Paraneoplastic limbic encephalitis, an uncommon presentation of a common cancer: Case report and discussion

Background: Paraneoplastic neurological disorders (PND) are defined as remote effects on the nervous system that are not caused directly by the tumor, its metastases, or metabolic disruptions. This syndrome occurs in less than 1 per 10,000 patients diagnosed with a malignancy. Many antibodies are found in the central nervous system in PND, the most well known are Anti-Hu, Tr, CV2 Ta, Yo, Ri and amphiphysin. Paraneoplastic limbic encephalitis occurs due to involvement of the limbic system secondary to an autoimmune response to neurons of the brain provoked by the antibodies. Patients, thus, present with seizures, changes in mood, memory, and personality.
Case Report: Fifty-nine years-old female patient presented with seizures, decreased concentration and memory changes. Laboratory workup was remarkable for hyponatremia. Further workup included brain computerized tomography (CT) and magnetic resonance imaging (MRI), which suggested a diagnosis of encephalitis for limbic encephalitis. Anti-Hu, anti-Ma and NMDA-receptor antibodies were requested of which Anti Hu antibodies were positive. Transbronchial biopsy was obtained which confirmed the diagnosis of small cell lung cancer.
Conclusions: A very high index of suspicion should thus be present when patients present with paraneoplastic abnormalities. It must be emphasized that limbic encephalitis (LE) occurs at an early stage of the disease development and therefore the detection of paraneoplastic LE can lead to a quicker identification of the underlying malignancy and a better outcome.

Keywords: memory changes, Seizures, small cell lung cancer, Limbic System, paraneoplastic disorder