Utility of the combination of median nerve SEPs and auditory brainstem responses for diagnosing Bickerstaff brainstem encephalitis

OBJECTIVE: To investigate the utility of median nerve somatosensory evoked potentials (SEPs) and auditory brainstem responses (ABRs) in the early diagnosis of Bickerstaff brainstem encephalitis (BBE). METHODS: Data from patients diagnosed with BBE between 2001 and 2022 were extracted. Patients who underwent SEPs and ABRs within two weeks of onset were included. Normal P13/14 onset (P13/14o) latency with lost or depressed N20, or with prolonged P13/14o-N20 onset interval, was interpreted as indicating an intracranial lesion. The P14b subcomponent, which has been attributed to the thalamocortical tract, was also evaluated. RESULTS: Fourteen patients were identified, all with normal brain MRI. Abnormal SEPs indicating intracranial lesion were observed in 12 patients (86 %). Among them, P14b was identified in six patients. ABRs were abnormal in only three patients (21 %). Normal ABRs with abnormal SEPs were observed in 11 patients (79 %). CONCLUSIONS: The combination of abnormal median nerve SEPs and normal ABRs was a frequent finding in patients with BBE. Impaired cortical SEPs with intact P14b as well as normal ABRs may suggest that the consciousness disturbance in BBE is mainly of supratentorial origin. SIGNIFICANCE: Evaluation of median nerve SEPs and ABRs is promising for the early diagnosis of BBE.