Spinal muscular atrophy (SMA) can be diagnosed when certain findings are present.
Criteria for the diagnosis of SMA:
(1) history of a motor disorder, with symmetrical weakness and muscular atrophy
(2) evidence of motor unit disease on physical examination
(3) evidence of degeneration of anterior horn cells in the spinal cord and brainstem (lower motor neurons)
The diagnosis is confirmed by changes in the SMN1 gene.
