Nusinersen in adults with type 3 spinal muscular atrophy: long-term outcomes on motor and respiratory function.

INTRODUCTION: Nusinersen was approved for 5q spinal muscular atrophy (SMA), irrespective of age, SMA type or functional status. Nonetheless, long-term data on adults with milder phenotypes are scarce. We aimed to characterize evolution on motor and respiratory function in our cohort of adults with type 3 SMA.

METHODS: We conducted a longitudinal retrospective single-center study, including adults (≥18 years) with type 3 SMA under nusinersen for > 22 months. We reported on motor scores and spirometry parameters.

RESULTS: Ten patients were included, with a median follow-up of 34 months (range = 22-46). Four patients (40%) were walkers. None used non-invasive ventilation. In Revised Upper Limb Module (RULM) and Expanded Hammersmith Functional Motor Scale (HFMSE), difference of medians increased at 6, 22 and 46 months comparing to baseline (-0.5 vs. + 1.5 vs. + 2.5 in RULM; + 4.0 vs. + 7.5 vs. + 6.0 in HFMSE). Two (50%) walkers presented a clinically meaningful improvement in 6-min walk distance. We did not report any clinically meaningful decrement in motor scores. Spirometry parameters showed an increasing difference of medians in maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) (-3 vs. + 13.4 vs. + 28.7 percentage points of predicted value for MIP; + 11.8 vs. + 13.1 vs. 13.3 percentage points of predicted value for MEP).

DISCUSSION: Our cohort supports a sustained benefit of nusinersen in adults with type 3 SMA, in motor and respiratory function. Multicentric studies are still warranted.