Wright, M.-A.S.Y.; (2011) Investigation of cortical excitability in epilepsy using transcranial magnetic brain stimulation. Doctoral thesis , UCL (University College London).

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Abstract

This thesis describes a study of 70 patients with epilepsy and a normal control group. Subjects were studied with Transcranial Magnetic Brain Stimulation using a variety of parameters including measurement of motor evoked potentials, active and resting motor threshold, paired pulse inhibition and facilitation and cortical silent period. Data from normal subjects, 40 patients with temporal lobe epilepsy (TLE) and 17 patients with neocortical epilepsy was collected. The following data were acquired from some or all of each group: resting motor threshold (RMT), active motor threshold (AMT), cortical silent period (CSP), and conditioning-test stimulation data from which were derived measures of intracortical inhibition (SICI) and facilitation (SICF). Data were also obtained regarding drug treatment and seizure timing. Groups of subjects were compared. TLE patients were studied serially to examine the effects of seizures on TMS parameters. The main findings were that the groups differed regarding RMT and AMT, probably reflecting drug treatment; the patients groups differed in SICF; serial studies of the TLE patients showed changes in SICI and SICF which preceded seizures. RMT and AMT were elevated following seizures. Comparing the TLE and neocortical patient groups, there was higher SICF in the mTLE group. The difference between the patient groups demonstrates that epilepsies arising from distinct areas of the brain effect cortical excitability measured from the motor cortex in different ways. Repetitive TMS (rTMS) was undertaken in 11 subjects with refractory localisation related epilepsy. No effect of rTMS on the number of EEG spikes was seen as a result of a single session of rTMS, suggesting a variety of possibilities; rTMS may have no beneficial effect on focal seizures; the stimulus parameters may have been unsuitable; the chosen outcome measure – number of spikes – may be too inherently variable to show an effect after a relatively brief period of rTMS.

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