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

Electrodiagnostic tests of the visual pathway and applications in neuro-ophthalmology

This article describes the main visual electrodiagnostic tests relevant to neuro-ophthalmology practice, including the visual evoked potential (VEP), and the full-field, pattern and multifocal electroretinograms (ffERG; PERG; mfERG). The principles of electrophysiological interpretation are illustrated with reference to acquired and inherited optic neuropathies, and retinal disorders that may masquerade as optic neuropathy, including ffERG and PERG findings in cone and macular dystrophies, paraneoplastic and vascular retinopathies. Complementary VEP and PERG recordings are illustrated in demyelinating, ischaemic, nutritional (B12), and toxic (mercury, cobalt, and ethambutol-related) optic neuropathies and inherited disorders affecting mitochondrial function such as Leber hereditary optic neuropathy and dominant optic atrophy. The value of comprehensive electrophysiological phenotyping in syndromic diseases is highlighted in cases of SSBP1-related disease and ROSAH (Retinal dystrophy, Optic nerve oedema, Splenomegaly, Anhidrosis and Headache). The review highlights the value of different electrophysiological techniques, for the purposes of differential diagnosis and objective functional phenotyping.

Retinal nerve fiber layer thickness and its correlation with visual symptoms and radiological features in pituitary macroadenoma

Objective

The aim of the study was to evaluate the association of the thickness of retinal nerve fiber layer (RNFL) with (i) visual symptoms and (ii) suprasellar extension defined by magnetic resonance imaging (MRI) in patients with pituitary macroadenoma.

Materials and Methods

RNFL thickness of 50 consecutive patients operated for pituitary macroadenoma between July 2019 and April 2021 were compared with standard visual examination findings and MRI measurements such as optic chiasm height, distance between the optic chiasm and adenoma, suprasellar extension, and chiasmal lift.

Results

The study group included 100 eyes of 50 patients operated for pituitary adenomas with suprasellar extension. RNFL thinning predominantly involved the nasal (84.26 ± 16.43 μm) and temporal quadrants (70.72 ± 14.80 μm) and correlated well with the visual field deficit (P < 0.001). Patients with moderate-to-severe deficit in visual acuity had a mean RNFL thickness <85 μm and patients with severe disc pallor had extremely thin RNFLs (<70 μm). Suprasellar extension defined as Wilsons Grade C, D, and E and Fujimotos Grades 3 and 4 were significantly associated with thin RNFLs <85 μm (P < 0.01). Chiasmal lift more than 1 cm and tumor chiasm distance of <0.5 mm were associated with thin RNFL (P < 0.002).

Conclusion

RNFL thinning correlates directly with the severity of visual deficits in patients with pituitary adenoma. Wilsons Grade D and E, Fujimoto Grade 3 and 4, chiasmal lift more than 1 cm, and chiasm tumor distance <0.5 mm are strong predictors of RNFL thinning and poor vision. Pituitary macro adenoma and other suprasellar tumors need to be excluded in patients with preserved vision but having obvious RNFL thinning.

Bi-nasal sectors of ganglion cells complex and visual evoked potential amplitudes as biomarkers in pituitary macroadenoma management

The study aimed to evaluate the retinal ganglion cell structure using optical coherence tomography and the visual pathway function employing visual evoked potentials in the diagnosis and monitoring of patients with pituitary macroadenoma. A descriptive, cross-sectional, and longitudinal study (3 and 12 months follow-up) was conducted on forty-two patients. Thirty-five age-matched healthy controls were used in the cross-sectional one. Full neuro-ophthalmological evaluation (structural and functional) was carried out including global and segmented retinal nerve fiber layer/ganglion cell complex analysis and amplitude and latency of P100 component in the electrophysiology. Statistical data analysis was conducted with R version 3.6.3 and Python version 3.8. Associations were evaluated using Spearman's correlations. Amplitude sensitivities were 0.999, and bi-nasal sectors of ganglion cell complex thickness specificities were 0.999. This structural parameter had the highest diagnostic value (area under curve = 0.923). Significant associations were found between bi-nasal sectors with amplitude at 12' (rho > 0.7, p < 0.01) and median deviation of the visual field (rho > 0.5, p < 0.01) at 3 months. Pre-surgical values of bi-nasal sectors and amplitude can predict post-surgically median deviation and amplitude (Oz, 12') at 3 months with r ² > 0.5. Bi-nasal sectors of ganglion cell complex and visual evoked potentials P100 amplitude are efficient biomarkers of visual pathway damage for pituitary macroadenoma patients' management. Pre-surgical values of the bi-nasal sector and visual evoked potentials' amplitude could help to predict the restoration of parvocellular pathway traffic after decompression.

A Factorial Analysis on Visual Outcomes of Transsphenoidal Surgery for Pituitary Macroadenoma

Objective  Sellar lesions are possible reversible causes of vision loss. This study is to provide quantitative objective measurement of efficacy of surgery for non-functioning pituitary adenoma and discuss different factors that could affect visual outcome of non-functioning pituitary adenoma.

Method  This is a single centre, retrospective study conducted at a tertiary neurosurgery referral centre. 108 cases of sellar tumors which underwent surgery during the 3-year period from early June 2015 to late May 2018 were reviewed. Pituitary adenoma that were non-functioning and without apoplexy at initial presentation were selected for the study. We have analyzed the correlation of different factors with the visual outcome, including the extent of vertical decompression in terms of change in tumor height post operation and the extent of lateral decompression in terms of change in Knosp grading. Visual outcome was represented by the visual impairment score (VIS), an integrated measurement of visual acuity and visual field deficit.

Results  Preoperative absolute tumor height and supracarotid height correlated with preoperative VIS scale ( p  ≤ 0.01). Absolute Knosp grading correlates significantly with VA ( p  = 0.001) and VF ( p  ≤ 0.001) of that particular eye. Although most patients had an objective improvement in visual acuity (VA) (88%) and visual field (VF) (99%) after operation, a larger reduction in tumor height and successful Knosp downgrading after surgery is associated with better VIS improvement. ( p  = 0.025) Change in supracarotid height shows trend in correlating with change in VIS ( p  = 0.084).

Conclusion  Height of tumor measured from genu of cavernous ICA correlates better with visual outcome than absolute tumor height. The extent of both vertical and lateral decompression of non-functioning pituitary adenoma are important determinants that lead to better visual outcome. As endoscopic approach is able to achieve a greater degree of lateral decompression, it is a preferred approach in pituitary surgery to achieve a better visual outcome.

Past, present and future role of retinal imaging in neurodegenerative disease

Retinal imaging technology is rapidly advancing and can provide ever-increasing amounts of information about the structure, function and molecular composition of retinal tissue in humans in vivo. Most importantly, this information can be obtained rapidly, non-invasively and in many cases using Food and Drug Administration-approved devices that are commercially available. Technologies such as optical coherence tomography have dramatically changed our understanding of retinal disease and in many cases have significantly improved their clinical management. Since the retina is an extension of the brain and shares a common embryological origin with the central nervous system, there has also been intense interest in leveraging the expanding armamentarium of retinal imaging technology to understand, diagnose and monitor neurological diseases. This is particularly appealing because of the high spatial resolution, relatively low-cost and wide availability of retinal imaging modalities such as fundus photography or OCT compared to brain imaging modalities such as magnetic resonance imaging or positron emission tomography. The purpose of this article is to review and synthesize current research about retinal imaging in neurodegenerative disease by providing examples from the literature and elaborating on limitations, challenges and future directions. We begin by providing a general background of the most relevant retinal imaging modalities to ensure that the reader has a foundation on which to understand the clinical studies that are subsequently discussed. We then review the application and results of retinal imaging methodologies to several prevalent neurodegenerative diseases where extensive work has been done including sporadic late onset Alzheimer's Disease, Parkinson's Disease and Huntington's Disease. We also discuss Autosomal Dominant Alzheimer's Disease and cerebrovascular small vessel disease, where the application of retinal imaging holds promise but data is currently scarce. Although cerebrovascular disease is not generally considered a neurodegenerative process, it is both a confounder and contributor to neurodegenerative disease processes that requires more attention. Finally, we discuss ongoing efforts to overcome the limitations in the field and unmet clinical and scientific needs.

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

In this study, we investigated the correlation between pattern electroretinogram (PERG) and optical coherence tomography angiography (OCTA) parameters for diagnosis in patients with normal-tension glaucoma (NTG). Forty-nine normal individuals (49 eyes) and 60 patients with NTG (60 eyes) were enrolled. OCTA and PERG parameters, such as macular vessel density (VD) and the amplitude of N35–P50 and P50–N95, were measured. Correlation analyses were performed between the parameters, and the area under the curve (AUC) was used to identify their diagnostic ability for NTG. Macular VD and the amplitude of N35–P50 and P50–N95 showed significant differences between the normal individuals and patients with NTG. Correlation between P50 and N95 amplitude and macular VD was significant in the normal and early glaucoma groups. Macular VD showed a higher AUC value (0.730) than that of P50–N95 amplitude (0.645) in the early glaucoma group. In the moderate to severe glaucoma group, the AUC value of the amplitude of P50–N95 (0.907) was higher than that of macular VD (0.876). The results indicate that PERG and OCTA parameters may identify glaucoma in its early stage, based on the severity of glaucomatous damage in patients with NTG.

Electrophysiology in neuro-ophthalmology

This chapter reviews common applications of visual electrophysiology relevant to neuro-ophthalmology practice. The use of standard tests and extended protocols are described including the cortical visual evoked potential and pattern and full-field electroretinogram (PERG; ERG) methods, the latter including the photopic negative response. Abnormalities of these recordings are rarely specific but provide valuable diagnostic guidance and an objective measure of visual pathway function, difficult or impossible to infer by other methods. The electrophysiological phenotypes associated with Leber hereditary optic neuropathy, OPA1- and SSBP1-associated dominant optic atrophy, and WFS1-related syndromes are described. Typical changes in retinal and optic nerve function tests associated with acquired disease are highlighted, including those related to demyelination, ischemic, compressive, nutritional and toxic, and nonorganic etiologies. The importance of complementary testing using different electrophysiological techniques is emphasized, for the purposes of differential diagnosis and in disorders that may masquerade as optic nerve pathology.

Visual acuity and its postoperative outcome after transsphenoidal adenoma resection

Transsphenoidal surgery (TSS) represents the gold standard of pituitary adenoma resection, providing a safe and minimal invasive treatment for patients suffering from symptoms of mass effect. The aim of this study is to analyze the postoperative improvement of visual function after adenoma resection and to identify prognostic factors for the postoperative clinical recovery. We performed a retrospective analysis of all consecutive patients treated via a transsphenoidal approach for pituitary adenomas from April 2006 to December 2019 in a high-volume neurosurgical department. Our primary outcome was postoperative visual acuity and visual field impairment; the clinical findings were followed up to 3 months after surgery and correlated with clinical and radiographic findings. In total, 440 surgeries were performed in our department for tumors of the sella region in a time period of 13 years via transsphenoidal approach, and 191 patients included in the analysis. Mean age was 55 years, and 98% were macroadenomas. Mean preoperative visual acuity in patients with preoperative impairment (n = 133) improved significantly from 0.64/0.65 to 0.72/0.75 and 0.76/0.8 (right eye R/left eye L) postoperatively and at 3 months follow-up (p < 0.001). Visual acuity significantly depended on Knosp classification but not Hardy grading. The strongest predictor for visual function recovery was age. Transsphenoidal pituitary tumor resection remains a safe and effective treatment in patients with preoperative visual impairment. It significantly improves visual acuity and field defects after surgery, and recovery continues at the 3 months follow-up examination.

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

PURPOSE

The purpose of this study was to assess visual function by visually evoked potentials in adults with orbital and other primary brain tumors affecting the optic pathway.

METHODS

In this retrospective case-control series, patients with orbital (intraconal and extraconal) or midline/chiasmatic tumors were included. Visually evoked potentials using pattern-reversal visually evoked potential and flash visually evoked potential stimuli were performed according to the international standards. Outcome measures were visually evoked potential parameters of amplitude (µV) and peak times (ms) measured both for the P100 component (pattern-reversal visually evoked potentials) and the N2P2 complex (flash visually evoked potential). Individual results were also compared with gender-based normative values.

RESULTS

A group of 21 adult patients (17 females) and age- and sex-matched controls were evaluated. Tumor location was intraconal (6 meningiomas, 3 hemangiomas, 1 glioma), extraconal (6 meningiomas), and midline (3 pituitary adenomas, 2 hypothalamic/chiasmatic low-grade gliomas). Abnormal fundus (76%), abnormal pupillary reflexes (71%), reduced visual acuity (62%), strabismus (48%), and proptosis (38%) were present. Visually evoked potential abnormalities were found in at least one eye of all cases. Affected eyes had significantly reduced amplitudes and prolonged peak times for pattern-reversal visually evoked potentials (p < .001) and significantly reduced amplitudes for flash visually evoked potential (p < .001). In unilateral orbital tumors, abnormally prolonged pattern-reversal visually evoked potential peak times were also detected in some contralateral eyes (n = 6/16).

CONCLUSION

Visually evoked potential abnormalities were found in all adult patients with orbital and other intracranial primary tumors, even in eyes with normal exam and good visual acuity. Visually evoked potential can be used as a non-invasive ancillary test to characterize and monitor visual function in subjects with these neoplastic lesions.

Preoperative visual evoked potential in the prediction of visual outcome after pituitary macroadenomas surgery

OBJECTIVE

The purpose of the present study is to investigate longitudinal changes in Visual evoked potential (VEP) parameters as an objective test after transsphenoidal surgery, its correlation with subjective tests and clinical value of VEP in the prediction of visual outcome.

METHODS

Fifty patients with pituitary macroadenoma who underwent surgical removal of the tumor recruited in this study. All the patients underwent ophthalmic examination, static automated perimetry (SAP), VEP and magnetic resonance imaging (MRI) preoperatively and 3 months after surgery.

RESULTS

Fifty patients with pituitary macroadenoma (size: 25.1 ± 9.9 mm) were recruited in the study. Before surgery, the pattern of VEP showed a prolonged latency with reduced amplitude in eyes with abnormal visual acuity or abnormal visual field. The P100 wave latencies and amplitudes showed significant correlation with visual acuity and SAP scores. After surgery, visual acuity and visual field improvements were seen in 51% and 65.6% of eyes, respectively. Mean SAP and visual acuity scores increased significantly (p < 0.01), P100 wave latency declined and amplitude improved after surgery but not significantly. The mean age of patients, size of tumors and preoperative P100 wave latency were significantly lower in eyes with visual field and acuity improvement.

CONCLUSION

VEP is a helpful quantitative and objective complementary test to visual acuity and SAP exams for assessing pre-operative visual abnormalities and post-operative visual outcome in patients with pituitary macroadenoma.