Dissertação para obtenção do Grau de Mestre em
Engenharia BiomédicaPurpose: The purpose of this thesis was to provide quantitative measures of the
co-registration of transcranial magnetic stimulation (TMS) and electroencephalogram
(EEG). The EEG is used to study changes in the neuronal activity evoked by the
non-invasive technique TMS. These effects are determined mainly based on clinical
judgment. Current uses in the diagnosis of epilepsy are based only on EEG, not taking
into consideration the low sensitivity in the interictal period, in particular if routine recordings are used.
Methods: Patient data was gathered, analyzed and compared to healthy controls. A
total of ten patients and eighteen healthy subjects underwent sessions of 75 TMS pulses.
The responses to the pulses were filtered and averaged. The use of topographical
scalp plots of amplitude and power, and time-series analysis of power in search for
late responses provide results which enable separation of epilepsy patients and healthy
controls. By investigating the significance of the results it is also possible to determine, in a quantitative way how reliable the methods are for distinguishing between the two groups.
Results: The definition of what is a response is critical in this project, and as such must consider: significant power change, be above a certain amplitude, and be localized. Still, this procedure results in a non distinguishable threshold to separate both groups.
Conclusions: Analysis of the receiver operating characteristic (ROC) curves also led to the understanding the method established is not entirely reliable because it cannot in fact determine differences. Since all patients were under treatment with anti-epileptic drugs(AEDs), it becomes necessary to elaborate a pilot study with recently diagnosed subjects where hyperexcitability is still present
