Neoplastic cauda equina syndrome: a neuroimaging-based review

Cauda equina syndrome refers to dysfunction of the cauda equina, the collection of ventral and dorsal lumbar, sacral and coccygeal nerve roots that surround the filum terminale. This most commonly occurs as a result of compression by a herniated lumbosacral disc. However, the syndrome may also complicate metastatic cancer or a primary neoplasm within or infiltrating the spinal canal. An accurate and timely diagnosis is critical to avoid irreversible loss of neurological function. The clinician and radiologist must therefore be aware of the many possible causes to guide timely management. Here we review the diverse neoplastic causes affecting the cauda equina nerve roots from a neuroimaging-based perspective. We divide them by location into intramedullary neoplasms at the conus (such as astrocytoma), intradural-extramedullary neoplasms (such as schwannoma and leptomeningeal metastases) and extradural neoplasms (such as spinal metastases from systemic neoplasms). We also discuss the clinical features associated with cauda equina tumours, with special focus on cauda equina syndrome.