Event related potentials in patients with transient global amnesia--a prospective controlled study

The aim of this study is to evaluate changes in the latencies and amplitudes of event-related potential (ERP) components as well as cognitive habituation in patients with transient global amnesia (TGA) in order to further characterize the pathology of this syndrome.

Clinical data of 43 consecutive patients with TGA was collected at a university neurology department. Follow-up examination was performed at an average of 17months after TGA. Results were compared to 43 age- and sex-matched healthy control subjects.

All ERP latencies of patients examined within 10days after the TGA period were significantly increased, and the P3 amplitude was significantly decreased as compared to healthy control subjects. The rate of pathological P3 latencies was significantly higher in TGA patients. A normal P3 latency habituation was detected in 84% of all healthy controls (mean habituation 10ms) and in 33% of all TGA patients (mean habituation -6ms). There was no significant improvement of all latencies and the other ERP parameters, including the loss of habituation, after a mean observation period of 17months. The data of three patients who were measured during the TGA period suggest a severe impairment of ERP during this period.

Our findings give new insight into the pathology of TGA and put into question if TGA is an event of a simple transient character. In this first investigation of cognitive habituation in patients with TGA, we found a characteristic loss of cognitive habituation similar to observations in migraine.