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Relation of Interictal Spike Frequency to 1 H‐MRSI‐Measured NAA/Cr
Author(s) -
Serles Wolfgang,
Li Li Min,
Caramanos Zografos,
Arnold Douglas L.,
Gotman Jean
Publication year - 1999
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/j.1528-1157.1999.tb01605.x
Subject(s) - ictal , epilepsy , nuclear magnetic resonance , nuclear medicine , temporal lobe , electroencephalography , spike (software development) , partial epilepsy , magnetic resonance imaging , chemistry , neuroscience , medicine , physics , psychology , radiology , management , economics
Summary:Purpose: Whereas EEG spiking and decreases of the neuronal marker N ‐acetyl‐aspartate (NAA) both localize well the epileptic focus, the significance of the intensity of these variables is unclear. Therefore we investigated whether the frequency of interictal surface spikes is related to the degree of N ‐acetyl‐aspartate/creatine (NAA/Cr) ratio decrease as measured by proton magnetic resonance (MR) spectroscopic imaging ( 1 H‐MRSI) in patients with intractable partial epilepsy. Methods: We retrospectively studied 14 patients, nine with temporal lobe epilepsy and five with frontal lobe epilepsy. Spikes that occurred during prolonged video‐EEG monitoring from electrodes placed according to the International 10–20 system were counted blinded to the 1 H‐MRSI results. Eight electrode positions (F3/4, C3/4, T3/4, T5/6) were assigned to underlying brain subregions in the 1 H‐MRSI volume of interest. We converted NAA/Cr ratios into z‐scores (NAA/Cr z ) to compared NAA/Cr values directly across subregions. We calculated Spearman rank‐order (ρ) and Pearson product‐moment ( r ) correlations between spike frequency and NAA/Cr z values overall, as well as within each brain subregion. Results: We found an overall negative relation between spike‐frequency data and NAA/Cr z data (ρ=−0.341). When analyzing only spiking subregions, this negative relation became slightly stronger (ρ=−0.442; r =−0.338). When data from the eight sites were considered separately, this negative relation remained in most instances. Conclusions: Our results reveal a trend toward higher interictal spike frequencies on surface EEG in regions of pronounced neuronal metabolic damage or dysfunction. This suggests that both variables parallel an underlying pathologic substrate, although the pathophysiologic processes may be distinct.