In order to be diagnosed with Spinal Muscular Atrophy, symptoms need to be present. In most cases a diagnosis can be made by the SMN gene test ... In some cases, when the SMN gene test is not possible or does not show any abnormality, other tests such as an EMG electromyography (EMG) or muscle biopsy may be indicated.
SMA type I, also known as severe infantile SMA or Werdnig Hoffmann disease, is the most severe, and manifests in the first year of life. This type generally onsets quickly and unexpectedly after birth; babies diagnosed with Type I SMA do not generally live past one year of age.
Infantile SMA is the most severe form. Some of the symptoms include:
* muscle weakness
* poor muscle tone
* weak cry
* limpness or a tendency to flop
* difficulty sucking or swallowing
* accumulation of secretions in the lungs or throat
* legs that tend to be weaker than the arms
* hypotonia [abnormally low muscle tone]
, areflexia [below normal or absent reflexes]
, and multiple congenital contractures (arthrogryposis) associated with loss of anterior horn cells
* feeding difficulties
* increased susceptibility to respiratory tract infections
* developmental milestones, such as lifting the head or sitting up, can't be reached.
In general, the earlier the symptoms appear, the shorter the life span. The onset is sudden and dramatic. Once symptoms appear the motor neuron cells quickly deteriorate shortly after. The disease can be fatal and there is no cure for SMA yet known.