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Spinal Cord Diseases

The spinal cord is the connection between the brain and all muscles of the body, with the exception of the cranial nerves to the head and neck. The spinal cord can be damaged in many ways, producing various symptom patterns. These patterns enable a doctor to determine the location, or level, of spinal cord damage. The spinal cord can be cut in an accident, compressed, destroyed by infection, damaged when its blood supply is cut off, or affected by diseases (such as spinal cord cysts, cervical spondylosis, or multiple sclerosis) that alter its nerve function. Considerable differences exist in terms of clinical complications after traumatic and nontraumatic spinal cord injury (SCI).

Spinal cord disease, especially compression of the long tracts, may lead to an unpleasant sensation in the extremities that also is enhanced by increased intraspinal pressure or movements that stretch the cord (e.g., neck flexion, straight leg raising). Neck or back pain may also be conspicuous. The associated signs vary with the extent of the lesion and speed of its development. Acute cord compression, as from an epidural hemorrhage, is associated with pain and the rapid onset of a paraparesis or quadriparesis that may not be reversed by decompressive surgery. In contrast, a gradually evolving compressive lesion may be painless and leads to a slowly progressive deficit that often recovers after decompression. Laterally placed lesions lead to a Brown-Séquard syndrome, posterior lesions to bilateral posterior column dysfunction with impaired position and vibration appreciation, anterior lesions to weakness, and intramedullary lesions to a dissociated sensory loss, with impairment of pain and temperature appreciation and preservation of posterior column sensation.

Herniation

With advancing years, the nucleus pulposus of the intervertebral discs becomes harder, less resilient, and more susceptible to trauma. Tears tend consequently to develop in the annulus, through which a portion of the nucleus pulposus may herniate. Herniation is generally in a lateral direction and may lead to compression of the nerve roots as they enter the intervertebral foramina, but sometimes occurs centrally, so that the spinal cord or cauda equina is compressed. In some instances, the protruded disc material loses its continuity with the nucleus pulposus and becomes a free fragment within the spinal canal. Disc herniations occur most commonly in the lumbosacral or cervical region. The early recognition of thoracic disc herniations is important, however, because there is only limited space in the thoracic portion of the spinal canal and delay in diagnosis may lead to an irreversible myelopathy.

Protrusion of an intervertebral disc may lead to a radiculopathy. Approximately two-thirds or more of all compressive root lesions involve the lumbosacral roots. The L5 and S1 roots are involved most commonly. Multiple lumbosacral radiculopathies may occur with protrusion of a single intervertebral disc that compresses the roots as they descend in the cauda equina. Lumbosacral polyradiculopathies may also result from spinal stenosis, and in rare instances, from lateral disc protrusion, but bilateral involvement is then often asymmetrical.

Lumbar spinal stenosis is an important cause of disability in middle-aged or elderly patients. Superimposed minor disc disease then leads to symptoms that may be disabling. The disorder can be congenital or acquired. The congenital disorder is caused by a reduction in the normal dimensions of the spinal canal and occurs in achondroplastic dwarfs. Acquired lumbar stenosis usually is caused by degenerative disease of the spine and is typically associated with hyperplasia, fibrosis, and cartilaginous changes in the annulus, posterior longitudinal ligament, and ligamentum flavum.

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