The importance of the electrophysiological tests in the early diagnosis of ganglion cells and/or optic nerve dysfunction coexisting with pituitary adenoma: an overview

Abstract

Background and methodsBased on the available literature, it is suggested, in the clinical evaluation of the chiasmal tumors, that the following electrophysiological tests: visual evoked potentials to pattern-reversal stimulation, multifocal visual evoked potentials (mfVEPs), and pattern electroretinogram (PERG) play an important role in the diagnosis of the optic nerve and retinal dysfunction in the course of pituitary tumors.ResultsMacroadenomas and also microadenomas may cause dysfunction of retinal ganglion cells (RGCs) and their axons, even in the absence of changes in the routine ophthalmological examination, retinal sensitivity in standard automated perimetry, and retinal nerve fiber layer thickness in optical coherent tomography. The most frequently observed changes in electrophysiological tests were as follows: in PVEPs—the crossed/uncrossed asymmetry distribution, altered waveform, increase in P100-wave peak time, and/or reduction in amplitude; in mfVEPs—the peak time prolongation and/or amplitude reduction in C1-wave; in PERG—the reduction in N95-wave amplitude and decreased N95:P50 amplitude ratio. Hemifield PVEPs were more often abnormal than full-field PVEPs. Multi-channel recording is recommended for the assessment of the anterior visual pathway. The use of mfVEP offers the possibility to register localized disturbances of the optic nerve and ganglion cells. Additionally, an amplitude of N95-wave reduction in PERG correlated with a lack of postoperative visual acuity recovery. The postoperative improvement in the visual field was found to be associated with a normal N95:P50 amplitude ratio. The RGCs dysfunction manifested by decrease in PhNR/b-wave amplitude ratio was associated with the worse visual fields outcome. A review of the literature summarizing the electrophysiological testing in the pituitary adenoma is discussed.ConclusionIn patients with pituitary tumor, detection of the early dysfunction of the visual pathway may lead to modification of the medical treatment regimen and reduce the incidence of irreversible optic nerve damage.

Visual acuity and its postoperative outcome after transsphenoidal adenoma resection

“…Our retrospective study focused on clinical factors predicting visual function recovery. Recent publications reported on more objective measurements to assess the prognosis, such as parafoveal and peripapillary perfusion [20], retinal nerve fiber layer thickness [21], and electrophysiological testing [19]. These measurements, together with clinical parameters and symptoms should be accounted all together to prevent irreversible optic nerve damage.…”

Visual function assessed by visually evoked potentials in adults with orbital and other primary intracranial tumors

“…Previous reports of visual electrophysiological testing in brain tumors [21][22][23][24][25][26][27][28][29][30][31][32][33] supported VEPs as an objective tool to evaluate the optic nerve function in addition to psychophysical testing. A disparity between visual acuity testing and VEPs had been inferred in the study of four patients with chiasmal gliomas presenting abnormal or non-detectable PRVEPs but good visual acuity scores.…”

“…19 Checkerboard patternreversal VEPs (PRVEP) are linked to activation of particular retinotopic fields in V1 by time-locked contrast-based stimuli, whereas flash VEP (FVEP) expresses massive cortical enhancement by luminance variation. 20 The well-established importance of VEPs in neuro-ophthalmological settings includes evaluation of the optic pathways threatened by neoplastic lesions, [21][22][23][24][25][26][27][28][29] intraoperative monitoring, 27,[30][31][32] and post-resection. 3,22,30,31 Of particular interest is the opportunity to evaluate visual function in neuro-oncologic patients with media opacities, poor cooperation, non-verbal, or unable to provide reliable information on psychophysical testing.…”

The role of pattern electroretinograms and optical coherence tomography angiography in the diagnosis of normal-tension glaucoma

“…In this study, we used the following PERG parameters 6 , 43 , 44 : (1) amplitude of N35–P50: the first positive value, calculated as the voltage difference between the first prominent negative value and the first prominent positive value, (2) amplitude of P50–N95: the first negative value, calculated as the voltage difference between the maximum peak and the subsequent trough, and (3) the implicit time (latency) for N35, P50, and N95: the time from the start of the checkerboard reversal to the appearance of a peak for each component.…”