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Photosensitive Epilepsy Studied by Functional Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy
Author(s) -
Chiappa Keith H.,
Hill Rosamund A.,
HuangHellinger Frank,
Jenkins Bruce G.
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.tb00899.x
Subject(s) - occipital lobe , photic stimulation , visual cortex , functional magnetic resonance imaging , ictal , epilepsy , stimulation , neuroscience , cortex (anatomy) , stimulus (psychology) , magnetic resonance imaging , gyrus , haemodynamic response , psychology , nuclear magnetic resonance , medicine , visual perception , radiology , physics , heart rate , blood pressure , perception , psychotherapist
Summary: Purpose: To study metabolic and hemodynamic correlates of photic stimulation‐triggered discharges. Methods: Simultaneous EEG, functional MRI (fMRI) and magnetic resonance spectroscopy (MRS) were performed in nine patients with photosensitive epilepsy and in 12 normal subjects. Results: Prominent visual cortex activation was seen in all normal subjects and patients, and no fMRI‐registered hemodynamic abnormalities were correlated with the brief photoparoxysmal spike‐wave activity evoked in the photosensitive patients. However, irrespective of the presence of a spike‐wave response to the photic stimulation, the photosensitive patients showed four findings not seen in the normal subjects: (a) slightly, but significantly, elevated lactate levels in the occipital cortex in the resting state; (b) an increased area of visual cortical activation with photic stimulation; (c) simultaneous with the occipital cortex stimulus‐induced increased fMRI signal, there were noncontiguous areas of signal attenuation most prominent in perirolandic regions; and (d) a marked decrement (undershoot) of fMRI signal intensity immediately after the photic stimulation in the occipital cortex and in the region of the posterior cingulate gyrus. Conclusions: These findings suggest abnormal interictal metabolism and increased vascular reactivity in the photosensitive patients.