THE DYSTROPHIC RETINA IN MULTISYSTEM DISORDER - THE ELECTRORETINOGRAMIN NEURONAL CEROID-LIPOFUSCINOSES

The neuronal ceroid lipofuscinoses (NCL) are neurodegenerative disorde rs with psychomotor deterioration, seizures, visual failure and premat ure death, all associated with abnormal storage of lipoproteins within lysosomes. The most common forms of NCL are an infantile form (INCL, CLN1), a late infantile form (LINCL, CLN2) and a juvenile onset form ( JNCL, CLN3). The electroretinogram (ERG) is abnormal early in all thre e of these forms and eventually is totally ablated. The purpose of thi s report is to describe the ERG in INCL, LINCL and JNCL. The ERGs of 7 patients who were examined by the author over the past 15 years were reviewed. Ganzfeld ERG responses were recorded using the ISCEV standar d protocol and an intensity response series over a 3.7 log unit range. The earliest ERG manifestation of INCL is a marked loss of the scotop ic and photopic b-wave with relative preservation of the a-wave; this defect, which was evident for both rods and cones, suggests preservati on of photoreceptor outer segment function with severe disturbance of transmission of the signal to the second-order neuron, the bipolar cel ls. For LINCL, the rod responses were mildly abnormal but more preserv ed than in INCL or JNCL. The cone b-wave amplitudes in patients with e arly LINCL were severely subnormal with prolonged implicit times. Pati ents with JNCL invariably showed severe to profound ERG abnormalities when first tested, with essentially no rod-mediated activity and marke d loss of a-wave amplitudes with even greater loss of b-wave amplitude s, creating electronegative configuration waveforms. Differences in th e ERG responses were thus found that provide further clues to the earl iest site of pathology within the retina.