Pattern Electroretinograms and Visual Evoked Potentials in Idiopathic Intracranial Hypertension

Abstract

A subclinical visual dysfunction can be detected by psycho-physical methods in early-stage papilledema associated with idiopathic intracranial hypertension (IIH). We recorded steady-state pattern electroretinograms (PERGs) and visual evoked potentials (VEPs) to sinusoidal gratings of variable spatial frequency [0.6,1.0,1.4, 2.2 and 4.8 cycles/degree (cpd)] in 18 patients with IIH and early papilledema and in 21 age-matched controls. Spatial frequency selective reductions in the mean PERG (at 1–4.8 cpd) and VEP (at 4.8 cpd) amplitudes were found in patients in comparison with controls. The response functions of amplitude versus spatial frequency of patients’ PERG and VEP displayed a low-pass shape, whereas in normal subjects PERG and VEP functions showed a bandpass and a high-pass shape, respectively. PERG and VEP abnormalities were found in 14 (77.7%) and 10 (55.5%) out of 18 patients, respectively. Most of these abnormalities involved only selected spatial frequencies (1.4–4.8 cpd). These results indicate spatial-frequency-dependent functional losses on both PERG and VEP in early papilledema, and suggest a potential value of these responses for detecting subtle visual abnormalities in IIH.

Pattern electroretinogram as a function of spatial frequency after retrobulbar optic neuritis

“…Most of the PERG abnormalities found in individual patients were observed at the peak of normal spatial tuning function (1.4 c/deg). Changes in the PERG spatial tuning with selective attenuations at intermediate spatial frequencies have been also observed in early glaucoma [10,12], diabetes [9] and optic nerve compression [30]. In monkeys with experimental glaucoma, Johnson et al [12] reported that PERG losses were greatest for checks of intermediate size and that these losses predicted the histologically defined optic nerve fiber loss.…”

Sustained Raised Intracranial Pressure Implicated Only by Pattern Reversal Visual Evoked Potentials after Cranial Vault Expansion Surgery

“…Changes in ICP have well-documented affects on visual evoked potential (VEP) amplitude and latency and are therefore ideal for monitoring visual function in children with craniosynostosis [6, 7, 8, 9]. Therefore, since June 1999, all children with craniosynostosis seen at the eye clinic at Great Ormond Street Hospital have undergone flash and pattern VEP recordings as part of their routine ophthalmic assessment.…”

Objective Measures of Visual Function in Papilledema

“…In one study, PERG detected abnormalities in a higher proportion of subjects than VEP, suggesting that it is more sensitive for detection of papilledema pathology. 20 In the other study correlations between PERG and both visual field loss and structural loss of RGCs were demonstrated. 35 …”

“…Falsini et al reported the association between VEP amplitude and stimulus spatial frequency to be different in IIH and control subjects with IIH subjects having decrease of normalized amplitudes with high spatial frequency stimuli, while control subjects had decrease of amplitudes with low spatial frequency stimuli. 20 Liasis et al reported progressive amplitude decrease prior to ICP lowering surgery in craniosynostosis in 8 patients and recovery following operative intervention to lower ICP in all of them. 18 …”

“…Studies have measured PERG in mild active papilledema with minimal or no visual field loss 20 and in post-papilledema atrophy with visual field loss (Table 4). 35 Both found reduced amplitudes to be associated with papilledema.…”