Parietal lobe source localization and sensitivity to hyperventilation in a patient with subclinical rhythmic electrographic discharges of adults (SREDA).
OBJECTIVE
Subclinical rhythmic electrographic discharges of adults (SREDA) is currently considered a benign EEG pattern of uncertain significance. The underlying cortical sources and generating mechanisms are unknown. We performed a source localization analysis of SREDA with the aim of better understanding this unusual EEG pattern.


METHODS
Multiple spontaneous episodes of typical SREDA were recorded in a patient during continuous EEG monitoring. Additional SREDA episodes were induced by hyperventilation. Source localization was carried out using statistical non-parametric mapping (SNPM) of low resolution electromagnetic tomography (LORETA).


RESULTS
SNPM of both time- and frequency-domain LORETA revealed a widespread biparietal cortical origin of SREDA, the anatomical distribution of which included the parietal operculum and the known vascular watershed areas between anterior, middle and posterior cerebral arteries. Vigorous deep hyperventilation induced SREDA on three of four attempts. Mean duration of the hyperventilation-induced SREDA was approximately three times longer than spontaneous events.


CONCLUSIONS
Investigations in this patient with typical SREDA revealed hyperventilation sensitivity and a posterior hemispheric source localization maximal in the parietal cortex bilaterally, in large part overlying the anatomical distribution of the vascular watershed areas.


CONCLUSIONS
The source localization results and sensitivity to hyperventilation suggest some sort of association between cerebral vascular supply and SREDA, as originally proposed by Naquet et al. [Naquet R, Louard C, Rhodes J, Vigouroux M. A propos de certaines décharges paroxystiques du carrefour temporo-pariéto-occipital. Leur activation par l'hypoxie. Rev Neurol 1961;105:203-207.].
Zumsteg
Dominik
D
Division of Neurology, Krembil Neuroscience Centre, University of Toronto, Toronto Western Hospital, 399 Bathurst St., Toronto, Ont., Canada M5T 2S8.
Andrade
Danielle M
DM
Del Campo
J Martin
JM
Wennberg
Richard
R
D000368:Aged; D000927:Anticonvulsants / Q000627:therapeutic use; D001927:Brain Diseases / Q000188:drug therapy / Q000503:physiopathology*; D004569:Electroencephalography; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D010296:Parietal Lobe / Q000502:physiology*; D014635:Valproic Acid / Q000627:therapeutic use
D000927:Anticonvulsants; D014635:Valproic Acid