SYNGAP-1 developmental and epileptic encephalopathy: Utility of corpus callosotomy and neuromodulation

Variants in SYNGAP1 cause a rare childhood-onset developmental and epileptic encephalopathy (DEE). Limited reports describe palliative surgical procedures such as corpus callosotomy (CC) and vagus nerve stimulation (VNS) in SYNGAP1-related DEE.

A retrospective chart review of de-identified medical records from the SynGAP Research Fund Citizen Health Database (Citizen) who underwent CC and/or VNS was conducted. This was supplemented with one child from our centre. Details related to epilepsy, comorbidities, genetics, electroencephalogram/neuroimaging findings and treatment response are summarized.

We identified 185 children with likely pathogenic/pathogenic variants in SYNGAP1; 156 had epilepsy (n = 156/185, 84.3 %). Fifteen children had palliative procedures (15/156, 9.6 %). Eleven children had VNS (n = 11/15, 73.3 %), and the median follow-up was 3.3 years (IQR 5.6, 3.3). Seven children had an initial > 50 % seizure reduction (n = 7/11, 63.6 %), 2 had worsening (n = 2/11, 18.2 %), 1 had no change (n = 1/11, 9.1 %), and 1 had an unknown response (n = 1/11, 9.1 %). VNS response was sustained in 3 children (3/11, 27.3 %). Two children (n = 2/15, 13.3 %) had CC only with a mean follow-up of 3.1 years; 1 became seizure-free, and the other had > 50 % seizure reduction. Two children (n = 2/15, 13.3 %) underwent VNS then CC, 1 had a > 50 % overall seizure reduction, and one had minimal change; mean follow up from CC was 3.1 years. One child from our centre had a sustained > 80 % seizure reduction (1.5 years) following CC at 7 years.

The effect of VNS was variable and sustained in less children over time. CC appeared to be more effective in the few treated. Larger cohorts are required to confirm these findings in SYNGAP1-related DEE.