P.14.4 Diagnostic role of quantitative NMR imaging exemplified by 3 cases of juvenile dermatomyositis

Skeletal muscle diagnostic imaging is classically based on visual inspection of T1-weighted \NMR\ images and interpretation of patterns of fatty infiltration. The existence of oedematous/inflammatory/necrotic lesions is subjectively appreciated on T2-weighted images, typically acquired with the \STIR\ sequence to minimize fat confounding effects. Because it relies on identification of hyperintensities between and within muscles, the interpretation risk with T2-weighted images is to miss global, homogenous increases in T2. In this report, we demonstrate this concern to be more than theoretical. Three patients aged 6, 7 and 12 were referred for further investigation of progressive muscle wasting (P1) or clinical suspicion of dermatomyositis (P2, P3). All of them had normal \CK\ values. Whole-body \T1w\ showed no fatty infiltration in muscles. Standard \T2w\ imaging was normal in P1, showed discrete differences in signal intensity, particularly between anterior and posterior leg compartments in \P2\ and was moderately positive with hyperintense streaks in P3. Quantitative \T2\ maps were obtained from multi \TE\ spin echo data after extraction of the water component by tri-exponential fitting. In the 3 patients, muscle water \T2s\ were abnormally elevated in the scapular and pelvic girdles, the thighs and the legs: 45/51 muscles of P1, 46/60 of \P2\ and 47/51 of \P3\ had \T2s\ higher than 39 ms, the upper normal value. Mean \T2s\ were 42.3, 42.3 and 45.9 ms, with highest \T2s\ measured at 50.0, 51.9 and 53.3 ms in P1, \P2\ and \P3\ respectively. Juvenile dermatomyositis was histologically confirmed in all patients. After 3 months on steroid, \P1\ was rescanned. In the previously inflamed muscles, \T2\ had on average decreased by 3.4 ms (p < 0.001) and 17 muscles had resumed normal \T2\ values. Quantitative \T2\ mapping can be required to detect unambiguously muscle lesions as shown here in juvenile dermatomyositis. It is also essential to monitor response to treatment in the absence of biological biomarkers.

P. Carlier , N. Azzabou , P. Loureiro De sousa , B. Florkin , E. Deprez , N. Romero , D. Serre , V. Decostre , L. Servais

18th International Congress of The World Muscle Society , Volume 23 , Number 9–10 , page 814 - 2013

@Inproceedings{4-CALF13,
 author = {Carlier, P. and Azzabou, N. and Loureiro De sousa, P. and Florkin, B. and Deprez, E. and Romero, N. and Serre, D. and Decostre, V. and Servais, L.},
 title = {P.14.4 Diagnostic role of quantitative NMR imaging exemplified by 3 cases of juvenile dermatomyositis},
 booktitle  = {18th International Congress of The World Muscle Society},
 number = {9–10},
 series = {Neuromuscular Disorders},
 volume = {23},
 pages = {814},
 month = {Oct},
 year = {2013},
 publisher = {Elsevier},
 doi = {10.1016/j.nmd.2013.06.612},
 x-international-audience = {Yes},
 x-language = {EN},
 url = {http://publis.icube.unistra.fr/4-CALF13}
}