Median-evoked somatosensory potentials in severe brain injury: Does initial loss of cortical potentials exclude recovery?

• Bilaterally lost cortical median-evoked SSEP may recover in severe brain injury.
• Electrophysiological recovery may be accompanied by good functional outcome.
• Functional outcome seems to depend on the cause of severe brain injury.
• Caution is warranted in predicting a poor prognosis based only on SSEP.
• Performing only one SSEP may lead to underestimation of the possibility of recovery.

ObjectiveIn patients with severe brain injury (SBI) median-evoked somatosensory potentials (M-SSEP) serve as a prognostic tool. Bilateral loss of cortical responses (BLCR) is usually thought to be a reliable marker of poor prognosis. Prognostic accuracy to predict a poor outcome depends on the cause of coma and is best in hypoxic-ischemic encephalopathy (HIE) reaching almost 100% which is in contrast to patients with other etiologies of coma, especially traumatic brain injury (TBI). Only little evidence exists on the possibility of electrophysiological recovery of BLCR in repeated or serial SSEP-examinations and detailed functional outcome in these cases.Methods28 patients (78.6% male, 21.4% female, mean age 43.1 ± 18.6 years) from our in-patient early (post-acute) neurorehabilitation center with BLCR in their first M-SSEP were re-examined after a mean interval of 66 ± 55.8 days. SBI was caused by different etiologies. We retrospectively analyzed (a) the recovery rate from BLCR in consecutive M-SSEP and (b) the detailed functional outcome of those patients with recovered cortical responses.Results14/28 (50%) patients with primarily BLCR showed re-occurrence of cortical potentials, either uni- or bilaterally. Of the 14 patients, one died due to a non-neurological cause. Of the remaining 13 patients 6 – most of them suffering from traumatic brain injury (TBI) – could be transferred to further continuing neurorehabilitation and achieved good functional long-term outcome. BLCR in HIE still had a poor prognosis with none of our patients achieving an outcome better than vegetative state.ConclusionsElectrophysiological recovery from primarily BLCR seems possible and is accompanied by good functional outcome in a relevant number of patients. Thus caution is warranted in predicting a poor prognosis based predominantly on SSEP, especially in patients with TBI. Focusing SSEP-examination on the early days after severe brain injury and performing only one examination in the case of BLCR may lead to systematic underestimation of the possibility of recovery.