A rhizotomy (//ry-ZOT-ə-mee) is a term chiefly referring to a neurosurgical procedure that selectively destroys 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 selective dorsal rhizotomy (SDR) for spastic cerebral palsy has been the main use of rhizotomy for neurosurgeons specialising in spastic CP since the 1980s; in this surgery, the spasticity-causing nerves are isolated and then targeted and destroyed. The sensory nerve roots, where spasticity is located, are first separated from the motor ones, and the nerve fibres to be cut are then identified via electromyographic stimulation. The ones producing spasticity are then selectively lesioned with tiny electrical pulses.
In spasticity, rhizotomy precisely 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. These over-firing, non-GABA-absorbing nerves generate unusual electrical activity during the EMG testing phase in SDR and are thus considered to be the source of the patient's hypertonia; they are eliminated with the electrical pulses once identified, while the remaining nerves and nerve routes carrying the correct messages remain fully intact and untouched. This means that the spasticity is permanently dissolved, and that this is done without affecting nervous system sensitivity or function in other areas, because the only nerves destroyed are the over-firing ones responsible for the muscle tightness.
The terms rhizotomy and neurotomy are also increasingly becoming interchangeable in the treatment of chronic back pain from degenerative disc disease. This is a procedure called a facet rhizotomy and is not a surgical procedure but is instead done on an outpatient basis using a simple probe to apply radiofrequency waves to the impinged pain-causing nerve root lying between the facet joint and the vertebral body. Such radio frequency nerve lesioning results in five to eight or more months of pain relief before the nerve regenerates and another round of the procedure needs to be performed. A facet rhizotomy is just one of many different forms of radiofrequency ablation, and its use of the "rhizotomy" name should not be confused with the SDR procedure.