-Spinal muscular atrophy (SMA), a potentially devastating and clinically underrecognized neuromuscular disorder, marked by progressive weakness and muscle atrophy resulting from the dysfunction and loss of motor neurons of the spinal cord, typically presenting early in life, has been recognized recently by the National Institute of Neurological Disorders and Stroke (NINDS) as ‘a very probably curable disease' [Sproule, D, Kaufmann, P 2010]. -SMA is a leading genetic cause of death in infancy with an estimated incidence of 1/6000 to 1/10,000 live births [Merlini et al. 1992; Emery, 1991; Pearn, 1978, 1973], with over 95% of people with SMA harboring a homozygous deletion of the Survival of Motor Neurons 1 (SMN1) gene located on chromosome 5q13 [Melki et al. 1994; Gilliam et al. 1990].
-Patients with SMA type 1 (WerdnigHoffmann) are the most severely affected and never achieve the ability to sit independently. They become symptomatic in infancy, often require a feeding tube to maintain adequate nutrition, and even with proactive respiratory management typically have a severely shortened life expectancy [Oskoui et al. 2007; Werdnig, 1891].
-SMA leads to predominantly proximal muscle atrophy and weakness, and the potential for medical complications such as scoliosis, joint contractures and ventilatory impairment [Wang et al. 2007]. This latter complication is primarily the result of respiratory muscle weakness, which prevents the normal expansion and clearance of the lungs leading to a restrictive defect.
-In recent years, advances in pulmonary care and the increasing application of noninvasive ventilatory support has dramatically improved the morbidity and mortality associated with pulmonary decline, particularly among children with severe (type 1 and 2) disease phenotypes [Oskoui et al. 2007; Bach et al. 2001, 2000]. Improvements in physical therapy management and advances in surgical approaches to scoliosis, including the use of vertical expandable prosthetic titanium rib and related ‘growing rods’ approaches [Hell et al. 2005], have allowed a more effective and timely management of secondary musculoskeletal complications. The optimization of nutritional management to avoid potential complications arising from both malnutrition [Messina et al. 2008] and obesity [Sproule et al. 2009] has also emerged as an area of increased attention in recent years [Wang et al. 2007].