Electroretinogram in Duchenne/Becker muscular dystrophy

The authors studied all cases with dystrophinopathy consecutively reviewed between May 1995 and December 1996 by means of electroretinography (ERG), which was recorded using skin eyelid electrodes and with standard flash stimulation. This methodology can detect the functional abnormalities associated with dystrophinopathies. The most valuable parameter is the ratio of B-wave amplitude to A-wave amplitude (B/A amplitude ratio), which was greater than 2 in all normal control patients (n = 10) and nondystrophinopathic muscular dystrophy (MD) patients (n = 2). It was less than 2 in 100% (n = 16) of Duchenne muscular dystrophy (DMD) patients (mean ratio 0.73; range 0.4-1.26). It was less than 2 in 71% (n = 7) of Becker muscular dystrophy (BMD) patients (mean ratio 1.12; range 0.88-1.37), and less than 2 in 50% (n = 4) of definitive DMD carriers. Twenty-nine percent of BMD, 50% of DMD carriers, and the only case with asymptomatic dystrophinopathy had normal ratios (greater than 2). The differences between the mean ratios of control, DMD, and BMD groups were statistically significant, all of them with P < 0.001. ERG abnormalities of dystrophinopathies were associated with the more severe muscular phenotype but not with the presence or location of gene deletion. ERG is an easy and simple technique that is useful in cases of suspected dystrophinopathy with a nonconclusive molecular study. It is less useful in patients who are DMD carriers.