Objective: To describe the effect of bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) for post-hypoxic myoclonus and associated local field potential (LFP) activity.

Background: Post-hypoxic myoclonus can be severely disabling and refractory to multiple medications. Few cases of pallidal DBS for the treatment of post-hypoxic myoclonus have been reported, but there are no published analyses of LFP activity in these patients.(1-4)

Method: A 58-year-old woman developed severe, refractory myoclonus following cardiopulmonary arrest secondary to status epilepticus related to alcohol withdrawal. The generalized, primarily action-induced myoclonus impaired speech and necessitated assistance with ambulation and all activities of daily living despite levetiracetam, clonazepam, piracetam, and valproic acid. Four years after cardiac arrest the patient underwent bilateral GPi DBS. Contacts for stimulation were selected according to highest beta power on BrainSense survey. Streaming at monthly programming sessions recorded LFP activity in response to stimulation changes. We compared ratings on Unified Myoclonus Rating Scale (UMRS) items pre- and post-DBS.

Results: Highest beta power occurred at 24.41 Hz (left) and 23.44 Hz (right) from contact combinations 1-3 and 9-11, respectively, and did not suppress with stimulation titration. Activity in this band persisted throughout stimulation optimization visits though myoclonus frequency and amplitude at rest and with action improved. Spectrographs of all frequencies and their magnitude from each streaming session showed periods of broadband activity which became less frequent at six months post-DBS compared to initial programming. Six-month settings were: Right GPi C+10- 3.5 V/90 µsec/180 Hz; Left GPi C+2- 3.5 V/90 µsec/180 Hz accompanied by improved fluency of speech, dexterity, ability to stand unassisted, and gait. Rest myoclonus decreased by 90% and action myoclonus by 42%.

Conclusion: Pallidal stimulation can improve post-hypoxic myoclonus that is refractory to oral treatment. Our case demonstrates clinical improvement in myoclonus and functional gains after DBS focused at stimulation contacts with highest beta synchrony, which may correspond to motor pathways relevant for treatment of movement disorders. Stimulation optimization led to reduced periods of broadband activity which may signify the neurophysiologic response to stimulation and requires further investigation.

References: Asahi T, Kashiwazaki D, Dougu N, et al. Alleviation of myoclonus after bilateral pallidal deep brain stimulation for Lance-Adams syndrome. J Neurol. 2015;262(6):1581-1583. doi:10.1007/s00415-015-7748-x
Kobayashi K, Katayama Y, Otaka T, et al. Thalamic deep brain stimulation for the treatment of action myoclonus caused by perinatal anoxia. Stereotact Funct Neurosurg. 2010;88(4):259-263. doi:10.1159/000315464
Ramdhani RA, Frucht SJ, Kopell BH. Improvement of Post-hypoxic Myoclonus with Bilateral Pallidal Deep Brain Stimulation: A Case Report and Review of the Literature. Tremor Other Hyperkinet Mov (N Y). 2017;7:461. Published 2017 May 19. doi:10.7916/D8NZ8DXP
Yamada K, Sakurama T, Soyama N, Kuratsu J. Gpi pallidal stimulation for Lance-Adams syndrome. Neurology. 2011;76(14):1270-1272. doi:10.1212/WNL.0b013e31821482f4

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MDS Abstracts - https://www.mdsabstracts.org/abstract/post-hypoxic-myoclonus-after-bilateral-pallidal-stimulation-a-case-report/