Spinal Muscular Atrophy

Incidence: 7.8 -10:100,000 live births.

Estimated panethnic disease frequency: ∼1:11,000.

Airway: Intubation can be difficult.

Pts may need postop respiratory support.

Anesthetic risk varies significantly between the different types of SMA.

Pts may display increased sensitivity and prolonged effect of neuromuscular blockers.

Postop respiratory depression could be catastrophic.

Concomitant pulmonary disease and bulbar dysfunction.

Gastroesophageal reflux.

Prolonged effects of nondepolarizing neuromuscular blockers (even after reversal).

Neuromuscular monitoring can be unreliable.

SMA is an autosomal recessive neuromuscular disease.

The disorder leads to degeneration of the anterior horn cells of the spinal cord, which causes muscle weakness.

The rate of progression varies between pts and is classified in four categories:

• SMA I (Werdnig-Hoffman disease): Onset of symptoms before 6 mo of age

• SMA II (Dubowitz type): Onset between 6 and 18 mo

• SMA III (Kugelberg Welander disease): Present later in childhood

• SMA IV (adult type): Onset during middle or late age

Prognosis for long-term survival depends on the type and ranges from neonatal death to onset of weak muscles in adulthood.

Respiratory failure is the major cause of mortality.

Scoliosis and chest wall muscle weakness may predispose to pulmonary dysfunction.

Normal intellectual and emotional capacity.

Autosomal recessive inheritance can occur with deletions or mutations in the survivor motor neuron genes located on chr5q13.

The loss of full-length SMN protein leads to degeneration of anterior spinal motor neurons and, in severe cases, degeneration of brainstem nuclei.

Degeneration of spinal anterior neurons and brainstem nuclei correspond to a range of clinical characteristics, including global hypotonia, pulmonary insufficiency, and autonomic and bulbar dysfunction.