Normal Early Investigations Do Not Exclude Bickerstaff Brainstem Encephalitis: Highlighting Diagnostic and Treatment...

Bickerstaff brainstem encephalitis (BBE) is a rare immune-mediated disorder characterized by ophthalmoplegia, cerebellar ataxia, and impaired consciousness. It is now recognized as a variant of Guillain-Barré syndrome (GBS), sharing common pathogenic mechanisms with Miller Fisher syndrome. However, early diagnosis remains challenging, particularly when initial investigations are normal. We report a 20-year-old previously healthy woman presenting with rapidly progressive ophthalmoplegia, bulbar dysfunction, flaccid quadriparesis, areflexia, and impaired consciousness following a febrile upper respiratory illness. Early cerebrospinal fluid analysis and brain MRI were normal. Anti-GQ1b antibodies were positive, and nerve conduction studies showed isolated proximal conduction abnormalities with absent F-waves. The patient developed respiratory failure requiring mechanical ventilation and was treated with an extended course of plasma exchange, resulting in near-complete recovery. This case highlights a critical diagnostic pitfall: BBE, a variant of GBS, can present with a life-threatening brainstem syndrome despite entirely normal early investigations. We emphasize the value of recognizing the paradoxical combination of areflexia and extensor plantar responses and the use of F-wave studies as an early electrophysiological foothold when standard studies are unrevealing. Furthermore, it demonstrates that even in catastrophic, ventilator-dependent presentations, an extended course of plasma exchange can lead to a favorable outcome, suggesting a potential therapeutic strategy for severe presentations of BBE.