Table 1.
Patient characteristics.
Fig 1.
Each device contains 19 red (654 nm) diodes that provide illuminance up to 25000 Lux.
Table 2.
Utility of VEP recording channels.
Table 3.
Relationship between VEP amplitude and visual outcome.
Table 4.
Contingency table of VEP and new visual impairment.
Fig 2.
Distribution of N75 latencies.
The median N75 latency was 87 ms.
Fig 3.
Impaired vision is associated with reduced N75 amplitude.
Box plot showing the distribution of the N75 amplitude in eyes with intact and impaired preoperative visual function. The median N75 amplitude for the intact vision group (3.92±4.09 μV, range 1.78 to 19.39 μV) was higher than that of the impaired vision group (2.03±1.16 μV, range 0.68 to 5.03 μV). Mann-Whitney P < 0.001.
Fig 4.
Asymmetric vision and VEP in a patient with a lesion in the anterior visual pathway.
(A) Anterior skull base meningioma infiltrating the sinus cavernosus of the sphenoid sinus and the right optic canal (patient 11). (B) Goldmann perimetry for the left eye: intact visual field. (C) Goldmann perimetry for the right eye: major visual field defect. (D) VEP of the left eye was highly reproducible throughout surgery (N75 at 74 ms, P100 at 83 ms). (E) In the right eye, the patient’s vision was reduced eye and VEP recording was not feasible.
Fig 5.
Transient VEP loss due to manipulation of the optic nerve.
(A) Preoperative MR image showing a recurrent craniopharyngeoma compressing the optic nerve. (B) Initially, VEP responses of the left eye were reproducible (N75 at 80 ms) in channel Oz/A+. Later in surgery the surgeon manipulated the left optic nerve. At 15:00, the VEP decrease reached the warning criterion (50%) and a warning was issued to the surgeon who consequently altered the surgical strategy. At 15:15, VEP recovered about 15min. later with prolonged latencies. At 15:29, the VEP waveform recovered at the end of the procedure. (C) VEP responses of the right eye in channel Oz/A+ remained unchanged during the manipulation.
Fig 6.
Transient VEP loss due to aneurysm clipping.
(A) Sagittal view. Fusiform dissecting aneurysm (23mmx20mmx22mm) of the posterior cerebral artery in the P2 segment (Patient 23). Clinically, it manifested with a light hemiparesis on the left side. (B) Lateral view. (C) Intraoperative screenshot after the placement of two clips. (D) Initially, VEP responses were reproducible (N75 at 93 ms) in channel O2/A+. The first clip placement led to a VEP loss after three minutes. Two minutes after the occlusion was released, the VEP recovered to its original waveform. The VEPs in channel O1/A+ remained unchanged during clipping. (E) A second transient clip placement resulted in the same pattern of VEP change.