Spinal Muscular Atrophy

Spinal Muscular Atrophy, the number one genetic killer of children under the age of two, is a group of inherited and often fatal diseases that destroys the nerves controlling voluntary muscle movement involved with crawling, walking, head and neck movements, swallowing, and breathing.  Weakness in the legs is generally greater than weakness in the arms.  Some abnormal movements of the tongue, called fasciculations, may be present in individuals with severe forms of the disease.  Sensory functions (sight, hearing, touch, etc.) are unaffected.  SMA does not impair either intelligence or development of the personality.  In fact, many individuals with SMA are exceptionally bright and academically accomplished.

There are at least three distinct types of SMA, which vary greatly in terms of symptoms, severity, and long-term outlook.  Classification is made on the basis of the degree of motor development attained and by age of the patient at diagnosis.


Type I (acute/severe)

Type I acute SMA is also called Werdning-Hoffmann disease or infantile-onset spinal muscular atrophy.  The diagnosis is usually made before six months of age, and in the majority of cases, before three months.  These infants have severe muscle weakness and frequently have difficulty swallowing and feeding.  Most children with SMA Type I are never able to lift their heads.  There is general weakness in the intercostal and accessory respiratory muscles.  The prognosis for children with this most-severe form of SMA is quite poor, chiefly as a result of respiratory failure.  Although most do not survive beyond two years, some live to be four or older.


Type II (chronic)

Typically, children with SMA Type II demonstrate normal motor development up to six or eight months of age.  They may sit unsupported, but are unable to reach a sitting position without assistance.  Diagnosis of SMA Type II is almost always made before two years of age, frequently because the children show no inclination to walk.  Later, however, they may be able to stand or even walk with the assistance of braces or other forms of support.  Feeding and swallowing problems are not usually associated with Type II.  As with Type I, children with SMA Type II rely primarily on their diaphragm for breathing.


Type III (mild)

SMA Type III, the mildest form of the disease, is also called Wohlfart-Kugelberg-Werander Syndrome.  Diagnosis is usually made around two years of age, after the child has acquired the ability stand and/or walk without assistance.  The use of a walker and braces may become necessary; a lightweight, manual wheelchair may be useful for traveling distances.  Most people with mild SMA have fairly benign symptoms and do not become progressively weaker with age.


There is no way around the fact that a diagnosis of SMA Type I is devastating.  However, new technologies, techniques, and an improved understanding on the part of healthcare professionals can ease some of the difficulties and anxieties of caring for the complex medical needs of these infants and young children.  When the struggle to keep a child alive and comfortable is lessened, parents may devote more time and attention to their child’s intellectual development and emotional health.  Importantly, more time is available for family and personal needs.  Although life will be short, the illness places no limits on a child’s ability to feel happy and loved.