Functional imaging with intraoperative ultrasound: detection of somatosensory cortex in dogs with color-duplex sonography.
OBJECTIVE
To evaluate the capability of intraoperative color-duplex sonography to detect eloquent flow-activated areas and their anatomic relationship in dogs.


METHODS
After craniotomy, the sensory cortex of eight dogs was identified by recording the highest amplitude detected with a grid electrode evoked with somatosensory evoked potential stimulation of the nervus ischiadicus. A 7.5-MHz linear array transducer was placed on the dura, and eight images were taken in color-coded capture mode during baseline and somatosensory evoked potential stimulation of the ipsilateral (nonevoked) and contralateral (evoked) sensory cortex. The differences in flow velocity intensities were statistically compared (Wilcoxon test) in three arbitrary velocity ranges and across all colored pixels in a region of interest between baseline and stimulation in both hemispheres.


RESULTS
Comparing both hemispheres during stimulation, the evoked sensory cortex demonstrated an increase of 10% in the number of counted colored pixels during stimulation, whereas the number of counted colored pixels in the ipsilateral sensory cortex decreased by 2% (P < 0.05), indicating an overall increase in measured flow during stimulation. Comparing differences during nonstimulation and stimulation in single hemispheres, the lowest of the three velocity ranges (approximately 10-20 mm/s) demonstrated a statistically significant (P = 0.01) increase during stimulation, whereas no change was observed during stimulation in the ipsilateral hemisphere. This increase has been confirmed by regional cerebral blood flow measurement with colored microspheres.


CONCLUSIONS
This study indicates, for the first time, the capability of intraoperative ultrasound to detect functionally important areas during evoked stimulation.
Woydt
Michael
M
Neurosurgical Department, University of Würzburg, Würzburg, Germany. m.woydt@nch.uni-wuerzburg.de
Kripfgans
Oliver D
OD
Fowlkes
Brian J
BJ
Roosen
Klaus
K
Carson
Paul L
PL
D000818:Animals; D004285:Dogs; D007432:Intraoperative Period; D013003:Somatosensory Cortex / Q000000981:diagnostic imaging* / Q000502:physiology* / Q000601:surgery; D018615:Ultrasonography, Doppler, Color