MScanFit shows promise as novel SMA monitoring tool in study
Tool’s use found 'feasible' for assessing health of nerve, muscle cells
A novel monitoring tool called MScanFit may be a reliable way to assess the health of nerve and muscle cells in people with spinal muscular atrophy (SMA), a new study found.
“This study demonstrated that MScanFit is feasible for the assessment of SMA patients,” the scientists wrote, noting the results “showed a good correlation with SMA [disease characteristics] and functional clinical outcome.”
“We would suggest the use of this noninvasive neurophysiological tool for monitoring the course of the disease and treatment response,” the team added.
Their study, “Motor unit number estimation via MScanFit MUNE in spinal muscular atrophy,” was published in the journal Muscle and Nerve.
MScanFit used for monitoring motor units, or MUNE, in SMA
SMA is caused by the death and degeneration of motor neurons, which are the nerve cells responsible for controlling muscle movements. One common method for monitoring SMA in clinics is via compound muscle action potential (CMAP) scans. CMAP scans are tests that measure the electrical activity of motor neurons and the muscles they control.
The MScanFit tool works to calculate a variable called the motor unit number estimate, or MUNE, from data acquired in these CMAP scans. MUNE essentially is a reflection of how many individual motor neurons are signaling to muscles, with higher scores typically indicating a greater number of functioning motor units.
In this study, MScanFit was used to calculate MUNEs for 23 people with SMA — nine with type 2 and 13 with type 3 — as well as 12 people without the genetic disease. Where feasible, three different muscles were assessed: the abductor pollicis brevis in the wrist, the abductor digiti minimi in the foot, and the tibialis anterior in the calf.
The results showed that SMA patients had significantly lower MUNEs than did individuals without the disease.
We showed that MScanFit is sensitive to detecting the loss of motor units in the selected muscles [tested].
MUNEs also varied among SMA patients, with higher values in patients with the milder type 3 than the more severe type 2. Similarly, SMA patients who were able to walk had significantly higher MUNEs than patients who were unable to walk.
“The estimated number of motor units was different across the [types] of the disease and the functional status of patients, and strongly correlated with clinical measures,” the researchers wrote.
The researchers noted that MScanFit has only been tested in SMA patients in a few prior studies, and those studies only assessed muscles in the wrist. These findings show the tool also can be applied to other muscles throughout the body, the team said.
“We showed that MScanFit is sensitive to detecting the loss of motor units in the selected muscles [tested],” the researchers wrote.
Overall these results indicate that MUNEs calculated by MScanFit may be a useful measure to track the progression of SMA, and also could help monitor patients’ responses to treatments. The scientists noted, however, that further studies are needed — particularly research that will track how these values change over time.
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