Acoustic and surface EMG diagnosis of pediatric muscle disease

The ratio of acoustic myography (AMG) amplitude to surface electromy-ography (EMG) amplitude is proposed as a measure of mechanical output compared with electrical activity of the contractile system. AMG to EMG ra-tios were measured from 16 children with muscle disease diagnosed by clinical criteria, EMG, and/or muscle biopsy. These were compared with the ratios from 11 normal volunteers spanning the same age range (7-16 years). AMG to EMG ratios were significantly ( P < 0.01) different for the two populations. Using a linear discriminant function to define the normal range for AMG to EMG ratios yielded a sensitivity of 82 % (13 of 16 abnor-mals diagnosed) and a specificity of 91 % (1 0 of 1 1 normals). These find-ings suggest that surface recordings may provide significant diagnostic in-formation in muscle disease. The accuracy may be improved further by using additional muscles (e.g., paraspinals) and evoked twitches. Key words: pediatric muscle disease. muscle sounds electromyography muscular dystroph