Atypical Imaging Findings in Anti-GQ1b Brainstem Encephalitis

Brainstem encephalitis is a rare neurological entity with different etiologies.1 When associated with ophthalmoplegia, ataxia, disturbance of awareness, in the setting of a positive antiganglioside (GQ1b) antibody serology, a diagnosis of Bickerstaff’s brainstem encephalitis (BBE), a postinfectious autoimmune condition, can be made.1–3 A large majority of the patients have a monophasic course with generally good outcomes.4 We report the case of a 63-year-old male with a history of tongue cancer, treated with surgery and adjuvant radiotherapy in 2012, who presented with progressive headache, diplopia, and gait unsteadiness in 2 days. Please note some inherent differences in contrast windowing and slice thickness and orientation due to images acquired in scanners of different vendors under different conditions. A wide differential diagnosis was considered, given the atypical imaging findings in this patient, including an infectious etiology (a viral or bacterial disease), an autoimmune process (Behcet’s disease, neurosarcoidosis, or other vasculitis entities), brain tumor, and paraneoplastic encephalomyelitis.1,3 However, the absence of systemic symptoms, negative autoimmune, viral, and bacterial screenings, made these differential diagnoses unlikely.