A selective dorsal rhizotomy (SDR), also known as a rhizotomy, dorsal rhizotomy, or a selective posterior rhizotomy, is a neurosurgical procedure that selectively cut problematic nerve roots of the spinal cord. This procedure has been well-established in the literature as a surgical intervention and is used to relieve negative symptoms of neuromuscular conditions such as spastic diplegia and other forms of spastic cerebral palsy. The specific sensory nerves inducing spasticity are identified using electromyographic (EMG) stimulation and graded on a scale of 1 (mild) to 4 (severe spasticity). Abnormal nerve responses (usually graded a 3 or 4) are isolated and cut, thereby reducing symptoms of spasticity.
Spasticity is defined as a velocity-dependent increase in muscle tone in response to a stretch. This upper motor neuron condition results from a lack of descending input from the brain that would normally release the inhibitory neurotransmitter gamma amino butyric acid (GABA), which serves to dampen neuronal excitability in the nervous system. Spasticity is thought to be caused by an excessive increase of excitatory signals from sensory nerves without proper inhibition by GABA. Two common conditions associated with this lack of descending input are cerebral palsy and acquired brain injury.
Background
Selective dorsal rhizotomy (SDR), less often referred to as selective posterior rhizotomy (SPR), is the most widely used form of rhizotomy, and is today a primary treatment for spastic diplegia, best done in the youngest years before bone and joint deformities from the pull of spasticity take place. Still, it can be performed safely and effectively 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 particular muscles in the first place. After SDR, the person's spasticity is usually eliminated, revealing the "real" strength (or lack thereof) of the muscles underneath. SDR's result is fundamentally unlike orthopedic surgical procedures, where spasticity is left untreated.
Because there is always temporary weakness after SDR, patients should work hard to strengthen the weak muscles with physical therapy and learn habits of movement and daily tasks in a body without spasticity.
SDR is usually performed on the pediatric spastic cerebral palsy population between the ages of 2 and 6. This is the age range where orthopedic deformities from spasticity have not yet occurred or are minimal. It is also variously claimed by clinicians that another advantage of doing the surgery so young is that it is inherently easier for these young children to restrengthen their muscles and to re-learn how to walk, often having the effect that later in life, they do not even remember the period when they lived with the spasticity at all. However, recent cases of successful SDR procedures among those with spastic diplegia across all age ranges (years 3–50) have proven its universal effectiveness and safety regardless of the age of the spastic diplegic patient. A counter-argument against the prevailing view concerning the younger years is that it may actually be quicker and easier to restrengthen an older patient's musculature, and regaining walking may happen faster with an older patient because the patient is fully matured and very aware of what is going on, and so may work harder and with more focus than might a young child. These two schools of thought have equally objectively valid bases for their formation and, thus, are each defended quite intensely by their respective proponents.
History
In 1913 Otfrid Foerster in Germany reported the results of dorsal root rhizotomy on patients with spastic cerebral palsy. Rhizotomy for spasticity purposes did indeed then proceed to take about a fifty-year hiatus. In 1967 Claude Gros and his colleagues at the neurosurgical hospital (CHU Gui de Chauliac) in Montpellier resurrected posterior rhizotomy for spasticity. Fasano of Italy in 1978 introduced 'selective' posterior rootlet rhizotomy for cerebral palsy patients and Warwick Peacock developed the Gros technique in Cape Town, South Africa, by exposing the cauda equina, rather than at the spinal cord level. Peacock moved to Los Angeles in 1986 and began widely campaigning for SDR's viability in cerebral palsy spasticity relief. Peacock and the surgeons he subsequently trained developed the procedure further using their own clinical-intellectual refinements and refinements in medical equipment and technology that occurred from the 1980s through the 2000s (decade).