Cauda equina syndrome caused by lumbar leptomeningeal metastases from lung adenocarcinoma mimicking a schwannoma

BACKGROUND: Cauda equina syndromes (CESs) due to leptomeningeal metastases from primitive lung tumors are rare. Despite recent advancements in neuro-oncology and molecular biology, the prognosis for these patients remains poor. Here, we present a case in which a patient developed lumbar leptomeningeal metastases from lung carcinoma that contributed to a CES and reviewed the appropriate literature. CASE DESCRIPTION: A 55-year-old female presented with the left lower extremity sciatica/weakness. Two years ago, a then 53-year-old female had received Gamma Knife stereotactic radiosurgery (SRS) for a cerebellopontine angle schwannoma. Recently, she underwent resection of lung carcinoma and SRS for a right hemispheric cerebellar metastasis. Now at age 55, she presented with the left lower extremity sciatica/weakness. When her new lumbar MR was interpreted as showing a L5 schwannoma, a L4-L5 laminectomy was performed at surgery, the authors encountered multifocal leptomeningeal metastases densely infiltrating the cauda equina. Although only subtotal resection/decompression of tumor was feasible, she did well for the ensuing year. The histological diagnosis confirmed the lesion to be a poorly differentiated lung adenocarcinoma. CONCLUSION: Patients with a history of prior metastatic lung cancer may present with spinal leptomeningeal metastases resulting in a CES.