Motor cortex excitability in transient global amnesia.

OBJECTIVE

To investigate the physiology of motor cortical areas in patients with transient global amnesia (TGA).

MATERIALS AND

METHODS

We performed transcranial magnetic stimulation (TMS) and single photon emission computed tomography (SPECT) in 13 patients during and after the acute phase of a typical episode of TGA. Measures of cortical excitability included motor threshold (MT) to magnetic stimulation, cortical silent period (SP) duration and intracortical inhibition (ICI) using a paired-pulse TMS technique.

RESULTS

We found thalamic hypoperfusion and an ipsilateral significantly decreased ICI during the acute phase of TGA.

CONCLUSIONS

Reduced activity in inhibitory circuits may explain why PET studies of patients with TGA showed neocortical hypometabolism. Our findings are consistent with the hypothesis that frontal cortex dysfunction probably due to damage affecting the thalamocortical circuits may play an important role in the pathogenesis of the syndrome.