Spasticity - Neurosurgery for Spasticity

Spasticity

Neurosurgery for Spasticity

What types of neurosurgery are performed for spasticity?
The principal neurosurgical procedure for spasticity is done on the spinal cord. This procedure is called selective dorsal rhizotomy (SDR) or selective posterior rhizotomy. "Rhizotomy" means cutting of nerve roots, the fibers lying just outside the vertebral column that transmit nerve impulses to and from the spinal cord. "Dorsal" or "posterior" indicates that the target nerve roots are those that lie at the backside of the cord. These nerves carry sensory information to the cord from muscle. "Selective" indicates that only certain nerve roots are cut.

Sensory nerves are targeted because researchers believe they play an important role in generating spasticity. Normally, excitatory signals from these sensory nerves are counterbalanced by inhibitory signals from the brain, maintaining normal muscle tone (See Spasticity Pathophysiology). When brain or spinal cord damage upsets this balance, excess sensory signaling can lead to spasticity. It is thought that SDR improves spasticity by partially restoring the proper balance.

Surgery on the brain and cerebellar stimulation of the brain have been used in the past with limited success and are currently not recommended for the treatment of spasticity. Peripheral nerve surgery (neurectomy) is another surgical treatment for spasticity that has received little support from clinicians due to complications.

Who is an appropriate candidate for SDR?
SDR is used to treat severe spasticity of the lower extremities that interferes with mobility or positioning. Most experience with SDR has been in children with cerebral palsy. SDR has also been performed on adults with spasticity from cerebral palsy or other etiologies. The best candidate for SDR is a person with good strength and balance, little or no fixed contractures in the lower limbs, and strong motivation and support. Like other surgical procedures, SDR is used only when less invasive procedures are unable to control spasticity adequately.

How is the surgery performed?
SDR is performed under general anesthesia. The procedure usually lasts about 4 hours. The base of the spinal cord is exposed for 2-3 inches along its length, and candidate nerve rootlets are stimulated electrically. Those that lead to abnormal responses are cut. Usually 25-50% of all tested rootlets are cut.

How long does recovery take?
SDR requires about a seven-day postoperative recovery in the hospital. Initial care involves strict bed rest, a urinary catheter, and an intravenous line for fluids and pain medication. Limited physical therapy begins after 1-2 days, with more vigorous activity in the days following. A 3-4 week recovery at home should be anticipated before returning to work or school.

What are the possible complications from SDR?
During surgery, bronchospasm, or airway constriction, is possible. Patients with a history of bronchospasm or airway disease may be started on bronchodilators before the surgery begins. Regurgitation and aspiration (entry of food into the airways) can occur as well. The risk of aspiration may be reduced by increasing the preoperative period without food intake and using medications to reduce stomach acidity.

Pain, altered sensation, and fatigue may continue for a number of weeks after the operation, as may changes in sleep and bladder or bowel function. Long-term complications may include low back pain, scoliosis or kyphosis (spine curves), and hip displacement. It may be possible to reduce the likelihood of developing these long-term complications through appropriate physical therapy. Changes in surgical procedure have reduced the frequency of complications in recent years.

What are the expected results from SDR?
The extent of functional improvement after SDR will vary with the individual patient. Factors include the extent of mobility before the operation, underlying strength and balance, the availability of regular physical therapy after SDR, and the patient's motivation and ability to undertake the rehabilitation process.

Studies of SDR in children with cerebral palsy have shown that most patients experience a reduction in spasticity and an increase in range of motion immediately after surgery, which persists for at least a year. There have been relatively few longer-term follow-up studies, but these indicate tone reduction may last for a number years.

Although spasticity reduction can help improve function, it doesn't always. Most studies have shown some benefit in mobility for those with spastic diplegia (leg spasticity), but less for those with spastic quadriplegia (spasticity in all four limbs). Improvements in self-care, including bladder and bowel care, have also been documented.

Orthopedic surgery to relieve or reduce contracture may still be needed following SDR. Contracture surgery is delayed until the maximum improvements from SDR have been attained, typically a year or more following surgery. Some evidence indicates that earlier SDR decreases the incidence of later contracture.

As with any other spasticity treatment, SDR must be incorporated into an overall spasticity management plan. Particulary important is an ongoing physical therapy program following surgery to maximize the benefits available from the surgery.

The Surgical Treatment of Spasticity
Henry G. Chambers, MD
MF Brin, MD, editor
Muscle Nerve 1997; 20 (suppl 6): S121-S128.

Abstract: The surgical treatment of spasticity has been aimed at four different levels: the brain, the spinal cord, peripheral nerves, and the muscle. Stereotactic neurosurgery, whether involving the globus pallidum, ventrothalamic nuclei, or the cerebellum, has had little success. Cerebellar pacemakers have been tried; results have been mixed but not ultimately encouraging. Selective posterior rhizotomy is currently the most widely used and effective central nervous system procedure. Posterior rootlets in L2-S2 are exposed and tested with electrical stimulation. Those showing abnormal response are transected. Contraindications include weakness and marked fixed contracture. Neurectomy has been tried for spasticity, but the results have not been encouraging and the adverse effects may be severe. Musculoskeletal surgery remains an important procedure for treatment of contractures secondary to spasticity.

Key Points:

The surgical treatment of spasticity has been aimed at four different levels: the brain, the spinal cord, peripheral nerves, and the muscle. Each approach has its strengths and weaknesses; none of them completely eliminate spasticity

A wide range of associated problems can confound the evaluation and complicate treatment of spasticity

Stereotactic neurosurgery with temperature-controlled electrocoagulation is not currently warranted in the treatment of spasticity

Nonspecific cerebellar stimulation has no proven role in the treatment of spasticity, though further technical refinements may change this

Longitudinal myelotomy of the conus medullaris is designed to interrupt the spinal reflex arc between the anterior and posterior horns within the spinal cord. It is a technically difficult operation with significant morbidity

Selective posterior rhizotomy involves nerve roots from L2 to S2. Usually between one quarter and one half of all nerve rootlets tested are cut

Temporary, occasionally complete anesthesia or dysesthesias may occur, though these may be overcome by overlap among adjacent dermatomes

Weakness is an important contraindication to rhizotomy

The limited efficacy studies of SPR have been encouraging, though not entirely conclusive

There is little role for surgical neurectomy in spasticity management

Musculoskeletal surgery is common, though its effects on spasticity are variable and unpredictable