Bickerstaff brainstem encephalitis is a clinical syndrome of ophthalmoplegia, 
cerebellar ataxia, and central nervous system signs and is associated with the 
presence of anti-GQ1b antibodies. There is a clinical continuum between 
Bickerstaff brainstem encephalitis and Miller Fisher syndrome. We describe the 
case of an 11-year-old boy with encephalopathy, external ophthalmoplegia, 
brainstem signs, and ataxia with raised titers of anti-GQ1b antibodies. He 
presented following a respiratory illness and had laboratory evidence of recent 
infection with Mycoplasma pneumoniae. M pneumoniae infection has been associated 
with both Bickerstaff brainstem encephalitis and Miller Fisher syndrome. This is 
only the second case in the literature of Bickerstaff brainstem encephalitis 
with raised titers of anti-GQ1b antibodies described in association with M 
pneumoniae infection. The patient responded to intravenous immunoglobulin 
administration.