DIFFERENT SUSCEPTIBILITIES OF THE GENICULATE AND EXTRAGENICULATE VISUAL PATHWAYS TO HUMAN CREUTZFELDT-JAKOB DISEASE (A COMBINED NEUROPHYSIOLOGICAL-NEUROPATHOLOGICAL STUDY)

Flash evoked visual potentials (FEPs) of 7 patients with advanced Creutzfeldt-Jakob disease (CJD) were compared with those recorded in 7 patients with senile dementia of the Alzheimer type (SDAT), in 13 age- and sex-matched healthy volunteers and in 7 neuropsychiatrically normal subjects whose occipital evoked responses were increased in amplitude (amplitude controls). Post-mortem examination was performed in 4 of 7 CJD patients in order to map pathological changes along the visual pathways, including the retino-geniculo-striate and extrageniculate pathways. Normal FEPs were typified by 2 constant early components (P1 and N2) followed by several (3 or more) late components that were characterized by marked interindividual variability. Amplitude controls had enlarged (from 14 to 44.8-mu-V, mean 25.7) P1 component. Both SDAT and CJD patients had normal early FEP waves (P1 and N2) and important alterations of the late FEP components. Moreover, a late positive component was responsible for abnormally enlarged FEPs (52.6 and 58.2-mu-V) in 2 CJD patients. Finally, electroretinograms, recorded in 1 CJD patient, were normal. These findings suggested relative functional integrity of the retino-geniculo-striate pathway associated with important dysfunction of the cortical visual processing in both SDAT and CJD patients. Pathological studies disclosed preservation of optic nerves, chiasmas, lateral geniculate nuclei and Gennari's strip of the striate cortex but associated with important spongiform change, neuronal loss and gliosis in the superior colliculi (layer II), pulvinar, extrastriate cortex and layers II-III, V and VI of the striate cortex. We conclude that different visual pathways have different susceptibilities to CJD: important functional and anatomical alterations of the intracortical and extrageniculate pathways contrast with relative preservation of the retino-geniculo-striate pathway.