The flash and pattern VEP as a diagnostic indicator of dementia.

Ninety-one patients with forgetfulness, confusion and depression were referred for visual evoked potential and electroencephalographic investigation. The patients were subdivided, on clinical symptoms alone, into a group of 41 with evidence of dementia and a patient control group of 50 with effective disorders. A second control group of 30 normal volunteers of equivalent age was used. In dementia the P2 component of the flash visual evoked potential is delayed, while the pattern reversal P100 component is of normal latency. This unusual combination of results from the two different visual stimuli is shown to be more specific than either the electroencephalogram or computerised tomography in the diagnosis of dementia.