Fahim et al. Journal of Medical Case Reports 2010, 4:408 http://www.jmedicalcasereports.com/content/4/1/408 impaired coordination, sensory loss or muscle wasting. The rest of her systemic examination results were within normal limits. There was evidence of significant postural hypotension contributing to the clinical presentation of collapse and brief loss of consciousness. An electrocar- diogram showed a normal sinus rhythm. However, a chest radiograph (Figure 1) was abnormal with left hilar shadowing. A biochemical profile showed hyponatremia with a serum sodium level of 128mmol/L. In view of her significant smoking history the most likely diagnosis was bronchogenic carcinoma with brain metastasis, and so a computed tomography (CT) scan of the thorax and head was arranged. The thoracic CT scan (Figure 2) revealed confluent left hilar lymphadenopathy encasing the left lower lobe pulmonary artery, and a parenchymal opacity in the left lower lobe was highly suggestive of bronchogenic carcinoma. The contrast-enhanced CT scan of her head (Figure 3) did not show any significant abnormality. Flexible fiber-optic bronchoscopy results were normal and bronchial washings were negative for malignant cells. We therefore performed a CT-guided biopsy (Figure 4) of the left lower lobe lesion. It was suggestive of neoplastic infiltration of lung parenchyma by small cell carcinoma. Furthermore, immunohisto- chemistry showed positive staining with CD56 (Figure 5), pancytokeratin, chromogranin and thyroid transcription factor 1 (TTF1), consistent with a diagnosis of small cell lung cancer. As there was no improvement in her cogni- tive function, a lumbar puncture was performed. The results of a cerebrospinal fluid (CSF) examination were unremarkable. In view of her persistent neurological symptoms, an MRI scan of the brain was performed that showed numerous small foci of increased T2- weighted signals scattered throughout the cerebral white matter, particularly in the frontal and parietal areas. Axial fluid attenuation inversion recovery (FLAIR) sequences showed hyperintense signals from the medial temporal lobe on the left (Figure 6) and right side Page 2 of 4 Figure 2 Computed tomography (CT) scan showing parenchymal opacity in the apical segment of the left lower lobe (arrow), highly suggestive of lung malignancy. (Figure 7), consistent with the radiological diagnosis of limbic encephalitis. There was no evidence of metastatic disease. A diagnosis of paraneoplastic limbic encephalitis associated with limited stage small cell lung cancer was made based on the clinical and radiological results. Our patient was treated with prophylactic cranial irradiation followed by platinum-based chemotherapy. Her Figure 1 Chest radiograph showing left hilar abnormality (arrow) and opacity in the left mid zone. Figure 3 Computed tomography (CT) image of our patient’s brain on presentation, without significant acute pathology.