[A case of Bickerstaff brainstem encephalitis concomitant with axonal Guillain-Barre syndrome and ballism successfully treated with intravenous immunoglobulin treatment].

A 39-year-old man acutely developed diplopia, vertigo, unsteady gait, and disturbance of consciousness following an upper respiratory infection. Neurological examination showed ophthalmoplegia, facial paralysis, tetraplegia and loss of deep tendon reflexes. Babinski reflex was positive on the left and there were bilateral flexor withdrawal reflexes. He also developed ballism-like involuntary movements in all extremities, loss of proprioception predominantly on the left, and severe truncal ataxia. Anti-GQ1b IgG antibody was selectively elevated in serum, and CSF protein was elevated to 53 mg/dl with cell count of 12/mm3. Nerve conduction study showed decreased amplitude of compound motor action potentials in all extremities, and no response in facial muscles. Cranial MRI showed no abnormalities whereas EEG was severely abnormal with lack of posterior dominant rhythm and the presence of continuous diffuse theta-waves. This case presented clinical characteristics of three syndromes concurrently-Fisher syndrome, Bickerstaff brainstem encephalitis, and Guillain-Barré syndrome-that may be collectively called 'anti-GQ1b IgG antibody syndrome'. The unique feature of the present case was development of deep coma and ballism-like movements, associated with selective increase of serum anti-GQ1b IgG antibody. It is thus conceivable that anti-GQ1b IgG antibody might underlie the pathogenesis of all three conditions.