Assessment of whole-body muscle MRI for the early diagnosis of Amyotrophic Lateral Sclerosis

Objectives: To evaluate muscle signal abnormalities on whole-body muscle MRI with T2 and diffusion-weighted imaging in early ALS stages.

Methods: 101 muscles were analyzed in newly diagnosed ALS patients and healthy controls on a whole-body MRI protocol including four-point T2-Dixon imaging and diffusion-weighted imaging (b0 and b800). Sensitivity and inter-observer agreement were assessed.

Results: 15 patients (mean age, 64 +/- 12 [SD], 9 men) who met the Awaji-Shima criteria for definite, probable or possible ALS and 9 healthy controls were assessed (mean age, 53 +/- 13 [SD], 2 men). 61 % of the muscles assessed in ALS patients (62/101) showed signal hyperintensities on T2-weighted imaging, mainly in the upper and lower extremities (legs, hands and feet). ALS patients had a significantly higher number of involved muscles compared to healthy controls (p = 0,006). Diffusion-weighted imaging allowed for the detection of additional involvement in 22 muscles, thus improving the sensitivity of whole-body MRI from 60 % (using T2-weighted imaging only) up to 80 % (with the combination of T2-weighted and diffusion-weighted imaging).

Conclusions: ALS patients exhibited significant muscle signal abnormalities on T2-weighted and diffusion-weighted imaging in early disease stages. Whole-body MRI could be used for pre-EMG mapping of muscle involvement in order to choose suitable targets, thus improving early diagnosis.