Gd. Herzon et Dl. Zealear, INTRAOPERATIVE MONITORING OF THE VISUAL-EVOKED POTENTIAL DURING ENDOSCOPIC SINUS SURGERY, Otolaryngology and head and neck surgery, 111(5), 1994, pp. 575-579
Iatrogenic blindness resulting from conventional and endoscopic sinus
surgery continues to be a major concern to the head and neck surgeon.
A new electrophysiologic monitoring technique has been developed that
can help avoid damage to the optic nerve and visual system. The approa
ch involves monitoring the visual evoked potential with presentation o
f flash stimuli to the eyes. Thirty patients with chronic sinusitis un
derwent endoscopic sinus surgery with visual evoked potential monitori
ng. The procedures were carried outwith patients under intravenous gen
eral anesthesia. Needle cortical electrodes were placed in the scalp.
A modified light-emitting diode array/goggle was positioned in front o
f the patient's closed eyes. A triggered flash of 2 Hz was delivered t
hrough the goggle to stimulate the patient's retina. Cortical response
s were amplified and averaged for 100 trials. Amplitude and peak-laten
cy changes were monitored to alert the surgeon to any change in the vi
sual response during the surgical dissection. Although no changes in r
esponse were noted during dissection, cold-water irrigation and reflec
ted telescopic light could produce variations in the recorded response
s, as will be discussed. Visual evoked potential monitoring may preven
t a surgeon from continuing a bilateral procedure when there is indica
tion of iatrogenic visual loss from dissection on the first side. Visu
al evoked potential also reassures the operator that no damage has occ
urred to the visual pathway at the conclusion of a case. Methods, case
selection, operative technique, and documentation of monitoring will
be discussed.