UNASSIGNED: The clinical features of posterior cortical atrophy (PCA), a rare condition often caused by Alzheimer\'s disease, have been recently defined, while little is known about its neurophysiological correlates.
UNASSIGNED: To describe neurophysiological alterations of the visual pathway as assessed using visual field test (VF), visual evoked potentials (VEP), and electroretinogram (ERG) in PCA patients.
UNASSIGNED: Studies reporting VF, VEPs, and ERG in PCA patients were selected according PRISMA method. Of the 323 articles that emerged from the literature, 17 included the outcomes of interest. To these data, we added those derived from a patient cohort enrolled at our clinic.
UNASSIGNED: The literature review included 140 patients, half of them (50%) presented with homonymous hemianopia or quadrantanopia. VEPs were available in 4 patients (2 normal findings, 1 decreased amplitude, and 1 increased latency) and ERG in 3 patients (substantially normal findings). Our case series included 6 patients, presenting with homonymous lateral hemianopia in 50% and contralateral cortical atrophy. VEPs showed normal amplitude in 66-83% according to the stimulation check, and increased latency in 67% in absence of myelin damage on MRI. Latency was increased in both eyes in 50% and only on one side in the other 50%. Such alterations were observed in patients with more severe and symmetric atrophy. ERG showed normal findings.
UNASSIGNED: Neurophysiological investigations of the visual pathway in PCA are almost absent in literature. Alterations involve both amplitude and latency and can be also monocular. A multiple-point involvement of the optical pathway can be hypothesized.

A 33-year-old female presented to the ophthalmology clinic with right periorbital redness and pain for 12 hours. CT revealed right optic nerve thickening and enlargement. Cranial MRI demonstrated abnormalities in the corpus callosum, bilateral hippocampi, thalamus, basal ganglia, temporal-parietal lobes, and the left frontal lobe. Ocular B-scan ultrasound showed elevated optic disc and high echogenic signals in the right vitreous cavity. The patient had a history of surgical resection, radiation therapy, and chemotherapy for a left occipital glioma two years prior, with pathology indicating astrocytoma (World Health Organization Grade Ⅱ). Combining the patient\'s history and diagnostic findings, the confirmed diagnosis is bilateral occipital astrocytoma with invasion into the right transverse sinus, bilateral optic pathways involvement related to the left occipital astrocytoma, and seeding of astrocytoma in the right vitreous cavity.
患者女性，33岁。因右眼眶周红肿、疼痛12 h就诊眼科。CT表现为右侧视神经增粗、肿大；头颅MRI可见胝体压部、双侧海马、丘脑、基底节、颞顶叶及左侧额叶异常信号；眼部B超可见右侧玻璃体腔高回声信号、视盘隆起。患者2年前有左侧枕叶胶质瘤手术、放疗、化疗病史，病理结果提示星形胶质细胞瘤（世界卫生组织分级Ⅱ级）。结合病史，确诊为左侧枕叶星形胶质细胞瘤右侧海绵窦侵犯，左侧枕叶星形胶质细胞瘤双侧视路侵犯，右侧玻璃体腔星形胶质细胞瘤种植。.

The visual system can regulate its sensitivity depending on the prevailing contrast conditions. This is known as contrast adaptation and reflects contrast gain changes at different stages along the visual pathway. Recently, it has been shown that depriving an eye of visual stimulation for a short period of time can lead to neuroplastic changes in ocular dominance as the result of homeostatic changes in contrast gain. Here we examine, on the basis of previously published results, whether the neuroplastic ocular dominance changes are just manifestation of the mechanism responsible for contrast adaptation. The evidence suggests that these two visual processes are separate and do not have a common neural substrate.

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disorder characterized by progressive cerebellar ataxia associated with retinal degeneration. The disease is rare in Japan, and this is the first full description of clinicopathological findings in a Japanese autopsy case of genetically confirmed SCA7 having 49 cytosine-adenine-guanine (CAG) trinucleotide repeats in the ataxin 7 gene. A 34-year-old Japanese man with no family history of clinically apparent neurodegenerative diseases presented with gait disturbance, gradually followed by truncal instability with progressive visual loss by the age of 42 years. He became wheelchair-dependent by 51 years old, neurologically exhibiting cerebellar ataxia, slow eye movement, slurred and scanning speech, lower limb spasticity, hyperreflexia, action-related slowly torsional dystonic movements in the trunk and limbs, diminished vibratory sensation in the lower limbs, auditory impairment, and macular degeneration. Brain magnetic resonance imaging revealed atrophy of the brainstem and cerebellum. He died of pneumonia at age 60 with a 26-year clinical duration of disease. Postmortem neuropathological examination revealed pronounced atrophy of the spinal cord, brainstem, cerebellum, external globus pallidus (GP), and subthalamic nucleus, microscopically showing neuronal cell loss and fibrillary astrogliosis with polyglutamine-immunoreactive neuronal nuclei and/or neuronal nuclear inclusions (NNIs). Degeneration was also accentuated in the oculomotor system, auditory and visual pathways, upper and lower motor neurons, and somatosensory system, including the spinal dorsal root ganglia. There was a weak negative correlation between the frequency of nuclear polyglutamine-positive neurons and the extent of neuronal cell loss. Clinicopathological features in the present case suggest that neurological symptoms, such as oculomotor, auditory, visual, and sensory impairments, are attributable to degeneration in their respective projection systems affected by SCA7 pathomechanisms and that dystonic movement is related to more significant degeneration in the external than internal GP.

A retrospective review of 29 patients with neurovascular compression syndrome (NVCS) involving the anterior visual pathway was conducted. Various patterns of NVCS and visual defects were identified, most commonly involving the optic nerve and internal carotid artery. Most patients were stable, except one with progressive visual field defects. Although mostly asymptomatic, NVCS can rarely cause compressive optic neuropathy. NVCS should be kept in the differential diagnosis of normal tension glaucoma, especially with progressive visual loss despite treatment. Patients with progressive visual loss may require decompression surgery. Non-contrast computed tomography scan may miss NVCS, and magnetic resonance imaging is diagnostic.

Charles Bonnet syndrome (CBS) is a rare clinical condition characterized by complex visual hallucinations in people with loss of vision. So far, the neurobiological mechanisms underlying the hallucinations remain elusive. This case-report study aims at investigating electrical activity changes in a CBS patient during visual hallucinations, as compared to a resting-state period (without hallucinations). Prior to the EEG, the patient underwent neuropsychological, ophthalmologic, and neurological examinations. Spectral and connectivity, graph analyses and signal diversity were applied to high-density EEG data. Visual hallucinations (as compared to resting-state) were characterized by a significant reduction of power in the frontal areas, paralleled by an increase in the midline posterior regions in delta and theta bands and by an increase of alpha power in the occipital and midline posterior regions. We next observed a reduction of theta connectivity in the frontal and right posterior areas, which at a network level was complemented by a disruption of small-worldness (lower local and global efficiency) and by an increase of network modularity. Finally, we found a higher signal complexity especially when considering the frontal areas in the alpha band. The emergence of hallucinations may stem from these changes in the visual cortex and in core cortical regions encompassing both the default mode and the fronto-parietal attentional networks.

The authors report intraoperative mapping with cortical visual evoked potentials during occipital tumor resection. This approach was valuable to reduce the risk of visual cortex and visual pathways damage and, accordingly, the likelihood of postoperative visual impairment. The peculiarity of this case is registration of clear cortical visual evoked potentials in various positions before and after tumor resection. Intraoperative monitoring was valuable to avoid damage to visual cortex and visual pathways during tumor resection. There was no postoperative visual deterioration. Moreover, we observed partial recovery of visual fields after resection of occipital malignant tumor.
В работе приводится клинический случай, показывающий возможность использования корковых зрительных вызванных потенциалов (ЗВП) при удалении опухоли затылочной доли для уменьшения риска повреждения зрительной коры и зрительных проводящих путей и, соответственно, для снижения вероятности ухудшения зрения после операции. Особенность клинического случая заключается в том, что нам удалось зарегистрировать четкие компоненты ЗВП в различных позициях до и после удаления опухоли. Благодаря проведенному мониторингу при удалении опухоли удалось обойти зрительную кору и проводящие зрительные пути. После нейрохирургического вмешательства с интраоперационной регистрацией корковых ЗВП нарастания зрительного дефицита не было, более того, отмечено частичное восстановление полей зрения после радикального удаления злокачественной опухоли затылочной доли.

BACKGROUND: It is unknown whether microangiopathic ischemic strokes outside the visual pathway go along with subclinical changes of the retinal structure or the visual system. The objectives of this prospective non-interventional case series were to investigate if spectral-domain optical coherence tomography (SD-OCT) or multifocal visual evoked potentials (mfVEPs) can detect structural retinal changes or functional impairment of the visual system in patients with microangiopathic ischemic stroke.
METHODS: We used SD-OCT to cross-sectionally analyze the retinal morphology of 15 patients with microangiopathic ischemic stroke according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification not affecting the visual pathway. We employed semi-automated segmentation of macular volume scans to analyze the thickness of the macular retinal layers and peripapillary ring scans to investigate the retinal morphology in comparison to a control group without stroke. Visual function was assessed by the mfVEP technique in 13 microangiopathic ischemic stroke patients.
RESULTS: First peak latency of mfVEPs was significantly delayed in the microangiopathic ischemic stroke group compared to the control patients. Neither the retinal layers nor the mfVEPs\' amplitude differed between the microangiopathic ischemic stroke patients and the control group.
CONCLUSIONS: In conclusion, microangiopathic ischemic stroke patients presented a delayed first peak latency in mfVEPs as a sign of subclinical functional impairment of the visual pathway. However, our case series suggests no influence on retinal structure resulting from microangiopathic ischemic stroke outside the visual system. Larger and longitudinal studies are needed to confirm these mfVEP findings.

In humans, each hemisphere comprises an overlay of two visuotopic maps of the contralateral visual field, one from each eye. Is the capacity of the visual cortex limited to these two maps or are plastic mechanisms available to host more maps? We determined the cortical organization of the visual field maps in a rare individual with chiasma hypoplasia, where visual cortex plasticity is challenged to accommodate three hemifield maps. Using high-resolution fMRI at 7T and diffusion-weighted MRI at 3T, we found three hemiretinal inputs, instead of the normal two, to converge onto the left hemisphere. fMRI-based population receptive field mapping of the left V1-V3 at 3T revealed three superimposed hemifield representations in the left visual cortex, i.e. two representations of opposing visual hemifields from the left eye and one right hemifield representation from the right eye. We conclude that developmental plasticity including the re-wiring of local intra- and cortico-cortical connections is pivotal to support the coexistence and functioning of three hemifield maps within one hemisphere.

A rare case of bilateral horizontal gaze palsy with intact vertical gaze eye movements and largely intact vestibulo-ocular reflex is presented owing to demyelinating lesions of the patient\'s bilateral paramedian pontine reticular formations and left infranuclear abducens nerve from the patient\'s recently diagnosed multiple sclerosis.
The purpose of this study was to report on a rare case of bilateral horizontal gaze palsy from a supranuclear lesion in a patient with a recent diagnosis of multiple sclerosis.
A 43-year-old African American woman presented urgently for evaluation of her inability to move her eyes into either horizontal gaze. Vertical conjugate movements remained intact, as did three of four extraocular muscles with horizontal vestibulo-ocular reflex testing, suggesting a supranuclear palsy. Magnetic resonance imaging revealed two demyelinating lesions in her inferior pons, which spared her nuclear and internuclear horizontal gaze pathways, as well as three of four extraocular muscles of her infranuclear horizontal gaze pathway as evidenced by her largely intact vestibulo-ocular reflex. This suggested bilateral paramedian pontine reticular formation lesions (supranuclear) and a mild left abducens nerve palsy (infranuclear).
Close evaluation of extraocular motilities and a solid understanding of the supranuclear, nuclear, internuclear, and infranuclear components of the horizontal gaze pathway can help identify challenging gaze palsies when encountered in a clinical setting. Appropriate neuroimaging can then be performed with an emphasis on the suspected location of the lesion(s) based on the patient\'s clinical findings.