Dixon-based MRI a Reliable, Sensitive Measure of Muscle Degeneration in CMT, Study Suggests

An imaging technique called 3D multiple gradient echo Dixon-based MRI may be a highly reliable and more sensitive tool for evaluating muscle degeneration in people with Charcot-Marie-Tooth (CMT) disease, a study reports. 

This technology enables the mapping and quantification of the proportion of fat within muscles and may have clinical value as an additional imaging tool to help track disease course and evaluate patients’ response to treatments.

The study, “Muscle fat quantification using magnetic resonance imaging: case–control study of Charcot–Marie–Tooth disease patients and volunteers,” was published in the Journal of Cachexia, Sarcopenia and Muscle.  

In light of the increasing studies testing potential treatments for CMT and advances in knowledge on the genetic basis of CMT, “an objective and reliable tool for assessing the status of patients including the evaluation of treatment response would be necessary,” the researchers said.

But one common problem is that there is no standardized method to assess muscle degeneration and muscle fat infiltration. The scoring systems that are currently available are limited because of variability in their results, and muscle biopsies are inconvenient for regular use.

A possible alternative is magnetic resonance imaging (MRI), which allows clinicians to determine the degree and distribution of fat infiltration in the muscles, a common feature in CMT that is associated with muscle degeneration.

In this study, the researchers were interested in exploring the use of a particular type of MRI, known as the 3D multiple gradient echo Dixon‐based MRI, to quantify the amount of intramuscular fat in people with CMT.

Dixon MRI is an emerging technique for measuring the proportion of fat within tissues. It takes advantage of the fact that water and fat have different chemical shifts, which can be used to distinguish their contribution to the makeup of tissues.

Moreover, some studies have reported encouraging results using Dixon‐based MRI for fat quantification in skeletal muscle, including in the calf muscles of CMT patients.

The researchers compared Dixon‐based muscle scans between 18 adults with CMT and 18 healthy volunteers, matched by age and sex, scanning the upper and lower third of both thighs for each individual.

They chose to measure thigh instead of calf muscles because fat infiltration in the thigh is less prominent, and little is known about the relation between fat accumulation and the clinical status of patients. 

Results showed that the method was highly reproducible, with excellent consistency between measurements done by different clinicians.

Data also demonstrated that, on average, CMT patients had a significantly higher proportion of fat in their thigh muscles than volunteers. Only one muscle in the upper thigh called the adductor magnus, did not follow this trend.

Even in muscles classified as Goutallier Grade 0, which is considered a grossly normal muscle in terms of fat content, showed a significantly higher mean fat proportion than that of the volunteers.

This could be evidence of the sensitivity of the technique to indicate early fat infiltration, “which may be difficult to identify through visual assessment” of scans, according to the researchers.

The significant increase in intramuscular fat detected in CMT patients may be also attributed to the sensitivity of the method, “which may not have been revealed by less advanced MRI techniques,” they said.

Moreover, the technique was seen to be highly reproducible and required a relatively short scan time (72.5 seconds). Thus, the team believes it may easily be incorporated as part of a routine imaging sequence in neuromuscular disease patient evaluation.