A single intramuscular injection of botulinum toxin A — more commonly known as botox — can significantly reduce upper limb spasticity and improve functional outcomes in children with cerebral palsy, a study finds.
The study, “Effect of botulinum toxin type-A in spasticity and functional outcome of upper limbs in cerebral palsy,” was published in the Journal of Clinical Orthopaedics and Trauma.
Spasticity, or muscle stiffness, is known to be a major cause of functional impairment and abnormal posture in children with cerebral palsy (CP), with upper limb spasticity the most common form. In children, whose muscles are still developing, this can lead to abnormal posturing and painful physical deformities that can complicate otherwise simple daily tasks.
Several treatment options have been used to reduce spasticity and improve the function of the hand and upper limbs in children with CP.
Botulinum toxin A (BoNT) is often used to control spasticity, with many studies showing that it is both safe and effective. BoNT is a potent neurotoxin that acts by reducing the release of acetylcholine (a neurotransmitter or chemical messenger) from neurons to the muscles, which decreases muscle hyperactivity.
In the study, researchers evaluated the effect of a single intramuscular (into the muscle) injection of BTX-A to reduce upper limb spasticity and improve functional outcomes in 28 children, 4–12 years old, with spastic CP. The children were monitored for a minimum of six months.
Spasticity was measured using the Modified Ashworth Scale (MAS) and the Modified Tardieu Scale (MTS). Functional outcomes were measured using the Manual Ability Classification System (MACS) and the Canadian Occupational Performance Measure (COPM) before treatment, and at three and six months after treatment.
MACS is a medical classification system used to describe how children with CP use their hands to handle objects during daily activities, with a particular focus on the use of both hands together; COPM is an outcome measure designed to capture a participant’s self-perception of performance in everyday living over time.
The muscles chosen to be injected were those that would most hamper normal upper limb function and grip capacity, based on clinical examination. “Muscle groups that provided significant resistance to passive range of motion, contributing to abnormal limb positioning or inhibiting function were identified for injection,” the researchers wrote.
Pronator teres (a long, thin muscle that is located on the underside of the forearm) was the most frequently injected muscle, followed by the flexor carpi ulnaris (another forearm muscle that flexes and moves wrists) and the adductor pollicis (a muscle in the hand that moves the thumb).
Results indicated a significant decrease in spasticity at the level of the arm, forearm, and wrist, as measured by a significant decrease in MAS and MTS scores at three months after treatment. However, MAS and MTS scores increased at six months post-injection.
“This trend shows that effect of Botulinum weans off after three months with return of local spasticity,” the researchers said.
Importantly, results from MACS and COPM, which reflect functional outcomes, showed significant sustained improvement at three and six months, despite the return of local spasticity.
“COPM scores were significantly lower as the age of child increased,” the researchers wrote. “This may suggest that BTX-A may have more beneficial effect in younger age group.”
Overall, BTX-A injections were well-tolerated by all patients. Both patients and parents reported some discomfort at the injection site for the first 24 hours, and four children reported a temporary decrease in grip strength lasting four to six weeks.
“[Intramuscular] BTX-A injected using anatomical landmarks had significant improvement in both clinical and functional outcome measures,” the researchers said.
According to the team, BTX-A is safe and effective to treat spasticity in the upper limbs of CP patients and is capable of improving motor function without causing major side effects.