Spinal Muscular Atrophy (SMA) is a progressive congenital neuromuscular disease that causes weakness that can involve respiratory muscles.1,2 SMA is associated with a loss of respiratory function that correlates with the severity of the disease phenotype.2 Dyspnea is reported by some to be the most common symptom in patients with SMA.3 Respiratory failure is a common cause of death in fatal forms of SMA.4,5
Chronic Management of Breathing Difficulty in SMA
Patients with neonatal and infantile onset of SMA (SMA types 0 and 1) will have significant respiratory involvement (and ultimately respiratory failure) due to SMA-related weakness.1,4,6 A consortium of SMA experts recommends that all symptomatic patients with severe SMA receive non-invasive positive pressure ventilation (bilevel NIV), not continuous positive airway pressure (CPAP).1 The experts advise considering the introduction of NIV before frank respiratory failure to prevent patients from experiencing the distress of dyspnea.1 Tracheotomy ventilation is an option for chronic management of breathing difficulty if NIV fails.1 The use of invasive means for chronic management of ventilation needs in SMA is a source of long-term controversy7 and should be approached on a case-by-case basis as a discussion between the multidisciplinary SMA care team and the patient’s caregivers.1,5,7 Ventilation weaning can be achieved in SMA.8
Patients with milder forms of SMA (i.e., SMA types 2 and 3) may experience some respiratory weakness as their disease progresses.9 In these patients, experts in SMA recommend assessment of respiratory function every 6 months with a low threshold for investigating nocturnal hypoventilation.1 These patient may only need nocturnal NIV, but clinicians should be aware of the possibility of a short-term need for NIV or CPAP during an acute illness.1 Ambulatory patients with a weak cough or recurrent respiratory infections should be evaluated by a pulmonary expert.1
Acute Management of Breathing Difficulty in SMA
Low-flow supplemental oxygen can be helpful in infants with cyanotic spells.5 In all forms of SMA, mucolytics can be considered for short-term palliation but should be eschewed for long-term use.1 CPAP can be used to maintain resting lung volume in patients unable to coordinate breathing with bilevel NIV but can fatigue patients with SMA or be difficult to wean if used long-term.1 NIV can be used in patients without prior respiratory support needs for post-operative breathing difficulty,10 and mechanical ventilation with intubation is an option in short-term management of respiratory distress in the setting of a respiratory illness in these less severely impacted patients.11
Palliative Management of Breathing Difficulty in SMA
A report suggests that respiratory distress is common in SMA during end-of-life care.3 Clinicians can start or increase doses of medications used to manage pain and anxiety such as morphine and benzodiazepines to ease dyspnea-related discomfort. Supplemental oxygen is typically given for palliation.3,5 Escalations of interventions should be considered on an individual basis; deep sedation is not typically indicated.3,12
1. 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.
2. Samaha FJ, Buncher CR, Russman BS, et al. Pulmonary Function in Spinal Muscular Atrophy. Journal of Child Neurology. 1994;9(3):326-329.
3. Di Pede C, Agosto C, De Tommasi V, et al. Symptom management and psychological support for families are the cornerstones of end-of-life care for children with spinal muscular atrophy type 1. Acta Paediatr. Jan 2018;107(1):140-144.
4. Kolb SJ, Kissel JT. Spinal Muscular Atrophy. Neurol Clin. Nov 2015;33(4):831-846.
5. Roper H, Quinlivan R. Implementation of “the consensus statement for the standard of care in spinal muscular atrophy” when applied to infants with severe type 1 SMA in the UK. Arch Dis Child. 2010;95(10):845-849.
6. De Sanctis R, Pane M, Coratti G, et al. Clinical phenotypes and trajectories of disease progression in type 1 spinal muscular atrophy. Neuromuscul Disord. Jan 2018;28(1):24-28.
7. Mitchell I. Spinal muscular atrophy type 1: what are the ethics and practicality of respiratory support? Paediatr Respir Rev. 2006;7 Suppl 1:S210-211.
8. Bach JR. Noninvasive Respiratory Management of Patients With Neuromuscular Disease. Ann Rehabil Med. Aug 2017;41(4):519-538.
9. Chabanon A, Seferian AM, Daron A, et al. Prospective and longitudinal natural history study of patients with Type 2 and 3 spinal muscular atrophy: Baseline data NatHis-SMA study. PLoS One. 2018;13(7):e0201004.
10. Forget P, Lois F, Pendeville P. Postoperative use of nasal intermittent positive pressure in a patient with spinal muscular atrophy type II. Acta Anaesthesiol Belg. 2008;59(2):99-101.
11. Wampole A, Schroth M, Boriosi J. Survival of a child with spinal muscular atrophy and acute respiratory distress syndrome. Pediatr Pulmonol. Aug 2015;50(8):E29-31.
12. Garcia-Salido A, de Paso-Mora MG, Monleon-Luque M, et al. Palliative care in children with spinal muscular atrophy type I: What do they need? Palliat Support Care. Apr 2015;13(2):313-317.