Stimulus-responsive and task-dependent activations in occipital regions during pitch perception by early blind listeners

Although it has been established that cross-modal activations occur in the occipital cortex during auditory processing among congenitally and early blind listeners, it remains uncertain whether these activations in various occipital regions reflect sensory analysis of specific sound properties, non-perceptual cognitive operations associated with active tasks, or the interplay between sensory analysis and cognitive operations. This fMRI study aimed to investigate cross-modal responses in occipital regions, specifically V5/MT and V1, during passive and active pitch perception by early blind individuals compared to sighted individuals. The data showed that V5/MT was responsive to pitch during passive perception, and its activations increased with task complexity. By contrast, widespread occipital regions, including V1, were only recruited during two active perception tasks, and their activations were also modulated by task complexity. These fMRI results from blind individuals suggest that while V5/MT activations are both stimulus-responsive and task-modulated, activations in other occipital regions, including V1, are dependent on the task, indicating similarities and differences between various visual areas during auditory processing.

'Visual' cortices of congenitally blind adults are sensitive to response selection demands in a go/no-go task

Studies of occipital cortex plasticity in blindness provide insight into how intrinsic constraints interact with experience to determine cortical specialization. We tested the cognitive nature and anatomical origins of occipital responses during non-verbal, non-spatial auditory tasks. In a go/no-go task, congenitally blind (N=23) and sighted (N=24) individuals heard rapidly occurring (<1/s) non-verbal sounds and made one of two button presses (frequent-go 50%, infrequent-go 25%) or withheld a response (no-go, 25%). Rapid and frequent button presses heighten response selection/inhibition demands on the no-go trials: In sighted and blind adults a right-lateralized prefrontal (PFC) network responded most to no-go trials, followed by infrequent-go and finally frequent-go trials. In the blind group only, a right-lateralized occipital network showed the same response profile and the laterality of occipital and PFC responses was correlated across blind individuals. A second experiment with spoken sentences and equations (N=16) found that no-go responses in occipital cortex are distinct from previously identified occipital responses to spoken language. Finally, in resting-state data (N=30 blind, N=31 blindfolded sighted), no-go responsive 'visual' cortex of blind relative to sighted participants was more synchronized with PFC and less synchronized with primary auditory and sensory-motor cortices. No-go responsive occipital cortex showed higher resting-state correlations with no-go responsive PFC than language responsive inferior frontal cortex. We conclude that in blindness, a right-lateralized occipital network responds to non-verbal executive processes, including response selection. These results suggest that connectivity with fronto-parietal executive networks is a key mechanism for plasticity in blindness.

Neurological and behavioral features of locomotor imagery in the blind

In people with normal sight, mental simulation (motor imagery) of an experienced action involves a multisensory (especially kinesthetic and visual) emulation process associated with the action. Here, we examined how long-term blindness influences sensory experience during motor imagery and its neuronal correlates by comparing data obtained from blind and sighted people. We scanned brain activity with functional magnetic resonance imaging (fMRI) while 16 sighted and 14 blind male volunteers imagined either walking or jogging around a circle of 2 m radius. In the training before fMRI, they performed these actions with their eyes closed. During scanning, we explicitly instructed the blindfolded participants to generate kinesthetic motor imagery. After the experimental run, they rated the degree to which their motor imagery became kinesthetic or spatio-visual. The imagery of blind people was more kinesthetic as per instructions, while that of the sighted group became more spatio-visual. The imagery of both groups commonly activated bilateral frontoparietal cortices including supplementary motor areas (SMA). Despite the lack of group differences in degree of brain activation, we observed stronger functional connectivity between the SMA and cerebellum in the blind group compared to that in the sighted group. To conclude, long-term blindness likely changes sensory emulation during motor imagery to a more kinesthetic mode, which may be associated with stronger functional coupling in kinesthetic brain networks compared with that in sighted people. This study adds valuable knowledge on motor cognition and mental imagery processes in the blind.

Visuo-spatial attention to the blind hemifield of hemianopic patients: Can it survive the impairment of visual awareness?

The general aim of this study was to assess the effect produced by visuo-spatial attention on both behavioural performance and brain activation in hemianopic patients following visual stimulus presentation to the blind hemifield. To do that, we tested five hemianopic patients and six age-matched healthy controls in an MRI scanner during the execution of a Posner-like paradigm using a predictive central cue. Participants were instructed to covertly orient attention toward the blind or sighted hemifield in different blocks while discriminating the orientation of a visual grating. In patients, we found significantly faster reaction times (RT) in valid and neutral than invalid trials not only in the sighted but also in the blind hemifield, despite the impairment of consciousness and performance at chance. As to the fMRI signal, in valid trials we observed the activation of ipsilesional visual areas (mainly lingual gyrus - area 19) during the orientation of attention toward the blind hemifield. Importantly, this activation was similar in patients and controls. In order to assess the related functional network, we performed a psychophysiological interactions (PPI) analysis that revealed an increased functional connectivity (FC) in patients with respect to controls between the ipsilesional lingual gyrus and ipsilateral fronto-parietal as well as contralesional parietal regions. Moreover, the shift of attention from the blind to the sighted hemifield revealed stronger FC between the contralesional visual areas V3/V4 and ipsilateral parietal regions in patients than controls. These results indicate a higher cognitive effort in patients when paying attention to the blind hemifiled or when shifting attention from the blind to the sighted hemfield, possibly as an attempt to compensate for the visual loss. Taken together, these results show that hemianopic patients can covertly orient attention toward the blind hemifield with a top-down mechanism by activating a functional network mainly including fronto-parietal regions belonging to the dorsal attentional network.

Transient vision loss after optic nerve sheath fenestration

Optic nerve sheath fenestration (ONSF) is a well-known, relatively safe, and effective surgical treatment for visual loss related to papilledema. Visual loss following ONSF is uncommon but can occur from direct surgical trauma, ischemic optic neuropathy, orbital or intrasheath hemorrhage, or arterial occlusion. Transient severe (e.g., light perception (LP) or no light perception (NLP) visual loss) after ONSF is uncommon but has been reported. We describe a case of LP vision following uncomplicated ONSF with orbital imaging demonstrating significant postoperative inflammation and slow recovery after intravenous steroid treatment. We discuss the various mechanisms for this phenomenon after ONSF. To our knowledge, this is the first clinico-radiologic description with follow up and recovery of this postoperative complication of ONSF to be reported in the English language ophthalmic literature.

Prenatal Sonographic Abnormal Appearances of the Fetal Hyaloid Artery: From Normal Variants to Pathology

This is a case series on the abnormal sonographic appearance and outcome of the fetal hyaloid artery (HA) detected during between 1987 and 2015 at one medical center. Fifteen cases were detected during fetal anatomy scans, usually performed at 14 to 16 weeks' gestation. Three other cases were diagnosed following referral for a second opinion. In nine fetuses, the HA regressed normally throughout pregnancy. Of them, eight neonates had normal outcomes and one had cataract at the same eye. All nine other cases ended with adverse outcomes. Failure of the HA to regress in the third trimester appears to be an indicator of congenital blindness.

Long-term consequences of developmental vascular defects on retinal vessel homeostasis and function in a mouse model of Norrie disease

Loss of Norrin signalling due to mutations in the Norrie disease pseudoglioma gene causes severe vascular defects in the retina, leading to visual impairment and ultimately blindness. While the emphasis of experimental work so far was on the developmental period, we focus here on disease mechanisms that induce progression into severe adult disease. The goal of this study was the comprehensive analysis of the long-term effects of the absence of Norrin on vascular homeostasis and retinal function. In a mouse model of Norrie disease retinal vascular morphology and integrity were studied by means of in vivo angiography; the vascular constituents were assessed in detailed histological analyses using quantitative retinal morphometry. Finally, electroretinographic analyses were performed to assess the retinal function in adult Norrin deficient animals. We could show that the primary developmental defects not only persisted but developed into further vascular abnormalities and microangiopathies. In particular, the overall vessel homeostasis, the vascular integrity, and also the cellular constituents of the vascular wall were affected in the adult Norrin deficient retina. Moreover, functional analyses indicated to persistent hypoxia in the neural retina which was suggested as one of the major driving forces of disease progression. In summary, our data provide evidence that the key to adult Norrie disease are ongoing vascular modifications, driven by the persistent hypoxic conditions, which are ineffective to compensate for the primary Norrin-dependent defects.

Memory-guided drawing training increases Granger causal influences from the perirhinal cortex to V1 in the blind

The perirhinal cortex (PRC) is a medial temporal lobe structure that has been implicated in not only visual memory in the sighted, but also tactile memory in the blind (Cacciamani & Likova, 2016). It has been proposed that, in the blind, the PRC may contribute to modulation of tactile memory responses that emerge in low-level "visual" area V1 as a result of training-induced cortical reorganization (Likova, 2012, 2015). While some studies in the sighted have indicated that the PRC is indeed structurally and functionally connected to the visual cortex (Clavagnier, Falchier, & Kennedy, 2004; Peterson, Cacciamani, Barense, & Scalf, 2012), the PRC's direct modulation of V1 is unknown-particularly in those who lack the visual input that typically stimulates this region. In the present study, we tested Likova's PRC modulation hypothesis; specifically, we used fMRI to assess the PRC's Granger causal influence on V1 activation in the blind during a tactile memory task. To do so, we trained congenital and acquired blind participants on a unique memory-guided drawing technique previously shown to result in V1 reorganization towards tactile memory representations (Likova, 2012). The tasks (20s each) included: tactile exploration of raised line drawings of faces and objects, tactile memory retrieval via drawing, and a scribble motor/memory control. FMRI before and after a week of the Cognitive-Kinesthetic training on these tasks revealed a significant increase in PRC-to-V1 Granger causality from pre- to post-training during the memory drawing task, but not during the motor/memory control. This increase in causal connectivity indicates that the training strengthened the top-down modulation of visual cortex from the PRC. This is the first study to demonstrate enhanced directed functional connectivity from the PRC to the visual cortex in the blind, implicating the PRC as a potential source of the reorganization towards tactile representations that occurs in V1 in the blind brain (Likova, 2012).

Visual BOLD Response in Late Blind Subjects with Argus II Retinal Prosthesis

Retinal prosthesis technologies require that the visual system downstream of the retinal circuitry be capable of transmitting and elaborating visual signals. We studied the capability of plastic remodeling in late blind subjects implanted with the Argus II Retinal Prosthesis with psychophysics and functional MRI (fMRI). After surgery, six out of seven retinitis pigmentosa (RP) blind subjects were able to detect high-contrast stimuli using the prosthetic implant. However, direction discrimination to contrast modulated stimuli remained at chance level in all of them. No subject showed any improvement of contrast sensitivity in either eye when not using the Argus II. Before the implant, the Blood Oxygenation Level Dependent (BOLD) activity in V1 and the lateral geniculate nucleus (LGN) was very weak or absent. Surprisingly, after prolonged use of Argus II, BOLD responses to visual input were enhanced. This is, to our knowledge, the first study tracking the neural changes of visual areas in patients after retinal implant, revealing a capacity to respond to restored visual input even after years of deprivation.

Digital Evaluation of Orbital Cyst Associated with Microphthalmos: Characteristics and Their Relationship with Orbital Volume

Purpose

To study the characteristics of orbital cyst associated with microphthalmos in a group of Chinese patients, and to analyze the relationship between orbital cyst and orbital volume.

Design

Cross-sectional comparative study.

Participants

120 patients who were diagnosed as unilateral clinical blind microphthalmos, in which 20 patients had orbital cyst in the affected eye.

Method

Participants had computed tomography (CT) scan. CT images were analyzed with a computer-aided software.

Main Outcome Measures

Volume and position of orbital cyst, microphthalmic to contralateral ratio (MCR) of orbital volume, height and depth and orbital rim displacement.

Results

38.1% of the cysts located anterior to or at the equator of the globe, 75% of which located infratemporally and all of which were outside the muscle cone. Most (84.6%) of the posterior cysts were inside the muscle cone. The anterior cysts were larger than the posterior cysts (p = 0.005). MCR of orbital volume (p<0.001), height (p = 0.004) and width (p = 0.043) were significantly higher in patients with orbital cyst than controls. For patients with orbital cyst, larger cyst-plus-globe volume of the affected eye was associated with higher MCR of orbital volume (r = 0.630, p = 0.003). Patients with large cyst-plus-globe volume had higher MCR of orbital volume (p = 0.002), height (p = 0.014), width (p = 0.005) and depth (p = 0.002) and less displacement in inferior (p = 0.004) orbital rim, compared with patients with small cyst-plus-globe volume, but the differences between patients with small cyst-plus-globe volume and patients without cyst were not significant.

Conclusions

Microphthalmic eyes with large cyst-plus-globe volume showed better similarity with the contralateral eyes, comparing with microphthalmic eyes without orbital cyst or with small cyst-plus-globe volume. It suggested that the existence of orbital cysts (especially large cysts) in microphthalmic eyes might play a positive role in the orbital development.

[Tubulointerstitial nephritis syndrome and uveitis]

Intermediate uveitis is described as inflammation in the anterior vitreous, ciliary body and the peripheral retina. It is a subset of uveitis where the vitreous is the major site of damage. It has been reported to be associated with many local and systemic inflammatory and infectious diseases. An infrequent cause is the tubulointerstitial nephritis and uveitis syndrome. We report a case of an acute visual acuity loss related with renal failure in a 64 years old woman with Hashimoto disease. It was an acute tubulointerstitial nephritis and uveitis syndrome case.

Network Modeling for Functional Magnetic Resonance Imaging (fMRI) Signals during Ultra-Fast Speech Comprehension in Late-Blind Listeners

In many functional magnetic resonance imaging (fMRI) studies blind humans were found to show cross-modal reorganization engaging the visual system in non-visual tasks. For example, blind people can manage to understand (synthetic) spoken language at very high speaking rates up to ca. 20 syllables/s (syl/s). FMRI data showed that hemodynamic activation within right-hemispheric primary visual cortex (V1), bilateral pulvinar (Pv), and left-hemispheric supplementary motor area (pre-SMA) covaried with their capability of ultra-fast speech (16 syllables/s) comprehension. It has been suggested that right V1 plays an important role with respect to the perception of ultra-fast speech features, particularly the detection of syllable onsets. Furthermore, left pre-SMA seems to be an interface between these syllabic representations and the frontal speech processing and working memory network. So far, little is known about the networks linking V1 to Pv, auditory cortex (A1), and (mesio-) frontal areas. Dynamic causal modeling (DCM) was applied to investigate (i) the input structure from A1 and Pv toward right V1 and (ii) output from right V1 and A1 to left pre-SMA. As concerns the input Pv was significantly connected to V1, in addition to A1, in blind participants, but not in sighted controls. Regarding the output V1 was significantly connected to pre-SMA in blind individuals, and the strength of V1-SMA connectivity correlated with the performance of ultra-fast speech comprehension. By contrast, in sighted controls, not understanding ultra-fast speech, pre-SMA did neither receive input from A1 nor V1. Taken together, right V1 might facilitate the “parsing” of the ultra-fast speech stream in blind subjects by receiving subcortical auditory input via the Pv (= secondary visual pathway) and transmitting this information toward contralateral pre-SMA.

Impacted iron nail in the orbit and maxillary sinus through a corneo-scleral perforation: a case report

INTRODUCTION

Open globe injury is one of the commonest ophthalmic emergencies, and when accompanied by intraocular foreign bodies, the condition carries a poorer prognosis.

OBJECTIVE

To report a rare case of perforating injury of the globe with an iron nail which got lodged in the maxillary sinus.

CASE

A ten-year-old boy presented with the history of sudden painful loss of vision in his right eye. He reported that he was hit forcefully by the tail of a cow a day before the presentation. There was no perception of light in that eye. The ocular examination revealed a full thickness corneo-scleral perforation with prolapsed uveal tissue. The X-ray of the right orbit showed an impacted foreign body in the inferior orbit and computed tomography scan of the orbit confirmed the presence of a vertically impacted metal piece in the right orbit and right maxillary sinus. The repair of the perforation and removal of the impacted nail was done in two stages. The globe anatomy was maintained but the vision could not be restored due to the grave nature of the trauma.

CONCLUSION

Perforating globe injury is an important cause of monocular blindness.

The retrobulbar "spot sign" as a discriminator between vasculitic and thrombo-embolic affections of the retinal blood supply

PURPOSE

Sudden retinal blindness is a common complication of temporal arteritis (TA). Another common cause is embolic occlusion of the central retinal artery (CRA). The aim of this prospective study was to examine the diagnostic value of hyperechoic material in the CRA for the exclusion of vasculitis as a cause. The authors used orbital color-coded sonography (OCCS) for the detection of hyperechoic material.

MATERIALS AND METHODS

24 patients with sudden vision loss were included in the study after the exclusion of other causes (e. g. vitreous bleeding, retinal detachment). Parallel to routine diagnostic workup, OCCS was performed in all patients.

RESULTS

7 patients with a diagnosis of TA presented with different degrees of hypoperfusion in the CRA without hyperechoic material (referred to as "spot sign") detected by OCCS. Diagnostic workup in the remaining 17 patients revealed other causes of sudden vision loss, such as central retinal artery occlusion (CRAO) (12), anterior ischemic optic neuropathy (AION) (2), upstream vascular stenosis or occlusion (2) and delayed reperfusion of the CRA (1). The hyperechoic "spot sign" was visible in 10 of 12 patients (83 %) with embolic CRAO. The detection of embolic CRAO using the "spot sign" had a sensitivity of 83 % and a specificity of 100 %. The missing "spot sign" in patients with TA was a highly specific finding (p-value 0.01).

CONCLUSION

The detection of the "spot sign" specifically minimizes the probability of TA as a reason for sudden blindness.

Monocular blindness during therapy for cerebral neurocysticercosis

Neurocysticercosis is endemic in India, cerebral and ocular manifestations being common. A 32 yr old man on treatment with Albendazole for cerebral neurocysticercosis for 10 days presented with 3 days of painful uniocular blindness. He had only light perception in the left eye, left pupil was non-reactive to light and left disc was edematous. B-scan of eye revealed retinal detachment due to sub retinal cyst and CT brain showed multiple parenchymal cysticerci. The natural history of ocular neurocysticercosis or enhanced sub-retinal inflammation due to Albendazole therapy could have resulted in the retinal detachment in this case.

[Delayed loss of vision after hammer and chisel injury]

Eye injuries caused by foreign bodies are a common diagnosis in many patients with an ocular emergency. A high percentage of foreign bodies are located in the cornea and are easily removed, but an intralenticular foreign body after eye injury is very rare. A 28-year-old man referred to our department with increasing loss of vision in the right eye 1 month after an accident with a hammer and chisel. At the time of admission the patient complained of a significant loss of vision and a traumatic cataract was diagnosed. The examination showed a deep stromal corneal scar and an anterior subcapsular cataract with posterior contusional rosette. Slit-lamp examination in mydriasis aroused the suspicion of an intralenticular foreign body. An X-ray examination of the right orbit was performed, but apart from a shadow, which was interpreted by the radiologists as a "pixel artefact", it revealed no presence of a foreign body. A computed tomography examination was also undertaken and confirmed the suspicion of an intralenticular foreign body, which was confirmed by an ultrasound scan. The intralenticular foreign body was removed during cataract surgery and an IOL was successfully implanted in the intact capsular bay. The day after the surgical intervention BCVA was 1.0. Every ocular trauma with a foreign body should be examined in mydriasis in order to exclude an intralenticular foreign body. Conventional X-ray images may not always be efficient enough to detect a foreign body. If an intraocular foreign body is suspected a thin-slice computed tomography examination of the orbit should be performed.

Sudden loss of vision--investigation and management

BACKGROUND

Sudden vision loss usually requires urgent ophthalmic assessment. Diagnosis and management requires the judicious use of a wide range of serological and imaging investigations to guide appropriate treatment and referral.

OBJECTIVE

This article follows on from the previous discussion of the role of history and examination to discuss the appropriate investigation and management of common causes of sudden visual loss.

DISCUSSION

The key historical and examination findings have now been extracted and synthesised and these inform the next step. The general practitioner must now decide upon the most appropriate and timely investigation pathway or the need for, and urgency of, referral.

An unusual parasagittal tumour with acute blindness and response to cerebrospinal fluid shunting

We report a seven-year-old girl who presented with a sudden tumor apoplexy due to a parasagittal hemangiopericytoma. Following tumor excision, the child was noted to have bilateral optic nerve dysfunction and progressive papilledema, despite rapid overall neurological improvement. Based on the clinical features, we feel that this case represents an unusual form of visual deterioration related to impaired CSF absorption somehow precipitated by the acute tumour apoplexy. This unusual case of blindness responded significantly to CSF shunting. Several reports exist describing raised intracranial pressure with papilledema caused by nonthrombotic sinus occlusion due to tumors in proximity to the posterior superior sagittal sinus, torcular herophili and the jugular outlet. Communicating hydrocephalus, pseudotumor syndrome or intracranial venous sinus obstruction should be considered when otherwise inexplicable visual loss coexists with optic nerve dysfunction and papilledema. We emphasize the importance of a thorough search for the cause of visual loss.

Isolated monocular visual loss as an initial manifestation of polycythemia vera

A 25-year-old man developed prolonged loss of vision in the left eye. Examination revealed that visual acuity was 20/20 in the right eye and 10/20 in the left eye, with a left relative afferent pupillary defect. Fundoscopy showed multiple cotton wool spots in the left whole retina with normal optic disc. Fluorescein angiography (FA) revealed markedly delayed arterial, venous and recirculation time in the left eye without retinal arterial or venous occlusion. Bone marrow aspirate confirmed polycythemia vera. After the patient underwent phlebotomy, his visual acuity markedly improved and cotton wool spots in the retina disappeared. On follow-up FA, delayed arterial and venous filling, and recirculation time also became normalized. This case suggests that ischemic damage of the retina due to the great viscosity of blood may be a possible mechanism of monocular visual loss in polycythemia vera. Clinicians should be aware that isolated monocular visual loss may be an initial manifestation of polycythemia vera, since if untreated, polycythemia vera carries a high risk of permanent complications due to intravascular thrombosis.

Visual loss in a prone-positioned spine surgery patient with the head on a foam headrest and goggles covering the eyes: an old complication with a new mechanism

A patient developed central retinal artery occlusion during surgery in the prone position with eye protectors placed over his eyes. We discuss the potential hazards of using such a device (the Dupaco Opti-Gard) in this setting.

Blinding Orbital Cellulitis: A Complication of Strabismus Surgery

A 56-year-old healthy man underwent left medial rectus recession and lateral rectus resection for esotropia. The next day he developed severe left periocular pain with decreased vision, an afferent pupillary defect, periorbital edema, limited ocular motility, and proptosis. Computed tomography showed fat stranding and less than 90 degrees of posterior globe tenting. Despite intravenous antibiotics to treat orbital cellulitis, and a lateral canthotomy and cantholysis to decompress the orbit, visual acuity worsened to no light perception. The patient underwent emergent orbital decompression including release of the superior and inferior septum and outfracturing of the orbital floor and medial wall; however, there was no recovery of vision. Blinding orbital cellulitis is a rare complication after strabismus surgery. Despite poor prognosis, prompt diagnosis and aggressive treatment may maximize visual potential.

A positron emission tomography study during auditory localization by late-onset blind individuals

Individuals deprived of vision early in life often demonstrate exceptional abilities in their remaining sensory modalities in order to compensate for their handicap. Recent studies have shown that some of these abilities also extend to those who have lost their sight later in life. It is not clear, however, what mechanisms underlie these abilities. Here, we examined cortical activation using positron emission tomography in late-onset blind participants during a free-field auditory localization task. Even though no behavioral enhancements were observed in this testing condition relative to sighted controls, the results revealed that the occipital cortex was nonetheless activated during task execution. We conclude that late-onset blind individuals do manifest cerebral reorganization, although its functional relevance to the task is less clear.

Cerebral venous hypertension and blindness: A reversible complication

A 57-year-old woman developed blindness during treatment for sarcoidosis-induced end-stage renal disease. An initial renal transplantation failed, and hemoaccess was maintained with multiple central catheters and upper extremity prosthetic arteriovenous grafts. A successful second transplantation eliminated her need for hemodialysis, but a right brachial to internal jugular graft remained patent. Progressive visual loss 2 years after transplantation prompted ophthalmic evaluation which initially revealed unilateral left optic nerve edema and visual loss, ultimately worsening over several months to no light perception in the left eye, 20/60 vision in the right eye, and bilateral papilledema. Arteriography demonstrated cerebral venous hypertension attributed to the functioning hemoaccess graft. Permanent graft occlusion normalized the papilledema, and visual field defects in the right eye and visual acuity returned to 20/20 in the right eye.

Impaired Clearance of Microemboli and Cerebrovascular Symptoms During Carotid Stenting Procedures

BACKGROUND

Transcranial Doppler monitoring shows a high prevalence of microemboli during carotid artery stenting (CAS); however, the occurrence of cerebrovascular symptoms (CVSs) does not seem to be related to the microembolic load.

OBJECTIVE

To evaluate embolic and hemodynamic transcranial Doppler monitoring findings and their relationships with the occurrence of procedural CVSs. Patients Fifty-four patients who had carotid stenosis of more than 70% underwent a total of 57 CAS procedures during transcranial Doppler monitoring of mean blood flow velocity and microembolic signals in the middle cerebral artery. The occurrence of transient ischemic attack, transient monocular blindness, and stroke during the CAS procedure was considered CVSs.

RESULTS

Nine (15.8%) of the 57 patients had CVSs during the procedure (ie, 6 patients with transient ischemic attack, 1 with transient monocular blindness, 1 with a minor stroke, and 1 with a major stroke). The mean blood flow velocity median values were statistically significantly lower (P < .001) in the group of 9 patients with CVSs (36 cm/s; interquartile range, 32.3-38.5) compared with the 48 without CVSs (48 cm/s; interquartile range, 41.5-52). The median number of isolated microembolic signals was similar in the 2 groups (72; interquartile range, 66-81 vs 75; interquartile range, 67-83.5). The median number of microembolic signal showers (clusters of too many signals to be counted separately in one cardiac cycle) presented a nonsignificant prevalence in the patients with CVSs (9; interquartile range, 7.5-11.2) compared with the ones without CVSs (8.2; interquartile range, 7-9).

CONCLUSION

The low flow velocity in the middle cerebral artery may impair the clearance of the microembolic load and should be considered a precursor of CVSs during the CAS procedure.

Cross-modal plasticity revealed by electrotactile stimulation of the tongue in the congenitally blind

In sensory substitution, information acquired with one sensory modality is used to accomplish a task which is normally subserved primarily by another sensory modality. We used PET to study cross-modal plasticity in the congenitally blind, using electrotactile stimulation of the tongue. Blind (n = 6) and sighted blindfolded controls (n = 5) were scanned before and after they were trained to use their tongue in a Snellen orientation detection task. Results showed that both groups of subjects learned the discrimination orientation task after seven 1 h training sessions. Before training, no significant changes in regional cerebral blood flow (rCBF) were observed in the occipital cortex in either group. In sharp contrast, activity in the occipital cortex increased after practice for the blind, but not for the sighted, providing evidence for training-induced plasticity in the blind. An inter-regional correlation analysis showed that task-related rCBF changes in left posterior parietal cortex were positively correlated with rCBF changes in the occipital area of the trained blind. These data reveal that cross-modal plasticity in the blind develops rapidly and that the occipital cortex is part of a functional neural network for tactile discrimination in conjunction with the posterior parietal cortex. Our data further show that the tongue can act as a portal to convey somatosensory information to visual cortex.

Penetrating orbitocranial gunshot injuries

BACKGROUND

The aim of this study was to analyze the effect of a surgical management protocol and other important clinical features on the prognosis of patients who had penetrating orbitocranial gunshot injuries.

METHODS

Thirty-five patients (30 unilateral, 5 bilateral) who had penetrating orbitocranial gunshot injuries were analyzed. The wounds were mainly caused by shrapnel fragments or bullets. Craniotomy was the standard treatment in all patients. Investigated clinical features included Glasgow Coma Scale (GCS) score on admission, the mode and the extent of brain injury, and the presence of an intracranial retained foreign body. The prognostic importance of complications such as infection, intracranial hemorrhage, cerebrospinal fluid leak, and epileptic seizures was also investigated. The mechanism and the injury characteristics of the patients were evaluated by predicting the visual outcome of the victims according to a newer classification system as well as other variables pertinent to this specific clinical setting of severe eye trauma. Final visual acuities of the patients were also measured.

RESULTS

The outcome of 35 penetrating orbitocranial gunshot injured patients was as follows: death in 3 patients, vegetative state in 1, severe disability in 2, moderate disability in 2, and good recovery in 27 cases. Localization and extent of the injury and GCS score on admission were the most important indicator for good neurological outcome. The predictors for good visual outcome were type B, grade 1, zone I, and relative afferent pupillary defect-negative injuries. The predictors for poor outcome were type A, grade 5, zone III, and relative afferent pupillary defect-positive injuries.

CONCLUSION

The prognosis of the injury depends on the course of the bullet or shrapnel fragment and the interdisciplinary care. An extensive preoperative evaluation of penetrating orbital trauma and a combined ophthalmic and neurosurgical approach are recommended to minimize the morbidity of the patients. However, complete removal of the foreign material in a deep or ventricular localization is not mandatory because careful debridement and tight closure of dura provides desired outcome. Evaluation of trauma mechanism and injury characteristics according to the Ocular Trauma Classification System seems to predict accurately the visual outcomes in this series.

Orbital apex syndrome after ethmoidal artery ligation for recurrent epistaxis

A 34-year-old man with severe, recurrent epistaxis underwent external anterior and posterior ethmoidal artery ligation on the right side. Visual loss from optic neuropathy and complete ophthalmoplegia developed after surgery. Computed tomography revealed surgical clips within the right orbital apex. Emergent removal of the surgical clips and medial wall decompression were performed. Four weeks later, his visual acuity and extraocular motility were unchanged, and diffuse pallor of the right optic disc was observed. Orbital apex syndrome can be a complication of ethmoidal artery ligation. Severe visual loss and ophthalmoplegia may persist despite prompt recognition and treatment.

Blindness and rectus muscle damage following spinal surgery

PURPOSE

To report a rare case of blindness and rectus muscle damage from ocular compression after spinal surgery.

DESIGN

Observational case report.

METHODS

A 16-year-old girl underwent scoliosis surgery in the prone position. After surgery, she complained of visual loss in the right eye. Examination showed no perception of light, periorbital bruising, corneal haze, fixed dilated pupil, and loss of adduction beyond the midline.

RESULTS

Orbital computed tomography scan showed a swollen medial rectus with no other orbital pathology. The muscle swelling can be explained by ischemia from compression of the globe against the medial wall of the orbit. Ocular compression also caused retinal and optic nerve ischemia, resulting in loss of vision. Medial rectus function recovered with time, but the patient continues to have no light perception.

CONCLUSIONS

Blindness after spinal surgery is a rare but devastating complication, and all precautions to avoid ocular compression must be taken.

Cortical processing of tactile language in a postlingually deaf-blind subject

We compared neural activation detected by magnetoencephalography (MEG) during tactile presentation of words and non-words in a postlingually deaf-blind subject and six normal volunteers. The left postcentral gyrus, bilateral inferior frontal gyri, left posterior temporal lobe, right anterior temporal lobe, bilateral middle occipital gyri were activated when tactile words were presented to the right hand of the deaf-blind subject. This set of activated regions was not observed in the normal volunteers, although activation of several combinations of these regions was detected. Positron emission tomography confirmed the location of the MEG-activated areas in the deaf-blind subject. Our results demonstrated that the deaf-blind subject is heavily involved in interpreting tactile language by enhancing cortical activation of cognitive and semantic processing.

Posterior ocular malformations in children: somatic, neuroradiological and cognitive aspects

AIM

To investigate associated neurological, endocrinological and cognitive dysfunctions in children with visual impairment caused by optic nerve hypoplasia or optic nerve/fundus coloboma and/or microphthalmus.

METHODS

Forty children born between 1990 and 1998 were assessed by neurological examination, re-evaluation of neuroradiological investigations, review of medical records and examination of cognitive levels.

RESULTS

Neurological dysfunctions (epilepsy and/or motor impairment) were found in 13/28 children with optic nerve hypoplasia and in 3/12 children with coloboma/microphthalmus. The optic pathways were thin in 22/24, an abnormal posterior pituitary gland and/or thin infundibulum was found in 16/22 and absence of septum pellucidum in 14/27 children with optic nerve hypoplasia. Other types of cerebral abnormalities occurred in 9/26 children. Among children with coloboma/microphthalmus, the optic pathways were thin in 4/8 children but none had pituitary or cerebral midline abnormalities. Sixteen children with optic nerve hypoplasia were receiving hormone substitution but none of the children with coloboma/microphthalmus. Thirteen of the 16 children with optic nerve hypoplasia and with an abnormal pituitary region had endocrinological deficiencies. Mental retardation was found in 9/24 of the children with optic nerve hypoplasia and in 5/10 of the children with coloboma/microphthalmus.

CONCLUSION

Endocrinological. neurological and neuroradiological defects seem more common in children with optic nerve hypoplasia than in children with coloboma. A pituitary region that appears abnormal in magnetic resonance imaging seems to predict endocrinological deficits in children with optic nerve hypoplasia.

Occipito-parietal cortex activation during visuo-spatial imagery in early blind humans

Using positron emission tomography, regional cerebral blood flow was studied in five early blind and five control volunteers during visuo-spatial imagery. Subjects were instructed to generate a mental representation of verbally provided bidimensional patterns that were placed in a grid and to assess pattern symmetry in relation to a grid axis. This condition was contrasted with a verbal memory task. Cerebral activation in both groups was similar during the visuo-spatial imagery task. It involved the precuneus (BA 7), superior parietal lobule (BA 7), and occipital gyrus (BA 19). These results are in accordance with previous studies conducted in sighted subjects that indicated that the same occipito-parietal areas are involved in visual perception as well as in mental imagery dealing with spatial components. The dorsal pathway seems to be involved in visuo-spatial imagery in early blind subjects, indicating that this pathway undergoes development in the absence of vision.

Noninvasive identification of human central sulcus: a comparison of gyral morphology, functional MRI, dipole localization, and direct cortical mapping

The locations of the human primary hand cortical somatosensory and motor areas were estimated using structural and functional MRI, scalp-recorded somatosensory-evoked potential dipole localization, expert judgments based on cortical anatomy, and direct cortical stimulation and recording studies. The within-subject reliability of localization (across 3 separate days) was studied for eight normal subjects. Intraoperative validation was obtained from five neurosurgical patients. The mean discrepancy between the different noninvasive functional imaging methods ranged from 6 to 26 mm. Quantitative comparison of the noninvasive methods with direct intraoperative stimulation and recording studies did not reveal a significant mean difference in accuracy. However, the expert judgments of the location of the sensory hand areas were significantly more variable (maximum error, 39 mm) than the dipole or functional MRI techniques. It is concluded that because expert judgments are less reliable for identifying the cortical hand area, consideration of the findings of noninvasive functional MRI and dipole localization studies is desirable for preoperative surgical planning.

Structural and functional analyses of the occipital cortex in visual impaired patients with visual loss before 14 years old

Single photon emission tomography (SPECT) perfusion images of the brain of individuals with complete visual loss before the age of 14 were carried out and compared to those of visually normal subjects, in order to assess hypothetical differences in brain structural and metabolism between the two groups. Study group was comprised by 2 females and 3 males, aged 30 +/- 10 years. Controls were composed by 6 females and 5 males aged 41.5 +/- 3.8 years. All individuals were submitted to physical and neurological examinations, and to MRI and to SPECT. Blind subjects presented larger perfusion measurements bilaterally in their medial temporal lobes (p=0.030, right side; p=0.01, left side), but smaller perfusion measurements in their left frontotemporal area than controls (p=0.026). Intragroup analysis of the study group disclosed asymmetric perfusion, lesser in the left temporal and parietal areas (p=0.026 and p<0.0001, respectively) compared to the right side. In the healthy controls, reduced perfusion was also noted at the left parietal areas when compared to the right side (p=0.035). The study revealed that completely blind patients that became visually impaired before the age of 14 in spite of not having MRI detectable changes in their brain's anatomy do present increases in perfusion of their left and right medial temporal lobes, and a reduction in the perfusion of the left frontotemporal area, as compared to normal controls. While the increases in blood flow may reflect compensatory mechanisms for visual deprivation, the significance of the diminished perfusion in the left frontotemporal area remains elusive.

Temporary bilateral blindness after acute lidocaine toxicity

IMPLICATIONS

This case report describes an uncommon complication (blindness) occurring after an inadvertent overdosage of a frequently used local anesthetic (lidocaine) during a regional anesthetic procedure. The discussion focuses on the suspected pathophysiology of the blindness.

[Pterional orbital decompression in traumatic orbital hematomas]

The results are presented for pterional orbital decompression in 12 patients with symptomatic traumatic retrobulbar hematoma after various traumatic mechanisms. Pre- and postoperative course, neuroradiological findings, additional brain or facial injuries as well as outcome of eye function are analyzed in detail. Mean time delay between trauma and decompression was 56 h (2.4 days), with a wide range from 2 h to 15 days. Preoperative exophthalmos and pupillary disturbances as well as restrictions of extraocular movements decreased in all patients after orbital decompression and removal of the retrobulbar hematoma if the bleeding was localized. Visual acuity remained normal or showed significant improvement in seven patients, four of whom experienced complete recovery. In three patients the eye remained amaurotic. No complications related to the operation were seen. The pterional orbital decompression described here represents an effective alternative approach for patients with sight-threatening retrobulbar hematoma, especially in cases where it is necessary to gain space for the orbit in addition to evacuating space-occupying blood or bone clots and treating neighbouring lesions. Immediate detection and adequate treatment of orbital hematomas is mandatory to achieve an acceptable outcome of eye function.

Acute cortical blindness complicating pre-eclampsia

Cortical blindness in pre-eclampsia due petechial hemorrhages, ischemia, focal edema and infarction of the occipital cortex, is mostly reversible.

Temporary monocular blindness associated with acute carotid thrombosis: a case report

We report upon a patient with multiple, progressive episodes of temporary monocular blindness associated with acute thrombosis and a critical internal carotid artery stenosis. Carotid angiography demonstrated an anatomically compelling situation consisting of a critical reduction of flow distal to a preocclusive internal carotid artery stenosis accompanied by intraluminal thrombus. The patient was managed successfully by urgent thrombectomy and carotid endarterectomy. This case report highlights principles in management of patients with the unstable neurologic condition of temporary monocular blindness associated with an anatomically compelling situation demonstrated on angiography.

Auditory triggered mental imagery of shape involves visual association areas in early blind humans

Previous neuroimaging studies identified a large network of cortical areas involved in visual imagery in the human brain, which includes occipitotemporal and visual associative areas. Here we test whether the same processes can be elicited by tactile and auditory experiences in subjects who became blind early in life. Using positron emission tomography, regional cerebral blood flow was assessed in six right-handed early blind and six age-matched control volunteers during three conditions: resting state, passive listening to noise sounds, and mental imagery task (imagery of object shape) triggered by the sound of familiar objects. Activation foci were found in occipitotemporal and visual association areas, particularly in the left fusiform gyrus (Brodmann areas 19-37), during mental imagery of shape by both groups. Since shape imagery by early blind subjects does involve similar visual structures as controls at an adult age, it indicates their developmental crossmodal reorganization to allow perceptual representation in the absence of vision.

Necrosis of the tongue and unilateral blindness in temporal arteritis

While blindness is one of the typical clinical presentations of temporal arteritis, tongue necrosis, on the other hand, is an unusual complication of the disease. An 80 year old male patient presenting a sudden massive swelling of the tongue was admitted to the Hospital of Yverdon. The swelling rapidly progressed to a complete necrosis of the tongue within a few days. The clinical presentation, the dramatic evolution of the necrosis, and sudden unilateral blindness despite prompt treatment confirmed our diagnosis of temporal arteritis. However, all the examinations, including biopsy of the right temporal artery, remained non-specific for the disease. Our diagnosis was based on the unusual clinical presentation of the disease.

Occipital activation by pattern recognition in the early blind using auditory substitution for vision

This PET study aimed at investigating the neural structures involved in pattern recognition in early blind subjects using sensory substitution equipment (SSE). Six early blind and six blindfolded sighted subjects were studied during three auditory processing tasks: a detection task with noise stimuli, a detection task with familiar sounds, and a pattern recognition task using the SSE. The results showed a differential activation pattern with the SSE as a function of the visual experience: in addition to the regions involved in the recognition process in sighted control subjects, occipital areas of early blind subjects were also activated. The occipital activation was more important when the early blind subjects used SSE than during the other auditory tasks. These results suggest that activity of the extrastriate visual cortex of early blind subjects can be modulated and bring additional evidence that early visual deprivation leads to cross-modal cerebral reorganization.

Liposuction and ischemic optic neuropathy. Case report and review of literature

Ischemic optic neuropathy occurred in a patient following liposuction. Perioperative anemia and hypotension may be the cause of this complication. Correction of anemia with transfusion improved the hemoglobin and hematocrit but the right eye remained blind. Liposuction should be added to the list of the surgical procedures that may produce ischemic optic neuropathy as an isolated complication.