Presenile dementia--the use of the flash and pattern VEP in diagnosis.

Flash, pattern reversal and pattern onset-offset VEPs were recorded in 17 patients with a clinical diagnosis of presenile dementia. The results were compared with those from two control groups--17 normal volunteers of equivalent ages and 17 patients from the same psychiatric hospital with affective disorders but no clinical evidence of dementia. The flash P2 component was found to be significantly delayed in the group of patients with dementia, but the latency of the P1 component and pattern VEP components were all within normal limits. This unusual finding presents a useful index for the diagnosis of presenile dementia.