title: Cauda equina syndrome caused by isolated spinal extramedullary-intradural cauda equina metastasis is the primary symptom of small cell lung cancer: a case report and review of the literatrure.
abstract: OBJECTIVE
  To describe a case of extramedullary-intradural metastases causing cauda equina syndrome (CES) as the primary syndrome of lung cancer, and to review the pertinent medical literature.
  
  
  BACKGROUND
  Intradural spinal metastasis is rare, accounting for 6% of all spinal metastases. Of all primary lesion types, lung carcinoma is about 40-85%. Extramedullary-intradural metastases of lung cancer causing CES is unusual.
  
  
  METHODS
  A 55-year-old patient with symptoms of low back pain that radiated to bilateral lower legs with painful paresthesias and piecemeal sphincter disturbances and lead to urinary incontinence, and constipation at last for three months. The MRI showed that there was an isolated, well-demarcated, intradural extramedullary mass at the L3, 4 levels.
  
  
  RESULTS
  The patient was admitted to the hospital as the severe cauda equina syndrome (CES) and considering the possibility of nerve system neoplasms for surgery. After a series of examinations, the X-ray and computed tomography (CT) detected a tumor in the left upper lobe with hilar and mediastinal lymph node metastases. The concluded diagnosis through histopathologic examination with immunohistochemistry after the patient received an L3-L4 laminectomy and tumor excision and biopsy was extramedullary-intradural spinal metastasis of the small cell lung cancer (SCLC). The patient had a rapid improvement of the CES.
  
  
  CONCLUSIONS
  Although the majority of cauda equina tumors are primary tumors, extramedullary-intradural metastasis should be considered before surgery in patients with rapid developed CES.
authors: Department of Trauma and Orthopaedics, Peking University People's Hospital Beijing, China.
authors: Jian
authors: J
authors: Xiong
authors: Department of Trauma and Orthopaedics, Peking University People's Hospital Beijing, China.
authors: Peixun
authors: P
authors: Zhang
keywords: Cauda equina syndrome; extramedullary intradural spinal metastasis; small cell lung cancer