A selective dorsal rhizotomy (SDR), also known as a rhizotomy, dorsal rhizotomy, or a selective posterior rhizotomy, is a neurosurgical procedure that selectively cuts problematic nerve roots in the spinal cord. This procedure has been well-established in the literature as a surgical intervention and is used to relieve negative symptoms of neuromuscular conditions such as spastic diplegia and other forms of spastic cerebral palsy. The specific sensory nerves inducing spasticity are identified using electromyographic (EMG) stimulation and graded on a scale of 1 (mild) to 4 (severe spasticity). Abnormal nerve responses (usually graded a 3 or 4) are isolated and cut, thereby reducing symptoms of spasticity.
Spasticity is defined as a velocity-dependent increase in muscle tone in response to a stretch. This upper motor neuron condition results from a lack of descending input from the brain that would normally release the inhibitory neurotransmitter gamma amino butyric acid (GABA), which serves to dampen neuronal excitability in the nervous system. Spasticity is thought to be caused by an excessive increase of excitatory signals from sensory nerves without proper inhibition by GABA. Two common conditions associated with this lack of descending input are cerebral palsy and acquired brain injury.
Background
Selective dorsal rhizotomy (SDR), less often referred to as selective posterior rhizotomy (SPR), 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 and joint deformities from the pull of spasticity take place. Still, 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 particular muscles in the first place. After SDR, the person's spasticity is usually eliminated, revealing the "real" strength (or lack thereof) of the muscles underneath. SDR's result is fundamentally unlike orthopedic surgical procedures, where spasticity is left untreated.
Because there is always temporary weakness after SDR, patients should work hard to strengthen the weak muscles with physical therapy and learn habits of movement and daily tasks in a body without spasticity.
SDR is usually performed on the pediatric spastic cerebral palsy population between the ages of 2 and 6. This is the age range where orthopedic deformities from spasticity have not yet occurred or are minimal. It is also variously claimed by clinicians that another advantage of doing the surgery so young is that it is inherently easier for these young children to restrengthen their muscles and to re-learn how to walk, often having the effect that later in life, they do not even remember the period when they lived with the spasticity at all. However, recent cases of successful SDR procedures among those with spastic diplegia across all age ranges (years 3–50) have proven its universal effectiveness and safety regardless of the age of the spastic diplegic patient. A counter-argument against the prevailing view concerning the younger years is that it may actually be quicker and easier to restrengthen an older patient's musculature, and regaining walking may happen faster with an older patient because the patient is fully matured and very aware of what is going on, and so may work harder and with more focus than might a young child. These two schools of thought have equally objectively valid bases for their formation and, thus, are each defended quite intensely by their respective proponents.
History
In 1913 Otfrid Foerster in Germany reported the results of dorsal root rhizotomy on patients with spastic cerebral palsy. Rhizotomy for spasticity purposes did indeed then proceed to take about a fifty-year hiatus. In 1967 Claude Gros and his colleagues at the neurosurgical hospital (CHU Gui de Chauliac) in Montpellier resurrected posterior rhizotomy for spasticity. Fasano of Italy in 1978 introduced 'selective' posterior rootlet rhizotomy for cerebral palsy patients and Warwick Peacock developed the Gros technique in Cape Town, South Africa, by exposing the cauda equina, rather than at the spinal cord level. Peacock moved to Los Angeles in 1986 and began widely campaigning for SDR's viability in cerebral palsy spasticity relief. Peacock and the surgeons he subsequently trained developed the procedure further using their own clinical-intellectual refinements and refinements in medical equipment and technology that occurred from the 1980s through the 2000s (decade).
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 Peacock), has performed over five thousand SDR surgeries since 1987, some of them on adults, and is the originator of the L1-single-level 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 the 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 method, and SLCH has become internationally known as a major provider of SDR surgery to those in need. This clinic believes that patients with spastic diplegia, hemiplegia, or quadriplegia should have spasticity reduced first through SDR before undergoing muscle 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 relativelymild cases of spastic diplegia.
In September 2008, 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, 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. In 2011, Anderson reported that another 16-year-old patient of his was considering undergoing the rhizotomy, but that patient subsequently decided to put her decision on hold . And in July 2011, after offering her several months of consultation, the medical team at the Continuing Care department of Gillette Children's Specialty Healthcare performed an SDR procedure on a local young-adult Minnesota resident.Meanwhile, many countries such as the United Kingdom, Russia, and China adopted the dorsal rhizotomy to treat spastic cerebral palsy.
Medical uses
Not all people with spastic cerebral palsy benefit from SDR. For those under 18 years of age, rhizotomy requires that they be: At least two years of age Diagnosis of spastic diplegia, spastic triplegia, 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 cerebral palsy No severe damage to the basal ganglia on MRI examination Potential for improvement in functional skills
For adults between 19 and 50 years of age, rhizotomy requires: Diagnosis of spastic diplegia and hemiplegia. History of premature birth Currently can ambulate independently. No fixed orthopedic deformities that either prevent current walking or would prevent walking after SDR. Potential for functional gains after SDR. Motivated to attend physical therapy and perform home exercise program.
Long-term effects The long-term effects of SDR have been reported. Selective dorsal rhizotomy surgery has been performed routinely over the past several decades on children with spastic cerebral palsy, and the accumulated evidence indicates positive long-term outcomes.
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. Still, spasticity hampers the development of skills and/or causes gait patterns like the scissors gait. In adults, the primary requirements are that the person be able to ambulate independently, but spasticity limits energy, flexibility, walking speed, and balance and sometimes causes pain/muscle spasms.
Criteria The criteria for patient eligibility from the St. Louis Children's Hospital are:
Walk independently
After the surgery, all patients walking independently before surgery regained independent walking within a few weeks after surgery. Patients maintain independent walking for the long term; when others have more difficulty walking independently they may eventually need an assistive device. In nearly all cases, spasticity can be eliminated and the quality of independent walking improves; however, physical therapy and braces become unnecessary after SDR. Orthopedic surgery is rarely required after SDR.
Walk with walkers or crutches
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 walk 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.
Contraindications There are a few clinical situations in which someone is not likely to be a suitable candidate for the surgery. These include those who have had meningitis, a congenital (birth-originating) brain infection, congenital hydrocephalus unrelated to premature birth, head trauma, or certain familial diseases. Also precluded are people who have a "mixed" CP with predominant dystonia, and those who have severe scoliosis. However, as with any procedure, an individual evaluation is needed to determine eligibility.
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.