Neuro-ophthalmology

Bauer C, Yazzolino L, Hirsch G, Cattaneo Z, Vecchi T, Merabet LB. Neural correlates associated with superior tactile symmetry perception in the early blind. Cortex 2015;63:104-117.Abstract
Symmetry is an organizational principle that is ubiquitous throughout the visual world. However, this property can also be detected through non-visual modalities such as touch. The role of prior visual experience on detecting tactile patterns containing symmetry remains unclear. We compared the behavioral performance of early blind and sighted (blindfolded) controls on a tactile symmetry detection task. The tactile patterns used were similar in design and complexity as in previous visual perceptual studies. The neural correlates associated with this behavioral task were identified with functional magnetic resonance imaging (fMRI). In line with growing evidence demonstrating enhanced tactile processing abilities in the blind, we found that early blind individuals showed significantly superior performance in detecting tactile symmetric patterns compared to sighted controls. Furthermore, comparing patterns of activation between these two groups identified common areas of activation (e.g. superior parietal cortex) but key differences also emerged. In particular, tactile symmetry detection in the early blind was also associated with activation that included peri-calcarine cortex, lateral occipital (LO), and middle temporal (MT) cortex, as well as inferior temporal and fusiform cortex. These results contribute to the growing evidence supporting superior behavioral abilities in the blind, and the neural correlates associated with crossmodal neuroplasticity following visual deprivation.
Gupta M, Leskov I, Kruger JM, Cestari DM. Intermittent Horner syndrome in a pediatric patient. J Neuroophthalmol 2014;34(2):149-50.Abstract
Intermittent Horner syndrome is uncommon in both the adult and pediatric population. We describe a case of a pediatric patient with an intermittent Horner syndrome. Infrared photography and videography were used to help establish the diagnosis.
Huang L, Sun X, Luo G, Liu S, Liu R, Mansouri B, Wong VWL, Wen W, Liu H, Wang A-H. Interocular Shift of Visual Attention Enhances Stereopsis and Visual Acuities of Anisometropic Amblyopes beyond the Critical Period of Visual Development: A Novel Approach. J Ophthalmol 2014;2014:615213.Abstract
Aims. Increasing evidence shows that imbalanced suppressive drive prior to binocular combination may be the key factor in amblyopia. We described a novel binocular approach, interocular shift of visual attention (ISVA), for treatment of amblyopia in adult patients. Methods. Visual stimuli were presented anaglyphically on a computer screen. A square target resembling Landolt C had 2 openings, one in red and one in cyan color. Through blue-red goggles, each eye could only see one of the two openings. The patient was required to report the location of the opening presented to the amblyopic eye. It started at an opening size of 800 sec of arc, went up and down in 160 sec of arc step, and stopped when reaching the 5th reversals. Ten patients with anisometropic amblyopia older than age 14 (average age: 26.7) were recruited and received ISVA treatment for 6 weeks, with 2 training sessions per day. Results. Both Titmus stereopsis (z = -2.809, P = 0.005) and Random-dot stereopsis (z = -2.317, P = 0.018) were significantly improved. Average improvement in best corrected visual acuity (BCVA) was 0.74 line (t = 5.842, P < 0.001). Conclusions. The ISVA treatment may be effective in treating amblyopia and restoring stereoscopic function.
Singer JM, Kreiman G. Short temporal asynchrony disrupts visual object recognition. J Vis 2014;14(5):7.Abstract
Humans can recognize objects and scenes in a small fraction of a second. The cascade of signals underlying rapid recognition might be disrupted by temporally jittering different parts of complex objects. Here we investigated the time course over which shape information can be integrated to allow for recognition of complex objects. We presented fragments of object images in an asynchronous fashion and behaviorally evaluated categorization performance. We observed that visual recognition was significantly disrupted by asynchronies of approximately 30 ms, suggesting that spatiotemporal integration begins to break down with even small deviations from simultaneity. However, moderate temporal asynchrony did not completely obliterate recognition; in fact, integration of visual shape information persisted even with an asynchrony of 100 ms. We describe the data with a concise model based on the dynamic reduction of uncertainty about what image was presented. These results emphasize the importance of timing in visual processing and provide strong constraints for the development of dynamical models of visual shape recognition.
Sümbül U, Song S, McCulloch K, Becker M, Lin B, Sanes JR, Masland RH, Seung SH. A genetic and computational approach to structurally classify neuronal types. Nat Commun 2014;5:3512.Abstract
The importance of cell types in understanding brain function is widely appreciated but only a tiny fraction of neuronal diversity has been catalogued. Here we exploit recent progress in genetic definition of cell types in an objective structural approach to neuronal classification. The approach is based on highly accurate quantification of dendritic arbor position relative to neurites of other cells. We test the method on a population of 363 mouse retinal ganglion cells. For each cell, we determine the spatial distribution of the dendritic arbors, or arbor density, with reference to arbors of an abundant, well-defined interneuronal type. The arbor densities are sorted into a number of clusters that is set by comparison with several molecularly defined cell types. The algorithm reproduces the genetic classes that are pure types, and detects six newly clustered cell types that await genetic definition.
Nassi JJ, Gómez-Laberge C, Kreiman G, Born RT. Corticocortical feedback increases the spatial extent of normalization. Front Syst Neurosci 2014;8:105.Abstract
Normalization has been proposed as a canonical computation operating across different brain regions, sensory modalities, and species. It provides a good phenomenological description of non-linear response properties in primary visual cortex (V1), including the contrast response function and surround suppression. Despite its widespread application throughout the visual system, the underlying neural mechanisms remain largely unknown. We recently observed that corticocortical feedback contributes to surround suppression in V1, raising the possibility that feedback acts through normalization. To test this idea, we characterized area summation and contrast response properties in V1 with and without feedback from V2 and V3 in alert macaques and applied a standard normalization model to the data. Area summation properties were well explained by a form of divisive normalization, which computes the ratio between a neuron's driving input and the spatially integrated activity of a "normalization pool." Feedback inactivation reduced surround suppression by shrinking the spatial extent of the normalization pool. This effect was independent of the gain modulation thought to mediate the influence of contrast on area summation, which remained intact during feedback inactivation. Contrast sensitivity within the receptive field center was also unaffected by feedback inactivation, providing further evidence that feedback participates in normalization independent of the circuit mechanisms involved in modulating contrast gain and saturation. These results suggest that corticocortical feedback contributes to surround suppression by increasing the visuotopic extent of normalization and, via this mechanism, feedback can play a critical role in contextual information processing.
Allmendinger AM, M Mallery R, Magro CM, Wang N, Egan RA, Samuels MA, Callahan A, Viswanadhan N, Klufas RA, Hsu L, Prasad S. Cauda equina involvement in Susac's syndrome. J Neurol Sci 2014;337(1-2):91-6.Abstract
Susac's syndrome is a rare autoimmune microangiopathy characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss. In many cases, the clinical triad is not fully present at the onset of symptoms. MRI studies often show characteristic punched out lesions of the central fibers of the corpus callosum, and leptomeningeal enhancement and deep gray matter lesions may also be seen. Here we present a case of Susac's syndrome in a middle aged man with the unique clinical finding of cauda equina syndrome and spinal MRI showing diffuse lumbosacral nerve root enhancement. Biopsy specimens of the brain, leptomeninges, and skin showed evidence of a pauci-immune endotheliopathy, consistent with pathology described in previous cases of Susac's syndrome. This case is important not only because it expands the clinical features of Susac's syndrome but also because it clarifies the mechanism of a disorder of the endothelium, an important target for many disorders of the nervous system.
Bansal AK, Madhavan R, Agam Y, Golby A, Madsen JR, Kreiman G. Neural dynamics underlying target detection in the human brain. J Neurosci 2014;34(8):3042-55.Abstract
Sensory signals must be interpreted in the context of goals and tasks. To detect a target in an image, the brain compares input signals and goals to elicit the correct behavior. We examined how target detection modulates visual recognition signals by recording intracranial field potential responses from 776 electrodes in 10 epileptic human subjects. We observed reliable differences in the physiological responses to stimuli when a cued target was present versus absent. Goal-related modulation was particularly strong in the inferior temporal and fusiform gyri, two areas important for object recognition. Target modulation started after 250 ms post stimulus, considerably after the onset of visual recognition signals. While broadband signals exhibited increased or decreased power, gamma frequency power showed predominantly increases during target presence. These observations support models where task goals interact with sensory inputs via top-down signals that influence the highest echelons of visual processing after the onset of selective responses.
Yoon MK, Piluek WJ, Ruggiero JP, McDermott MW, McCulley TJ. Orbital cerebrospinal fluid accumulation after complicated pterional-orbitozygomatic craniotomy. J Neuroophthalmol 2014;34(4):346-9.Abstract

We describe 2 patients who developed postoperative orbital cerebrospinal fluid (CSF) collection after orbitozygomatic pterional craniotomy. An 18-year-old woman underwent exploratory pterional-orbitozygomatic craniotomy. Five days postoperatively, after removal of a lumbar drain, proptosis and a compressive optic neuropathy developed. Computed tomography demonstrated a CSF collection contiguous with the craniotomy site. Resolution followed percutaneous aspiration and replacement of the lumbar drain. A 57-year-old woman underwent a pterional-orbitozygomatic craniotomy for removal of a left anterior clinoid meningioma, complicated by a large left hemorrhagic stroke requiring decompressive hemicraniectomy. Extracranial CSF collections accumulated in both the orbit and subgaleal spaces. Resolution followed placement of an external ventricular drain. Based on these cases, the mechanism seems to be the combination of iatrogenic formation of a communication with the subarachnoid space and elevated intracranial pressure. Resolution was achieved by normalizing intracranial pressure.

Vodopivec I, Lobo A-M, Prasad S. Ocular inflammation in neurorheumatic disease. Semin Neurol 2014;34(4):444-57.Abstract

Neuroimmunologic and systemic rheumatic diseases are frequently accompanied by inflammation of the eye, ocular adnexa, and orbital tissues. An understanding of the diverse forms of ophthalmic pathology in these conditions aids the clinician in making appropriate preventative, diagnostic, therapeutic, and prognostic decisions. In this review, the authors address ocular inflammation in neurorheumatic disease in three sections: first, they highlight current perspectives on immune mechanisms in the development of these disorders; next, they provide a framework for the recognition and evaluation of ophthalmologic inflammatory entities; finally, they discuss in detail several inflammatory conditions that affect the nervous system and the eye, emphasizing the features that should alert neurologists to initiate ophthalmologic evaluation. The conditions discussed include multiple sclerosis, neuromyelitis optica, chronic relapsing inflammatory optic neuropathy, Susac syndrome, Cogan syndrome, acute posterior multifocal placoid pigment epitheliopathy, Vogt-Koyanagi-Harada disease, Behçet disease, sarcoidosis, systemic lupus erythematosus, granulomatosis with polyangiitis (Wegener granulomatosis), polyarteritis nodosa, giant cell arteritis, IgG4-related disease, and Sjögren syndrome.

Shah AS, Prabhu SP, Sadiq MAA, Mantagos IS, Hunter DG, Dagi LR. Adjustable nasal transposition of split lateral rectus muscle for third nerve palsy. JAMA Ophthalmol 2014;132(8):963-9.Abstract
IMPORTANCE: Third nerve palsy causes disfiguring, incomitant strabismus with limited options for correction. OBJECTIVE: To evaluate the oculomotor outcomes, anatomical changes, and complications associated with adjustable nasal transposition of the split lateral rectus (LR) muscle, a novel technique for managing strabismus associated with third nerve palsy. DESIGN, SETTING, AND PARTICIPANTS: Retrospective medical record review appraising outcomes of 6 consecutive patients with third nerve palsy who underwent adjustable nasal transposition of the split LR muscle between 2010 and 2012 with follow-up of 5 to 25 months at a tertiary referral center. INTERVENTION: Adjustable nasal transposition of the split LR muscle. MAIN OUTCOMES AND MEASURES: The primary outcome was postoperative horizontal and vertical alignment. Secondary outcomes were (1) appraising the utility of adjustable positioning, (2) demonstrating the resultant anatomical changes using magnetic resonance imaging, and (3) identifying associated complications. RESULTS: Four of 6 patients successfully underwent the procedure. Of these, 3 patients achieved orthotropia. Median preoperative horizontal deviation was 68 prism diopters of exotropia and median postoperative horizontal deviation was 0 prism diopters (P = .04). Two patients had preoperative vertical misalignment that resolved with surgery. All 4 patients underwent intraoperative adjustment of LR positioning. Imaging demonstrated nasal redirection of each half of the LR muscle around the posterior globe, avoiding contact with the optic nerve; the apex of the split sat posterior to the globe. One patient had transient choroidal effusion and undercorrection. Imaging revealed, in this case, the apex of the split in contact with the globe at an anterolateral location, suggesting an inadequate posterior extent of the split. In 2 patients, the surgical procedure was not completed because of an inability to nasally transpose a previously operated-on LR muscle. CONCLUSIONS AND RELEVANCE: Adjustable nasal transposition of the split LR muscle can achieve excellent oculomotor alignment in some cases of third nerve palsy. The adjustable modification allows optimization of horizontal and vertical alignment. Imaging confirms that the split LR muscle tethers the globe, rotating it toward primary position. Case selection is critical because severe LR contracture, extensive scarring from prior strabismus surgery, or inadequate splitting of the LR muscle may reduce the likelihood of success and increase the risk of sight-threatening complications. Considering this uncertainty, more experience is necessary before widespread adoption of this technique should be considered.
Paramasivam S, Fay A, Fifi J, Berenstein A. O-015 image guided bleomycin sclerotherapy for orbital lymphatic malformation. J Neurointerv Surg 2014;6 Suppl 1:A8-9.Abstract

INTRODUCTION: Orbital lymphatic malformations (OLMs) are a unique subset of head and neck low flow vascular malformations, located either in the periorbital region or in the closed orbital cavity. We discuss our experience of minimally invasive strategies of treatment using advanced imaging and Bleomycin sclerotherapy to effectively treat these malformations. MATERIALS AND METHODS: Between 2008 and 2013, we have treated 54 cases of orbital low flow vascular malformations including 22 cases of OLMs of which 16 were treated using Bleomycin. This retrospective analysis was performed from patient charts, operative reports, operative images, pre-operative, and post-operative MR imaging. Bleomycin was used for sclerotherapy in all the cases with a maximum dose per session of treatment limited to 15 mgs. DIRECT PUNCTURE SCLEROTHERAPY TECHNIQUE: OLMs target was determined using pre-procedure MR imaging and direct puncture either per-cutaneous or per-conjunctival was achieved using ultrasound or i-guide guidance. In most lymphatic fluid was drained else the position confirmed with constrast injection under fluoroscopy. Bleomycin was used either undiluted or in various concentrations mixed with saline, or contrast material and recently we favor the use of Bleofoam mixed with 25% Human albumin and air. Microcystic LMs, were treated using gravity technique, the needle track was sealed with Surgiflo or Floseal. In cases of intra cystic or intra ocular haemorrhage with elevated orbital pressure, lateral canthotomy was performed to prevent permanent damage to vision and the contents of the orbit. Postoperatively, the patients recover in ICU and monitored for vision and orbital swelling. Bleomycin skin precautions were followed for 72 h in order to avoid skin hyperpigmentation. Optimal results were obtained at 6 to 8 weeks and assessed using follow-up MRI and ophthalmologic evaluation. RESULTS: The patient's age ranged from 1 to 45 years, with equal male to female ratio. Most cases (13/16) (80%) presented non acutely while three patients (20%) presented acutely with proptosis, visual disturbance and double vision due to haemorrhage within the malformation. Treatment completed in 14, one lost to follow up and the other is yet to be followed. The follow up period ranged from 6weeks to 6 months. 65% (9/14) needed less than three procedures while the remaining five patients needed between 3-5 procedures. All patients had improvement in proptosis; vision either remained stable or improved; volume reduction of more than 80% was noted in 57% (8/14), while the remaining patients 43% had volume reduction of 50-79%. One patient had transient mydriasis post procedure that completely recovered at three months. Another developed haemorrhage within the malformation immediate post sclerotherapy requiring lateral canthotomy, drainage and redo sclerotherapy. None of our patients developed skin pigmentation or pulmonary complication related to bleomycin usage. CONCLUSION: Bleomycin sclerotherapy combined with appropriate image guidance for precise target localization is an effective and safe treatment for OLMs. Bleomycin is a preferred sclerosant as it induces minimal inflammation and post procedure swelling. Standard precautions must be instituted to prevent cutaneous pigmentation and pulmonary fibrosis. DISCLOSURES: S. Paramasivam: None. A. Fay: None. J. Fifi: None. A. Berenstein: None.

Cattaneo Z, Lega C, Gardelli C, Merabet LB, Cela-Conde CJ, Nadal M. The role of prefrontal and parietal cortices in esthetic appreciation of representational and abstract art: a TMS study. Neuroimage 2014;99:443-50.Abstract
To explain the biological foundations of art appreciation is to explain one of our species' distinctive traits. Previous neuroimaging and electrophysiological studies have pointed to the prefrontal and the parietal cortex as two critical regions mediating esthetic appreciation of visual art. In this study, we applied transcranial magnetic stimulation (TMS) over the left prefrontal cortex and the right posterior parietal cortex while participants were evaluating whether they liked, and by how much, a particular painting. By depolarizing cell membranes in the targeted regions, TMS transiently interferes with the activity of specific cortical areas, which allows clarifying their role in a given task. Our results show that both regions play a fundamental role in mediating esthetic appreciation. Critically though, the effects of TMS varied depending on the type of art considered (i.e. representational vs. abstract) and on participants' a-priori inclination toward one or the other.
Bauer CM, Heidary G, Koo B-B, Killiany RJ, Bex P, Merabet LB. Abnormal white matter tractography of visual pathways detected by high-angular-resolution diffusion imaging (HARDI) corresponds to visual dysfunction in cortical/cerebral visual impairment. J AAPOS 2014;18(4):398-401.Abstract
Cortical (cerebral) visual impairment (CVI) is characterized by visual dysfunction associated with damage to the optic radiations and/or visual cortex. Typically it results from pre- or perinatal hypoxic damage to postchiasmal visual structures and pathways. The neuroanatomical basis of this condition remains poorly understood, particularly with regard to how the resulting maldevelopment of visual processing pathways relates to observations in the clinical setting. We report our investigation of 2 young adults diagnosed with CVI and visual dysfunction characterized by difficulties related to visually guided attention and visuospatial processing. Using high-angular-resolution diffusion imaging (HARDI), we characterized and compared their individual white matter projections of the extrageniculo-striate visual system with a normal-sighted control. Compared to a sighted control, both CVI cases revealed a striking reduction in association fibers, including the inferior frontal-occipital fasciculus as well as superior and inferior longitudinal fasciculi. This reduction in fibers associated with the major pathways implicated in visual processing may provide a neuroanatomical basis for the visual dysfunctions observed in these patients.
Lessell S, E Grzybowski A. Idiopathic opticochiasmatic arachnoiditis. J Neuroophthalmol 2014;34(3):251-4.Abstract

: A critical review of the literature indicates that idiopathic opticochiasmatic arachnoiditis, once considered an important consideration in patients with otherwise unexplained optic atrophy, is not a valid disease entity.

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