178 “A different kettle of fish”: a journey looking for the cause of paraneoplastic limbic encephalitis
A 54-year-old lady was admitted with confusion and seizures. Brain MRI revealed left temporal lobe high T2 signal. CSF showed 14 lymphocytes, raised protein. IV Aciclovir was started for viral encephalitis. Reducing dose of Dexamethasone lead to reduction of mass effect in left temporal area. She was discharged home on Phenytoin, Carbamazepine, Levetiracetam and Clonazepam. Within 3 months she was readmitted with focal status epilepticus. Repeated CSF demonstrated raised protein =0.68 g/l, low serum/CSF ratio and positive OCBs. Left temporal lobe lesion extended. Brain biopsy showed non-specific inflammatory changes and gliosis. Standard paraneoplastic antibodies were negative. CT chest detected 1 cm nodule in right upper lobe. PET scan showed diffuse increased uptake in left temporal lobe; focal moderate uptake at right lung apex; low uptake in mediastinum. Right upper lobe lesion was fully excised, histology showing squamous cell lung carcinoma. Cognitive impairment, focal seizures, hyperphagia worsened. Clinical status remained unchanged following repeated steroid and immunoglobulin therapy. Pre-/post-operative serum showed reactivity to brain tissue of unknown antibody. Mediastinal lymph node removal confirmed combined small and large cell neuroendocrine carcinoma. Squamous cell lung carcinoma is not commonly associated with paraneoplastic neurological phenomenon. Clinicians should look further for other underlying tumours to explain paraneoplastic limbic encephalitis.