Paraneoplastic limbic encephalitis in a patient with small cell lung cancer. Case report

Paraneoplastic limbic encephalitis (PLE) is a rare autoimmune neurological syndrome caused by selective involvement of the limbic system with the development of neuropsychiatric symptoms and cognitive impairment. PLE is associated with malignancies. We observed PLE in a patient with small cell lung cancer (SCLC). Patient B. complained of severe weakness, headache attacks, irritability, memory loss, and cramps in the muscles of the limbs for 2 months. Contrast-enhanced magnetic resonance imaging of the brain showed signs of PLE. Anti-neuronal antibodies were detected in the blood serum: anti-Hu, anti-CV2 and anti-Ma2, anti-amphiphysin. In the cerebrospinal fluid, anti-Hu antibodies, lymphocytosis of 88%, and increased protein of 0.6 g/L were found. The patient was consulted by a neurologist and diagnosed with PLE. No treatment was administered. After 2 months, the patient reported a significant deterioration. Memory impairment progressed, convulsive seizures with short-term loss of consciousness became more frequent, and the patient became aggressive and withdrawn. Positron emission tomography combined with computed tomography with 18F-fluorodeoxyglucose was performed. There was an excessive radiopharmaceutical uptake in a limited area of the medial parts of the left temporal lobe. A tumor was detected in the upper lobe of the right lung. A bronchoscopy with biopsy was performed. Histological examination showed SCLC. Clinical diagnosis: SCLC of the right lung, stage IIb cT2bN1M0; PLE. Cytotoxic and immunotherapy were administered. The case shows that PLE is a rare neurological syndrome associated in most cases with SCLC, usually in the early stages of the malignancy. Neuropsychiatric and cognitive disorders and seizures are predominant in clinical presentation. PLE neuroimaging is performed using contrast-enhanced magnetic resonance imaging and positron emission tomography combined with computed tomography with 18F-fluorodeoxyglucose, the latter being the method of choice. The presence of antineuronal antibodies in serum and cerebrospinal fluid confirms the autoimmune (paraneoplastic) nature of the process.