Focal increases in perfusion and decreases in hemoglobin oxygenation precede seizure onset in spontaneous human epilepsy.
OBJECTIVE
Optical recording of intrinsic signals provides the highest combined spatial and temporal resolution with broad spatial sampling for measuring cerebral blood volume (CBV) and hemoglobin oxygenation in cerebral cortex. Few opportunities arise to apply this laboratory method to record spontaneous seizures in unanesthetized human brain during neurosurgery. We report such a rare opportunity in a man with recurrent focal epilepsy arising from a cavernous malformation.


METHODS
We recorded intrinsic optical signals (IOS) from human cortex intraoperatively during spontaneous seizures arising from brain surrounding a small cavernous malformation in an awake patient using only local anesthesia with simultaneous electrocorticography. The IOS was recorded at two wavelengths, one an isosbestic point for hemoglobin to measure CBV (570 nm) and the other at a wavelength more sensitive to deoxygenated hemoglobin (Hbr) (610 nm). A modified Beer-Lambert calculation was used on two separate but similar seizures to approximate changes in Hbr, CBV as well as oxygenated hemoglobin (HbO(2)).


RESULTS
Electrographically recorded seizures (n = 3) elicited a focal increase in both Hbr and CBV that lasted for the duration of the seizure, indicating that perfusion was inadequate to meet metabolic demand. Remarkably, these hemodynamic changes preceded the onset of the seizures by approximately 20 s and occurred focally over the known location of the lesion and the seizure onsets.


CONCLUSIONS
These findings demonstrate that the hemoglobin becomes deoxygenated in spite of large increase in CBV during spontaneous human focal seizures and that optically recorded hemodynamic events can be used both to predict and localize human focal epilepsy. Such data may someday be useful to assist in the presurgical evaluation of patients considered for epilepsy surgery and to predict the timing and location of seizure onsets.
Department of Neurosurgery, Weill Medical College of Cornell University, New York Presbyterian Hospital, 525 East 68th Street, New York, NY 10021, U.S.A.
Mingrui
M
Zhao
Minah
M
Suh
Hongtao
H
Ma
Challon
C
Perry
Andrew
A
Geneslaw
Theodore H
TH
Schwartz
D001810:Blood Volume / Q000502:physiology; D019069:Cell Respiration / Q000502:physiology; D002540:Cerebral Cortex / Q000098:blood supply / Q000378:metabolism*; D003936:Diagnosis, Computer-Assisted; D004569:Electroencephalography / Q000706:statistics & numerical data; D004828:Epilepsies, Partial / Q000209:etiology / Q000378:metabolism* / Q000601:surgery; D020786:Hemangioma, Cavernous, Central Nervous System / Q000150:complications / Q000601:surgery; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010092:Oximetry; D010100:Oxygen / Q000097:blood / Q000378:metabolism; D010108:Oxyhemoglobins / Q000032:analysis / Q000378:metabolism*; D012008:Recurrence; D012039:Regional Blood Flow / Q000502:physiology*; D013226:Status Epilepticus / Q000378:metabolism
D006454:Hemoglobins; D010108:Oxyhemoglobins; D010100:Oxygen