Functional monitoring for visual pathway using real-time visual evoked potentials and optic-radiation tractography.
OBJECTIVE
It has been difficult to obtain anatomic and functional information about the visual pathway during neurosurgical operations. The aim of this study was to combine the information of the visual evoked potentials (VEPs) and the anatomic navigation of the optic radiation by diffusion tensor imaging-based tractography for functional monitoring of the visual pathway.


METHODS
The subjects were two patients with brain lesions adjacent to the visual pathway. Diffusion tensor imaging-based tractography of the optic radiation was performed by selecting appropriate regions of interest and by fractional anisotropy. During surgery, cortical VEPs were recorded continuously under general anesthesia with sevoflurane. In Patient 2, the results of optic radiation tractography were imported to a neuronavigation system to better understand the spatial relationships between the lesions and the visual pathway (functional neuronavigation).


RESULTS
In Patient 1, the lesion did not seem to be attached to the optic radiation, and VEP profiles remained stable during resection. In Patient 2, who had a lesion adjacent to the posterior horn of the lateral ventricle, VEPs suddenly diminished when resection reached the optic radiation as illustrated on the neuronavigation system. As a result, complete left hemianopia developed after surgery in Patient 2.


CONCLUSIONS
We confirmed functional correlations of the results of diffusion tensor imaging-based tractography by monitoring intraoperative VEPs. The combination of continuous VEP and optic-radiation tractography is reliable to monitor the visual function and is helpful in performing neurosurgical planning near the visual pathway.
Department of Neurosurgery, University of Tokyo, Tokyo, Japan. kamady-k@umin.ac.jp
Kyousuke
K
Kamada
Tomoki
T
Todo
Akio
A
Morita
Yoshitaka
Y
Masutani
Shigeki
S
Aoki
Kenji
K
Ino
Kensuke
K
Kawai
Takaaki
T
Kirino
D000328:Adult; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D003199:Computer Systems; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation / Q000379:methods*; D016896:Treatment Outcome; D014795:Visual Pathways / Q000473:pathology* / Q000503:physiopathology*