Progressive myoclonus epilepsy associated with SACS gene mutations

Abstract

Pathogenic variants in the SACS gene (OMIM #604490) cause autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). ARSACS is a neurodegenerative early-onset progressive disorder, originally described in French Canadians, but later observed elsewhere.(1) Whole-exome sequencing of a large group of patients with unclassified progressive myoclonus epilepsies (PMEs) identified 2 patients bearing SACS gene mutations.(2) We detail the PME clinical features associated with SACS mutations and suggest the inclusion of the SACS gene in diagnostic screening of PMEs.

Figure.. Investigations of the reported patients

(A) Axial and sagittal sections of 3 T brain MRI performed in patient 1 showing diffuse brain atrophy, pronounced infratentorially and involving the corpus callosum. (B) Somatosensory evoked potentials performed in patient 2 (35 years) showing enlarged P25-N33 component (upper trace); long-loop reflex (bottom trace; latency 45 ms) was also enhanced. (C) EEG polygraphy in patient 2 (23 years) showing irregular spike-and-wave discharge associated with spontaneous myoclonus (left part of the traces) and action myoclonus elicited by the extension of both hands (right part). (D) Photoparoxysmal response at 10-Hz photic stimulation (patient 2, 13 years).