Treating Spasticity with Neurolytic Agents

What is spasticity?

Spasticity is the term used to describe muscles that are stiff or rigid.  Spasticity in children with traumatic brain injury, cerebral palsy, or spinal cord injuries is very common.  Normally, the brain tells a muscle to relax or stiffen as needed.  In children with spasticity, the muscles receive few or no messages from the brain. This results in stiff and rigid muscles that cannot relax. Spasticity can affect any muscle of the body and interfere with the ability to walk and do a variety of daily activities.  It can also cause pain and difficulties with sleep.

Spasticity treatments include therapy, braces, injectable medications (neurolytic agents), medications taken by mouth or delivered by a pump, and different types of surgeries.

Neurolytic Agents

Neurolytic blocking agents, such as botulinum toxin and phenol, are medicines that block or reduce the messages sent from the brain and spinal cord to the muscles. These medications cause the muscles to relax.

Physicians recommend botulinum toxin or phenol blocks to meet individual child needs. Common examples include:
-To reduce muscle tone that interferes with a child’s walking ability
-To reduce muscle tone that interferes with dressing and hygiene
-To reduce muscle tone that interferes with functional ability of hands and fingers
-To reduce muscle tone that interferes with the use of braces and splints
-To stop painful spasms

These two neurolytic blocking agents are given as injections into specific muscles. They may be used in combination with each other or in combination with other spasticity medications taken by mouth.

Botulinum Type A Toxin
Normally the brain sends nerve impulses or “messages” to the muscles to make the muscles contract and move. These messages are transmitted to the muscle by a chemical (acetylcholine). When injected into the muscle, Botulinum toxin works by temporarily blocking the release of this chemical and, as a result, the muscle does not receive the message to contract. It takes about 3 days for the medication to start to work and its effects last about 3 months. Injections can be repeated after 3 months. Side effects are rare and typically include temporary pain and soreness at the injection site. Less than 1% of patients report mild, flu like symptoms.

Phenol Block
Phenol is an alcohol based injection that partially “uncoats” the nerves. Nerves have an insulation or “coating” to help them transmit messages quickly. If we remove that layer, their messages travel more slowly and the muscle contractions that result from the nerve messages are weaker and less effective. This mechanism causes the muscles to relax. After about 5 to 6 months, the nerves “recoat” themselves so the effect of the medicine wears off.