Acceptability, validity and responsiveness of inertial measurement units for assessing motor recovery after gene therapy in infants with early onset spinal muscular atrophy: a prospective cohort study.

The study included 23 patients, but only 15 patients had baseline and 12-month sensor measurements for responsiveness, and only 14 patients had paired CHOPINTEND data. Patients 1 to 4 were included after gene therapy infusion, so baseline measurements were missing. Some patients living far away had follow-up in local centres where the IMU protocol was not implemented. Severe respiratory impairment, bulbar signs, need for respiratory support or profound motor deficit were excluded from gene therapy indication, so results may not apply to those infants. The presymptomatic child with normal development did not respect the protocol from 6 months and was excluded. Patient 12 died one month after therapy. The task lasted 25 minutes in a hospital room, not continuous daily-life monitoring; authors note 72 h wear-time is recommended for reliable uncontrolled conditions. No test-retest experiment was performed. Parameters combined left and right sensors and did not analyse individual axes, so they may not capture complex upper-limb movement. No knee sensors were used, so proximal lower-limb movement was not explored. The protocol required the child to lie supine and not crawl or flip, so it may not fit more mobile or less severe infants. The study was a measurement validation cohort, not a controlled efficacy trial, so it cannot separate gene therapy from steroid prophylaxis.

Do not conclude that gene therapy alone caused the 12-month sensor increases or that these sensors can replace clinical motor scores. Infants also received steroid prophylaxis, the responsiveness analysis included only 15 patients, and changes in sensor measures were not significantly correlated with changes in CHOPINTEND scores.