Maximizing the Benefit of Selective Dorsal Rhizotomy
A multidisciplinary team approach and patient selection are key to achieving best outcomes for cerebral palsy patients who undergo surgery to reduce muscle spasticity.
Having deep experience in performing surgery to reduce spasticity and improve motor function in children with cerebral palsy (CP), says Johns Hopkins pediatric neurosurgeon Shenandoah Robinson, does reduce the risk of complications and increase the likelihood of a good outcome. Robinson should know—she’s been doing the procedure for 15 years now. But what makes as much of a difference in achieving the goal of the child being able to walk independently, she adds, is a multidisciplinary team approach and patient selection.
“Outcomes are greatly influenced by having the resources of a team of pediatric neurosurgeons and neurologists, anesthesiologists, intensivists, orthopaedic surgeons and physiatrists, which we’re fortunate to have,” says Robinson. “Screening for patients and families who are committed to intensive physical therapy for up to a year following the surgery is also paramount.”
In the surgery, called selective dorsal rhizotomy (SDR), Robinson divides certain sensory nerve fibers entering the spinal cord from leg muscles, interrupting the abnormal circuit of nerve impulses in patients with CP that result in high muscle tone and spasticity. These patients, Robinson explains, lack inhibitory signals from the brain to dampen this feedback loop.
“So we cut a fraction of the sensory nerve roots to help restore the feedback loop into a more normal range and give patients more selective control of their muscles,” Robinson says.
Before cutting these nerve roots, however, Robinson, with the aid of a microscope, separates bowel, bladder and motor nerve roots to protect them. Each nerve root is electrically stimulated to ensure its correct identification, which is critical.
In another innovation, Robinson also uses a minimally invasive approach to minimize the removal of lamina covering spinal vertebrae. In traditional approaches, neurosurgeons have had to remove multiple pieces of bone to expose the spinal cord and nerves.
“In the older, more open technique, we would have to take out multiple levels of lamina to make a larger bone window,” says Robinson.
But what happens before and after the surgery also greatly influences outcomes. In evaluating patients for surgery, the multidisciplinary team conducts gait and motion analysis using sophisticated imaging, video and computer technology to capture movement patterns and the amount of energy patients use when walking and moving. Physical therapists assess patients’ range of motion, strength and their ability to participate in therapy. Orthopaedists like Ranjit Varghese assess how spasticity affects bones, muscles and body movement.
“For the child with spasticity, we do data analysis to measure where each of the joints and muscles is in space and time,” says Varghese. “That way we can evaluate both their orthopaedic and spasticity issues.”
In evaluating patients for the surgery, Robinson has found that children 3 to 10 years old who have good strength, are motivated to be more mobile and have strong family support tend to have the best outcomes.
“An ideal candidate might be the 4- or 5-year-old who has a hard time getting up but makes the connection that if he works hard in therapy maybe he can walk better and run with his siblings,” says Robinson. “They have to be cognitively mature enough to cooperate with the intensive therapy requirements afterward. A piece of that is the family commitment to therapy, too.”
There are also anesthetic considerations for children undergoing SDR surgery. Preoperatively, patients undergo a thorough assessment of their past medical history, including cardiac, gastrointestinal, neurologic and pulmonary systems. Additionally, while analgesics and antispasmodics are administered intra-operatively to preempt pain and muscle spasms post-operatively, muscle relaxants are not administered during electromyogram monitoring of muscles stimulated during the procedure.
“For children with cerebral palsy, other anesthetic considerations include cautious airway management, especially for patients with a history of gastroesophageal reflux, maintaining normothermia, and seizure management,” says Jessica George, who heads the Division of Pediatric Anesthesia’s enhanced recovery team.
After the four-hour surgery, patients may report their legs feel different and, in some cases, weaker—a consequence of losing their abnormal muscle tone in the surgery. But as spasticity is reduced, patients find it easier to increase their strength with therapy and exercise.
“Once you remove some of the abnormal tone, weakness may present itself, but that means you have the opportunity as a therapist to actually help strengthen muscles,” says Susan Dubroff, director of rehabilitation services at Mt. Washington Pediatric Hospital. “A high intensity of therapy is very important.”
In that regard, Robinson notes that her patients benefit from the Johns Hopkins Children’s Center’s close relationship with Mt. Washington Pediatric Hospital and the Kennedy Krieger Institute, both recognized for their pediatric physical therapy and brain injury rehabilitation programs.
“Our goal is to get these kids to be as normal as possible and to maintain that as they enter young adulthood and go off to college,” says Robinson.
For patients who still have problems with bone and joint alignment a year or more following SDR, Varghese offers single-event multilevel surgery to correct all remaining soft tissue and bone problems in one operation. Other spasticity treatments include oral medications and an intrathecal baclofen pump, an implanted drug delivery system. But SDR, he adds, is the biggest game changer for these patients.
“If SDR is done, it is life changing in that it takes the tone away and reduces the risk of future surgeries,” says Varghese. “But the biggest challenge in the surgery is patient selection. It is not easy to pick the kids who will benefit the most.”
For patients recommended to have the surgery, the multidisciplinary team follows a clinical pathway from the pre-operative visit through discharge to an intensive physical therapy program. Click here to learn more about spasticity treatments offered at the Johns Hopkins Children’s Center. To make an appointment, please call 410-955-7337.