LGI1 encephalitis manifesting as a delayed paraneoplastic response of squamous cell lung cancer on remission

The leucine-rich glioma-inactivated protein 1 (LGI1) antibody-related autoimmune encephalitis can occur alone or in the setting of a malignancy and manifest with faciobrachial dystonic seizures (FBDS), cognitive decline, hyponatremia, and neuropsychiatric disorders. The importance of differentiating this entity from acute delirium cannot be overemphasized. This review provides a detailed account of a 71-year-old man with previous diagnosis of lung cancer who presented with subacute onset behavioural changes, urinary retention, and FBDS. Investigation revealed hyponatremia, bilateral mesial temporal lobe high signal abnormality worse on the right on MRI and CSF positive anti-LGI1 antibodies (1:30). The patient was treated with immunosuppressive therapy with consequent symptom improvement. This case emphasizes the need to have a high index of suspicion for this disease entity in patients presenting with new onset behavioural changes and the importance of identifying the typical FBDS, as early initiation of treatment confers a positive outcome for diseased patients.