Role of corpus callosum in unconscious vision.

The existence of unconscious visually triggered behavior in patients with cortical blindness (e.g., homonymous hemianopia) has been amply demonstrated and the neural bases of this phenomenon have been thoroughly studied. However, a crosstalk between the two hemispheres as a possible mechanism of unconscious or partially conscious vision has not been so far considered. Thus, the aim of this study was to assess the relationship between structural and functional properties of the corpus callosum (CC), as shown by probabilistic tractography (PT), behavioral detection/discrimination performance and level of perceptual awareness in the blind field of patients with hemianopia. Twelve patients were tested in two tasks with black-and-white visual square-wave gratings, one task of movement and the other of orientation. The stimuli were lateralized to one hemifield either intact or blind. A PT analysis was carried out on MRI data to extract fiber properties along the CC (genu, body, and splenium). Compared with a control group of participants without brain damage, patients showed lower FA values in all three CC sections studied. For the intact hemifield we found a significant correlation between PT values and visual detection/discrimination accuracy. For the blind hemifield the level of perceptual awareness correlated with PT values for all three CC sections in the movement task. Importantly, significant differences in all three CC sections were found also between patients with above-vs. chance detection/discrimination performance while differences in the genu were found between patients with and without perceptual awareness. Overall, our study provides evidence that the properties of CC fibers are related to the presence of unconscious stimulus detection/discrimination and to hints of perceptual awareness for stimulus presentation to the blind hemifield. These results underline the importance of information exchange between the damaged and the healthy hemisphere for possible partial or full recovery from hemianopia.

Insights into Anton Syndrome: When the brain denies blindness.

INTRODUCTION: Anosognosia, a neurological condition, involves a lack of awareness of one's neurological or psychiatric deficits. Anton Syndrome (AS), an unusual form of anosognosia, manifests as bilateral vision loss coupled with denial of blindness. This systematic review delves into 64 studies encompassing 72 AS cases to explore demographics, clinical presentations, treatments, and outcomes. MATERIALS AND METHODS: The study rigorously followed PRISMA guidelines, screening PubMed, Google Scholar, and Scopus databases without timeframe limitations. Only English human studies providing full text were included. Data underwent thorough assessment, examining patient demographics, etiological variables, and treatment modalities. RESULTS: Sixty-four studies met the stringent inclusion criteria. Examining 72 AS cases showed a median age of 55 (6 to 96 years) with no gender preference. Hypertension (34.7 %) and visual anosognosia (90.3 %) were prevalent. Stroke (40.3 %) topped causes. Management included supportive (30.6 %) and causal approaches (30.6 %). Improvement was seen in 45.8 %, unchanged in 22.2 %, and deterioration in 11.1 %. Anticoagulation correlated with higher mortality (p < 0.05). DISCUSSION: AS, an unusual manifestation of blindness, stems mainly from occipital lobe damage, often due to cerebrovascular incidents. The syndrome shares features with Dide-Botcazo syndrome and dates back to Roman times. Its causes range from strokes to rare conditions like multiple sclerosis exacerbation. Accurate diagnosis involves considering clinical presentations and imaging studies, distinguishing AS from similar conditions. CONCLUSION: This comprehensive review sheds light on AS's complex landscape, emphasizing diverse etiologies, clinical features, and treatment options. Tailored treatments aligned with individual causes are crucial. The study's findings caution against blanket anticoagulation therapy, suggesting a nuanced approach. Further research is pivotal to refine diagnostics and optimize care for AS individuals.

Distribution and causes of blindness and severe visual impairment in children at a tertiary referral centre in Rwanda.

AIM: To determine the prevalence and the causes of severe visual impairment and blindness (SVI/BL) in children at a tertiary referral centre in Rwanda. METHODS: In this retrospective study, files of all patients <18 years presenting during the year 2019 at the Kabgayi Eye Unit in Rwanda with SVI/BL (presenting visual acuity of <6/60 Snellen or lack of preferential looking behaviour) in at least one eye were analysed for age, sex, laterality, province of origin and cause of SVI/BL. Causes were categorised according to WHO standard classification. RESULTS: Out of 3939 children presenting to the clinic, 428 (10.9%) had SVI/BL in at least one eye. 165 (4.2%) patients had bilateral and 263 (6.7%) had unilateral condition. Of patients with BL/SVI, 36.7% were below the age of 6 years. In bilateral BL/SVI, the main causes were cataract (18%), refractive error (18%), keratoconus (13%), congenital eye anomaly (9%), glaucoma (8%), cortical blindness (8%) and retinoblastoma (6%). In unilateral BL/SVI it was trauma (46%), cataract (8%), keratoconus (8%), infectious corneal disease (7%) and retinoblastoma (7%). In preschool children, retinopathy of prematurity accounted for 7% of bilateral BL/SVI. Avoidable BL/SVI accounted for 87% of all cases. CONCLUSION: The high number of avoidable causes for SVI/BL may be reduced through several cost-effective ways.

Current knowledge and perspectives of contrast-induced neurotoxicity: A survey of Australian clinicians.

BACKGROUND: Contrast-induced Neurotoxicity (CIN) is an increasingly recognised complication following endovascular procedures. It remains a relatively unexplored clinical entity, and we sought to characterise clinician perspectives towards CIN, as well as identify gaps in knowledge and provide directions for future research. METHODS: An online survey was distributed to members of the Australian and New Zealand Society of Neuroradiology, as well as several Australian tertiary hospitals. Questions related to clinical exposure to CIN, diagnosis, management and pathophysiology were explored. Descriptive analysis was conducted on survey responses, and statistical analysis was performed using Chi-square and Fisher's exact test as appropriate. RESULTS: A total of 95 survey responses were recorded (26.8% response rate). Only 28.4% of respondents were comfortable in diagnosing CIN, and even fewer (24.2%) were comfortable in independently managing CIN patients. Based on clinician opinion, symptoms including impaired consciousness and cortical blindness were thought to be most associated with CIN, whilst the radiological findings of parenchymal oedema and cortical enhancement were considered to be most indicative of CIN. Most clinicians agreed that further investigation is required related to pathophysiology (86.3%), diagnosis (83.2%), and treatment (82.1%). CONCLUSION: CIN is a poorly understood complication following endovascular procedures. Significant gaps in clinical understanding are evident, and further investigation is vital to improve diagnosis and management.

Clinical and Genetic Characteristics of the Heidenhain Variant of Creutzfeldt-Jakob Disease.

BACKGROUND: The Heidenhain variant of Creutzfeldt-Jakob disease (HvCJD), as a rare phenotype of CJD, has been under-recognized. We aim to elucidate the clinical and genetic features of HvCJD and investigate the differences of clinical features between genetic and sporadic HvCJD to improve our understanding of this rare subtype. METHOD: HvCJD patients admitted to the Xuanwu Hospital from February 2012 to September 2022 were identified, and published reports on genetic HvCJD cases were also reviewed. The clinical and genetic features of HvCJD were summarized, and the clinical features between genetic and sporadic HvCJD were compared. RESULTS: A total of 18 (7.9%) HvCJD patients were identified from 229 CJD cases. Blurred vision was the most common visual disturbance at the disease's onset, and the median duration of isolated visual symptoms was 30.0 (14.8-40.0) days. DWI hyperintensities could appear in the early stage, which might help with early diagnosis. Combined with previous studies, nine genetic HvCJD cases were identified. The most common mutation was V210I (4/9), and all patients (9/9) had methionine homozygosity (MM) at codon 129. Only 25% of cases had a family history of the disease. Compared to sporadic HvCJD, genetic HvCJD cases were more likely to present with non-blurred vision visual symptoms at onset and develop cortical blindness during the progression of the disease. CONCLUSIONS: HvCJD not only could be sporadic, but also, it could be caused by different PRNP mutations. Sporadic HvCJD was more likely to present with blurred vision visual symptoms at onset, and genetic HvCJD was more likely to develop cortical blindness with the disease's progression.

Síndrome de Anton-Babinsky / Anton-Babinski Syndrome

Introducción: El síndrome de Anton-Babinsky es un trastorno neuropsiquiátrico poco frecuente, que se manifiesta por anosognosia y ceguera cortical, debido a lesiones en las áreas visuales asociativas de la corteza occipital sin presentar afectación en la vía visual. En adultos mayores sus manifestaciones clínicas suelen ser atípicas y la valoración geriátrica integral permite orientar el diagnóstico, que se puede asociar con síndromes geriátricos. Objetivo: Describir las manifestaciones clínicas, síndromes geriátricos, paraclínicos y tratamiento de un paciente con Síndrome de Anton-Babinsky. Caso clínico: Paciente de 85 años, quien durante un postoperatorio inmediato de cirugía ocular (pterigión) presentó alteración fluctuante del estado de conciencia, alucinaciones visuales, disminución de la agudeza visual bilateral y anosognosia. La analítica sanguínea no reportó alteraciones y la tomografía computarizada de cráneo documentó isquemia occipital bilateral, se le diagnosticó síndrome de Anton-Babinsky. Conclusiones: El síndrome de Anton-Babinsky puede tener presentación atípica a través de síndromes geriátricos. La valoración geriátrica integral permite realizar un diagnóstico y manejo multicomponente oportuno con el objetivo de influir en el pronóstico tanto a corto como a largo plazo(AU)

Introduction: Anton-Babinski syndrome is a rare neuropsychiatric disorder, with a manifestation of anosognosia and cortical blindness, due to lesions in the associative visual areas of the occipital cortex without presenting visual pathway impairment. In elderly adults, its clinical manifestations are usually atypical and a comprehensive geriatric assessment allows to guide the diagnosis, which can be associated with geriatric syndromes. Objective: To describe the clinical manifestations, geriatric syndromes, paraclinical findings and treatment of a patient with Anton-Babinski syndrome. Clinical case: This is the case of an 85-year-old patient who, during the immediate postoperative period after ocular surgery (pterygium), presented a fluctuating alteration of consciousness, visual hallucinations, decreased bilateral visual acuity and anosognosia. Blood analysis reported no alterations and cranial computed tomography documented bilateral occipital ischemia; the patient was diagnosed with Anton-Babinski syndrome. Conclusions: Anton-Babinski syndrome may have an atypical presentation through geriatric syndromes. Comprehensive geriatric assessment allows for timely multicomponent diagnosis and management with the aim of influencing both short- and long-term prognosis(AU)

Acute cortical blindness caused by neuropsychiatric systemic lupus erythematosus.

A man in his 30s, who presented with fevers and a diffuse purpuric rash, developed sudden-onset visual loss on day 2. He was unable to perceive light in either eye. Examination by a neurologist confirmed cortical blindness, and the MRI showed subtle juxtacortical infarcts and leptomeningeal enhancement in the occipital region. Further history taken in the patient's native language revealed a history of untreated systemic lupus erythematosus. A diagnosis of central nervous system lupus was made and he was treated promptly with pulse methylprednisolone and cyclophosphamide. His vision gradually improved to 80% on day 10 and eventually returned to baseline. He continued with high-dose prednisolone and monthly cyclophosphamide for 6 months and remained on hydroxychloroquine and mycophenolate mofetil with no relapses. This case shows the importance of approaching the uncommon but potentially dangerous issue of acute visual loss with a broad differential.

A rare case of cortical blindness following vaccination against SARS-CoV-2.

A 61-year-old male presented with sudden loss of vision in both the eyes about 8 days after the first shot of coronavirus disease 2019 (COVID-19) vaccine (Covishield). On examination, the visual acuity was no perception of light in both the eyes. Contrast-enhanced magnetic resonance imaging (MRI) with diffusion-weighted imaging showed acute cerebral infarcts involving bilateral parieto-occipital region. Considering the temporal correlation with the vaccine shot and absence of any other precipitating factor, we hypothesized that this was probably an immunologic response to the vaccine.

Knowledge Assessment on Cortical Visual Impairment Among Ophthalmologists in Nepal.

INTRODUCTION: Cortical visual impairment (CVI) in children is a retro chiasmal visual tract disorder where there is with an impairment in the visual acuity and/or functionality of vision-guided task, including motor planning in the presence of normal ocular findings or minimal ocular morbidity. The study was conducted to assess the knowledge about CVI among ophthalmologists practicing in Nepal. MATERIALS AND METHODS: This was a cross sectional study. Data collection was done by administering a preformed, validated questionnaire that was sent via email to all the ophthalmologists registered under the Nepal Ophthalmic Society. The email mentioned the aim of the study along with the questionnaire. RESULTS: A total of 146 (37.82%) ophthalmologists responded to the questionnaire. Forty four percent of the participants were general ophthalmologists, 28% were pediatric ophthalmologists and 67% were ophthalmologists from other subspecialty. The median age of participants was 37.6 years. Most of the ophthalmologist had a good knowledge about the cause, common risk factors, clinical risk factors, management and prognosis of CVI. However only 29.5% of participants were aware of the investigation of choice for diagnosing CVI and 31.7% were aware of the leading causes of visual impairment in the developed countries. The study also established that the knowledge score was higher in pediatric ophthalmologists than the general ophthalmologist and ophthalmologists from other specialties. CONCLUSION: Most of the ophthalmologists had a good knowledge about the cause, common risk factors, clinical features, management and prognosis of CVI. However only a limited number of participants were aware of the investigation of choice for diagnosing CVI and the leading causes of visual impairment in the developed countries. Majority of the participants rarely examined patients with CVI which does not correlate with the high prevalence of perinatal hypoxia, the commonest cause of CVI, in our country.

Pheochromocytoma manifesting as cortical blindness secondary to PRES with associated TMA: a case report and literature review.

BACKGROUND: Pheochromocytomas are neoplasms originating from neuroectodermal chromaffin cells leading to excess catecholamine production. They are notorious for causing a triad of headaches, palpitations, and sweats. Though the Menard triad is one to be vigilant of, symptomatic presentation can vary immensely, hence the tumor earning the label "the great masquerader." CASE PRESENTATION: We report a case of pheochromocytoma initially presenting with cortical blindness secondary to posterior reversible encephalopathy syndrome and thrombotic microangiopathy from malignant hypertension. Our patient was seen in our facility less than a week prior to this manifestation and discharged after an unremarkable coronary ischemia work-up. In the outpatient setting, she had been prescribed multiple anti-hypertensives with remarkably elevated blood pressure throughout her hospitalization history. CONCLUSION: Pheochromocytoma presenting with malignant hypertension and hypertensive encephalopathy should be expected if left untreated; nonetheless, the precipitation of cortical blindness is rare in the literature. This case contributes an additional vignette to the growing literature revolving adrenal tumors and their symptomatic presentation along with complex management. It also serves to promote increased diagnostic suspicion among clinicians upon evaluating patients with refractory hypertension.

Hepatic Encephalopathy Induced Transient Cortical Blindness.

Hepatic encephalopathy describes a spectrum of potentially reversible neuropsychiatric abnormalities seen in a patient with severe liver dysfunction with porto-systemic shunting. Cortical blindness can be a rare presentation of hepatic encephalopathy and can even precede the onset of altered sensorium. We report a case of 57 years female with chronic liver disease who presented with bilateral loss of vision, with no focal neurological deficits. From clinical and laboratory examination, a diagnosis of hepatic encephalopathy with cortical blindness was proposed. Her visual disturbances gradually improved with the treatment of hepatic encephalopathy. Keywords: Cortical blindness; end stage liver disease; hepatic encephalopathy; papilledema.

Hepatic cortical blindness.

Hepatic cortical blindness is an unusual clinical complication of hepatic encephalopathy, and its epidemiology has not been studied in detail. Herein, we present a case report of a 37-year-old male with liver cirrhosis and immunoglobulin A nephropathy who noted visual impairment after eating high-protein food. In addition to the case report, all previously documented cases of hepatic cortical blindness occurring across the globe published from inception until August 2019 were reviewed. The incidence of hepatic cortical blindness is low, and diagnoses are easily missed. The diagnosis of hepatic cortical blindness is dependent on symptoms, and patients may experience several attacks of vision loss. Most patients experience complete blindness, but vision loss recovers within 10 min to one month. Early detection and therapy for hepatic encephalopathy may improve patient outcome.

Training with optic flow stimuli promotes recovery in cortical blindness.

BACKGROUND: Cortical blindness is a form of severe vision loss that is caused by damage to the primary visual cortex (V1) or its afferents. This condition has devastating effects on quality of life and independence. While there are few treatments currently available, accumulating evidence shows that certain visual functions can be restored with appropriate perceptual training: Stimulus sensitivity can be increased within portions of the blind visual field. However, this increased sensitivity often remains highly specific to the trained stimulus, limiting the overall improvement in visual function. OBJECTIVE: Recent advances in the field of perceptual learning show that such specificity can be overcome with training paradigms that leverage the properties of higher-level visual cortical structures, which have greater capacity to generalize across stimulus positions and features. This targeting can be accomplished by using more complex training stimuli that elicit robust responses in these visual structures. METHODS: We trained cortically blind subjects with a complex optic flow motion stimulus that was presented in a location of their blind field. Participants were instructed to train with the stimulus at home for approximately 30 minutes per day. Once performance plateaued, the stimulus was moved deeper into the blind field. A battery of pre- and post-training measures, with careful eye tracking, was performed to quantify the improvements. RESULTS: We show that 1) optic flow motion discrimination can be relearned in cortically blind fields; 2) training with an optic flow stimulus can lead to improvements that transfer to different tasks and untrained locations; and 3) such training leads to a significant expansion of the visual field. The observed expansion of the visual field was present even when eye movements were carefully controlled. Finally, we show that regular training is critical for improved visual function, as sporadic training reduced the benefits of training, even when the total numbers of training sessions were equated. CONCLUSIONS: These findings are consistent with the hypothesis that complex training stimuli can improve outcomes in cortical blindness, provided that patients adhere to a regular training regimen. Nevertheless, such interventions remain limited in their ability to restore functional vision.

Delayed-onset hypoxic cortical blindness: coming back from the abyss.

PURPOSE: To report a case of typical delayed-onset hypoxic cortical blindness that occurred few days after resuscitation from drowning in a young male. METHODS: Neurological and ophthalmological examination were performed including optical coherence tomography (OCT), Goldmann perimetry, pattern electroretinogram (pERG), pattern and flash visual evoked potentials (pVEP and fVEP) and brain magnetic resonance imaging (MRI). RESULTS: At presentation, at day 12 post-hypoxic incident, best corrected visual acuity (BCVA) was reduced to hand motion OU with an abolished optokinetic nystagmus, a normal fundus and no relative afferent pupillary defect. Macular and peripapillary OCT were normal. Goldmann perimetry revealed bilateral centrocecal scotoma. pERG was normal while pVEPs were undetectable and fVEPs were abnormal with delayed, decreased and disorganized responses, without interhemispheric asymmetry. Brain MRI disclosed a bilateral cortical-subcortical occipital hypersignal with laminar necrosis and thus confirmed the diagnosis of delayed-onset hypoxic cortical blindness. Visual rehabilitation, including visual stimulation in the scotomatous areas, was associated with a dramatic and rapid visual improvement with a BCVA of 20/32 OU, an ability to read after 2 weeks (day 30 post-hypoxic incident), and a reduction in the size of the scotoma. CONCLUSION: Delayed-onset hypoxic cortical blindness is a rare presentation of cortical blindness that develops few days after a cerebral hypoxic stress. While initial presentation can be catastrophic, visual improvement may be spectacular and enhanced with visual rehabilitation.

Rehabilitation of visual perception in cortical blindness.

Blindness is a common sequela after stroke affecting the primary visual cortex, presenting as a contralesional, homonymous, visual field cut. This can occur unilaterally or, less commonly, bilaterally. While it has been widely assumed that after a brief period of spontaneous improvement, vision loss becomes stable and permanent, accumulating data show that visual training can recover some of the vision loss, even long after the stroke. Here, we review the different approaches to rehabilitation employed in adult-onset cortical blindness (CB), focusing on visual restoration methods. Most of this work was conducted in chronic stroke patients, partially restoring visual discrimination and luminance detection. However, to achieve this, patients had to train for extended periods (usually many months), and the vision restored was not entirely normal. Several adjuvants to training such as noninvasive, transcranial brain stimulation, and pharmacology are starting to be investigated for their potential to increase the efficacy of training in CB patients. However, these approaches are still exploratory and require considerably more research before being adopted. Nonetheless, having established that the adult visual system retains the capacity for restorative plasticity, attention recently turned toward the subacute poststroke period. Drawing inspiration from sensorimotor stroke rehabilitation, visual training was recently attempted for the first time in subacute poststroke patients. It improved vision faster, over larger portions of the blind field, and for a larger number of visual discrimination abilities than identical training initiated more than 6 months poststroke (i.e., in the chronic period). In conclusion, evidence now suggests that visual neuroplasticity after occipital stroke can be reliably recruited by a range of visual training approaches. In addition, it appears that poststroke visual plasticity is dynamic, with a critical window of opportunity in the early postdamage period to attain more rapid, more extensive recovery of a larger set of visual perceptual abilities.

Epidemiology of eye diseases among children with disability in rural Bangladesh: a population-based cohort study.

AIM: To describe the epidemiology of eye diseases among children with disability in rural Bangladesh. METHOD: We established a population-based cohort of children with disability using the key informant method. Children younger than 18 years with disability (i.e. physical, visual, hearing, speech, epilepsy) were included. We used detailed ophthalmological assessments following World Health Organization (WHO) protocols by a multidisciplinary team including an ophthalmologist, optometrist, physician, and physiotherapist. Visual impairment, blindness, and severe visual impairment (SVI) were defined by following WHO categories. RESULTS: Between October 2017 and February 2018, 1274 children were assessed (43.6% female; median [interquartile range] age 9y 10mo [6y -13y 7mo]). Overall, 6.5% (n=83) had blindness/SVI, and 5.6% (n=71) had visual impairment. In the group with blindness/SVI, 47% (n=39) had cortical blindness; of those, 79.5% (n=31) had cerebral palsy (CP). The other main anatomical sites of abnormalities in this group included lens (13.3%, n=11), cornea (10.8%, n=9), and optic nerve (9.6%, n=8). In the group with visual impairment, 90.1% (n=64) had refractive error. Overall, 83.1% (n=69) and 78.8% (n=56) of those with blindness/SVI and visual impairment had avoidable causes. Most children with blindness/SVI and visual impairment lacked access to education. INTERPRETATION: The burden of blindness/SVI/visual impairment is high among children with disability in rural Bangladesh, mostly due to avoidable causes. Overrepresentation of CP and cortical blindness in the group with blindness/SVI and refractive error in the group with visual impairment highlights the need for integration of ophthalmology assessment, eye care, and refraction services in comprehensive health care for children with disability including CP in rural Bangladesh.