Precisely placed phenol injections can relieve spasticity by inducing axon necrosis, essentially destroying the nerve causing the spasticity.
Precisely placed phenol injections can relieve spasticity by inducing axon necrosis, essentially destroying the nerve causing the spasticity.
As a focal treatment, the phenol needs to be injected at the motor points of the right muscles.
Targeting only the motor neve is very important, otherwise the patient could have sensory issues from the denaturation, according to , pediatric physical medicine and rehabilitation specialist at Norton Children’s Physical Medicine & Rehabilitation, affiliated with the UofL School of Medicine.
A 3% to 6% concentration of phenol at motor points of selected muscles or perineurally can induce axon necrosis. Phenol can last up to 12 months. Administration is similar to that of neurotoxin (botulinum), which acts presynaptically to inhibit the release of acetylcholine to weaken the muscle contraction. Neurotoxin lasts about three to six months.
As the physician needs to find the right motor point for good nerve impulses, phenol injections require sedation as the patient needs to be very still, according to Dr. McClanahan. That can be a limiting factor for some families who are hesitant to have the child anesthetized.
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Some insurers may be hesitant to cover a focal treatment in patients who haven’t failed to respond to a systemic therapy such as baclofen. In some states, stringent rules make it difficult to dose baclofen as a liquid, rather than a tablet, making treatment of infants difficult, Catherine Schuster, M.D., medical director of Norton Children’s Physical Medicine & Rehabilitation and an associate professor of pediatrics at the medical school, said in a recent continuing medical education opportunity.
Phenol denatures protein quickly. Precision, often using ultrasound guidance, is required to make sure only the nerves causing the spasticity are affected. Electrical stimulation, possibly in conjunction with ultrasound, also can identify the right phenol injection location.
Ultrasound guidance has been shown to require less phenol than when used with electrical stimulation alone.
