MedQuest, a new Quest department, will answer commonly asked medical questions.

Botox: Does It Help in MD?

by Margaret Wahl

Most physicians consulted by MDA prefer to use Botox (a brand name for botulinum toxin) to treat muscle overactivity in cerebral palsy, brain injury and certain other nervous system conditions, but not in conditions involving muscle weakness, such as muscular dystrophy.

In diseases like cerebral palsy, muscle overactivity causes spasticity (frequent or constant spasms or contractions), which can cause a limb to be positioned abnormally. In muscular dystrophy, muscle weakness, not spasticity, can cause abnormal limb positioning, which can evolve into contractures (in which the abnormal position becomes fixed because of tissue changes).

Botox works in spasticity as a profound muscle-weakening agent that blocks transmission of nerve signals to muscles, allowing the limbs muscles to relax. Since increased weakness is the last thing someone with a neuromuscular disease wants, Botox isnt often used in MD.

That having been said, a few physicians are thinking of using Botox to improve limb positioning in specific cases. The first trials to test this kind of Botox use, if they occur, will likely be in people who are no longer walking. In those cases, the increased weakness in the injected leg muscles might be less important than relieving discomfort from abnormal positioning.

Here are some excerpts from an experts answer to a question about Botox in MD:

Q: My 7-year-old daughter has a diagnosis of possible congenital muscular dystrophy with severe turning in [varus] of her feet. She had a tendon transfer with heel cord lengthening (see "Cutting the Cord," October 2001) four years ago without much success.

Can a child with CMD undergo Botox injection into the lower leg muscles, along with casting? What would the Botox do to her nervous system? What would the effects of Botox be on her muscular dystrophy?

Edward Goldstein, MDA clinic director at Scottish Rite Childrens Medical Center in Atlanta, answered this question in October 2002.

A: Botox, made by the Allergan Corp. of Irvine, Calif., is the trade name for botulinum toxin type A. This is the same toxin (poison) that causes the disease botulism, which usually occurs when someone eats food thats been canned improperly. In the can, a bacterium called Clostridium botulinum can grow and produce a toxin.

In MD, contractures can keep the limbs in abnormal positions. Surgery, bracing and other techniques help to relieve these contractures, but most doctors caution against Botox injections, which can weaken muscles further.

When the botulinum toxin enters the bloodstream, it circulates to the junctions where nerves communicate with muscles. During the 1980s, several daring physicians experimented with botulinum toxin to treat people with diseases involving muscular overactivity.

Botulinum toxin proved to be safe and effective in conditions involving spasms in the neck and face. Its use was then extended to people who have limb spasticity.

Spasticity produces extension [straightening] of the legs and overactivity in the calf muscles, which makes the toes point down and inward a foot position sometimes referred to as varus deformity. Injection of the calf muscles with botulinum toxin weakens these muscles, and, in association with casting, can effectively eliminate varus deformity in selected patients.

This brings us to your daughter, who poses a difficult problem. I follow a number of patients who have developed varus deformity of their feet in the setting of progressive weakness.

These patients feet are turned inward due to the severe weakness in the tibialis anterior muscle (which raises the foot) and the peroneus muscles (which roll the feet away from each other).

In patients with muscular dystrophy, increasing muscle weakness is seldom beneficial. There are no medical studies regarding the effect of Botox on weak muscles, but there are theoretical concerns that botulinum toxin could accelerate damage to dystrophic muscles.

However, since your daughters diagnosis is uncertain, your childs physicians may be suspicious that relative overactivity in the muscles producing varus foot deformity is at play. Id consider performing a test called dynamic EMG.

If overactivity is found, you could use Botox to weaken the stronger muscles. But botulinum toxin wont have any effect on permanent contractures a tightening of the soft tissues in the foot and ankle. Those contractures must be addressed independently by stretching, bracing, casting or orthopedic surgery.

Botox injections typically used dont produce any systemic signs of botulism. The toxin doesnt enter the brain, so it doesnt produce sedation. Pain during injection typically lasts only several minutes.

Infrequent side effects include infection, localized bleeding, a cool feeling in the injected limb, flulike symptoms, rash, allergic reaction and excessive weakness.

On a more practical level, your daughter may be using the remaining strength in her calves to stabilize her feet while walking. Weakening her calves may potentially impede function, rather than helping her gait.

 

Note: Goldstein has received an educational grant from Allergan to study the effect of Botox on children with spasticity due to cerebral palsy.