Insider's View

John W. Griffin, M.D., is professor and director of the Department of Neurology at Johns Hopkins. He has more than 30 years’ exper-ience in diagnosing and treating disorders of the nervous system.

In this issue, Dr. Griffin discusses primary lateral sclerosis (PLS), a disease that, in early stages, is often difficult to distinguish from ALS. Both affect motor neurons. But PLS progresses slowly and doesn’t attack respiratory muscles. It’s not fatal, though it can incapacitate patients.

You have an interesting approach to diagnosing PLS.

Perhaps. I’m of the opinion that there’s not a lot of value in spending time, during a patient’s early visits, to do the nerve conduction tests that might tell us it’s ALS rather than PLS. At this point, nothing can stop lower motor neurons from becoming involved and there’s no difference in therapy early on.

What’s the major problem in PLS?

It’s spasticity. It’s a huge problem and a frustrating one. One of the ironies is that people may have trouble moving, but it’s not because of great muscle weakness—as you’d find in ALS— it’s because muscles are so tight and stiff. So both types of patients can’t get around, but for different reasons.
A lot of our effort goes to loosening spasticity—not an easy thing. And you have to consider that lessening tone and stiffness, with drugs, may also increase perceived weakness. But if muscles are still strong, it’s not a bad move for patients.

What do we know about spasticity?

Amazingly little. Very little research has been done on it. We do know generally what happens. Every section of the spinal cord receives input from inhibiting neurons that come both from the cord itself and from the brain. Good movement is as dependent on suppressing muscle contraction as it is on developing it! So spasticity comes from failure of the inhibiting neurons. Then muscles won’t relax. And certain ones tend to dominate. The muscles that keep knees stiff overshadow those that bend them, for example. But as for what causes the neurons to fail, we just don’t know yet.

What can you do for patients?

You try to manage the symptoms. You use physical therapy. You use drugs, like baclofen, that ease too-strong muscle tone. Baclofen, for example, interferes with the nerve transmitters that cause the stiffness. And if tightness in a small muscle causes a disproportionate amount of trouble, say a contracted thigh muscle leaves a patient barely able to walk, then injecting muscle antitoxin into it can bring a useful weakening.

Next > From the Clinic
Marsha Davis, the registered dietitian for Johns Hopkins’ ALS Clinic, is expert in the nutritional needs of ALS patients, as well as in ways to manage their changes in eating style.