N/A

Bickerstaff brainstem encephalitis (BBE) and Wernicke encephalopathy (WE) share overlapping features, including encephalopathy, ophthalmoplegia, and ataxia. However, their MRI patterns differ: WE typically affects the medial thalami, mammillary bodies, and periaqueductal gray, while BBE usually shows normal MRI or, when abnormal, affects the brainstem, cerebellum, or thalamus. We report a rare case of Anti-GQ1b-Antibody syndrome with imaging features initially suggestive of WE, highlighting diagnostic pitfalls.

Case:
A 44-year-old man with hypertension, polysubstance use disorder (including alcohol, currently in remission on buprenorphine) presented with 1–2 weeks of progressive cognitive decline, ophthalmoplegia, and ataxia. The patient had experienced unintentional weight loss and poor appetite for several months prior to presentation, of unclear etiology, initially suggesting thiamine deficiency. Laboratory evaluation revealed low vitamin B12 and folate, and high-dose thiamine was initiated before confirmatory serum thiamine levels. Brain MRI showed symmetric T2/FLAIR hyperintensities in bilateral medial thalami and mammillary bodies, initially favoring WE.
Neurologic examination was notable for disorganized and tangential speech, ophthalmoplegia with gaze restriction and nystagmus, dysmetria, and hyperreflexia. Of note, vivid well-formed visual hallucinations of snakes in his room (consistent with peduncular hallucinosis) were reported throughout his hospital stay. Despite thiamine repletion, deficits persisted. Conflicting clinical features—including alcohol abstinence for years with normal phosphatidylethanol levels, a biomarker indicating recent alcohol consumption—prompted consideration of alternative etiologies. Repeat MRI showed ongoing signal abnormalities involving the tectum, hypothalamus, and periaqueductal gray matter with interval development of right tectal enhancement.
CSF demonstrated albuminocytologic dissociation (protein 95 mg/dL, 1 WBC). Serum anti-GQ1b antibody was positive at 1:400 by EIA (enzyme immunoassay). Intravenous immunoglobulin 2g/kg was initiated with early clinical improvement.

N/A

This case underscores that BBE can rarely mimic WE on imaging, despite distinct patterns. Persistent deficits despite thiamine repletion should prompt consideration of BBE, with early recognition critical for initiating immunotherapy and improving outcomes.