Tethered Cord (TC)
X-ray of Tethered Cord (see red arrow)
Normally the spinal cord is a freely moving structure within the spinal canal. The term tethered spinal cord describes a condition in which the spinal cord is abnormally fastened to an immovable structure such as a lipoma (fatty mass), vertebra, dura (the membrane covering the spinal cord) or skin. The spinal cord is then fixed between two points: first at the tethering structure and second at the base of the brain. Thus, vertebral structures that move as a result of growth, daily activity, or pathological skeletal change (scoliosis or curvature of the spine) will stretch the spinal cord abnormally. The result is that this segment of tethered spinal cord is stretched beyond its tolerance and damage to blood vessels, nerve cells, and nerve fibers occurs.
There are many conditions that will result in tethering of the spinal cord. These include the presence of bony protrusions or tough membranous bands that prevent the cord from moving, as well as lipomas and tumors (mostly benign), myelomeningocele (also known as spina bifida), cysts, scarring and trauma.
Most signs and symptoms of tethered spinal cord can be traced to the lower (lumbosacral) spinal cord and associated nerves (cauda equina). This area is very susceptible to stretching, leading to damaging effects. The most common findings or complaints include decrease in strength of the legs, loss of bowel and bladder control, deformity of the legs or hips, back or leg pain, loss of reflexes and sensation in the legs, as well as curvature of the spine. Often there are skin abnormalities overlying the tethered cord--such as midline dimples, sinuses or tracts leading from the skin toward the spinal cord, birthmarks, fatty lumps, or small tufts of hair.
If a lesion is suspected, evaluation should be performed promptly. This would include routine spine x-rays (which almost always show some bony abnormality), MRI to show the anatomy of the cord and any tethering lesions, possible somatosensory evoked potentials ( to evaluate the nerves and transmission of electrical impulses through the spinal cord), and an evaluation of bladder function, as well as EMG (electromyography - an evaluation of nerve conduction).
The operating microscope, high-speed drill, carbon dioxide laser and ultrasonic dissector all assist in decreasing blood loss, risk of tissue trauma, and operative time during surgery. In deciding when and under what conditions surgery is indicated, the following principles should be kept in mind: 1) The natural course of the congenital spinal lesions that produce tethered cord is associated with progressive neurologic deterioration and disability 2) Early recognition, evaluation and diagnosis are possible and extremely important 3) Early operative treatment prevents deterioration and may result in neurologic recovery 4) Operation before symptoms and abnormal findings appear may preserve normal neurologic, orthopedic and urologic function.
Author: Dr. John P. Laurent, M.D.
© Donald Willemsen