Selective Dorsal Rhizotomy - An Excellent Treatment Option For Spastic Celebral Palsy In Children and Young Adults
T. S. Park, MD
Director, Center for Cerebral Palsy Spasticity
Neurosurgeon-in-Chief, St. Louis Children's Hospital
Shi H. Huang Professor of Neurosurgery
Washington University School of Medicine
St. Louis, Missouri
Introduction
Cerebral palsy (CP) inflicts life-long disabilities on over 500,000 children and adults in the United States alone. Moreover, the prevalence of CP has not declined in recent years despite remarkable advances in neonatal care and in this nation, approximately 8,600 new patients are diagnosed each year with the disorder. Spastic CP is the most common subtype of cerebral palsy. Spastic diplegia and spastic quadriplegia affect approximately 60% of patients. Additionally, spasticity coexists with dyskinesia and ataxia in mixed subtypes of CP. Thus as a whole, spasticity afflicts 80-90% of all patients with CP.
Harmful Effects of Cerebral Palsy Spasticity
It is important to keep in mind that CP spasticity does not resolve spontaneously and exerts many harmful effects on patients. Patients with CP do not depend on spasticity for any activities. CP spasticity is particularly harmful to growing children as outlined below and Table 1; thus it requires an optimal treatment at an early age of patients. The most significant deleterious effect of CP spasticity is that it inhibits motor activities. Spasticity-induced Inhibition of motor activities does not abate if spasticity is left untreated. Equally important harmful effect of CP spasticity is that it decreases muscle and bone development, and causes deformities of the affected extremities.
Table 1: Harmful Effects of Spasticity In Children With Spastic Cerebral Palsy
Inhibition of voluntary movements.
Reduction of muscle extensibility.
Inhibition of longitudinal muscle growth.
Shortening of muscle.
Development of muscle contractures.
Development of bone and joint deformities.
Current Treatment Options for Spastic CP
Patients benefit from several currently available treatment options, including physical therapy, braces, antispasticity medications, Botox injection, Baclofen pump infusion, orthopedic surgery and selective dorsal rhizotomy (SDR). A choice of treatment should depend on the age of patients and specific problems at a given time. It should be noted that of all treatment options, only SDR can reduce permanently spasticity in many patients with spastic diplegia or quadriplegia.
Selective Dorsal Rhizotomy (SDR)
Of all the surgical procedures currently performed on patients with CP, SDR has undergone more thorough scientific scrutiny than any other procedure. Research and our own clinical experience in the last 17 years have shown that SDR is an excellent option for selected patients with spastic CP. Parents and patients need to inquire about SDR as a part of the management of CP.
Outline of the SDR Procedure
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. During SDR, the neurosurgeon divides each of the dorsal roots into 3-5 rootlets and stimulates each rootlet electrically. Muscle contraction responses from muscles in the lower extremities are tested by electrical stimulation to identify the rootlets that cause spasticity. The abnormal rootlets are selectively cut, leaving the normal rootlets intact.
Details of SDR Procedure at St. Louis Children's Hospital
SDR begins with a 1- to 2-inch incision along the center of the lower back just below the rib cage. The tip of the spinal cord is located with ultrasound and other methods. A back portion of a single lumbar vertebra is removed to expose the spinal cord and nerve roots. After the sensory nerves are exposed, each sensory nerve root is divided into 3-5 rootlets. Each rootlet is tested to record electrical patterns in muscles. The rootlets with abnormal muscle contraction are cut and a part of rootlets are preserved.
Possible Complications
SDR is a complex neurosurgical procedure but the risk of surgery in experienced hands is minimal. However, risks shortly after surgery include paralysis of the legs and bladder, impotence, sensory loss, meningitis, and leakage of the spinal fluid. Late complications include spine deformities and back pain. In our over 1100 patients, only patient developed leakage of the spinal fluid and no other complication occurred. The removal of bone from a single lumbar vertebra has prevented SDR-related spine problems in our patients.
Candidates for SDR
Our current indications for SDR are depicted in Table 2. Primary beneficiaries of SDR are children with spastic diplegia secondary to premature birth. Children with spastic quadriplegic CP can also benefit from SDR. The optimal age for SDR is 2 to 6 years. Because of the significant deleterious effects of spasticity as outlined above, early treatment is recommended to reduce the chance of severe orthopedic deformities of the lower extremities. SDR is not considered for children under the age of 2 years since 30 % of children who had been diagnosed with CP at the age of 1 year subsequently became free of symptoms. Adolescents and young adults under 40 years of age can also make good functional gains from SDR. The risk of dorsal rhizotomy in adolescents and adults is no greater than in young children, when performed through a single level laminectomy. It is possible that reduction of spasticity will lessen the impact of aging on physical stresses due to CP, e.g., abnormal stress on bones and muscles, wear and tear on joints, and increasing joint and muscle pain.
Table 2: Indications of Selective Dorsal Rhizotomy For Spastic Cerebral Palsy.
Diagnosis - spastic diplegia or quadriplegia.
Age - 2 to 40 years.
History of premature birth or neonatal asphyxia.
Bilateral schizencephaly underlying spastic diplegia.
Emerging locomotive functions.
Potential for significant postoperative functional gains.
Patients should have sufficient motor function underlying the spasticity to potentially become ambulators, either assisted or independent. In some patients with spastic quadriplegia, SDR is recommended to improve sitting posture and upper extremity movement. Patients are not candidates when their motor impairment is severe enough to require support even for sitting. In the selecting patients over 18 years of age for SDR, we take additional factors into consideration: Independent ambulation; Fixed orthopedic deformities; Back pain; Level of motivation; Other medical problems.
Outcome of SDR
Spasticity: At present, SDR is the only surgical procedure that can produce permanent reduction of spasticity in CP. In our patients with spastic diplegia always reduces spasticity, and recurrences have been rare. In patients with spastic quadriplegia, however, SDR can fail to reduce spasticity. Recurrence of spasticity is relatively common in severely involved nonambulatory patients with spastic quadriplegia.
Strength: SDR does not cause permanent weakness. However, patients will experience transient motor weakness that may last a few weeks to months after SDR. It is important to note that SDR does not result in floppy extremities, even immediately after the operation. Because a varying degree of motor weakness is always present in CP, when spasticity is reduced or eliminated, the motor weakness underlying spasticity becomes more noticeable.
Patients who walk independently always resume independent walking within a few weeks after SDR. Patients who walk with crutches will also resume crutch walking within several weeks after SDR. Patients who walk well with a walker prior to SDR resume assisted walking within several weeks. Patients who use a walker and assistance require much longer to resume the level of walking they were capable of before SDR.
Motor Function: SDR results in improvements in sitting, standing, walking, and balance control in walking. Typically, improvements in motor function are most noticeable during the first 6 months after SDR. After that, improvements are slow but steady. In children, these improvements can continue up to 10 years of age. In adults and adolescents, improvements continue for approximately 2 years after SDR.
Deformities: Patients with CP almost invariably have some deformities in the lower extremities. Common deformities are hip subluxation, hasmstring and heel cord tightness, and foot deformities. These deformities can be improved by SDR. Hip subluxation can progress if left untreated. In most patients, SDR can halt the progression and it does not exacerbate or increase the risk of hip subluxation. However, some children under 5 years of age who have poorly developed hip joints do show progression of hip subluxation regardless of treatment. Early SDR, at 2-4 years of age, can prevent the development of deformities. For this reason, we favor early surgery. Also, SDR will reduce deformities and makes it easier to treat deformities later with orthopaedic surgery.
Orthopaedic Surgery: Many patients with spastic CP require multiple orthopaedic operations. Our study showed that early SDR may reduce the rate of subsequent orthopaedic procedures. It is important to remember that deformities are due not only to spasticity but also to motor impairment and consequent limited muscle stretching in daily activities. That is, muscles without spasticity can still develop contractures if they are not used and stretched fully. Therefore, many patients will still require follow-up with orthopaedic surgeons after SDR.
Other Improvements
SDR can also improve the gross range of motion of the upper extremities, potty training, cognitive function, speech and emotions.
Conclusions
Research and clinical experience in the past 17 years indicate that many patients with spastic diplegia and quadriplegia can benefit from SDR. We encourage all patients with CP to inquire about SDR as a surgical option before patients receive any surgical treatment, including orthopedic surgery.
More information about SDR is available at: www.stlouischildrens.org/sdr.
