Comparison of visual evoked potential changes in patients with alzheimer, vascular dementia and minimal cognitive Impairment with healthy people: a case-control study

Alzheimer dementia as the most common cause of dementia is a chronic, progressive, irreversible and incurable disease. The second most common cause of dementia after Alzheimer is vascular dementia. One of the systems involved in dementia is the visuospatial system and visual evoked potential (VEP) can be one of the diagnostic methods for this disease. Therefore, the present study aims to compare visual evoked potential changes in Alzheimer dementia, vascular dementia and patients with minimally conscious impairment (MCI) with healthy people.

A case-control study was performed on referred clients to Shariati Hospital, Tehran, Iran, from April 2015 to September 2016. Patients with cognitive impairment went through Montreal cognitive assessment (MOCA) test and divided into three groups of Alzheimer dementia, vascular dementia and patients with minimally conscious impairment. Subjects with normal cognition were included in the control group. The visual evoked potential test was performed on all participants in two  Methods pattern shift visual evoked potential (Ps-VEP) and flash visual evoked potential (f-VEP) and results were compared between groups.

Forty patients were studied in four groups (three patient groups and one control group). 70 percent in Alzheimer group and 60 percent in vascular dementia group had abnormal pattern shift visual evoked potential. Only in Alzheimer group visual evoked potential P100 latency was significantly higher than control group and in other groups, there was no significant difference. Also there was no significant difference between groups in the study of flash visual evoked potential variables including P1, N2, P2 and N3.

This study showed that only Alzheimer was associated with a significant increase in visual evoked potential P100 latency. On the other hand the other hand, there was no significant difference in flash visual evoked potential variables including P1, N2, P2 and N3 between different groups which shows that flash visual evoked potential cannot differentiate between Alzheimer dementia, vascular dementia, patients with minimally conscious impairment and normal people.