Spinal Muscular Atrophy: Retained Secretions and Aspiration

Spinal Muscular Atrophy: Retained Secretions and Aspiration

Children with Spinal Muscular Atrophy (SMA) types 0 and 1 have significant weakness in bulbar and respiratory muscles, which can lead to difficulty in managing secretions.1 Reduced secretion clearance is a risk factor for acute respiratory decompensation.2,3 Aspiration is common in SMA type 1 and can lead to fatal complications.4,5

Patients with infantile SMA need regular evaluation of the sufficiency of their coughing and secretion management.1,2 It does not appear that patients with SMA elaborate more secretions as a by-product of their disease.1 The cough process is markedly degraded by SMA and appears to be the origin of the known chronic pulmonary infection risk in SMA.4 Patients with SMA have no known defect in sensing airway secretions to trigger a cough response.1 The deep inspiration preceding a cough will be reduced by respiratory weakness4 but can be augmented by non-invasive ventilation.1 The ability to close the glottis can be impaired in SMA and expose the patient to refluxed gastric secretions.1,4 Finally, the ability to generate expiratory effort and open the airway to expel secretions will be diminished in SMA.1 Thus, virtually every step of the cough and gag reflexes in SMA are compromised due to weakness.

In the setting of near total loss of cough reflex as a means of managing secretions, an expert consensus panel in SMA recommends a proactive approach for secretion management and prevention of aspiration.2 The experts advise the teaching and routine use of augmented secretion clearance techniques in the home setting for prophylaxis against aspiration. They advocate for aggressive respiratory care protocols in the home and hospital setting in response to acute illness.2 They advise investigation to diagnose gastroesophageal reflux and definitive treatment with a Nissen fundoplication when pathological reflux is present and it is deemed safe to perform the procedure.2 Successful gastrostomy and Nissen fundoplication is reported to reduce pulmonary infection risk by approximately 50% in SMA.6

Experts are more cautious with advice regarding other interventions. They recommend only short-term use of nebulized interventions (aside from appropriate asthma management) because, when used chronically, 3% and 7% nebulized saline and mucolytics can thin normal secretions and worsen secretion management by increasing secretion volumes.2 Experts have not reached a clear consensus on the use of botulinum toxin as a longitudinal means to reduce salivary gland to reduce oral secretions.2 Experts advise that high frequency chest wall oscillation therapy is ineffective in SMA without adequate coughing.2

References

1. Bush A, Fraser J, Jardine E, et al. Respiratory management of the infant with type 1 spinal muscular atrophy. Arch Dis Child. Jul 2005;90(7):709-711.

2. Finkel RS, Mercuri E, Meyer OH, et al. Diagnosis and management of spinal muscular atrophy: Part 2: Pulmonary and acute care; medications, supplements and immunizations; other organ systems; and ethics. Neuromuscul Disord. Mar 2018;28(3):197-207.

3. Wang CH, Finkel RS, Bertini ES, et al. Consensus statement for standard of care in spinal muscular atrophy. J Child Neurol. Aug 2007;22(8):1027-1049.

4. Birnkrant DJ, Pope JF, Martin JE, et al. Treatment of type I spinal muscular atrophy with noninvasive ventilation and gastrostomy feeding. Pediatr Neurol. May 1998;18(5):407-410.

5. Bach JR. Medical considerations of long-term survival of Werdnig-Hoffmann disease. Am J Phys Med Rehabil. May 2007;86(5):349-355.

6. Durkin ET, Schroth MK, Helin M, et al. Early laparoscopic fundoplication and gastrostomy in infants with spinal muscular atrophy type I. J Pediatr Surg. Nov 2008;43(11):2031-2037.