Researcher: Wilma van de Wassenberg, PhD

Other supervisors: Nico Leenders, MD, PhD, Han van der Hoeven, MD, PhD

Thesis defense: 2008 (winner BCN Thesis award)

Electroencephalogram (EEG) measures the electric activity produced by the brain with electrodes placed on the scalp. It is used for monitoring or as diagnostic tool for neurological disorders. In practice a maximum of 21 electrodes are generally used for a clinical EEG recording. However, EEG systems with 128 and 256 electrodes are also available and used for fundamental research. In this thesis we investigate whether the extra information obtained with 128-channel recordings is clinically relevant. We have focused on evoked potentials (EPs). EP is the electric activity of the brain caused by a stimulus (e.g. a flashlight).
We showed that a measure often used for evoked potentials, the peak amplitude, can be estimated more accurately by using 128 channels recordings than by conventional recordings. Therefore this technique might be more sensitive to pathological changes.
In addition, we developed a new technique to estimate EP symmetry (similarity of EPs generated in left and right hemisphere). This technique might be useful for diagnosis of neurological disorders with brain damage in one hemisphere.
Both methods have been applied to a group of patients with parkinsonism; neurological symptoms typical for Parkinson’s disease. No differences could be observed in amplitude or symmetry between patients with different parkinsonian disorders. Therefore, (so far) these methods cannot be used as diagnostic tool for neurological disorders.
Future research will show whether small adaptations to the stimulation method or analysis technique will result in an improvement of the diagnostic value and whether these methods are useful for other neurological disorders.

References

• van de Wassenberg WJ1, van der Hoeven JH, Leenders KL, Maurits NM. 128-channel somatosensory evoked potentials in the differential diagnosis of parkinsonian disorders. Parkinsonism Relat Disord. 2009 Sep;15(8):564-71. PMID: 19303347.
• van de Wassenberg WJ1, Kruizinga WJ, van der Hoeven JH, Leenders KL, Maurits NM. Multichannel recording of tibial-nerve somatosensory evoked potentials. Neurophysiol Clin. 2008 Oct;38(5):277-88. PMID: 18940615.
• van de Wassenberg WJ1, van der Hoeven JH, Leenders KL, Maurits NM. Quantifying interhemispheric symmetry of somatosensory evoked potentials with the intraclass correlation coefficient. J Clin Neurophysiol. 2008 Jun;25(3):139-46. PMID: 18469724.
• van de Wassenberg W1, van der Hoeven J, Leenders K, Maurits N. Multichannel recording of median nerve somatosensory evoked potentials. Neurophysiol Clin. 2008 Feb;38(1):9-21. PMID: 18329546.