Spasiticty is the most common movement disorder in children with cerebral palsy. The incidence remains at approximately 1.2 to 2.5 per 1000 children at early school age and there has been no decline in the incidence of cerebral palsy despite improved medical care, suggesting that birth asphyxia has a less prominent role in the causation of cerebral palsy than was previously thought.
There is a wide plethora of treatment options for spasticity in cerebral palsy, both medical and surgical, as well as interventions such as physiotherapy. New medical modalities include intrathecal baclofen (infused into the thecal sac through a programmable pump) and botolinium toxin injections given to temporary paralyze the spastic muscles. The surgical procedures that have been used include cerebellar stimulation, dorsal entry root lesioning, rhizotomies (sectioning of nerves, both motor and/or sensory), and orthopaedic procedures such as tendon lengthening or transfers.
Neurosurgical treatment today is generally limited to selective dorsal rhizotomy (SDR), the implantation of baclofen pumps for intrathecal baclofen infusion and focal or open neurectomies e.g tibial neurectomy.
Complete dorsal rhizotomies, i.e. completely sectioning the dorsal (sensory) nerve roots were done in the early 1900s to treat spasticity. These procedures were effective as complete dorsal rhizotomy effectively cuts out the stimuli from the afferent 1A action potentials on the interneuronal pool (in the spinal cord) which activates the stretch reflexes and which are normally modulated by the descending tracts. The loss of these modulating effects in cerebral palsy results in an overall decrease in inhibition in the activities of the alpha motor neuron. However, complete sensory deafferentation gave rise to complications such as sensory ataxia and decubitus ulcers in hypoasthetic areas
The procedure evolved over the years and today, during selective dorsal rhizotomy (as the operation has come to be known), a lumbar laminotomy is done to expose the L2 to S1 nerve roots bilaterally. The dorsal nerve roots of L2 to S1 are indentified using electrophysiology and divided into six to eight rootlets. The extent of dorsal root sectioning (usually between 40-60%) is guided by electrophysiological monitoring and clinical assessment intra-operatively. Following surgery, the loss of tone in the lower limbs is readily appreciated and intense physiotherapy is given to retrain the musculature and gait.
SDR is not suitable for all patients with cerebral palsy. It reduces only spasiticity and does not treat other movements disorders in CP such as dystonia or athetosis. Careful selection of patients is important to ensure a successful outcome. Patients likely to have good outcome from SDR include children less than 6 years old with diplegic or quadriplegic cerebral palsy with adequate muscle strength in the lower limbs and trunk, reasonable cognition (to understand the rigors of physiotherapy), no lower limb abnormalites or previous orthopaedic procedures and who have good parental support. This list is not exhaustive and selection is usually done by a team comprising the physiotherapist, paediatric neurologist, neurosurgeon, orthopaedic surgeon in the setting of a combined cerebral palsy clinic.
Three recently published randomised controlled trials1,2,3 and a meta-analysis of these trials4, have shown that selective dorsal rhizotomy, qualitatively and quantitatively, reduced spasticity in children with cerebral palsy. These trials (Class 1 evidence) showed that selective dorsal rhizotomy reduced spasticity, improved range of movements and strength and improved functional limitations in children who underwent the operation. There are other studies (Class 2 evidence) in the literature showing improved disability, and improvements in upper limbs and cognitive function in children following SDR5. In contrast, there is only Class 2 evidence for improvement of impairment following intrathecal baclofen but no evidence in the literature on functional improvement or disability6.
References
1. Steinbok P, Reiner AM, Beauchamp RD, Armstrong RW, Cochrane DD, Kestle J. (1997) A randomized clinical trial to compare selective posterior rhizotomy plus physiotherapy with physiotherapy alone in children with spastic diplegic cerebral palsy. Developmental Medicine & Child Neurology 39: 178-84
2. McLaughlin JF, Graubert C, Hays RM, Roberts TS, Price R, Temkin N. (1998) Selective dorsal rhizotomy: efficacy and safety in an investigator-masked randomized clinical trial. Developmental Medicine & Child Neurology 40: 220-32
3. Wright FV, Sheil EM, Drake JM, Wedge JH, Naumann S. (1998) Evaluation of selective dorsal rhizotomy for the reduction of spasticity in cerebral palsy: a randomized controlled trial. Developmental Medicine & Child Neurology 40: 239-47
4. McLaughlin J, Bjornson K, Temkin N, Steinbok P, Wright V, Reiner A, Roberts T, Drake J, O’Donnell M, Rosenbaum P, Barber J, Ferrel A. (2002) Selective dorsal rhizotomy: meta-analysis of three randomized controlled trials. Developmental Medicine & Child Neurology 44: 17-25
5. Loewen P, Steinbok P, Holsti L, MacKay M. (1998) Upper extremity performance and self-care skill changes in children with cerebral palsy following selective posterior rhizotomy. Pediatric Neurosurgery 29: 191-8
6. Gerszten PC, Albright AL, Barry MJ. (1997) Effect of ambulation of continuous intrathecal baclofen infusion. Pediatric Neurosurgery 27:40-44