Chiasmal syndromes

Atrophy of the optic chiasm is associated with microvascular diabetic complications in type 1 diabetes

Introduction

Diabetic neuropathy and diabetic eye disease are well known complications of type 1 diabetes. We hypothesized that chronic hyperglycemia also damages the optic tract, which can be measured using routine magnetic resonance imaging. Our aim was to compare morphological differences in the optic tract between individuals with type 1 diabetes and healthy control subjects. Associations between optic tract atrophy and metabolic measures, cerebrovascular and microvascular diabetic complications were further studied among individuals with type 1 diabetes.

Methods

We included 188 subjects with type 1 diabetes and 30 healthy controls, all recruited as part of the Finnish Diabetic Nephropathy Study. All participants underwent a clinical examination, biochemical work-up, and brain magnetic resonance imaging (MRI). Two different raters manually measured the optic tract.

Results

The coronal area of the optic chiasm was smaller among those with type 1 diabetes compared to non-diabetic controls (median area 24.7 [21.0-28.5] vs 30.0 [26.7-33.3] mm2, p<0.001). In participants with type 1 diabetes, a smaller chiasmatic area was associated with duration of diabetes, glycated hemoglobin, and body mass index. Diabetic eye disease, kidney disease, neuropathy and the presence of cerebral microbleeds (CMBs) in brain MRI were associated with smaller chiasmatic size (p<0.05 for all).

Conclusion

Individuals with type 1 diabetes had smaller optic chiasms than healthy controls, suggesting that diabetic neurodegenerative changes extend to the optic nerve tract. This hypothesis was further supported by the association of smaller chiasm with chronic hyperglycemia, duration of diabetes, diabetic microvascular complications, as well as and CMBs in individuals with type 1 diabetes.

Discriminating Between Compressive Optic Neuropathy With Glaucoma-Like Cupping and Glaucomatous Optic Neuropathy Using OCT and OCTA

Purpose

To discriminate between compressive optic neuropathy with glaucoma-like cupping (GL-CON) and glaucomatous optic neuropathy (GON) by comparing the peripapillary retinal nerve fiber layer (pRNFL) thickness and retinal microvasculature using optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA).

Methods

In this retrospective cross-sectional study, OCT scans were performed on 28 eyes of GL-CON, 34 eyes of GON, and 41control eyes to determine the pRNFL thickness, ganglion cell complex thickness, and cup/disc ratio. OCTA scans were conducted for 12 eyes of GL-CON, 15 eyes of GON, and 15 control eyes to measure the vessel density of the peripapillary and macular areas. Analysis of covariance was used to perform the comparisons, and the area under the curve was calculated.

Results

The GON eyes had a significantly thinner pRNFL in the inferior quadrant and greater vertical cup/disc ratio than the GL-CON eyes. In the radial peripapillary capillary segment, the vessel density of the GON in the inferior sectors was significantly lower than in the GL-CON. The superficial macular vessel density in the whole-image, peritemporal, perinasal, and peri-inferior sectors was significantly smaller in the GON group than in the GL-CON group. The best parameter for discriminating between GL-CON and GON was the superficial macular vessel density in the peritemporal sector.

Conclusions

GL-CON eyes showed a characteristic pattern of pRNFL and retinal microvascular changes.

Translational Relevance

GL-CON can be effectively distinguished from GON by detecting the alterations in the pRNFL and retinal microvasculature using OCT and OCTA.

Physical Examination for Endocrine Diseases: Does It Still Play a Role?

A physical examination represents a fundamental step in diagnosing diseases. Due to the role that hormones play in the regulation of numerous biological processes in various organs and systems, endocrine diseases cause a variety of clinical manifestations that can be easily identified with a careful physical examination and can guide the clinician to specific diagnoses. Furthermore, the presence of specific clinical signs in various endocrine-metabolic diseases can predict the risk of developing comorbidities and serious adverse events. In this article, we present some of the main clinical signs of endocrine-metabolic diseases and the risk of comorbidities, summarizing the pathogenetic mechanisms that lead to their formation. The aim is to highlight how the identification of these specific signs can reduce the number of dynamic tests and the costs necessary to reach the diagnosis and allow the early identification of any complications associated with these diseases, improving the clinical management of affected patients.

MRI monitoring of macaque monkeys in neuroscience: Case studies, resource and normative data comparisons

Information from Magnetic Resonance Imaging (MRI) is useful for diagnosis and treatment management of human neurological patients. MRI monitoring might also prove useful for non-human animals involved in neuroscience research provided that MRI is available and feasible and that there are no MRI contra-indications precluding scanning. However, MRI monitoring is not established in macaques and a resource is urgently needed that could grow with scientific community contributions. Here we show the utility and potential benefits of MRI-based monitoring in a few diverse cases with macaque monkeys. We also establish a PRIMatE MRI Monitoring (PRIME-MRM) resource within the PRIMatE Data Exchange (PRIME-DE) and quantitatively compare the cases to normative information drawn from MRI data from typical macaques in PRIME-DE. In the cases, the monkeys presented with no or mild/moderate clinical signs, were well otherwise and MRI scanning did not present a significant increase in welfare impact. Therefore, they were identified as suitable candidates for clinical investigation, MRI-based monitoring and treatment. For each case, we show MRI quantification of internal controls in relation to treatment steps and comparisons with normative data in typical monkeys drawn from PRIME-DE. We found that MRI assists in precise and early diagnosis of cerebral events and can be useful for visualising, treating and quantifying treatment response. The scientific community could now grow the PRIME-MRM resource with other cases and larger samples to further assess and increase the evidence base on the benefits of MRI monitoring of primates, complementing the animals’ clinical monitoring and treatment regime.

[Chiasmatic syndrome]

The optic chiasm is an essential anatomical structure in neuro-ophthalmology. The systematization of the visual pathways results from the arrangement of the retinal ganglion cell fibers. It explains the signs of chiasmal syndrome. A good knowledge of the anatomy permits to correlate visual field defects with imaging results. It is now possible to map the organization of the ganglion cell fibers within the chiasm. Their hemidecussation allows for stereoscopic vision in humans. The causes of chiasmal syndrome are multiple, but tumors and compressive causes predominate. The proximity of the pituitary region to the chiasm accounts for the frequency of chiasmal syndrome, which involves ophthalmologists not only through dysfunction of the visual pathway, which may be the presenting sign, but also through possible complications throughout the course of the disease. This review aims to synthesize the embryology, anatomy and principles of work-up for chiasmal syndrome as well as its many possible causes.

The Chiasmal Compression Index: An Integrative Assessment Tool for Visual Disturbances in Patients with Pituitary Macroadenomas

OBJECTIVE

Visual status is routinely evaluated by neuro-ophthalmologic examination and computerized visual field (VF) tests in patients with chiasmal compression secondary to pituitary macroadenoma. Currently, no relevant data exists to accurately quantify the extent of optic apparatus compromise to further guide clinical decision-making. We aimed to assess for a possible quantitative correlation between optic chiasm geometric properties on magnetic resonance imaging (MRI) and VF deficits.

METHODS

Visual assessments and concurrent MRI scans were retrospectively reviewed from patients treated for pituitary macroadenoma in a single medical institution. Chiasm width, chiasm minimal and maximal height, and chiasm angle were measured on MRI coronal plane images by 3 independent reviewers (for the sake of variability analysis). VF numerical summary parameters were also retrieved.

RESULTS

A total of 30 patients were included in the final analysis. Average VF index was 70% (±30), and averaged mean deviation was 10.0 db (±9). Chiasm angle and width (which together represents the bending and stretching of the chiasm by the upward directed compression; both of which demonstrated high inter- and intraobserver agreement) showed strong correlation with VF loss. Chiasmal compression index derived from those parameters showed even stronger correlation.

CONCLUSIONS

The strong correlation demonstrated by our results of this relatively simple radiologic measurement with VF status, despite the relatively small cohort, calls for further investigation in this promising direction, and may facilitate with basic assessment and clinical decision-making for patients with equivocal neuro-ophthalmologic evaluation, as well as with poor compliance.

Sudden bilateral vision loss due to third ventricular cavernous angioma with intratumoral hemorrhage - case report

Background

We report a rare case of sudden bilateral vision loss due to third ventricular cavernous angioma with intratumoral hemorrhage.

Case presentation

A 45-year-old woman presented decreased visual acuity in both eyes. Her best corrected visual acuity was 0.1 in the right eye and 0.15 in the left eye. Goldmann perimetry showed bilateral central scotomas and bitemporal visual field defects. MRI demonstrated a lesion with mixed hypo- and hyperintensity at the optic chiasm, which was thought to be an intratumoral hemorrhage. The patient underwent bifrontal craniotomy. The tumor was exposed via an anterior interhemispheric approach, and histological evaluation of the mass led to a diagnosis of cavernous angioma. Six months after the surgery, her best corrected visual acuity was 0.9 in the right eye and 0.9 in the left, with slight bitemporal visual field defects.

Conclusion

Third ventricular cavernous angioma is considered in the differential diagnosis of chiasmal syndrome. Contrast-enhanced MRI and FDG-PET might be useful for differential diagnosis of cavernous angioma from other chiasmal tumors including glioblastoma.

Visual Outcome of Patients with Pituitary Adenomas Following Surgery and Its Contributory Factors at a Tertiary Hospital in Ghana

Background

Craniotomy and transphenoidal microsurgery are surgical options for treatment of pituitary adenoma at Korle Bu Teaching Hospital(KBTH). Despite major advances and reported success rates of transphenoidal resection globally, paucity of local data regarding visual outcome of either procedure exists. We evaluated the visual outcome of patient with pituitary adenoma following surgery in a tertiary hospital in Ghana.

Methods

This is a prospective study of 18 of 45 consecutive new patients with pituitary adenoma seen from November 2010 to July 2013 at Korle-Bu Teaching Hospital(KBTH), Accra, Ghana. Sixteen (88.9%) of the 18 had surgery by transphenoidal route and 2(11.1%) by craniotomy. All patients had macroadenoma (tumour size >1cm) and histological confirmation of diagnosis. Pre-operative and post-operative visual acuity and its relationship to tumour size and duration of symptoms before diagnosis were evaluated.

Results

Data on 18 patients aged 33–60 years, mean (SD) 45.9±8.5, was analysed. Eleven (61.1%) were females. Visual blur, 15(83.3%), and headache,13(72.2%), were predominant presenting complaints. Common neuro-ophthalmic signs included unilateral or bilateral optic atrophy, 17(94.4%), Relative Afferent Pupillary Defect (RAPD) in 8(44.4%) and impaired colour vision in 32 of 36(88.9%) eyes. Preoperatively, 8(22.2%) and 13(36.1%) of 36 eyes were visually impaired or blind respectively. Postoperatively, 6(16.7%) eyes were visually impaired and 17(47.2%) eyes blind. Blindness was associated with late presentation (p<0.005) and larger tumour width (p<0.036).

Conclusions

More than a third of eyes of patients with pituitary adenoma were blind before and after surgery. Blindness was associated with late presentation and larger tumours. Transphenoidal surgery may be beneficial following early diagnosis to avoid irreversible blindness/visual impairment.

Compressive Lesions of the Optic Chiasm: Subjective Symptoms and Visual Field Diagnostic Criteria

We investigated the diagnostic ability of a new criterion (simple temporal depression) for compressive lesions of the optic chiasm. The subjects were 124 eyes with compressive lesions of the optic chiasm. The controls were 84 eyes. The Humphrey (Carl Zeiss) visual field test was used for visual field testing. The simple temporal depression index was calculated as the ratio of the sums of the thresholds for one line on the nasal side and temporal side of the vertical meridian. The result of new index was 87% sensitivity and 99% specificity. This result suggested that our new criterion will assist the diagnosis in the future.

Twelve cases of pituitary metastasis: a case series and review of the literature

PURPOSE

The pituitary gland is an unusual site for metastatic spread, but as patients with metastatic malignancy are living longer, it may become more prevalent. Compression of important anatomy adjacent to the sella may produce disabling symptoms and endocrine derangement, leading to significant morbidity.

METHODS

An ambispective review of patient records between 2013 and 2017 from three neurosurgical centres was performed. After identifying cases, further investigation was performed to evaluate patient demographic, symptoms at presentation, radiological and histological findings, management, and outcome.

RESULTS

Our investigation identified 12 patients with pituitary metastasis. The average age of the cases was 63.4 years, with breast (n = 4) and lung (n = 4) being the most common primary cancers. In half the cases there was a history of metastatic disease, while in one-quarter of cases, pituitary symptoms were the first sign of malignancy. Adenohypophyseal dysfunction (83%), diabetes insipidus (DI) (75%), headache (67%) and visual field defects (67%) were the most common findings at presentation. Glucocorticoid replacement increased the sensitivity for diagnosis of DI. All cases were contrast enhancing on MRI and the endoscopic trans-sphenoidal approach was preferred for biopsy and debulking.

CONCLUSIONS

The pituitary should not be overlooked as a site of metastasis and sellar symptoms may be the first presentation of neoplastic disease. Any biochemical or clinical sign of pituitary pathology in a patient with known cancer should raise suspicion for sellar metastasis. Moreover, the development of DI or ophthalmoplegia from any pituitary lesion is suggestive of metastatic disease even in patients with no known primary.

Chiasmal syndrome: Clinical characteristics in patients attending an ophthalmological center

Purpose

To present the clinical characteristics of a group of patients with the diagnosis of chiasmal syndrome who attended a large ophthalmological institute.

Methods

Retrospective, observational clinical study with the review of medical records of patients with a diagnosis of chiasmal syndrome. The following variables were assessed: demographic characteristics, chief complaint upon presentation, best-corrected visual acuity (BCVA), presence or absence of diplopia, pupillary responses, optic nerve head morphology, etiology, and results from the ancillary tests including Ishihara test, Goldmann visual field (GVF) perimetry and neuroimaging.

Results

A total of 104 met the inclusion criteria, with a median age of 52 years (range 4-86 years). Fifty-four patients (51.9%) were referred to our institution with a diagnosis of a causative etiology for chiasmal syndrome, while in 50 (48.1%) the diagnosis was performed at our center. The most common presenting symptom was low visual acuity in 57 patients (54.8%), and the most common GVF defect was bitemporal hemianopsia in 39 patients (78 eyes, 39.8%). Pupillary abnormalities were present in 58 patients (55.7%), the optic nerve revealed pallor at any degree in 67 patients (64.4%) and the Ishihara test was affected in 65 patients (62.5%). The most common diagnosis was pituitary macroadenoma.

Conclusion

The ophthalmologist participates in the diagnosis and rehabilitation of patients with chiasmal syndrome. Low visual acuity is the most common symptom at presentation, and bitemporal hemianopia the most frequent GVF defect. Examination of the optic nerve head and pupillary responses, and ancillary tests including Ishihara test and neuroimaging are relevant for diagnosis.

Reconciling visual field defects and retinal nerve fibre layer asymmetric patterns in retrograde degeneration: an extended case series

BACKGROUND

Accurate diagnosis in patients presenting with lesions at various locations within the visual pathway is challenging. This study investigated functional and structural changes secondary to such lesions to identify patterns useful to guide early and effective management.

METHODS

Over 10,000 records from patients referred for optic nerve head assessment were reviewed and 31 patients with a final diagnosis of likely neuropathic lesions posterior to the eye were included in the current study. Fundus photographs, optic coherence tomography images and visual field tests were evaluated for changes with respect to retinal nerve fibre layer topography and prediction of structure-function paradigms. Emerging clinical patterns were examined for their consistency with the likely anatomical origin of the underlying insult in the presence of varying diagnoses.

RESULTS

Data from patients with lesions along the visual system allowed identification of retinal nerve fibre layer asymmetry correlated with visual field defects and ganglion cell analysis. Bilateral discordance in retinal nerve fibre loss easily discernible from an altered pattern of the temporal-superior-nasal-inferior-temporal curve was characteristic for post-chiasmal lesions. These sometimes-subtle changes supported diagnosis in cases with multiple aetiologies or with ambiguous visual field analysis and/or ganglion cell loss.

CONCLUSION

Intricate knowledge of the retinal architecture and projections allows coherent predictions of functional and structural deficits following various lesions affecting the visual pathway. The integration of adjunct imaging and retinal nerve fibre layer thinning will assist clinicians to guide clinical investigations toward a likely diagnosis in the light of significant individual variations. The case series presented in this study aids in differential diagnosis of retrograde optic neuropathies by using retinal nerve fibre layer asymmetric patterns as an important clinical marker.

Visual pathway impairment by pituitary adenomas: quantitative diagnostics by diffusion tensor imaging

OBJECTIVE Despite ample experience in surgical treatment of pituitary adenomas, little is known about objective indices that may reveal risk of visual impairment caused by tumor growth that leads to compression of the anterior visual pathways. This study aimed to explore diffusion tensor imaging (DTI) as a means for objective assessment of injury to the anterior visual pathways caused by pituitary adenomas. METHODS Twenty-three patients with pituitary adenomas, scheduled for transsphenoidal tumor resection, and 20 healthy control subjects were included in the study. A minimum suprasellar tumor extension of Grade 2-4, according to the SIPAP (suprasellar, infrasellar, parasellar, anterior, and posterior) scale, was required for inclusion. Neuroophthalmological examinations, conventional MRI, and DTI were completed in all subjects and were repeated 6 months after surgery. Quantitative assessment of chiasmal lift, visual field defect (VFD), and DTI parameters from the optic tracts was performed. Linear correlations, group comparisons, and prediction models were done in controls and patients. RESULTS Both the degree of VFD and chiasmal lift were significantly correlated with the radial diffusivity (r = 0.55, p < 0.05 and r = 0.48, p < 0.05, respectively) and the fractional anisotropy (r = -0.58, p < 0.05 and r = -0.47, p < 0.05, respectively) but not with the axial diffusivity. The axial diffusivity differed significantly between controls and patients with VFD, both before and after surgery (p < 0.05); however, no difference was found between patients with and without VFD. Based on the axial diffusivity and fractional anisotropy, a prediction model classified all patients with VFD correctly (sensitivity 1.0), 9 of 12 patients without VFD correctly (sensitivity 0.75), and 17 of 20 controls as controls (specificity 0.85). CONCLUSIONS DTI could detect pathology and degree of injury in the anterior visual pathways that were compressed by pituitary adenomas. The correlation between radial diffusivity and visual impairment may reflect a gradual demyelination in the visual pathways caused by an increased tumor effect. The low level of axial diffusivity found in the patient group may represent early atrophy in the visual pathways, detectable on DTI but not by conventional methods. DTI may provide objective data, detect early signs of injury, and be an additional diagnostic tool for determining indication for surgery in cases of pituitary adenomas.

Progressive loss of vision caused by asymptomatic pituitary macroadenoma: role of OCT

Introduction

Most pituitary adenomas are clinically inactive. In patients with long-standing compression of the optic chiasm, ganglion cells may undergo axonal degeneration. Spectral domain optical coherence tomography (SD-OCT) is able to identify retinal nerve fiber layer (RNFL) and ganglion cell loss in the retina. We present a case in which SD-OCT was used to diagnose an asymptomatic pituitary macroadenoma.

Clinical case

A 48-year-old female presented with progressive vision loss in both eyes. SD-OCT identified atrophy of the ganglion cell and nerve layers, with preservation of outer layers bilaterally. Magnetic resonance imaging of the brain showed a pituitary macroadenoma. The pathological diagnosis was nonfunctioning adenoma.

Discussion

As macroadenomas enlarge, they can induce uncrossed axon loss, resulting in nasal field defects and reduced visual acuity. In these cases, there is atrophy of the nasal and temporal portions of the optic disc, thus occupying a horizontal band across the disc. SD-OCT is able to identify RNFL loss in eyes with band atrophy of the optic nerve, which correlates with visual field defects found in perimetry. SD-OCT is a useful tool to assess the structural and functional damage of ganglion cells. In our case the SD-OCT demonstrated a symmetrical loss of the RNFL and the ganglion cell layer in both eyes, indicating important optic nerve damage.

Physiological Correlates and Predictors of Functional Recovery After Chiasmal Decompression

BACKGROUND

The intrinsic abilities and limits of the nervous system to repair itself after damage may be assessed using a model of optic chiasmal compression, before and after a corrective surgical procedure.

METHODS

Visual fields (VFs), multifocal visual evoked potentials (mfVEP), retinal nerve fiber layer (RNFL) thickness, and diffusion tensor imaging were used to evaluate a patient before and after removal of a meningioma compressing the chiasm. Normally sighted individuals served as controls. The advantage of each modality to document visual function and predict postoperative outcome (2-year follow-up) was evaluated.

RESULTS

Postsurgery visual recovery was best explained by critical mass of normally conducting fibers and not associated with average conduction amplitudes. Recovered VF was observed in quadrants in which more than 50% of fibers were identified, characterized by intact mfVEP latencies, but severely reduced amplitudes. Recovery was evident despite additional reduction of RNFL thickness and abnormal optic tract diffusivity. The critical mass of normally conducting fibers was also the best prognostic indicator for functional outcome 2 years later.

CONCLUSIONS

Our results highlight the ability of the remaining normally conductive axons to predict visual recovery after decompression of the optic chiasm. The redundancy in anterior visual pathways may be explained, neuroanatomically, by overlapping receptive fields.

Visual Defects in Patients With Pituitary Adenomas: The Myth of Bitemporal Hemianopsia

OBJECTIVE

The objective of this study was to test the hypothesis that bitemporal hemianopsia (BHA) is the most common visual field (VF) defect in patients with pituitary macroadenoma and to assess the degree of optic pathway compression necessary to produce visual defects.

MATERIALS AND METHODS

We reviewed the MRI findings and medical records of 119 patients with pituitary macroadenoma who had undergone formal assessment of VFs. We then evaluated the degree of optic pathway displacement caused by the pituitary macroadenoma, as observed on MR images. The classifications of optic pathway displacement included no contact, abutment but no displacement, mild displacement (< 3 mm), and moderate displacement (≥ 3 mm). Qualitative analysis classified VFs as normal or as having defects that were monocular, bitemporal, mixed (bitemporal with additional defects), homonymous, or nonspecific.

RESULTS

A total of 89 of 115 patients had an abnormal VF. Only one patient had true BHA. The most common defects were bitemporal or mixed defects (in 49 of 115 patients [42.6%]), likely because more than just the chiasm is often compressed by the pituitary macroadenoma. Classification of optic pathway displacement by the pituitary macroadenoma was as follows: 23 patients had no contact, eight had abutment but no displacement, 27 had mild displacement, and 57 had moderate displacement. In 78 of the 92 patients (84.8%) with pituitary macroadenoma that had contact with the optic pathway, contact was with the optic chiasm and the prechiasmal optic nerve. Of the 49 patients with bitemporal or mixed defects, 42 had moderate displacement of the optic pathway caused by their tumors.

CONCLUSION

BHA is exceedingly uncommon in patients with pituitary macroadenoma. However, although bitemporal and mixed defects are the most common abnormal VF findings, they were found in only 42.6% of patients. Such defects rarely occur if the tumor displaces the optic pathway less than 3 mm from baseline.

The influence of pituitary adenoma size on vision and visual outcomes after trans-sphenoidal adenectomy: a report of 78 cases

OBJECTIVE

The aims of this study were to investigate the quantitative relationship between pituitary macroadenoma size and degree of visual impairment, and assess visual improvement after surgical resection of the tumor.

METHODS

The medical records of patients with pituitary adenoma, who had undergone trans-sphenoidal adenectomy between January 2009 and January 2011, were reviewed. Patients underwent an ocular examination and brain MRI before and after surgery. The visual impairment score (VIS) was derived by combining the scores of best-corrected visual acuity and visual field. The relationship between VIS and tumor size/tumor type/position of the optic chiasm was assessed.

RESULTS

Seventy-eight patients were included (41 male, 37 female). Thirty-two (41%) patients experienced blurred vision or visual field defect as an initial symptom. Receiver operating characteristic curve analysis showed that tumors <2.2 cm tended to cause minimal or no visual impairment. Statistical analysis showed that 1) poor preoperative vision is related to tumor size, displacement of the optic chiasm in the sagittal view on MRI and optic atrophy, and 2) poorer visual prognosis is associated with greater preoperative VIS. In multivariate analysis the only factor significantly related to VIS improvement was increasing pituitary adenoma size, which predicted decreased improvement.

CONCLUSION

Results from this study show that pituitary adenomas larger than 2 cm cause defects in vision while adenomas 2 cm or smaller do not cause significant visual impairment. Patients with a large macroadenoma or giant adenoma should undergo surgical resection as soon as possible to prevent permanent visual loss.

Educating the blind brain: a panorama of neural bases of vision and of training programs in organic neurovisual deficits

Vision is a complex function, which is achieved by movements of the eyes to properly foveate targets at any location in 3D space and to continuously refresh neural information in the different visual pathways. The visual system involves five main routes originating in the retinas but varying in their destination within the brain: the occipital cortex, but also the superior colliculus (SC), the pretectum, the supra-chiasmatic nucleus, the nucleus of the optic tract and terminal dorsal, medial and lateral nuclei. Visual pathway architecture obeys systematization in sagittal and transversal planes so that visual information from left/right and upper/lower hemi-retinas, corresponding respectively to right/left and lower/upper visual fields, is processed ipsilaterally and ipsialtitudinally to hemi-retinas in left/right hemispheres and upper/lower fibers. Organic neurovisual deficits may occur at any level of this circuitry from the optic nerve to subcortical and cortical destinations, resulting in low or high-level visual deficits. In this didactic review article, we provide a panorama of the neural bases of eye movements and visual systems, and of related neurovisual deficits. Additionally, we briefly review the different schools of rehabilitation of organic neurovisual deficits, and show that whatever the emphasis is put on action or perception, benefits may be observed at both motor and perceptual levels. Given the extent of its neural bases in the brain, vision in its motor and perceptual aspects is also a useful tool to assess and modulate central nervous system (CNS) in general.

Cortical and white matter mapping in the visual system-more than meets the eye: on the importance of functional imaging to understand visual system pathologies

Information transmission within the visual system is highly organized with the ultimate goal of accomplishing higher-order, complex visuo-spatial and object identity processing. Perception is dependent on the intactness of the entire system and damage at each stage—in the eye itself, the visual pathways, or within cortical processing—might result in perception disturbance. Herein we will review several examples of lesions along the visual system, from the retina, via the optic nerve and chiasm and through the occipital cortex. We will address their clinical manifestation and their cortical substrate. The latter will be studied via functional magnetic resonance imaging (fMRI) and Diffusion Tensor Imaging (DTI), enabling cortical, and white matter mapping of the human brain. In contrast to traditional signal recording, these procedures enable simultaneous evaluation of the entire brain network engaged when subjects undertake a particular task or evaluate the entirety of associated white matter pathways. These examples provided will highlight the importance of using advanced imaging methods to better understand visual pathologies. We will argue that clinical manifestation cannot always be explained solely by structural damage and a functional view is required to understand the clinical symptom. In such cases we recommend using advanced imaging methods to better understand the neurological basis of visual phenomena.

Visual acuity and pattern of visual field loss at presentation in pituitary adenoma

Our purpose was to analyse the demographics, prevalence and pattern of visual field defects in patients with pituitary adenoma. We prospectively recruited 103 consecutive patients (206 eyes) presenting to a neurosurgical unit with pituitary adenoma. Ophthalmological examination and standard automated perimetry (Humphrey, 24-2 threshold) was performed. Severity of visual field defects was also assessed. The mean population age was 53.9 years (standard deviation=15). Visual loss was the most common reason for presentation (39%) followed by endocrine abnormality (21%) and headache (15%). Patients with endocrine abnormality on presentation were 10.9 years younger than those presenting with visual loss (p=0.001). Bitemporal defects were the most prevalent pattern (n=22, 41%) followed by homonymous defects (n=7, 13%). Of the patients with visual field loss, 33% had unilateral visual field defects. The mean visual acuity in those with bitemporal defects was 6/7.5 with half of these patients having 6/6 vision in both eyes. In conclusion, the majority of patients with pituitary adenoma have visual acuity better than 6/7.5 despite having visual field defects. While a bitemporal pattern of visual field loss is the most common, a significant proportion of patients had unilateral and altitudinal defects. Assessment of the visual field is essential to rule out chiasmal compression.

Arginine vasopressin immunoreactivity is decreased in the hypothalamic suprachiasmatic nucleus of subjects with suprasellar tumors

Suprasellar tumors with compression of the optic chiasm are associated with an impaired sleep-wake rhythm. We hypothesized that this reflects a disorder of the biological clock of the human brain, the suprachiasmatic nucleus (SCN), which is located just above the optic chiasm. In order to test this hypothesis, we investigated the expression of two key neuropeptides of the SCN, that is, arginine vasopressin (AVP) and vasoactive intestinal peptide (VIP), as assessed by quantitative immunocytochemistry in post-mortem hypothalamic tissue of patients with a suprasellar tumor inducing permanent visual field defects. Post-mortem hypothalamic tissue of 5 patients with a suprasellar tumor inducing permanent visual field defects (acromegaly n = 2, nonfunctioning macro-adenoma n = 1, macroprolactinoma n = 1, infundibular metastasis of a colorectal adenocarcinoma n = 1) and 15 age- and gender-matched controls was obtained from the Netherlands Brain Bank. Total AVP immunoreactivity in the SCN was lower in patients with a suprasellar tumor than in controls (P = 0.03). By contrast, total VIP immunoreactivity was not different between patients and controls (P = 0.44). Suprasellar tumors leading to permanent visual field defects are associated with reduced AVP, but not VIP immunoreactivity, in the SCN. These findings raise the possibility that selective impairment of the SCN contributes to sleep-wake disturbances in these patients.

Localized bi-nasal macular edema in optic chiasmal syndrome

A 28-year-old healthy male complaining of vision loss in his right eye was discovered to have localized bi-nasal macular edema in the presence of a pituitary adenoma. The presence of a junctional scotoma composed by a central scotoma in the right eye associated with superior temporal quadrantanopia in the fellow eye was seen. The pattern detected in the visual field suggested the presence of an expansive mass at the level of the optic chiasm. Optical coherence tomography findings also revealed subtle macular thickness beyond normal in the superior and nasal quadrants of both maculae. This report illustrates the importance of suspecting a pituitary adenoma in the light of uncharacteristic retinal alterations.

Compression of the optic chiasm is associated with permanent shorter sleep duration in patients with pituitary insufficiency

OBJECTIVE

Patients with pituitary insufficiency often experience some degree of impaired sleep. Sleep-wake rhythm is regulated to a large extent by the suprachiasmatic nucleus (SCN). Because the SCN is located just superior to the optic chiasm, we hypothesized that a history of compression of the optic chiasm (CC) due to a tumour with suprasellar extension is associated with altered sleep patterns in patients with pituitary insufficiency.

DESIGN

Case-control study.

PATIENTS

We studied 38 patients (mean age 55·7 ± 13·1 years; 71·1% men) with CC and 18 patients (mean age 53·3 ± 16·6 years, 38·9% men) without CC.

MEASUREMENTS

Objective measures of sleep patterns were assessed by wrist actigraphy. Validated sleep questionnaires were used to evaluate subjective sleep parameters.

RESULTS

Objective total sleep duration was 36 min shorter in patients with CC than in patients without CC [454 (295-553) vs 490 (432-740) min, P = 0·034]. Moreover, patients with CC had a later habitual bedtime [23:15 (22:30-03:00) vs 22:55 (20:00-02:00) h, P = 0·044] and a later actigraphic sleep onset [23:57 (22:31-01:33) vs 23·16 (19:47-03:04) h, P = 0·020]. Linear regression analysis confirmed the difference in total sleep duration after adjustment for age, sex, body mass index, cranial radiotherapy and pituitary/hypothalamic surgery. Subjective sleep parameters were similar in both groups.

CONCLUSIONS

Compression of the optic chiasm due to a tumour with suprasellar extension is associated with permanent changes in total sleep duration in patients with pituitary insufficiency.

The optic nerve head in acquired optic neuropathies

Acquired optic neuropathies are a common cause of blindness in adults, and are associated with characteristic morphological changes at the optic nerve head. Accurate and prompt clinical diagnosis, supplemented with imaging where appropriate, is essential to optimize management of the optic neuropathy and to counsel the patient appropriately on its natural history. History taking, optic disc findings, visual field assessment and imaging of the nerve head and surrounding retinal nerve fiber layer are all paramount to achieving the correct diagnosis. This Review highlights the optic nerve head features that are common to the acquired optic neuropathies, and describes the features that can be used to differentiate these various conditions.

Transcranial approach for treatment for traumatic optic chiasm syndrome

To describe the visual outcome of patients with a traumatic optic chiasm syndrome, with and without neurosurgical intervention. The retrospective clinical interventional study included 14 patients, who either underwent a neurosurgical intervention with transcranial decompression of the optic canal (11 patients) in combination with a high-dosage systemic corticosteroid therapy or who received a high-dosage systemic corticosteroid treatment only (3 patients). In the surgical group, visual field improved after surgery in 6 (55%) patients and remained unchanged in 5 (45%) patients, while in none of the patients without surgery, the visual field improved. Neurosurgical decompression of the optic chiasm and optic nerve canal may be associated with a visual improvement in some patients with a traumatic optic chiasm syndrome.