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.