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Scalp‐Recorded, Ictal Focal DC Shift in a Patient with Tonic Seizure
Author(s) -
Ikeda Akio,
Yazawa Shogo,
Kunieda Takeham,
Araki Kasumi,
Aoki Tomokazu,
Hattori Hamo,
Taki Waro,
Shibasaki Hiroshi
Publication year - 1997
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.1528-1157.1997.tb00074.x
Subject(s) - ictal , scalp , epilepsy , electroencephalography , electrocorticography , tonic (physiology) , neuroscience , psychology , medicine , audiology , anatomy
Summary: Purpose: We recorded focal ictal DC shifts from scalp electrodes in a 9–year‐old boy with intractable, clinically generalized tonic seizures. The patient had a high intensity signal abnormality of the left temporal cortex with thickening of the gyri on T2–weighted MRI. Methods: Scalp digital EEGs were recorded using electrodes made of silver/silver chloride. The low frequency filter (LFF) was set at 0.016 Hz. Recorded seizures were subsequently analyzed with LFF settings of 1.0, 0.016 and 0.03 Hz. Results: All recorded seizures initially showed diffuse, low voltage, high frequency activity (electrodecremental pattern) followed 10–20 s later by quasirhythmic activity over the left frontotemporal region. In two seizures, LFF of 0.016–0.03 Hz revealed a slow negative shift over the left frontotemporal area simultaneously with onset of the bilateral electrodecremental pattern. However, in the other seizures, this initial slow negative shift was obscured by artifacts. Subsequent electrocorticography (ECoG) delineated frequent epileptiform discharges in the left temporal as well as frontal cortex. Conclusions: Scalp‐recorded ictal DC shifts may help identify focal epileptogenic brain area in patients with clinically generalized seizures although the technique is vulnerable to artifact.