‘Remote inhibition’ of motor cortex in Epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS): A TMS based cortical excitability study

• Published in: Seizure (London, England) Vol. 121; pp. 133 - 140
• Main Authors: Kamila, Gautam, Jauhari, Prashant, Gulati, Sheffali, Jain, Suman, Chakrabarty, Biswaroop, Kumar, Atin, Sankar, Jeeva, Pandey, RM
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2024
• Subjects: Cortical excitability; Default mode network (DMN); Epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS); Remote inhibition; Resting motor threshold (RMT); Transcranial magnetic stimulation (TMS); Epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS); Transcranial magnetic stimulation (TMS); Cortical excitability; Default mode network (DMN); Remote inhibition; Resting motor threshold (RMT)
• ISSN: 1059-1311; 1532-2688; 1532-2688
• DOI: 10.1016/j.seizure.2024.08.002

•The motor cortex stays remotely inhibited/hypoexcitable in EE-SWAS in comparison to age matched neurotypical controls.•Steroids disinhibit or reverse the epilepsy induced motor cortex suppression and improve electroclinical outcome in EE-SWAS.•TMS measured cortical excitability strongly correlates with SWI in sleep EEG. The study compared real-time motor cortex excitability using transcranial magnetic stimulation (TMS)-derived parameters between children with epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS) and age-matched neurotypical controls. The EE-SWAS group received steroids as standard of care and were longitudinally followed for three months. Children aged 5–12 years with immunotherapy-naive EE-SWAS (spike-wave-index≥50 %) and neurotypical controls were enrolled. Cognitive and behavioral assessments were performed using valid psychometric tools. Real-time motor cortex excitability was assessed by measuring resting motor threshold (RMT), short intra-cortical inhibition (SICI) and long intra-cortical inhibition (LICI) in both groups. In EE-SWAS group, a follow up evaluation with TMS at 4- and 12-week intervals, EEG, and neurobehavioral assessments at 12-weeks were performed to assess the effect of steroids on cortical excitability and to determine electroclinical outcome. Forty-eight children with suspected EE-SWAS and 26 neurotypical controls were screened; 20 were enrolled in each group. Children with EE-SWAS (mean age: 8.05 ± 1.76 years) had cognitive and behavioral problems (20/20), and ongoing seizures (12/20). At baseline, the dominant motor cortex was significantly inhibited in the EE-SWAS group compared to neurotypical children{RMT(%)[86.3 ± 6.96 vs 58.05 ± 4.71(p < 0.0001)]; LICI(%)[55.05 ± 4.39 vs 73.9 ± 3.75(p < 0.0001)]; SICI(%)[39.2 ± 4.36 vs 55.45 ± 4.78(p < 0.0001)]}. Reversal of motor cortex inhibition was sequentially observed in EE-SWAS group at 4- and 12-week follow-ups{(RMT[4, 12 weeks]: 71.45 ± 9.83, 63.45 ± 8.48); (LICI[4, 12 weeks]: 66.00 ± 6.26, 74.50 ± 5.36); (SICI[4, 12 weeks]: 49.35 ± 6.24, 56.05 ± 5.57)}[repeated-measures ANOVA: p < 0.0001]. Motor cortex is remotely inhibited in EE-SWAS, which may contribute to neurobehavioral impairment. Steroids can disinhibit/reverse the epilepsy-induced motor cortex inhibition leading to improvement in neurobehavior.