A Rare Cause of Cauda Equina Syndrome: Neuroendocrine Carcinoma of the Lung.

Cauda equina syndrome (CES) is a rare condition describing the constellation of symptoms resulting from the compression of the cauda equina. Metastatic lesions are a common cause of CES, with lung lesions often implicated as the primary source. A particularly rare cause of CES is leptomeningeal metastasis (LM) from primary solid tumors. In this case, a 63-year-old male presented with urinary and fecal retention, as well as altered sensation in the genitalia. The clinical diagnosis of CES was based on the constellation of symptoms. Computed tomography (CT) imaging demonstrated a metastatic lesion in the S2 and S3 sacral vertebral bodies, with extension into the right piriformis muscle. Magnetic resonance imaging (MRI) revealed an intramedullary lesion at L2 and leptomeningeal enhancement, indicative of metastasis. Further imaging identified a primary lesion in the right lower lobe of the lung, with additional metastases to the brain and liver. A pathological diagnosis of metastatic neuroendocrine carcinoma (NEC) was confirmed following a supraclavicular lymph node biopsy. The patient received steroid therapy, chemotherapy, and radiation to the pelvis. This case provides an important perspective on CES evaluation due to the scarcity of literature highlighting spinal metastases as the primary presentation in patients with NEC of the lung. The clinical diagnosis of CES should raise suspicion for metastasis and warrant further investigation.