Selective Dorsal Rhizotomy (SDR) has become accepted as a neurosurgical procedure for the treatment of spasticity associated with cerebral palsy and lower limb spasticity.

It involves the irreversible selective division of dorsal (sensory) rootlets as they emerge from the conus medullaris of the spinal cord.  These nerve roots make up the afferent (input) limb of the reflex arc that is exaggerated in spasticity.  The procedure takes place under general anaesthesia using intra-operative neurophysiology.

It is performed through a L1 (or L2) to S1 laminectomy or laminoplasty, or more recently (as practiced in Scotland) through a single level laminectomy at the position of the conus, as determined by intra-operative x-rays and confirmed by ultrasound.

There is close communication between the surgical team and a neurophysiology team during the procedure to map each sensory nerve root to its corresponding motor level and then test the motor response to stimulation.  The teams select the most abnormal 50 to 70 percent of nerve roots (those with the most exaggerated responses) at each level for division.  All motor nerve roots are preserved.

Cerebral palsy describes a group of permanent brain disorders originating during fetal development, birth or early childhood. It is associated with abnormalities of movement, balance and posture. The prevalence of cerebral palsy in developed countries is stable at around 2/1000 live births. Approximately 40% of cerebral palsy cases are children who have been born prematurely. Considering the breakdown of cerebral palsy subtypes; around 75% of children will have a predominantly spastic muscle tone of which one third will have a diplegic pattern (bilateral lower limb predominant).

Children who are born prematurely and have a very low birth weight (<1500g) are predisposed to periventricular leukomalacia (PVL) and germinal matrix haemorrhage, with post-haemorrhagic ventricular dilation. As the periventricular white matter is particularly susceptible to injury between 26 and 34 weeks of gestation, the leg fibres are predominantly affected.

Although the injury to the central nervous system is static, the clinical expression of cerebral palsy evolves as children grow.

Spasticity causes significant discomfort and stiffness, and associated spasms that cause pain and interfere with function. Growth during childhood, in the presence of spasticity, results in muscle shortening and contractures involving both tendon and soft tissues. In children, spasticity affects muscle growth and torsional abnormalities of the long bones, joint instability and premature degeneration.

Spasticity in cerebral palsy can make life very challenging for many children and may make caring responsibilities difficult for their parents and carers.