Background:
It is difficult to diagnose Bickerstaff's brainstem encephalitis (BBE) in the acute phase, and emergency physicians could diagnose BBE as an unknown cause of consciousness disturbance.
Case presentation:
A 75-year-old woman presented with dizziness and weakness in both arms 1 week after an upper respiratory infection. She experienced gradual worsening of consciousness, had dilated pupils and no light reflex. She was suspected of brainstem dysfunction at the upper part of the brainstem; however, there were not significant findings on magnetic resonance imaging, cerebrospinal fluid, or electroencephalography. The auditory brainstem response demonstrated a low voltage, but there was no prolonged latency. At a later date, she was diagnosed with BBE based on serum immunoglobulin G anti-GQ1b antibody. She was discharged home without any neurological sequelae.
Conclusion:
It is necessary to analyze serum immunoglobulin G anti-GQ1b antibodies to diagnose BBE. Auditory brainstem response would be helpful in detecting lesions and predicting functional recovery.