Emerging Technologies May Track
Progression As Treatments Tested

As more treatments become available for testing in neuromuscular disorders, it’s increasingly important to have reliable ways to measure what they’re doing in the body. Changes in function are, of course, a desirable result of any experimental treatment but, in many cases, the changes will be more subtle, at least in the short run. To measure those, technology will assume a larger role.

Impedance Myography Estimates Disease Severity

Investigators in the Department of Neurology at Beth Israel Deaconess Medical Center in Boston have determined that a new technique known as electrical impedance myography, or EIM, can be used to differentiate between healthy people and those with either amyotrophic lateral sclerosis (ALS) or an inflammatory muscle disease (such as dermatomyositis or polymyositis) and to estimate disease severity. They say the technique may be useful in following a disease course and measuring a patient’s response to treatment.

The study, which included 11 people with ALS, seven with inflammatory muscle disorders and 46 people without any neuromuscular disease, was published online in Muscle & Nerve July 31.

EIM failed to detect differences between abnormal muscles from ALS patients and inflammatory myopathy patients, but the investigators say they’re continuing to refine the technology.

For information about becoming part of that process, contact Seward Rutkove in Boston at (617) 667-3083 or eimstudy@bidmc.harvard.edu.

Motor Unit Loss Reflects Progression

The accuracy of another electrophysiological technique, called motor unit number estimation, or MUNE, in predicting disease onset and rate of progression in amyotrophic lateral sclerosis (ALS) was recently validated in an animal study.

MUNE, which estimates the number of motor units (a motor unit is a nerve fiber and the muscle fibers it stimulates) has been proposed as a reliable technique to track disease progression in patients with ALS and spinal muscular atrophy (SMA).

Now, Jeremy Shefner, director of the MDA/ALS Center at SUNY Upstate Medical University in Syracuse, N.Y., with Merit Cudkowicz and Robert Brown, both at the MDA/ALS Center at Massachusetts General Hospital in Boston, have tested the ability of MUNE to reflect functional changes in mice with ALS, publishing their results online Aug. 4 in Muscle & Nerve.

The team conducted two studies, each in mice with a predictable disease course because they were bred to carry varying numbers of ALS-causing SOD1 genes. In both groups, MUNE correlated with behavioral symptoms, and the slope of MUNE readings correlated with disease duration.

However, a single MUNE reading taken late in the disease course didn’t predict survival time. The researchers say that’s probably because measurements were made in the back legs, which didn’t reflect loss of motor units in the respiratory muscles, just as they wouldn’t in humans.

“The combination of animal and human studies suggests that MUNE is a valuable outcome measure for ALS clinical trials,” the researchers write, “and may prove useful clinically for following disease progression in individual patients.”