Swallowing and feeding after disease-modifying treatment for spinal muscular atrophy: a systematic review of assessment modalities and outcomes

Feeding and swallowing deficits are reported across the spectrum of spinal muscular atrophy (SMA), with more profound symptoms associated with more severe disease. Patients treated with disease-modifying therapies (DMTs) demonstrate significantly improved life expectancy and motor function relative to untreated counterparts; however, limited data exist regarding the impact of DMTs on bulbar integrity, with evidence suggesting bulbar symptoms may persist, even when motor function has improved. This systematic literature review was conducted to identify assessments used to evaluate swallowing in patients with SMA treated with DMTs, and to describe the impact of DMTs on swallowing and feeding outcomes. Embase, MEDLINE, and Cochrane central were searched from May 2021 to February 2024 for studies reporting swallowing and feeding outcomes in patients treated with nusinersen, onasemnogene abeparvovec, and risdiplam. Seventy-one studies were included. The majority of studies (99%, n = 71) reported functional swallow outcomes, such as oral intake status or patient-reported outcomes, and only 19% reported results from clinician-administered assessments. Results from imaging assessments were rarely reported (5%, n = 4 studies). Only 68% of studies reported results from both pre- and post-treatment assessments. Patients who received DMT prior to symptom onset were found to have good functional outcomes, with 84–100% receiving full oral nutrition. Treatment after symptom onset yielded variable results, with trends suggesting that treatment outcomes are influenced by the level of impairment at baseline and the type of swallowing assessment used. The ability to maintain pre-treatment swallow integrity was variable across studies. Although evidence suggests that DMTs can preserve or improve bulbar function in SMA, swallowing and feeding are not regularly or homogeneously assessed across the literature, making comparisons across studies difficult. Standardised and validated assessments of swallowing physiology and swallowing function are needed to understand what factors may influence bulbar outcomes with DMTs.