The spinal cord transmits information between the spinal cord and brain to the nerves and muscles. The distal or terminal portion of the spinal cord is also referred to as the conus medullaris.
In adults, the spinal cord terminates at approximately the level of L1. This space is created by the differential growth of the vertebral column compared with the spinal cord, which causes the spinal cord to ascend with growth. The nerve roots then descend through this fluid sac containing cerebrospinal fluid and are referred to as the cauda equina (“tail of a horse”). This is the collection of lumbar and sacral spinal nerve roots that course in a caudal direction to emerge from their respective foramina.
Compression of the spinal cord and nerve roots by tumors of the cauda equina and the conus medullaris produces pain and progressive deterioration of neurologic function, including motor weakness, sensory deficits, and bowel and bladder dysfunction. These symptoms are collectively known as the cauda equina syndrome.
The general classification of tumors of the cauda equina and the conus medullaris is according to the tissue compartment in which the tumors are located. This classification is based on their relationship to the meninges that enclose the central nervous system, as follows:
Extradural tumors – Arise outside the spinal cord and the meninges and the epidural tissue
Intradural-extramedullary tumors – Arise inside the dural sac, from the leptomeninges or the nerve root, outside the substance of the spinal cord parenchyma
Intramedullary tumors – Arise within the substance of the spinal cord
Tumors, disk herniations, fractures, and infection (ie epidural abscesses) are all possible causes of cauda equina syndrome. Determining the precise nature of the lesion (eg, intradural-extramedullary vs intramedullary) and the exact type of tumor (eg, ependymoma vs astrocytoma) based on clinical findings can be difficult.
The ability to noninvasively image the neural elements with magnetic resonance imaging (MRI) for evolving neurological deficits in addition to chronic conditions such as low back pain has facilitated the diagnosis of this disorder. See the image below.
Tumor of the conus medullaris.
The treatment for tumors of the cauda equina or conus medullaris is primarily surgical resection. Radiation therapy and intrathecal chemotherapy are reasonable adjuvants for the treatment of these tumors in patients with contraindications for surgical treatment.
In 1887, Sir Victor Horsley performed the first successful removal of a spinal cord tumor, an extramedullary-intradural fibromyxoma that was compressing the spinal cord. The patient subsequently regained gait function.
In 1907, Eiselsberg-Renzi first successfully removed an intradural intramedullary tumor. However, in 1905, Cushing reported the first attempted surgical resection of an intramedullary spinal neoplasm. In 1925, Charles Elsberg published the first large series of patients that underwent a resection of spinal cord neoplasms. Unfortunately, these patients endured significant associated morbidity and mortality related to operative techniques during this period.
In 1963, Greenwood reported a modern series on removal of intramedullary tumors with good success.
The conclusion was reached that because of the relatively direct surgical approach to the lumbar spinal canal, tumors in that area are amenable to successful surgical resection.
For patient education information, see the Back, Ribs, Neck, and Head Center; Cancer and Tumors Center; and Brain and Nervous System Center, as well as Back Pain, Lumbar Laminectomy, and Cauda Equina Syndrome.