Introduction

Limbic encephalitis typically presents with memory impairment, seizures and psychiatric disturbances. Even 10 years ago, autoimmune limbic encephalitis was considered almost always paraneoplastic but many other causes are now recognised, including autoimmune processes independent of a malignancy.1 In a recent series, clinical brainstem involvement (ataxia, dizziness, diplopia) occurred in 13 of 50 paraneoplastic limbic encephalitis cases, with hypothalamic involvement in 11 of 50.2 Parinaud's syndrome has not been reported as a feature of paraneoplastic limbic encephalitis. Parinaud's syndrome, first described in 1886,3 involves a combination of eye signs—most commonly, limitation of up and down gaze, failure of convergence, dissociation of lid and eye movements (ptosis, lid retraction) and convergence–retraction nystagmus. Reported underlying lesions usually localise to the dorsal midbrain. The most common causes are pinealomas, stroke and multiple sclerosis. There have been no reported immunological causes. We describe an extremely challenging case associated with an underlying neoplasm.