Selective Dorsal Rhizotomy (SDR)

Selective dorsal rhizotomy (SDR) is a neurosurgical procedure that reduces spasticity, most often in the legs, by permanently dividing a portion of the abnormal sensory nerve fibers that contribute to it. It is most commonly considered for children with spastic diplegic cerebral palsy, a form of cerebral palsy that mainly affects the legs, although careful assessment determines whether it is appropriate in each case.

Muscle tone is normally regulated by a feedback loop: sensory nerves carry information from the muscles to the spinal cord, and this information helps determine how much the muscle contracts. In spasticity, this feedback loop becomes overactive, so that sensory signals trigger an exaggerated and sustained muscle contraction. SDR aims to reduce this overactivity at its source, in the sensory nerve rootlets themselves, rather than only treating its effect on the muscle.

During surgery, the sensory (dorsal) nerve rootlets at the lower spinal cord are exposed and divided into smaller fibers. Using intraoperative electrical testing, the surgical team identifies which fibers are producing an abnormal response, one associated with spasticity rather than normal sensation, and selectively divides a proportion of these abnormal fibers while preserving the rest. This selective approach is intended to reduce spasticity while limiting the effect on normal sensation and strength.

SDR is not appropriate for every patient with spasticity. Careful patient selection is one of the most important factors in achieving a good outcome. Patients most commonly considered for SDR typically have:

• Spastic diplegia (spasticity mainly affecting the legs), most often related to cerebral palsy
• Spasticity that is the main factor limiting movement, rather than significant fixed contractures, weakness, or difficulties with movement coordination (dystonia or ataxia)
• Sufficient underlying strength and motor control to be able to use the reduction in spasticity functionally
• A realistic ability to participate in the intensive physiotherapy program that follows surgery

SDR is generally not recommended for patients whose spasticity is not the main limiting factor, whose movement difficulties are dominated by weakness, dystonia or poor selective motor control, or who would not be able to undertake structured post-operative rehabilitation.

A surgical evaluation for SDR is typically considered when spasticity in the legs is significantly limiting walking, positioning, comfort or care, despite appropriate use of physical therapy, bracing, oral medication and, where tried, botulinum toxin injections. The importance of careful patient selection cannot be overstated: SDR produces a permanent reduction in spasticity, so it is offered only after thorough multidisciplinary assessment confirms that a patient’s overall movement pattern is likely to benefit from reduced spasticity specifically, rather than from other aspects of their condition.

Surgery is performed under general anesthesia. Through an opening at the lower spine, the surgical team identifies the dorsal (sensory) nerve rootlets supplying the legs, tests each one using intraoperative electrical stimulation, and selectively divides the rootlets showing an abnormal response, guided by continuous neurophysiological monitoring throughout the procedure.

Assessment before SDR is multidisciplinary and typically includes:

• Detailed gait analysis and standardized spasticity and function scoring
• Neurological examination to distinguish spasticity from weakness, dystonia or ataxia
• Assessment of selective motor control and underlying strength
• Physiotherapy assessment of current function and rehabilitation potential
• MRI of the spine for surgical planning
• Discussion with the family (for pediatric patients) about the intensity of post-operative rehabilitation required

SDR aims to produce a durable reduction in lower-limb spasticity. Depending on the individual patient’s underlying strength and motor control, this may translate into improved ease of movement, a more efficient walking pattern, easier positioning and transfers, reduced pain, and easier caregiving. Treatment goals vary between patients: for a child with good underlying strength, the goal may be improved walking efficiency, while for a child who does not walk independently, the goal may be improved comfort, positioning and ease of care. SDR is not presented as a treatment that restores normal movement, and outcomes depend heavily on the rehabilitation that follows.

SDR is major spinal surgery and carries risks including infection, cerebrospinal fluid leak, temporary or, rarely, persistent changes in sensation, bladder or bowel function, and changes in muscle strength. Because the reduction in spasticity is permanent, it is not adjustable in the way that medication or a programmable device would be. SDR does not correct fixed joint contractures that may already be present, which may still require orthopedic treatment separately. SDR is not appropriate for every patient with spasticity, and it does not replace the need for ongoing physical therapy.

Intensive physiotherapy is not an optional add-on after SDR; it is central to the result. In the weeks and months after surgery, muscles that are no longer held tight by spasticity need to be actively strengthened and retrained, and a structured rehabilitation program is planned in advance of surgery, not arranged afterward. Recovery and functional improvement typically continue over an extended period following surgery, with regular follow-up to track progress and adjust the rehabilitation plan.