Early treatment may not resolve swallowing problems in SMA: Study
Children with spinal muscular atrophy (SMA) can still experience swallowing difficulties despite early treatment with disease-modifying therapies, a small study shows.
Swallowing was either incomplete, with liquid remaining in the mouth and/or esophagus, and/or unsafe due to aspiration (the inhalation of liquid into the lungs), in all of the children studied. Moreover, nearly half of them had silent aspiration, meaning they were unaware of it happening.
Swallowing problems improved in some children with treatment, while others who showed no difficulties at diagnosis developed swallowing problems over time, despite treatment.
The study, “Longitudinal changes of swallowing safety and efficiency in infants with spinal muscular atrophy who received disease modifying therapies,” was published in the journal Pediatric Pulmonology.
SMA is a rare, hereditary neuromuscular disease marked by progressive muscle weakness and atrophy (wasting), particularly in the proximal muscles, those closer to the center of the body.
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Due to weakness in the muscles that support the face, mouth, and neck, some patients, especially children with more severe types of SMA, experience problems with swallowing foods and/or liquids, a disorder called dysphagia. This can lead to low food intake, nutritional deficiencies, and impaired growth.
Dysphagia also increases the risk of aspiration pneumonia, a lung infection caused by inhaling food, liquid, or vomit into the lungs. Effectively closing the airways during swallowing to prevent aspiration relies on precise muscular movements that can be compromised in SMA.
Newborn genetic screening programs have allowed children to be diagnosed with SMA earlier, even before the onset of symptoms. However, features of dysphagia at such an early diagnosis, if present, have yet to be defined. In addition, the impact of early treatment on dysphagia remains unclear.
Therefore, scientists at the University of Florida examined the medical records of seven infants (five male), diagnosed with SMA via newborn screening, who had two or more swallowing assessments within 30 days of their first treatment. Among them, the median age at diagnosis was 10 days, with the first swallowing test at a median of 21 days.
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All patients received the one-time gene therapy Zolgensma (onasemnogene abeparvovec-xioi) at a median age of 29 days. Three also received Evrysdi (risdiplam), and one was treated with Evrysdi and Spinraza (nusinersen).
Swallowing was assessed by videofluoroscopic studies, in which foods/liquids are mixed with a harmless substance, such as barium, that is visible on X-rays. This allows the swallowing process to be monitored in real time. All participants were started on thin liquids, followed by those with higher consistencies.
Swallowing safety was assessed using the penetration aspiration scale (PAS) across all consistencies tested, with scores of three or more defined as unsafe swallowing with high aspiration. Swallowing efficiency was evaluated by the presence or absence of liquid residue in the mouth and/or esophagus after swallowing. Moderate or severe residue was considered abnormal.
Motor function improved for all treated patients over the study period, as assessed using the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders and the Neuromuscular Gross Motor Outcome.
At diagnosis, four out of seven patients exhibited unsafe swallowing, with high levels of aspiration while ingesting thin liquids. Among them, three showed silent aspiration, meaning they were unaware of aspiration and did not cough or attempt to clear the airway. With treatment, all three patients improved over time, one of whom also received Evrysdi, in part due to dysphagia.
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Importance of early testing, continuous monitoring of swallowing problems
These findings reinforce “the need for early evaluation and longitudinal formal assessments of swallowing after therapies, even in the case of children treated during the presymptomatic period,” the researchers wrote.
Two patients with low PAS scores at diagnosis, who required temporary feeding support, developed unsafe swallowing, regardless of treatment. One of them received add-on Evrysdi to help with swallowing and motor function.
Inefficient swallowing was found in five of the seven children due to the abnormal presence of liquid in the mouth and esophagus after swallowing, and one of them improved by 3 years of age. Another patient developed abnormal residue in subsequent swallowing studies, which improved at the most recent 30-month assessment.
Overall, all patients showed either unsafe or inefficient swallowing, or both, at least once during the study.
Based on the videofluoroscopic data, six of the seven patients needed feeding modifications, including eating position, food/liquid consistency, and the use of feeding tubes.
“Swallowing safety and efficiency can be impaired in patients with SMA despite early treatment,” the researchers concluded.
“Until larger and more comprehensive studies of the physiologic changes of swallowing are available in patients with SMA, we strongly recommend that abnormal presence of oral or pharyngeal residue be reported and monitored over time in this population,” the researchers added, “especially in patients with clinical symptoms, prolonged respiratory infections or suboptimal weight gain.”
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