Miller-Fisher syndrome mimicking Tolosa-Hunt syndrome: a case report

Miller-Fisher syndrome (MFS) may present as isolated ophthalmoplegia without ataxia or areflexia, leading to diagnostic confusion with Tolosa-Hunt syndrome (THS). We report a 78-year-old woman who presented with painful unilateral combined oculomotor and abducens nerve palsies. Initial brain magnetic resonance imaging (MRI) showed subtle enhancement of the left orbital apex and cavernous sinus, leading to a presumptive diagnosis of THS, but corticosteroid therapy was ineffective. Repeat orbital MRI was normal, and anti-ganglioside antibody testing demonstrated anti-GQ1b immunoglobulin G (IgG) and IgM positivity, establishing the diagnosis of MFS. This case highlights that painful unilateral multiple ocular motor nerve palsies may represent anti-GQ1b antibody syndrome even in the absence of ataxia, areflexia, or antecedent infection. Early testing for anti-GQ1b antibodies may facilitate timely diagnosis and help avoid unnecessary diagnostic investigations in patients presenting with atypical ophthalmoplegia.