Atypical Bickerstaff brainstem encephalitis: ataxic hypersomnolence without ophthalmoplegia.

Clinical and immunological evaluation of 'incomplete' Bickerstaff brainstem encephalitis (BBE). We studied two patients with postinfectious brainstem syndromes who presented at National University Hospital Singapore. Laboratory work-up included measurement of antiganglioside antibodies. Both patients displayed hypersomnolence and cerebellar-like ataxia in the absence of external ophthalmoplegia and carried high serum titres of IgG anti-GQ1b antibodies, strongly indicative of BBE. Ophthalmoplegia can be absent or incomplete in BBE, and the absence of this clinical feature should not exclude BBE from the clinicians' differential. Such cases of incomplete BBE could be defined as 'ataxic hypersomnolence without ophthalmoplegia'.