Prognostic role of somatosensory and auditory evoked potentials in paediatric hypoxic-ischemic encephalopathy managed with hypothermia: An illustrative case

Abstract

The contribution of clinical neurophysiology in the neurological prognosis of hypoxic-ischemic coma has been well established in adults: the bilateral absence of cortical somatosensory evoked potentials (SEP) is considered the single best indicator of adverse outcome, while the presence of the auditory mismatch negativity (MMN) is thought to herald arousal. To use MMN combined with serial EEG recordings, somatosensory and brainstem auditory evoked potentials (BAEP) in a paediatric case of postanoxic coma managed with hypothermia, since they have not yet been described in children. We report the case of a nine-year-old boy with hypoxic-ischemic encephalopathy due to cardiorespiratory arrest after accidental burial in sand, who was treated with therapeutic hypothermia for 72 hours. Serial EEG recordings, evoked potentials, brain CT scan and brain MRI were performed in the first few days after the event. SEP to median nerve stimulation showed bilateral absence of the N20 component, while the N13 and P14 peaks were preserved; BAEP showed normal I-V interpeak latency and normal hearing threshold. At the same time, the MMN component of auditory event related potentials, recorded in the classical oddball paradigm, was absent. Seventeen months after the accident, the patient is alive in persistent vegetative state. This case illustrates the particular significance of SEP and MMN together with EEG in gaining prognostic information, even in sedated and hypothermic patients, and encourages systematic study of these prognostic tools in paediatric postanoxic coma.