Temporally Dissociated Neurophysiologic Findings in Pediatric Bickerstaff Brainstem Encephalitis: A Case Report.

Bickerstaff brainstem encephalitis (BBE) is rare in children, and neurophysiologic abnormalities may be detected and resolve at different times. A 12-year-old boy developed ophthalmoplegia, ataxia, somnolence, hyporeflexia, and weakness after a respiratory illness. On illness day 3, cerebrospinal fluid protein and magnetic resonance imaging were normal. On day 4, distal limb studies and needle electromyography were unrevealing, but tibial F-wave persistence was reduced, bilateral R1 and R2 blink responses were absent despite preserved facial compound muscle action potentials, and electroencephalography showed slowing. By days 15-16, albuminocytologic dissociation was present and the blink reflex had normalized, whereas F-wave persistence had declined; sensory nerve conduction, lower-limb sympathetic skin responses, and brainstem auditory evoked responses were abnormal. By day 84, limb electrophysiology and electroencephalography were normal, while the auditory waveform abnormality persisted. This case demonstrates temporally dissociated detection and recovery across pathways and supports serial multimodal reassessment when early routine studies are nondiagnostic.