Dorsal rhizotomy was performed first by Abbe in the late nineteenth century to relieve pain,150 and Sherrington151 pioneered the use of this procedure to improve spasticity in decerebrate cats. In 1913, Foerster152 reported decreased spasticity and improvement in posture and function after the division of complete dorsal nerve roots in 159 patients, 88 of whom had congenital spastic paraplegia. Foerster152 divided the entire dorsal nerve roots from L2 to S2, sparing L4 to preserve knee extension for standing. He used intraoperative electrical stimulation to identify the nerve roots associated with knee extension and to distinguish between ventral and dorsal roots. Because this procedure caused disabling sensory deficits, it was modified such that only four-fifths of the dorsal lumbosacral nerve rootlets were sectioned, but it still caused troublesome sensorimotor deficits.
Much later, intraoperative electrical stimulation and electromyography allowed rootlets innervating functionally important muscles to be spared and rootlets innervating the most dysfunctional muscle groups (e.g., hip adductors and flexors) to be cut.153,154
During the 1970s, Fasano et al.155 found that certain dorsal rootlets displayed an abnormal response to stimulation in spastic patients. In a selective dorsal lumbosacral rhizotomy, rootlets that responded to electrical stimulation with expected brief muscular contraction were spared, whereas those that evoked abnormally prolonged contractions that often spread to adjacent muscle groups were divided.155 This Fasano procedure then was modified to identify better the sacral nerve roots involved in sphincter control. By performing a more caudal laminectomy, the surgeon can better expose the cauda equina and roots exiting the neural foramina, improving verification of nerve root levels and ventral versus dorsal rootlets. On completion of an L2 through S1 laminectomy, the dorsal nerve rootlets between L2 and S2 are electrically stimulated and selectively divided on the basis of intraoperative electromyography and visual observation and palpation of muscle responses. Between 25% and 50% of rootlets usually are divided, but more may be divided in severely affected individuals. Care must be taken to ensure that not all rootlets of a particular level are divided.128
Selective dorsal rhizotomy improves spasticity only and is indicated for patients in whom spasticity is the main physical handicap.
Clinical evaluation focuses on:
The muscle disturbance must be due to spasticity, not dystonia or athetosis. The ideal patient is a spastic diplegic child without significant weakness or fixed contractures who ambulates independently with a scissoring gait, flexed hips and knees, and an equinus foot posture.156,157
Potential neurosurgical complications include increased weakness, sensory loss, sexual dysfunction, and spinal instability or deformity. Other adverse effects include wound infection, urinary tract infection or cystitis, hemorrhage, cerebrospinal fluid leakage, and respiratory complications.
Dorsal cervical rhizotomy is rarely used, being reserved primarily for severe upper-extremity spasticity, dyskinesis, or athetosis. McCouch et al.158 found that the afferent endings for tonic neck reflexes were in the joints between the occiput, atlas, and axis. By performing complete dorsal rhizotomies of the C1 through C3 nerve roots, Kottke159 reported functional improvement in the upper extremities and more coordinated facial movement; in addition, reflex grimacing and symmetric and asymmetric tonic neck reflexes were abolished. Other groups, however, have reported reduced upper-extremity spasticity but limited functional improvement.160–162
In 1945, Munro163 described the technique of anterior rhizotomy to relieve painful spasticity in 10 patients with complete spinal cord injuries. The procedure is no longer performed owing to flaccid paralysis and atrophy that resulted.
Smyth and Peacock128 performed anterior rhizotomy on three patients with incapacitating upper-extremity choreoathetoid movements. Intraoperative electrical stimulation and electromyography identified the ventral rootlets of the fifth through seventh cervical nerves. These rootlets were divided, paralyzing the abductors of the shoulder and flexors and extensors of the elbows but preserving distal sensorimotor function. The violent arm movements ceased, but only partial function was preserved.128
Peripheral neurectomy involves sectioning the peripheral nerve or motor nerve branch to reduce overactivity of a muscle or muscle group. Because peripheral nerves contain motor and sensory fibers, division can cause sensory loss, weakness, and atrophy.
In the upper extremities, neurectomy of the musculocutaneous nerve can relieve spastic elbow flexion.164 Microneurosurgical ablation of fascicles in 52 spastic patients produced complete relief for 63% and some degree of improvement for 37%.165
Selective peripheral neurectomy of collateral motor branches of the brachial plexus has been shown to relieve spasticity in the shoulder in five patients.166
Peripheral neurectomies in the lower limbs can improve spastic calf muscles. Feve et al.167 noted clinical and electrophysiologic improvement in spasticity. They also reported abolition of ankle clonus and improved ankle angular variations in a large series of patients undergoing posterior tibial nerve collateral branch neurectomy. Tibial neurectomy improved gait significantly in some patients.168 However, Berard et al.169 found that symptoms recurred in 8 (61%) of 13 children with spastic hemiplegia who underwent unilateral tibial neurectomy.
Motor points are well-defined areas of the muscle that produce maximum contraction when the motor nerve branch passing through the muscle is stimulated. To relieve spasticity, motor blocks can be performed by injection of anesthetic agents or phenol into the peripheral nerve or muscle belly near the motor point and may last up to 6 months.167,170,171 Alcohol blocks provide a shorter duration of relief of spasticity, lasting 1 to 6 weeks, and may be helpful in evaluating responses in spastic children without fixed contractures before more permanent procedures are undertaken.172
Common injection sites include:128
A needle electrode is used to inject phenol and alcohol into the muscle belly after the motor point has been initially defined with a surface electrode. The peripheral nerve can also be injected either interneurally or perineurally. Both procedures present a risk of damage to afferent pathways.
Complications include causalgia and dysesthesias, cardiac arrhythmias, and permanent neurologic deficits.173
Reviewed and revised May 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
© 2014 Epilepsy.com. All rights reserved.