Limbic Encephalitis as a Manifestation of Small Cell Lung Cancer

Abstract

SESSION TITLE: Lung Cancer Student/Resident Case Report Posters SESSION TYPE: Student/Resident Case Report Poster PRESENTED ON: Tuesday, October 27, 2015 at 01:30 PM - 02:30 PM INTRODUCTION: Small cell lung cancer commonly presents with widespread metastasis, involving mediastinal and hilar lymph nodes. As this is a neuroendocrine tumor, paraneoplastic syndromes are common, and can precede the malignancy diagnosis. CASE PRESENTATION: Ms. S is a 73-year-old female with a 7 pack-year history of cigarette smoking who presented to our hospital with 2 weeks of altered mental status. Two weeks prior she saw a neurologist and on the same day experienced her first witnessed tonic-clonic seizure. She was started on levatiracetam for prophylaxis. Several days prior to admission she was noted to be persistently confused without return to baseline. On the day of admission Ms. S experienced a second seizure at home and was brought to our hospital. Family members denied recent travel, sick contacts or other associated symptoms. On neurological examination she was oriented to self only and unable to follow commands. The rest of her physical and neurological examination was unremarkable. MRI brain revealed symmetric non-hemorrhagic, non-enhancing abnormalities in the hippocampus consistent with encephalitis. Lumbar puncture showed 27 WBCs with 97% lymphocytes and normal glucose and protein. Intravenous acyclovir was started for presumed HSV encephalitis without improvement in symptoms. Serology for HSV, syphilis, hepatitis, West Nile Virus, and Cryptococcus were all negative. Repeat MRI 15 days later showed worsening encephalitis. At that time CT of the chest, abdomen and pelvis showed an enlarged para-tracheal lymph node measuring 2.1 cm x 1.8 cm without any abnormalities of the lung parenchyma. Biopsy of the lymph node showed small cell cancer. Ms. S was treated with plasmapheresis and IV prednisone with minimal improvement. She was then given one dose each of rituximab and cyclophosphamide followed by significant improvement in her neurologic symptoms. DISCUSSION: Small cell lung cancer presented in this patient as only a solitary lymph node and paraneoplastic encelphalitis, without any additional lung findings. Serologic testing for anti-Hu antibodies is positive in approximately 50% these patients. CONCLUSIONS: Limbic encephalitis has many etiologies including infectious, autoimmune and paraneoplastic. Once infectious etiologies have been ruled out, paraneoplastic encephalitis should be considered a possibility. Initial workup includes CT scan of the chest to detect small cell lung cancer, as it is the most common cancer associated with paraneoplastic limbic encephalitis. Even if no clear lung pathology exists on imaging, abnormal lymph nodes should be biopsied for possible diagnosis. Reference #1: Govindan, R et al. 2006, Journal of Clinical Oncology, vol. 24, no. 28, pp. 4539-4544. Reference #2: Alamowitch, S, et al. 1997, “Limbic encephalitis and small cell lung cancer. Clinical and immunological features”, Brain, vol. 120, no. 6, pp. 923-928. DISCLOSURE: The following authors have nothing to disclose: Katie Jeans, Eva Clark, Jayasimha Murthy No Product/Research Disclosure Information