Selective Dorsal Rhizotomy (SDR) Selective Dorsal Rhizotomy SDR involves sectioning (cutting) of some of the sensory nerve fibers that come from the muscles and enter the spinal cord. Two groups of nerve roots leave the spinal cord and lie in the spinal canal. The ventral spinal roots send information to the muscle; the dorsal spinal roots transmit sensation from the muscle to the spinal cord. At the time of the operation, the neurosurgeon divides each of the dorsal roots into 3-5 rootlets and stimulates each rootlet electrically. By examining electromyographic (EMG) responses from muscles in the lower extremities, the surgical team identifies the rootlets that cause spasticity. The abnormal rootlets are selectively cut, leaving the normal rootlets intact. This reduces messages from the muscle, resulting in a better balance of activities of nerve cells in the spinal cord. SDR begins with a 1-2 inch incision along the center of the lower back just above the waist. The spinous processes and a portion of the lamina are removed to expose the spinal cord and spinal nerves. Ultrasound and an x-ray locate the tip of the spinal cord, where there is a natural separation between sensory and motor nerves. A rubber pad is placed to separate the motor from the sensory nerves. The sensory nerve roots that will be tested and cut are placed on top of the pad and the motor nerves beneath the pad, away from the operative field. After the sensory nerves are exposed, each sensory nerve root is divided into 3-5 rootlets. Each rootlet is tested with EMG, which records electrical patterns in muscles. Rootlets are ranked from 1 (mild) to 4 (severe) for spasticity. The severely abnormal rootlets are cut. This technique is repeated for rootlets between spinal nerves L2 and S2. Half of the L1 dorsal root fibers are cut without EMG testing. When testing and cutting are complete, the dura mater is closed, and fentanyl is given to bathe the sensory nerves directly. The other layers of tissue, muscle, fascia, and subcutaneous tissue are sewn. The skin is closed with glue. There are no stitches to be removed from the back. Surgery takes approximately 4 hours. The patient goes to the recovery room for 1-2 hours before being transferred to the intensive care unit overnight. Advantages of SDR The SDR procedure has these significant advantages: Reduced risk of spinal deformities in later years Decreased post-rhizotomy motor weakness Reduced hip flexor spasticity by sectioning the first lumbar dorsal root Shorter-term, less intense back pain Earlier resumption of vigorous physical therapy Possible Complications The dorsal rhizotomy is a long and complex neurosurgical procedure. As in other major neurosurgical procedures, it presents some risks. Paralysis of the legs and bladder, impotence, and sensory loss are the most serious complications. Wound infection and meningitis are also possible, but they are usually controlled with antibiotics. Leakage of the spinal fluid through the wound is another risk. Abnormal sensitivity of the skin on the feet and legs is relatively common after SDR, but usually resolves within 6 weeks. There is no way to prevent the abnormal sensitivity in the feet. Transient change in bladder control may occur, but this also resolves within a few weeks. A few of our patients have experienced urinary tract infections and pneumonia.
Posted on: Thu, 09 Oct 2014 10:53:07 +0000
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