Treatment with Specific Enzyme May Keep Muscle Stiffness

A new study shows that an enzyme called hyaluronidase may be effective in reducing muscle spasticity resulting from neurological disorders.

The results were published in a study titled “Human Recombinant Hyaluronidase Injections For Upper Limb Muscle Stiffness in Individuals With Cerebral Injury: A Case Series,” in the journal EBioMedicine by a group of researchers from the NYU Langone Medical Center (North America).

Muscle spasticity is a condition characterized by muscle stiffness in one or more muscles and reduced joint movement, which causes pain and disability. This condition is associated with neurological damage caused by disorders that affect the connections between neurons that control muscle movement (motor neurons) and muscles, such as multiple sclerosis, stroke, traumatic brain injury, cerebral palsy, or spinal cord injury.

Existing treatments for muscle spasticity include drugs that relax the muscles, such as botulinum toxin, but these therapies can cause muscle weakness, making movement more difficult. The necessity for a treatment option that could effectively help patients with their movement problems led the team to consider the possible involvement of a sugar molecule, called hyaluronan. This molecule accumulates in the joints and muscles after neurological damage, promoting stiffness.

The team hypothesized that injections of an enzyme called hyaluronidase, which breaks down hyaluronan, would reverse its accumulation, reduce muscle stiffness, and increase joint movement. The team tested this idea by administering hyaluronidase injections in 20 patients ages 10 to 77 with moderate or severe spasticity in the arms resulting from neurological damage, and in whom other treatments had not been effective.

The neurological and musculoskeletal assessment of the patients was recorded in video in several time points: before the treatment; two, four, and six weeks after the injection; and three to five months after the injection.

Results showed that, whereas before the treatment the joints tested had moderate (50.6 percent) or severe (44.4 percent) stiffness, after the treatment these values decreased to 15.3 percent and 5.8 percent, respectively, within two weeks. The improvement in muscle stiffness induced by the injection lasted for at least three months, with no recorded muscle weakness or significant side effects.

“These findings fill a critical gap in the understanding of muscle stiffness, and present a promising treatment for spasticity, a vexing problem that affects millions of people worldwide,” Dr. Preeti Raghavan, the leading author of the study, said in a news release.

The team is planning to start a clinical trial to investigate the beneficial role of hyaluronidase injections and the effect of repeated administration of the treatment in a larger group of patients. Future studies are also warranted to determine whether hyaluronidase can be used to treat other disorders associated with muscle stiffness.

“This case series provides preliminary evidence for the safety and potential efficacy of hyaluronidase injections as a treatment for muscle stiffness that may enhance recovery in the spastic upper limb. More research may determine whether such a treatment is applicable to other disorders characterized by muscle stiffness,” Raghavan said.

If confirmed to be an effective therapy, hyaluronidase may provide a relatively less expensive option for patients with spasticity compared to other treatments. (one vial of hyaluronidase typically costs $50/±£50/±€45, and the complete treatment may require four to eight vials).