Rhizotomy

Rhizotomy

[rahy-zot-uh-mee]
A rhizotomy (ɹaɪˈzɑtəmi) is a neurosurgical procedure that selectively severs problematic nerve roots in the spinal cord, most often to relieve the symptoms of neuromuscular conditions such as multiple sclerosis, spastic diplegia and other forms of spastic cerebral palsy. In extreme cases, a rhizotomy may also be considered for a person suffering from severe back pain or a pinched nerve.

The sensory nerve roots are first separated from the motor ones. Identification of the nerve fibers to be cut is then made by means of electrical stimulation. The one(s) producing the pain or other problems are identified in this way, then selectively cut.

In spasticity, rhizotomy precisely identifies, targets, and destroys the damaged nerves that don’t receive gamma amino butyric acid, which is the core problem for people with spastic cerebral palsy. In this case, those nerves which, due to not receiving GABA, generate unusual electrical activity during the testing phase are considered to be the source of hypertonia, and are cut, while the remaining nerves and nerve routes carrying the correct messages remain fully intact.

Background

Dorsal rhizotomy or selective dorsal rhizotomy (SDR) is the most widely-used form of rhizotomy and is today a primary treatment for spastic diplegia, recommended to be done before any other treatment option, including orthopedic muscle-release surgery, is attempted. SDR is best done in the youngest years before deformities from spasticity take place, but in certain cases it can be performed on adults as well.

SDR is a permanent procedure that addresses the spasticity at its neuromuscular root: i.e., in the central nervous system that contains the misfiring nerves that cause the spasticity of those certain muscles in the first place. After a rhizotomy, assuming no complications, the person's spasticity is usually completely eliminated, revealing the "real" strength (or lack thereof) of the muscles underneath.

Because the muscles may have been depending on the spasticity to function, there is almost always extreme weakness after a rhizotomy, and the patient will have to work very hard to strengthen the weak muscles with intensive physical therapy, and to learn habits of movement and daily tasks in a body without the spasticity. Rhizotomy's result is fundamentally unlike orthopedic surgical procedures, where any release in spasticity is essentially temporary.

Rhizotomy is usually performed on the pediatric spastic cerebral palsy population between the ages of 2 and 6, since this is the age range where orthopedic deformities from spasticity have not yet occurred, or are minimal. Significantly older people with spastic cerebral palsy who desire rhizotomy to improve their function will either not qualify for the procedure because of the extent of their deformities, or will have to undergo rhizotomy first and follow it up closely with orthopedic surgeries to correct deformities.

St. Louis Children's Hospital has a Center for Cerebral Palsy Spasticity that is the only clinic in the world to have conducted concentrated first-hand clinical research on SDR and performed thousands of SDR surgeries, some of them on adults. It is the clinic's opinion that patients with spastic diplegia or quadriplegia should have spasticity reduced first through SDR before undergoing muscle release or tendon release procedures.

Procedural Outline

SDR begins with a 1- to 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 electromyography, 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.

Complications

There is always abnormal sensitivity and tingling of the skin on the feet and legs after SDR because of the nature of the nerves that have been worked on, but this 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.

In general, there is a combined 5-10% risk of any of the following more serious risks happening as a result of SDR.

  • Permanent paralysis of the legs and bladder
  • Permanent impotence
  • Sensory loss and/or numbness.
  • Wound infection and meningitis - usually controlled with antibiotics
  • Leakage of the spinal fluid through the wound.

A few patients in St. Louis have experienced urinary tract infections and pneumonia.

Criteria

(from St. Louis Hospital files)

Those who walk independently before SDR

After the surgery all patients who were walking independently before surgery regained the independent walking within a few weeks after surgery. Patients maintain independent walking for the long term; when some have more difficulty walking independently they may eventually need an assistive device-- however, in nearly all cases spasticity can be eliminated and the quality of independent walking improves; in many patients, physical therapy and braces become unnecessary after SDR. Orthopedic surgery is rarely required after SDR.

Those who walk with walkers or crutches before SDR

In children who are 2-7 years old and walk with a walker or crutches before SDR, independent walking after the procedure is possible. Once they have achieved independent walking, they can maintain it.

In children who are older than 7 years and walks with crutches, independent walking (inside or outside house) is possible. If they walk with walker at the age, they will most likely walk with a walker or crutches after the procedure, though it improves the quality of assisted walking and transition movements, and alleviates deformities of the legs. Many of these patients will need orthopedic surgeries after SDR.

Candidates for Rhizotomy

Not all patients with spastic cerebral palsy benefit from SDR. For those under 18 years of age, rhizotomy requires that they be:

  • At least 2 years of age
  • Diagnosis of spastic diplegia, spastic quadriplegia or spastic hemiplegia
  • Some form of independent mobility; for example, crawling or walking with or without an assistive device
  • History of premature birth; if born at full term, child must have typical signs of spastic diplegia
  • No severe damage to the basal ganglia on MRI examination
  • Potential for improvement in functional skills

For adults between 19 and 40 years of age, rhizotomy requires:

  • Diagnosis of spastic diplegia
  • History of premature birth
  • Currently ambulates independently without assistive device
  • Relatively mild fixed orthopedic deformities
  • Potential for functional gains after dorsal rhizotomy
  • Motivation to attend intensive physical therapy and perform home exercise program

On the limited number of adult spastic diplegic people treated with rhizotomy, satisfactory functional gains in adult patients are similar to those in children.

Required Circumstances

All candidates for rhizotomy must have good muscle strength in the legs and trunk. This is demonstrated by the ability to support full weight on the feet and hold a posture against gravity. There must also be evidence of adequate motor control, or the ability to make reciprocal movements for crawling or walking, and to move quickly from one posture to another. There must also be a a history of delayed motor development wherein the person has shown progression in motor development, but spasticity hampers the development of skills and/or causes gait patterns like the scissors gait. In adults, the primary requirements are that the person is able to ambulate independently, but spasticity limits energy, flexibility, walking speed and balance and sometimes causes pain/muscle spasms.

Post-Surgical Restrengthening

Most rehabilitation from SDR is done on an outpatient basis. Typical base restrengthening and restoration of full ambulatory function takes about twelve weeks of intensive physical therapy 4-5 times per week, but additional buildup and maintenance may require continued 4-5 times per week therapy as much as 6 months postoperatively and with decreasing frequency, for a total of about a year and four months after surgery.

Conditions That Preclude SDR

Individuals with CP who possess the following would most likely not be candidates for the surgery. They include those who have suffered meningitis, congenital brain infection, congenital hydrocephalus unrelated to premature birth, head trauma, or familial disease; people who have a mixed CP with predominant rigidity or dystonia, significant athetosis, or ataxia; and those who have severe scoliosis. However, as with any procedure, an individual evaluation is needed in all instances to determine eligibility.

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