Conus and Cauda Equina Tumors

Excerpt

Conus and cauda equina tumors represent a unique group of tumors due to their specific location in the spinal canal. The conus medullaris forms the last portion of the spinal cord from where the axons of the distal nerve roots originate and where the spinal bowel and bladder centers are located. The cauda equina is the conglomeration of the nerve roots of the lumbar and sacral spinal nerves distally to the conus area. These two areas form a transition between the central nervous system and the peripheral nervous system. Conus lesions will primarily affect the central functions, while cauda lesions will affect peripheral functions. As these two areas are in close proximity, lesions in one area can affect the function of the other area. Lesions in each area give rise to specific deficits and are appropriately called cauda equina syndrome (CES) and conus medullary syndrome (CMS). In this review, the tumors causing these syndromes are described.

Primary spinal cord tumors are less common than metastatic spinal tumors. Tumors of the spinal canal are classified in three ways depending on the tissue compartment in which they are found:

1. Extra-dural: arising outside of the dura mater

2. Intra-dural/Extra-medullary: arising within the dura mater but outside of the neural tissue

3. Intra-dural/Intra-medullary: arising within the dura mater and within the substance of the neural tissue

Tumors arising within the lumbar spine may involve either the vertebrae, the distal end of the spinal cord (conus medullaris), or the nerve roots (cauda equina). These tumors may be primary or metastatic, benign or malignant, and may have a broad range of presentations. The most common tumors involving the vertebrae are metastatic lesions with the most commonly involved area being the vertebral body. The most common tumors arising from the conus medullaris are ependymoma and astrocytoma. A metastatic lesion within the conus medullaris is possible but very uncommon. The most common tumor involving the cauda equina is a schwannoma.