Selective Dorsal Rhizotomy (SDR)

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.

The sensory nerve roots are first separated from the motor ones. Identification of the nerve fibres 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, and 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.


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 orthopaedic 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 orthopaedic surgical procedures, where any release in spasticity is essentially temporary.

Rhizotomy is usually performed on the paediatric spastic cerebral palsy population between the ages of 2 and 6, since this is the age range where orthopaedic 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 orthopaedic surgeries to correct deformities.

St. Louis Children’s Hospital has a Centre 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.

Further Information

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