Paper Title
Paraneoplastic Limbic Encephalitis

Abstract
Introduction Paraneoplastic Limbic Encephalitis (PLE) is an uncommon neurological disorder often linked to underlying malignancies, particularly small cell lung carcinoma (SCLC) [1]. It typically presents with acute neuropsychiatric symptoms and seizures [2]. This case report illustrates the diagnostic journey of a 65-year-old female smoker who manifested limbic encephalitis, ultimately revealing SCLC. Case report A 65-year-old postmenopausal woman, with a significant smoking history, presented with a 1-day history of abnormal body movements and behavioral disturbances, including aggression and akathisia. Initial evaluations were inconclusive, with normal baseline investigations and imaging, but biochemical profiling showed elevated lactate with metabolic acidosis. Cerebrospinal fluid (CSF) examination indicated lymphocytic pleocytosis with normal protein and glucose levels, initially suggesting viral meningoencephalitis. Despite starting Acyclovir, the patient's condition did not improve. Subsequent contrast-enhanced MRI of the brain revealed T2-weighted hyperintensity in the left medial temporal lobe and insular cortex, consistent with encephalitis. Further CSF analysis for autoimmune antibodies was positive for GABA B, pointing to autoimmune limbic encephalitis (ALE). The patient was treated with pulse dose corticosteroids (1g methylprednisolone for 5 days), but no improvement in psychotic behavior was observed, leading to increased doses of antipsychotics. A comprehensive malignancy workup with whole-body contrast-enhanced CT identified a 2 cm nodular lesion in the left para hilar lung parenchyma. Bronchoscopic biopsy confirmed SCLC, with immunohistochemistry showing positive markers for chromogranin and CD56. Conclusion This case emphasizes the importance of considering paraneoplastic syndromes in patients with acute neurological symptoms and a history of smoking. PLE can be an early manifestation of underlying malignancies such as SCLC.Timely recognition and appropriate diagnostic measures are crucial for initiating effective treatment. The patient was referred to medical oncology for management of SCLC, underscoring the necessity of a multidisciplinary approach for optimizing both oncological and neurological outcomes. References [1] Gozzard, P. et al. Paraneoplastic neurologic disorders in small cell lung carcinoma: A prospective study. Neurology 85, 235–239, https://doi.org/10.1212/WNL.0000000000001721 (2015). [2] Gultekin, S. H. et al. Paraneoplastic limbic encephalitis: neurological symptoms, immunological findings and tumour association in 50 patients. Brain: a journal of neurology 123(Pt 7), 1481–1494 (2000).