Electrophysiological changes associated with optic nerve compression caused by the distension of orbital varices

Verma, Amit S; Dwarika, Dorian; Reid, Robert A.; Ramchandani, Mahesh; Good, Peter

doi:10.1111/j.1600-0420.2007.00971.x

Cited by 2 publications

(2 citation statements)

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“…The investigation of visually evoked potentials (VEPs) is a valuable method to assess optic nerve damage, and the characteristics of VEPs have been reported (Gra¨nse 2006;Verma et al 2008). Pattern reversal VEPs (P-VEPs) are performed using different reversal rates: low temporal frequencies that allow the recovery of the visual system before the next stimulus is delivered (transient P-VEP) and higher (> 4 Hz) frequency rates that allow the response to reach a steady-state level (steady-state P-VEP).…”

Section: Introductionmentioning

confidence: 99%

Shift of temporal responsivity curve of pattern reversal visually evoked potentials to lower frequencies in patients after recovery from optic neuritis

Okuno¹,

Oku²,

Sugasawa³

et al. 2009

Acta Ophthalmologica

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ABSTRACT.Purpose: To investigate the responsivity of the visual system to pattern reversal stimuli of different reversal rates in optic neuritis patients after a full recovery of visual acuity. Methods: Thirty eyes with optic neuritis and 30 eyes of age-matched normal controls were studied. Steady-state pattern reversal visually evoked potentials (P-VEPs) were recorded using reversal rates of 2, 10, 20 and 30 Hz. The relationship between the amplitudes of the P-VEPs and reversal rate was analysed. The temporal responsivity curves of the two groups were compared. Results: The means ± standard deviations (SDs) of the P-VEP amplitudes in the normal controls were 7.08 ± 2.97, 8.60 ± 2.37, 4.69 ± 1.99 and 2.11 ± 1.24 lV at reversal rates of 2, 10, 20 and 30 Hz, respectively. The comparable amplitudes from the recovered optic neuritis patients were 8.01 ± 2.45, 6.57 ± 2.54, 2.73 ± 1.76 and 0.94 ± 1.27 lV. The mean amplitude of the P-VEPs elicited at a reversal rate of 2 Hz was not significantly different from that of normal controls. However, the amplitudes of the P-VEPs at reversal rates of 10, 20 and 30 Hz were significantly smaller in the recovered optic neuritis patients than in the controls. In addition, the average maximum amplitude of the P-VEPs was obtained at 10 Hz in normal subjects and at 2 Hz in the recovered optic neuritis patients. Conclusion: These results indicate that the peak of the temporal tuning curve of the P-VEP shifts to lower frequencies in recovered optic neuritis eyes, and that the reduced amplitudes at higher frequencies seem to be characteristic of the visual system of patients with recovered optic neuritis.Key words: optic neuritis -pattern visually evoked potential -pattern visually evoked response -temporal frequency -temporal responsivity curve

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Section: Introductionmentioning

confidence: 99%

Shift of temporal responsivity curve of pattern reversal visually evoked potentials to lower frequencies in patients after recovery from optic neuritis

Okuno¹,

Oku²,

Sugasawa³

et al. 2009

Acta Ophthalmologica

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“…In 2008, Verma et al. reported a case of optic nerve compression by orbital varices, which led to decreased amplitude of response to flash and checker pattern stimuli in the visual evoked potential during Valsalva's manoeuvre 3 . In our case, the likely explanation for pupillary dilatation during Valsalva's manoeuvre is that as the varices engorge with blood and enlarge, they compress the ciliary ganglion, thus inhibiting tonic pupillary constriction, either through a direct compressive effect or perhaps through local haemodynamic effects.…”

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confidence: 99%