifteen years. We describe three patients who underwent Globus Pallidus interna (GPi)-DBS at the NYU Langone Department of Neurosurgery. Despite varying stimulation parameters and contact combinations, none achieved substantial improvement of action and negative myoclonus or regained the ability to ambulate unassisted. We compared our results with previous reports. Our literature review identified ten cases of LAS treated with DBS since 2010. The target was GPi in 8/10 patients, the ventralis intermedius (VIM) nucleus in one, and the subtalamic nucleus (STN) in one. Varying degrees of improvement were reported, with some evidence suggesting that long pulse width and lower frequency might be more effective. However, most reports provided only partial Unified Myoclonus Rating Scale (UMRS) scores, with missing information on rest and reflex myoclonus as well as negative myoclonus. Due to the paucity of prior reports and the limited generalizability of existing evidence, the efficacy of DBS in LAS has yet to be demonstrated. Further case reports, both positive and negative, supported by neurophysiological measures, may help bridge this knowledge gap.