Fat fraction distribution in lower limb muscles of patients with CMT1A

Abstract

ObjectiveTo quantitatively describe the MRI fat infiltration pattern of muscle degeneration in Charcot-Marie-Tooth (CMT) type 1A (CMT1A) disease and to look for correlations with clinical variables.MethodsMRI fat fraction was assessed in lower-limb musculature of patients with CMT1A and healthy controls. More particularly, 14 muscle compartments were selected at leg and thigh levels and for proximal, distal, and medial slices. Muscle fat infiltration profile was determined quantitatively in each muscle compartment and along the entire volume of acquisition to determine a length-dependent gradient of fat infiltration. Clinical impairment was evaluated with muscle strength measurements and CMT Examination Scores (CMTESs).ResultsA total of 16 patients with CMT1A were enrolled and compared to 11 healthy controls. Patients with CMT1A showed a larger muscle fat fraction at leg and thigh levels with a proximal-to-distal gradient. At the leg level, the largest fat infiltration was quantified in the anterior and lateral compartments. CMTES was correlated with fat fraction, especially in the anterior compartment of leg muscles. Strength of plantar flexion was also correlated with fat fraction of the posterior compartments of leg muscles.ConclusionOn the basis of quantitative MRI measurements combined with a dedicated segmentation method, muscle fat infiltration quantified in patients with CMT1A disclosed a length-dependent peroneal-type pattern of fat infiltration and was correlated to main clinical variables. Quantification of fat fraction at different levels of the leg anterior compartment might be of interest in future clinical trials.

Overview of MR Image Segmentation Strategies in Neuromuscular Disorders

“…In a few clinical studies in which the manual segmentation has been performed in the 3D field of view, an inconsistent distribution of MRI biomarker values has been interestingly reported along the proximo-distal axis (2,(11)(12)(13). In addition, it has also been documented that individual muscles could be affected differently and that this difference could also occur among patients and neuromuscular disorders (5,(14)(15)(16). These results clearly emphasized the need of reliable automatic 3D segmentation methods and the relevance of evaluating muscles individually, rather than by muscle groups.…”

“…In addition, the processing of 3D datasets could be useful to investigate potential changes along the proximo-distal axis. Accordingly, fat infiltration patterns of individual muscles have been reported in a few clinical studies (5,16).…”

“…In addition, an excellent reliability was also quantified from the comparative analysis between fat fraction computed from the segmented images and from the manual segmentation. The method has been deemed sufficiently robust for clinical applications and assayed in cross-sectional studies, which evaluated the pattern of fat infiltration in muscles in two different neuromuscular pathologies (12,16).…”

Semi-Automatic MRI Muscle Volumetry to Diagnose and Monitor Hereditary and Acquired Polyneuropathies

“…Since the fatty degeneration of muscles usually increases concomitantly with disease progression [11], assessing the muscle fat fraction in neuropathy patients is another promising approach [31,[34][35][36]. Whereas the segmentation method used in this study does not allow for the calculation of fat fractions, we are currently working on a protocol for the semi-autonomic segmentation of both muscle volume and fat fraction to overcome this issue.…”

Quantitative assessment of sciatic nerve changes in Charcot–Marie–Tooth type 1A patients using magnetic resonance neurography

“…Quantitative magnetic resonance imaging (qMRI) techniques have been used in CMT over the past few years and structural abnormalities have been reported in nerves and muscles of the lower limbs, both proximally and distally [17]. Skeletal muscle MRI of the lower limbs showed a significantly increased fat fraction with a length‐dependent peroneal‐type pattern [18] and a high sensitivity to change over a 1‐year period [19]. Regarding the nerve pathological involvement, various metrics such as nerve volume [20], proton density (PD) [21] and magnetization transfer ratio (MTR) [22] have been quantified, but the proximal‐to‐distal pattern of the sciatic and tibial nerves has not been specifically analyzed so that the most relevant area for MR neurography remains unknown.…”