Atypical MRI findings in anti-GQ1b brainstem encephalitis
Background and aims: Brainstem encephalitis is a rare neurological disease with different etiologies. When it presents with ophthalmoplegia, ataxia, and impaired consciousness along with a positive anti-GQ1b, Bickerstaff brainstem encephalitis (BEE) should be suspected. MRI findings in BEE are generally mild and detected in approximately 30% of the cases. These concern mainly T2-weighted hyperintensities in the brainstem, thalamus, cerebellum and white matter of the brain.
Methods: Case report
Results: A 63-year-old male with history of carcinoma of the tongue, treated with surgery and radiotherapy in 2012, presented with progressive headache, diplopia and gait unsteadiness. He had normal vital signs, and neurological examination revealed an ataxic gait, complex bilateral ophthalmoplegia, vertical gaze-evoked nystagmus, dysarthria and dysphagia. A mild drowsiness was also apparent. No recent infectious illnesses were known. Brain MRI showed extensive T2-weighted hypertense lesions affecting the brainstem and cerebellar peduncles bilaterally, with multiple foci with ring enhancement after gadolinium administration. Additionally, some T2* hypointensities were identified in the same regions, indicative of microhemorrhagic foci. CSF analyses showed mild lymphocytosis (10 cells/µL) with a protein level of 81mg/dL, and no sign of viruses nor B. burgdorferi. Lab results showed a high titer anti-GQ1b antibody. The patient was treated with intravenous immunoglobulins for five days and made a gradual recovery over 6 weeks. Clinical follow-up at one month revealed only mild ataxic gait, ptosis and mild right eye adduction paresis. Subsequent MRI showed marked improvement with no contrast enhancement but maintained mild chronic hemorrhagic foci.
Conclusions: This case shows an atypical radiological presentation rarely observed in GQ1b brainstem encephalitis. Despite that, a near-complete clinical recovery occurred. Since only rarely may the MRI scan present significant abnormalities, anti-GQ1b should be considered as part of the lab tests for brainstem encephalitis, playing a crucial role for differential diagnosis.