Unmasking Probable Bickerstaff Brainstem Encephalitis in the Absence of Radiological and Cerebrospinal Fluid Clues

Bickerstaff brainstem encephalitis (BBE) is a rare immune-mediated neurological disorder characterized by a wide spectrum of clinical presentations, often following a preceding infection. Although supportive findings on neuroimaging, cerebrospinal fluid (CSF) analysis, and antiganglioside antibodies may aid diagnosis, the condition remains largely clinical, particularly in atypical cases. We report the case of a 60-year-old man who presented with acute onset of fever and altered sensorium, rapidly progressing to severe quadriparesis and respiratory failure requiring mechanical ventilation. Neuroimaging and CSF analysis were unremarkable, with no evidence of albuminocytological dissociation. Nerve conduction studies revealed severe sensorimotor neuropathy involving all four limbs. In view of poor response to empirical antimicrobial therapy and after exclusion of infectious etiologies, we suspected an autoimmune process and initiated the patient on intravenous immunoglobulin (IVIG). We observed significant clinical improvement from the second dose onward, with progressive recovery of sensorium, motor power, and respiratory function. We successfully weaned the patient off ventilatory support, decannulated, and discharged him without residual neurological deficits. This case highlights the diagnostic challenge that atypical presentations of Bickerstaff encephalitis pose in the absence of classical radiological and CSF findings. It underscores the importance of maintaining a high index of clinical suspicion and initiating timely immunotherapy, even when conventional diagnostic markers are lacking.