Electrical inexcitability of nerves and muscles in severe infantile spinal muscular atrophy

In early 1995, the candidate gene, the survival motor neuron (SMN) gene, was identified, making the confirmation of SMA by DNA analysis possible. 2 With the availability of a genetic test for SMA, many investigators are refining the diagnostic criteria published by the Consortium. Korinthenberg et al reported inexcitability of motor nerves in three siblings, each of whom died from SMA before 1 month of age. 4 In addition to a homozygous deletion of exons 7 and 8 of the telomeric SMN gene, all three siblings showed a large deletion in the region that includes all alleles of the multicopy markers Ag1-CA and C212, localised at the 5[variant prime] end of the two SMN gene copies.