Prolonged latencies of pattern reversal visual evoked early potentials in Alzheimer disease

We studied patients with Alzheimer disease, Parkinson disease, and amyotrophic lateral sclerosis (ALS) with a pattern reversal (checkerboard light diode) visual evoked potential (VEP) paradigm to observe the involvement of the visual system in these primary neurodegenerative diseases. All patients were in the mild or moderate stage of the disease. In Alzheimer disease there was a significant increase of the latency of the P55, N65, P100, and N130 components, as well as an increase of the P55-P100 interpeak latency, compared with matched normals. These alterations indicate dysfunction of both the retinocalcarine pathway and the cortex. Patients with Parkinson disease revealed a significant delay of the N130 component only. Patients with ALS had normal latency values of all VEP components. The P100-N130 amplitude was diminished in all these disease groups compared with age-matched controls.