Rhizotomy

A rhizotomy 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 spastic diplegia and other forms of spastic cerebral palsy.

Rhizotomy and neurotomy are becoming interchangeable terms in the treatment of chronic back pain from degenerative disc disease. In this instance, it is not a surgical procedure but one done on an outpatient basis using a simple probe to apply the radiofrequency waves to the offending (impinged) pain nerve root lying between the facet joint and the vertebral body resulting in 5-8+ months of pain relief before the nerve regenerates. The selective dorsal rhizotomy (SDR) for spastic cerebral palsy has been the main use of rhizotomy for today's neurosurgeons. In this surgery, the spasticity-causing nerves are isolated and then targeted and destroyed. The sensory nerve roots, where spasticity is located, are first separated from the motor ones, and the nerve fibres to be cut are then identified via electromyographic stimulation. The one(s) producing spasticity are then selectively lesioned with tiny electrical pulses.

In spasticity, rhizotomy 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, best done in the youngest years before bone/joint deformities from the pull of spasticity take place, but it can be performed safely and effectively 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. However, recent cases of successful SDR procedures among those with spastic diplegia across all major age ranges (years 3-40) has finally proven its universal effectiveness and safety regardless of the age of the spastic diplegic patient.

Although the concept of rhizotomy was conceived, tested and first reported in 1913 by Foerster, it was not in wide use for the treatment of spasticity until the last quarter of the 20th Century. Dr. Warwick Peacock of South Africa helped to begin the modern era of rhizotomy procedure in the early 1980s, and soon trained many other neurosurgeons in his technique; both Peacock and these other surgeons then went on to develop the procedure further using both their own intellectual refinements and refinements in medical equipment and technology that occurred from the 1980s through the 2000s.

Today, St. Louis Children's Hospital in St. Louis, Missouri has a "Center for Cerebral Palsy Spasticity" that is the only internationally-known clinic in the world to have conducted concentrated first-hand clinical research on SDR over an extended period. Its chief neurosurgeon in the field, Doctor T.S. Park (who was initially trained by Dr. Peacock), has performed thousands of SDR surgeries, some of them on adults, and is the originator of the L1-laminectomy modification to the SDR surgery in 1991, which sections the first dorsal root and enables the removal of significantly less spine-bone than in surgeries performed before 1991, as well as inherent release of the hip flexor muscles specifically as a result of that particular sectioning (prior to that, total hip flexor release was not necessarily possible). That L1-laminectomy modification has since become the standard, and SLCH has become internationally known as a major provider of the SDR surgery to those in need of it (for example, it is one of the first Google search results when inputting the word string "selective dorsal rhizotomy"). It is this 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, and other surgeons today share this view. A major qualifier in the cases taken on at SLCH, however, is that all of its adults have had only mild cases of spastic diplegia.

In September 2008, a ground-breaking SDR was performed that 'closed the gap' on concerns regarding age of the patient in SDR: Columbia-Presbyterian Children's Hospital's Richard C.E. Anderson performed an SDR surgery on a 28-year-old male with moderate spastic diplegia, which by the patient's own report has reduced his muscle tone nearly to the level of a "normal" person and enabled him to walk and exercise much more efficiently; also, Dr. Anderson in the past performed an SDR on a 16-year-old wheelchair-using female with severe spastic diplegia. Reportedly, that particular SDR enabled the young woman to ambulate, whereas before the surgery, she was too tight to do so.

Procedural outline
SDR begins with a 1- to 2-inch incision along the center of the lower back just above the waist. An L1 laminectomy is then performed: a section of the spine's bone, the spinous processes together with a portion of the lamina, are removed, like a drain-cap, to expose the spinal cord and spinal nerves underneath. 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 then placed to separate the motor from the sensory nerves. The sensory nerve roots, each of which will be tested and selectively eliminated, are placed on top of the pad, while the motor nerves are 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 corresponding elimination 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 typically now closed with glue, but there are sometimes stitches to be removed from the back after 3 weeks. The surgery takes approximately 4 hours and typically involves one neurosurgeon, one anesthesiologist, and possibly an assortment of assisting physicians (as in the New York City September 2008 case). The patient then goes to the recovery room for 1–2 hours before being transferred to the intensive care unit overnight. Transfer from the ICU to a recovery room in the hospital is then done to enable direct post-surgical observation by the neurosurgeon and surgical team, but this usually lasts only about 3 days, during which the team performs range-of-motion tests that they record and compare to pre-surgery levels. After that short period, the patient, depending on circumstances and appropriateness, is either transferred to inpatient recovery or is linked to an intense outpatient exercise program and discharged from the hospital.

According to clinicians, it usually takes about one year from the date of surgery to achieve maximum results from SDR. However, videos from St. Louis Children's Hospital website have shown continued marked improvement as much as 5 years post-surgery, and presumably, if the person keeps exercising intensely, potential for continued improvement and strengthening is, just as in a person born with normal muscle tone and range of motion, unlimited.

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.

If a certain degree of permanent numbness remains in certain leg-muscles, such as the quadriceps, ankles, and feet, this is usually not enough to prevent feeling and sensation, sensing of changes in temperature or pressure, etc. The affected muscle-areas simply feel less than before, and the trade-off in ease of movement is said to be immensely worth this change, should it occur.

In general, there is a combined 5-10% risk of any of the following more serious risks happening as a result of SDR. Because of technological advances in both the technology used in the surgery and also in the procedure itself, there have been no major cases of SDR that have had these side-effects.


 * Permanent paralysis of the legs and bladder.
 * Permanent impotence
 * Sensory loss and/or numbness that is severe enough to not feel anything any more in the legs (not paralysis; movement is retained)
 * Wound infection and meningitis - usually controlled with antibiotics
 * Leakage of the spinal fluid through the wound, also repairable; the surgical team watches very closely post-surgery for this

A few patients in St. Louis experienced urinary tract infections and pneumonia, but these were successfully treated.

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
 * No fixed orthopedic deformities that either prevent current walking or would prevent walking after SDR; in these cases orthopedic releases are to be done first, after which SDR can be discussed.
 * Potential for functional gains after SDR
 * Intense 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. There must also be evidence of adequate motor control, or the ability to make reciprocal movements for crawling or walking, and to move reasonably quickly from one posture to another. Chiefly, pediatric rhizotomy candidates are people with CP who have shown age-appropriate 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.

Conditions that preclude SDR
There are a few clinical situations in which it is likely that someone may not be a candidates for the surgery. These situations include those who have suffered meningitis, a congenital (birth-originating) brain infection, congenital hydrocephalus unrelated to the person's premature birth, a person who has suffered head trauma, or a person with some sort of familial disease (e.g., those with hereditary spastic paraplegia are said to not be SDR candidates). Also precluded are people who have a "mixed" CP with predominant rigidity or dystonia, significant athetosis, or ataxia; and those who have very severe scoliosis. However, as with any procedure, an individual evaluation is needed in all instances to determine eligibility.

Post-surgical restrengthening
Most rehabilitation from SDR is done on an outpatient basis, though it may also include an initial several-week inpatient component (but typically does not). Typical base restrengthening and restoration of full ambulatory function takes about twelve weeks (3 months) of intensive physical therapy 4-5 times per week, but subsequent buildup and maintenance beyond that initial several-week period is just as necessary, and may require continued 4-5 times per week therapy as much as 6 months postoperatively, for a total of about a year and four months after surgery in order to achieve maximum basic functionary movement from the surgery. Beyond that point, any continued strengthening is, as with any person's exercise regimen, undertaken strictly by the individual's own choice and direction.