Abnormal pattern electroretinograms with macular cherry-red spots: evidence for selective ganglion cell damage.

A macular cherry red spot is a strikingly visible abnormality indicating storage of an abnormal metabolic product by the retinal ganglion cells. The flash and pattern electroretinograms (ERG) and visual evoked potentials (VEP) of a patient with the cherry-red spot-myoclonus syndrome, a sialidosis due to neuraminidase deficiency, were studied. The flash ERG was normal but the pattern ERG had an abnormal waveform with a significantly attenuated p-q wave component. Corresponding flash VEPs were normal, but pattern VEPs were delayed. This case documents human evidence that the pattern ERG is organised in the ganglion cells whereas the flash ERG, as is well known, is generated in the distal retina.