Early EEG Detection of Treatable Non-Convulsive Status Epilepticus in Severe COVID-19-Associated Encephalopathy: A Case Report

BackgroundPersistent depressed consciousness in severe coronavirus disease 2019 (COVID-19) is commonly attributed to hypoxemia, systemic inflammation, sedative exposure, or metabolic disturbance. Non-convulsive status epilepticus (NCSE), however, may be overlooked without electroencephalography (EEG). This diagnostic principle also applies to persistent unexplained encephalopathy more broadly, particularly when impaired consciousness remains disproportionate to systemic illness.CaseAn 85-year-old woman with Parkinsonism, diabetes mellitus, and prior cerebrovascular disease developed severe COVID-19 pneumonia followed by persistent coma during intensive care. Brain computed tomography showed chronic atrophic change without acute structural lesions, and laboratory and cerebrospinal fluid findings did not identify a major alternative explanation for coma. On the day of EEG, arterial blood gas analysis showed adequate oxygenation without hypercapnia. EEG on hospital day 10 demonstrated abundant right-hemispheric rhythmic/periodic discharges at approximately 2 Hz and focal electrographic seizures arising from the right temporal region with spatiotemporal evolution, consistent with NCSE. Levetiracetam, lacosamide, and midazolam infusion were administered.OutcomeMidazolam infusion was followed by electrographic seizure resolution but did not produce immediate clinical awakening during sedation; spontaneous eye opening emerged approximately 4 days later. Follow-up EEG on hospital day 13 showed seizure resolution with residual diffuse slowing and a sporadic right-hemispheric spike.ConclusionThis case highlights early EEG as a practical diagnostic and treatment-monitoring tool in severe COVID-19-associated encephalopathy when depressed consciousness is persistent or disproportionate to systemic illness. More generally, EEG should be considered in persistent unexplained coma or encephalopathy after stabilization of cardiopulmonary factors.