Rhizotomy

A rhizotomy (rī-zŏt'ə-mē) is a neurosurgery that selectively severs problematic nerve roots in the spinal cord, most often to relieve the symptoms of neuromuscular conditions such as multiple sclerosis, spastic diplegia and other forms of spastic cerebral palsy. In extreme cases, a rhizotomy may also be considered for a person suffering from severe back pain or a pinched nerve. 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, 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 those producing too much muscle tone, and are cut, while the remaining nerves and nerve routes carrying the correct messages remain fully intact.

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Background

Chiefly, rhizotomy (also called dorsal rhizotomy, selective dorsal rhizotomy, and selective posterior rhizotomy) is a treatment for spasticity in cerebral palsy when the spasticity has proven unresponsive to less invasive procedures such as drug injections (baclofen, botox, phenol), orthaepedic muscle-release surgeries, or similar methods.

It 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, the patient that had suffered from severe muscle spasticity will be significantly less tight, have more range of motion and more fluidity in motion, and will never have to worry about the same muscles tightening up again, as they may have before the procedure.

This result is fundamentally unlike orthaepedic surgical procedures, where any release in spasticity is essentially temporary most of the time.

Types of Rhizotomies

Selective Posterior

Selective Posterior Rhizotomy requires that anesthesia be given in a manner that preserves the ability to elicit muscle contraction by stimulation of the sensory rootlets. The preferred site for performing a selective posterior rhizotomy is currently the lower spine between the bottom of the rib cage and the top of the hips, since it affords a secure identification of the roots at the point of exit from the spinal canal. The evolution of the current rhizotomy technique has been toward saving some of the sensory nerves, thus avoiding the side effects seen earlier in this century. The sensory nerve roots are separated from the motor ones and stimulated electrically; leg muscles are observed for contraction both by a clinical examiner and by EMG (an electrical device which records muscle contraction). Roots that cause abnormal muscle contraction are separated into their component rootlets which in turn are stimulated. Abnormally responding rootlets are cut. Sensory deprivation is usually not a problem with today's rhizotomies.

Percutaneous Retrogasserian Glycerol

The Department of Neurological Surgery at the University of Pittsburgh in Pennsylvania performed percutaneous retrogasserian glycerol rhizotomy (PRGR) over an 11-year interval on 53 patients with typical trigeminal neuralgia associated with multiple sclerosis. All patients had failed extensive medical trials prior to PRGR. Long-term follow-up — the median was 36 months — showed complete pain relief, i.e. where no further medication was needed, achieved in 29 of 49 evaluable patients, meaning a success rate of 59%. Eight patients, or 16%, had satisfactory pain control but required occasional medication, while twelve patients (25%) had initial unsatisfactory results with inadequate pain relief. Of the whole sample, nine patients underwent alternative surgical procedures. Sixteen patients (30%) subsequently required another glycerol rhizotomy to re-achieve pain control. Twenty-seven patients (60% of 45 patients evaluated for this finding) retained normal trigeminal sensation after injection. Major trigeminal sensory loss developed in a single patient who had four glycerol rhizotomies over a 25-month interval. No patient developed deafferentation pain. The Department concluded that PRGR is a low-morbidity, effective, and repeatable surgical procedure for the management of trigeminal neuralgia in multiple sclerosis.

Percutaneous Radiofrequency Lumbar Rhizolysis

Low back pain may arise from degenerative changes in the posterior joints of the lumbar spine. Pain impulses from these joints can be interrupted by coagulating this nerve with a radiofrequency wave, the probe having been placed in the area of the nerve percutaneously. Percutaneous lumbar rhizolysis was carried out under local anesthesia on an outpatient basis in 82 patients, most of whom had multiple level rhizolysis. Rhizolysis was successful in 67% of patients with mechanical low back pain without evidence of disc herniation and nerve-root compression or psychogenic pain, who had not previously undergone an operation for relief of the pain.

See also

• Spastic diplegia
• Cerebral palsy
• Baclofen
• Botox
• Phenol