Primary mitochondrial myopathy: 12-month follow-up results of an Italian cohort.

OBJECTIVES: To assess natural history and 12-month change of a series of scales and functional outcome measures in a cohort of 117 patients with primary mitochondrial myopathy (PMM). METHODS: Twelve months follow-up data of 117 patients with PMM were collected. We analysed the 6-min walk test (6MWT), timed up-and-go test (× 3) (3TUG), five-times sit-to-stand test (5XSST), timed water swallow test (TWST), and test of masticating and swallowing solids (TOMASS) as functional outcome measures; the Fatigue Severity Scale and West Haven-Yale Multidimensional pain inventory as patient-reported outcome measures. PMM patients were divided into three phenotypic categories: mitochondrial myopathy (MiMy) without extraocular muscles involvement, pure chronic progressive external ophthalmoplegia (PEO) and PEO&MiMy. As 6MWT is recognized to have significant test-retest variability, we calculated MCID (minimal clinically important difference) as one third of baseline 6 min walking distance (6MWD) standard deviation. RESULTS: At 12-month follow-up, 3TUG, 5XSST and FSS were stable, while TWST and the perceived pain severity (WHYMPI) worsened. 6MWD significantly increased in the entire cohort, especially in the higher percentiles and in PEO patients, while was substantially stable in the lower percentile (< 408 m) and MiMy patients. This increase in 6MWD was considered not significant, as inferior to MCID (33.3 m). NMDAS total score showed a slight but significant decline at 12 months (0.9 point). The perceived pain severity significantly worsened. Patients with PEO performed better in functional measures than patients with PEO&MiMy or MiMy, and had lower values of NMDAS. CONCLUSIONS: PMM patients showed a slow global decline valued by NMDAS at 12 months; 6MWT was a more reliable measurement below 408 m, substantially stable at 12 months. PEO patients had better motor performance and lower NMDAS than PEO&MiMy and MiMy also at 12 months of follow-up.

Upper body involvement in GNE myopathy assessed by muscle imaging.

Upper body muscle involvement has never been systematically investigated in GNE myopathy (GNEM). Aims of our study were to explore upper body involvement in GNEM patients by means of muscle MRI, to compare the degree of pathology with that of lower body and to validate the MRI pattern of the lower limbs in novel patients. MRI scans of 9 GNEM patients were retrospectively evaluated. T1-weighted and short-tau inversion recovery images were scored. As a result, serratus anterior was involved in all patients, followed by subscapularis and trapezius muscles. The majority of scans consistently showed hypotrophy of pectoralis minor. Conversely, cranial muscles including the tongue were always spared while pectoralis major and latissimus dorsi were relatively spared. We confirmed the known pattern of involvement in the pelvic girdle and limbs, that were more significantly affected than the upper girdle in all disease stages. Paraspinal muscles were also frequently affected displaying both a cranio-caudal and latero-medial gradient of severity along the body axis. Upper girdle MRI highlights a selective muscle involvement in GNEM, offering an added value in patients' diagnostic workup and deep stratification.