Left V1 Research Articles

Subregional structural and connectivity damage in the visual cortex in neuromyelitis optica

Patients with neuromyelitis optica (NMO) have shown structural and functional impairments in the visual cortex. We aimed to characterize subregional grey matter volume (GMV) and resting-state functional connectivity (rsFC) changes in the visual cortex in NMO. Thirty-seven NMO patients and forty-two controls underwent structural and functional MRI scans. The GMV and rsFC of each visual subregion were compared between the groups. Compared with controls, NMO patients had GMV reductions in the bilateral V1, V2, V3d, VP, and LO and in the left V3A. In canonical visual pathways, the relatively low-level subregions showed more significant GMV reductions than did the high-level ones. Regardless of GMV correction, NMO patients showed reduced rsFC in the bilateral LO and V4v and in the left V2. The GMVs of the bilateral V1 and LO and of the left V2 and V3d were negatively correlated with clinical disability in NMO patients; these correlation coefficients were associated with hierarchical positions in the visual pathways. These findings suggest that in NMO, the low-level visual subregions have more severe structural damage; structural damage is not the only factor affecting rsFC alterations of visual subregions; GMV reduction in the low-level visual subregions has the highest predictive value for clinical disability.

Intrinsic Functional Connectivity Alterations of the Primary Visual Cortex in Primary Angle-Closure Glaucoma Patients before and after Surgery: A Resting-State fMRI Study

PurposeTo investigate the altered intrinsic functional connectivity (iFC) of the primary visual cortex (V1) in primary angle-closure glaucoma (PACG) patients before and after surgery using resting-state functional MRI.Materials and MethodsTwenty-five preoperative PACG (pre-PACG) patients and 25 well-matched healthy controls (HCs) were included in this study, and 9 PACG patients were assessed again at least 3 months after treatment (post-PACG). We generated the iFC maps of the seed regions in the centers of the left and right V1 and conducted group comparisons. Then, the relationships between the altered iFC coefficients and clinical variables were investigated in the pre-PACG patients.ResultsCompared with the HCs, the pre-PACG patients showed decreased iFC between the left V1 and right V2 (covering the cuneus, calcarine and lingual gyrus) and increased iFC between the left V1 and left temporal-parietal region, left frontal opercula-insula-basal ganglia region, right insula-basal ganglia region, and right inferior parietal lobule (P < 0.01, corrected). Compared with the pre-PACG patients, the post-PACG patients showed increased iFC between the left V1 and bilateral V2, and between the left V1 and left or right postcentral gyrus; in addition, they showed decreased iFC between the left V1 and the dorsal-attention and frontoparietal-control networks. In the pre-PACG patients, visual activity (VA) was positively correlated with increased iFC between the left V1 and the left temporal-parietal region or the right inferior parietal lobule. Similar patterns of alterations were observed in the right V1-iFC in both the pre- and post-PACG patients.ConclusionsThe primary findings have demonstrated a gradual decrease in visual information integration in the left V1-V2 pathway and VA-related functional compensation in the pre-PACG patients, generating further evidence of functional restoration in post-PACG patients.

Spatiotemporal dynamics of similarity-based neural representations of facial identity

Humans' remarkable ability to quickly and accurately discriminate among thousands of highly similar complex objects demands rapid and precise neural computations. To elucidate the process by which this is achieved, we used magnetoencephalography to measure spatiotemporal patterns of neural activity with high temporal resolution during visual discrimination among a large and carefully controlled set of faces. We also compared these neural data to lower level "image-based" and higher level "identity-based" model-based representations of our stimuli and to behavioral similarity judgments of our stimuli. Between ∼50 and 400 ms after stimulus onset, face-selective sources in right lateral occipital cortex and right fusiform gyrus and sources in a control region (left V1) yielded successful classification of facial identity. In all regions, early responses were more similar to the image-based representation than to the identity-based representation. In the face-selective regions only, responses were more similar to the identity-based representation at several time points after 200 ms. Behavioral responses were more similar to the identity-based representation than to the image-based representation, and their structure was predicted by responses in the face-selective regions. These results provide a temporally precise description of the transformation from low- to high-level representations of facial identity in human face-selective cortex and demonstrate that face-selective cortical regions represent multiple distinct types of information about face identity at different times over the first 500 ms after stimulus onset. These results have important implications for understanding the rapid emergence of fine-grained, high-level representations of object identity, a computation essential to human visual expertise.

Interhemispheric Connections between the Primary Visual Cortical Areas via the Anterior Commissure in Human Callosal Agenesis.

Aim: In humans, images in the median plane of the head either fall on both nasal hemi-retinas or on both temporal hemi-retinas. Interhemispheric connections allow cortical cells to have receptive fields on opposite sides. The major interhemispheric connection, the corpus callosum, is implicated in central stereopsis and disparity detection in front of the fixation plane. Yet individuals with agenesis of the corpus callosum may show normal stereopsis and disparity vergence. We set out to study a possible interhemispheric connection between primary visual cortical areas via the anterior commissure to explain this inconsistency because of the major role of these cortical areas in elaborating 3D visual perception.Methods: MRI, DTI and tractography of the brain of a 53-year old man with complete callosal agenesis and normal binocular single vision was undertaken. Tractography seed points were placed in both the right and the left V1 and V2. Nine individuals with both an intact corpus callosum and normal binocularity served as controls.Results: Interhemispheric tracts through the anterior commissure linking both V1 and V2 visual cortical areas bilaterally were indeed shown in the subject with callosal agenesis. All other individuals showed interhemispheric visual connections through the corpus callosum only.Conclusion: Callosal agenesis may result in anomalous interhemispheric connections of the primary visual areas via the anterior commissure. It is proposed here that these connections form as alternative to the normal callosal pathway and may participate in binocularity.

Motion sickness increases functional connectivity between visual motion and nausea-associated brain regions.

The brain networks supporting nausea not yet understood. We previously found that while visual stimulation activated primary (V1) and extrastriate visual cortices (MT+/V5, coding for visual motion), increasing nausea was associated with increasing sustained activation in several brain areas, with significant co-activation for anterior insula (aIns) and mid-cingulate (MCC) cortices. Here, we hypothesized that motion sickness also alters functional connectivity between visual motion and previously identified nausea-processing brain regions. Subjects prone to motion sickness and controls completed a motion sickness provocation task during fMRI/ECG acquisition. We studied changes in connectivity between visual processing areas activated by the stimulus (MT+/V5, V1), right aIns and MCC when comparing rest (BASELINE) to peak nausea state (NAUSEA). Compared to BASELINE, NAUSEA reduced connectivity between right and left V1 and increased connectivity between right MT+/V5 and aIns and between left MT+/V5 and MCC. Additionally, the change in MT+/V5 to insula connectivity was significantly associated with a change in sympathovagal balance, assessed by heart rate variability analysis. No state-related connectivity changes were noted for the control group. Increased connectivity between a visual motion processing region and nausea/salience brain regions may reflect increased transfer of visual/vestibular mismatch information to brain regions supporting nausea perception and autonomic processing. We conclude that vection-induced nausea increases connectivity between nausea-processing regions and those activated by the nauseogenic stimulus. This enhanced low-frequency coupling may support continual, slowly evolving nausea perception and shifts toward sympathetic dominance. Disengaging this coupling may be a target for biobehavioral interventions aimed at reducing motion sickness severity.

Case report: Epicranial pain after radiotherapy for skull base meningioma – the first symptomatic epicrania fugax?

To date, no symptomatic forms of epicrania fugax (EF) have been reported. Here, we describe the first EF-type pain to be probably caused by an underlying disorder. A 77-year-old woman started suffering from left V1-V2 trigeminal neuralgia at 72 years of age. Neurologic examination was normal. Magnetic resonance imaging (MRI) showed a left middle sphenoid wing meningioma compressing the left trigeminal nerve medially. After trying several neuromodulators, she received stereotactic radiotherapy. One month later, the episodes of facial pain were significantly diminished, but she started feeling brief electric paroxysms across her left hemicranium that were clinically identical to those of backwards EF. Serial MRI showed persistence of the meningioma without changes. Although the pathogenesis of EF remains uncertain, this case is consistent with a symptomatic origin in the trigeminal root/pathway. The onset of the EF-like pain could have been caused by the compressive effect of the tumour or, most likely, by the radiation.

An Unusual Posttraumatic Pseudoaneurysm of Intracranial Segment (V4) of the Vertebral Artery

Traumatic pseudoaneurysm of the vertebral artery is an uncommon and one of the most difficult lesions to treat. Posttraumatic vertebral artery pseudoaneurysm is located mostly extracranially, and its intracranial occurrence is exceedingly rare. We report a case of an 18-year-old man who underwent successful treatment of posttraumatic intracranial pseudoaneurysm of V4 segment of the vertebral artery by endovascular embolization. The patient who sustained trauma in a road accident presented with the complaints of headache, giddiness, and vomiting for the last 13 days. On admission, he was conscious but drowsy with no focal neurologic deficit. CT scan of the brain was suggestive of no significant intracranial abnormality. As the patient had headache, vomiting, and drowsiness, the CT was unable to explain his clinical picture, so CT angiography was performed to exclude vascular abnormality. CT angiography of the brain was suggestive of left vertebral artery aneurysm arising from V4 segment of the left vertebral artery. DSA showed a large pseudoaneurysm arising from left V4 segment of the vertebral artery near origin of PICA. Because of its difficult location, surgical treatment is less preferable as compared with endovascular treatment. The patient underwent endovascular coiling of pseudoaneurysm. Postcoiling DSA showed complete occlusion of pseudoaneurysm. The patient had uneventful postoperative period and showed good recovery.

Aneurysmal Subarachnoid and Spinal Hemorrhage Associated With Systemic Lupus Erythematosus

A 42-year-old woman with systemic lupus erythematosis (SLE), positive lupus anticoagulant, elevated titers of IgG and IgM anticardiolipin antibody and β2 glycoprotein antibodies, idiopathic thrombocytopenia, and hemolytic anemia presented with menorrhagia and anemia. She received both platelet and red cell transfusions and had an unrevealing endometrial biopsy. She was treated with intravenous immunoglobulin therapy for autoimmune-mediated thrombocytopenia and was taking hydroxychloroquine 200 mg twice daily that was a home medication. She was started on prednisone 60 mg daily. During her hospitalization, she developed a sudden, severe, sharp, and pounding occipital and nuchal headache with sharp shooting pains radiating down the back of the neck. She was alert and oriented with normal cranial nerve function, motor strength, and sensation. Her headache was unsuccessfully treated with fioricet and acetaminophen. The day after headache onset, a noncontrast head computed tomography revealed a subarachnoid hemorrhage (SAH) extending from the interpeduncular fossa caudally to the cervicomedullary junction (Figure 1). Computed tomographic angiogram of the head and neck revealed a focal left vertebral artery stenosis with poststenotic aneurysmal dilation of the intradural (V4) segment. There were additional multifocal areas of beading and long tapered vessel narrowing involving the M2 division of the left middle cerebral artery and anterior cerebral arteries and M3 division of the right middle cerebral artery (Figure 1). Magnetic resonance brain demonstrated multifocal but posteriorly predominant T2 hyperintense lesions that resembled posterior reversible leukoencephalopathy syndrome (Figure 2). Conventional angiogram confirmed the global small and medium vessel vasculopathy with a left V4 vertebral artery fusiform aneurysm measuring 10.6 mm×5.5 mm distal to the origin of the left posterior inferior cerebellar artery (Figure 2). Figure 1. Lupus-associated central nervous system vasculitis and subarachnoid hemorrhage (SAH). A , Computed tomographic (CT) head demonstrating perimedullary SAH (black arrow). B , CT angiogram demonstrating focal stenosis of the intracranial …

Trigeminal Neuralgia Caused by Cerebellopontine Angle Arteriovenous Malformation Treated With Gamma Knife Radiosurgery

Trigeminal neuralgia is a facial pain syndrome characterized as sudden onset and lightening-like sensation over somatosensorial branch(es) of fifth cranial nerve. Rarely, some underlying diseases or disorders could be diagnosed, such as multiple sclerosis, brain tumors, and vascular malformations. The authors present a 47-year-old man with trigeminal neuralgia over left V2 and V3 dermatomes. He had a previous transarterial embolization and long use of carbamazepine with partial response to treatment. Gamma knife radiosurgery (GKR) was planned. A marginal dose of 15 Gy was given to 50% isodose line. His pain was relieved by GKR in 1.5 years. Treatment of posterior fossa arteriovenous malformations causing trigeminal neuralgia, with GKR has a very limited use in the literature. It, however, is obvious that success rate as pain relief, in a very challenging field of functional neurosurgery, is satisfactory. Large series, however, are in need to make a more comprehensive statement about efficacy and safety of the procedure in these pathologies.

Peripheral Neurectomy for Trigeminal Neuralgia: Simple Technique for a Complex Disease.

The decision to institute surgical alternatives in the management of pain for trigeminal neuralgia should be taken when drugs no longer provide relief or the patients cannot endure the adverse effects of the prescribed drugs. Classical trigeminal neuralgia (TN) is usually unilateral, characterized by recurrent, brief, very severe, shock-like and stabbing pain paroxysms in the 2nd and/or 3rd trigeminal branch. Trigeminal neuralgia is well recognised and distinctive in nature. The diagnosis and management of TN traditionally lies in the hands of neurologists, anaesthesiologists, oral and maxillofacial surgeons, neurosurgeons and neuroradiologists. Peripheral procedures are usually performed in patients not suitable for or not willing to undergo other procedures. However, no strict rules exist and each patient should be evaluated individually. This case report is an effort to reiterate that peripheral neurectomy is a less formidable procedure, with low morbidity, highly repeatable and easy to perform procedure in countries like India which has majority of rural population and cannot afford advanced treatments. Patients with TN usually describe attacks of intense pain lasting for several seconds on one side of the face [1,2]. The disease usually affects people with the age of 40 or older and has predilection for 1.5 times as many women as men [3]. A 65-year-old lady presented for the evaluation of pain in the left side of her lower jaw. Further evaluation revealed the history of three years of severe (score of 7 in the visual analogue scale), shock-like and throbbing pain in the left V3 region, lasting from a few hours to days that increased by talking, chewing, and with cold weather, eating food or drinking cold water. Patient described the trigger zone to be the mucosa of the alveolar ridge involving the first premolar region [Table/Fig-1]. She did not sleep well because of the pain. Patient was not a denture wearer nor were there any clinical signs of mucosal inflammation or any other pathology. Systemic disorder of hypertension or any other diseases were ruled out. She was prescribed the following medications: Tab Carbamazepine (200 mg every eight hours) for six months and tab Baclofen 10 mg daily was prescribed [4] which failed to alleviate her pain. Orthopantomogram was advised and didn’t show any pathology [Table/Fig-2]. Surgical plan was to perform a mental neurectomy under local anaesthesia. Maintaining asepsis, local anaesthesia with adrenaline 1:80,000 block of the left inferior alveolar nerve along with mental nerve block was performed. A three cornered flap was planned and raised along the crest to expose the mental nerve which was freed from its bony canal and adjacent soft tissues. The neurovascular bundle containing the nerve was ligated on either sides and excised [Table/Fig-3,​,4].4]. The foramen was blocked using bone wax [Table/Fig-5]. Ensuring complete haemostasis the wound was irrigated copiously and flaps sutured. The patient’s pain score reduced from 8 on VAS to 1 on VAS and was followed up for two years postoperatively; she remains symptom free with relief from pain. [Table/Fig-1]: Intra oral view of the patient. [Table/Fig-2]: OPG showing no abnormality. [Table/Fig-3]: Identification and release of nerve from the soft tissues. [Table/Fig-4]: Neurectomy performed. [Table/Fig-5]: Sealing of the canal with bone wax. [Table/Fig-6]: Postoperative intra oral view. Although medical modalities reduce the pain of TN in many patients, some don’t benefit from drugs as do others. Surgical alternatives are indicated when drugs fail to control pain, patients are not tolerant to the adverse effects of drugs, or in medically compromised patients [5]. TN is a rare disease which affects between 4 to 40 new patients – per 100,000 persons every year [3,6]. The pain usually responds to triggers zones caused by agents such as cold, heat, chewing, talking or touching the affected area [4]. Attacks may last for several minutes or hours, with pain-free periods between attacks being common, possibly continuing for weeks or even several years [1]. Many other treatments have been formulated for TN including other advanced surgical options, still peripheral neurectomy remains one of the most commonly performed procedures in literature and in practice for the treatment of TN in a country like India which has majority of rural population and cannot afford advanced treatment options with regards to TN [5].

Enigmatic intracranial cyst causing diplopia and trigeminal neuralgia

Chronic compression by intracranial cystic lesions can cause cranial nerve palsies and bony changes. With the advent of imaging techniques, grossly accurate diagnosis is possible. However, few cases do surprise the clinicians both intra, and postoperatively. A 27-year-old male presented to us with complaints of double vision for 4 months followed by sharp, shooting pain in the left V1 and V2 distribution for 1-month duration, on examination, he had left lateral palsy and decreased pin prick and temperature sensation in V1 distribution. On computed tomography scan, a cystic lesion noted which is isodense in the middle cranial fossa with erosion of the underlying bone. On magnetic resonance imaging lesion was iso to hyperintense on T1-Weighted and hyperintense on T2-Weighted, brilliantly enhancing on contrast administration. Provisional diagnosis was trigeminal schwannoma, left temporal craniotomy and total excision of the cyst done. Histopathological examination showed cyst wall lined with collagen. Postoperatively patient neuralgic pain subsided with persisting sixth nerve palsy.

Musical expertise modulates functional connectivity of limbic regions during continuous music listening.

Music is known to be an important facet of all human cultures (Merriam, 1964). Listening to music in order to influence moods, evoke strong emotions, and derive pleasure is becoming increasingly common, especially in this day and age when access to music is easy and quick. In recent years, exploring the neural correlates of musical emotions has attracted the attention of neuroscientists (Brattico & Pearce, 2013; Koelsch, Fritz, v. Cramon, Muller, & Friederici, 2006). However, the majority of these studies have not accounted for the effect of musical expertise, despite increasing evidence of structural and functional differences between musicians and nonmusicians, particularly in the regions of the cerebrum associated with motor, auditory, and visuospatial processing (Amunts et al., 1997; Angulo-Perkins et al., 2014; Baumann et al., 2007; Fauvel et al., 2014; Gaser & Schlaug, 2003; Herdener et al., 2010; Hutchinson, Lee, Gaab, & Schlaug, 2003; Hyde et al., 2009; Lee, Chen, & Schlaug, 2003; Pantev & Herholz, 2011; Schlaug, Jancke, Huang, Staiger, & Steinmetz, 1995; Schlaug, Jancke, Huang, & Steinmetz, 1995; Sluming, Taylor, Keller, Cezayirli, & Roberts, 2003; Wong, Skoe, Russo, Dees, & Kraus, 2007). In addition, musicians were found to have greater amounts of white matter in the anterior corpus callosum than nonmusicians (for a review, see Moore, Schaefer, Bastin, Roberts, & Overy, 2014). Furthermore, higher cerebellar volume is associated with male musicians than nonmusicians (Hutchinson et al., 2003; Sluming et al., 2003), particularly concerning the regions involved in representing movement (Gaser & Schlaug, 2003). In addition, musicians have been found to have greater sensitivity in processing and discriminating sounds in the auditory cortex (Musacchia, Strait, & Kraus, 2008; Pantev et al., 1998; Strait et al., 2009; Tervaniemi et al., 2001; Wong et al., 2007). In sum, long-term musical practice causes structural and functional changes in the brain, with subsequent enhanced representation of sounds and music (see Kraus & Chandrasekaran, 2010; Reybrouck & Brattico, 2015 for an overview).The neuroscientific studies on musical emotions have predominantly utilized the classical controlled paradigm wherein the condition of interest is interspersed with other tasks or baseline, thereby not providing the entire picture of emotional networks in the brain. Recent times have seen an increase in fMRI studies that employ the continuous listening paradigm, in which participants listen to music continuously, typically lasting the entire span of the piece, and without any intermittent task, for investigating neural processing of music (Abrams et al., 2013; Alluri et al., 2012, 2013; Burunat, Alluri, Toiviainen, Numminen, & Brattico, 2014; Toiviainen, Alluri, Brattico, Wallentin, & Vuust, 2014; Trost, Ethofer, Zentner, & Vuilleumier, 2012). However, those studies examined whole brain regional activations, not focusing on limbic system structures or on the modulation of neural activity and connectivity by musical expertise. A single fMRI study (Koelsch et al., 2013) has used full pieces of music to investigate the dynamics of emotion processing in the limbic system, albeit with participants without musical training.On the contrary, resting-state-based fMRI studies have dealt with investigating functional networks that emerge during prolonged periods of rest without any stimulus (Lee, Smyser, & Shimony, 2013). There is abundant literature examining restingstate connectivity and connectivity in the visual domain, especially in terms of decoding. However, there has been a scarcity of studies investigating functional connectivity in the auditory domain as a function of musical expertise. The first resting-state study investigating connectivity differences between musicians and nonmusicians in resting state was conducted by Luo et al. (2012). Their functional connectivity analysis was limited to five seed regions representing the right primary motor, left primary auditory, left primary somatosensory cortices, and the left primary visual and left V2 areas. …

The corpus callosum in human binocularity and strabismus

SummaryIntercortical visual transfer has been shown important in mammalian binocularity. The present study aims at demonstrating intercortical visual callosal transfer in 16 human subjects using DTI, fMRI and connectivity. With fMRI brain activation was analysed during central and peripheral retinal stimulation. These were compared with right and left sided stimuli during RE and LE fixation. Results were analysed in a 2 × 2 × 2 ANOVA with p = 0.005. Callosal fiber tracts were visualised with DTI. With fMRI it showed that RE fixation is associated more with significant signal changes in the corpus callosum, both with right and left V1 co‐activation. Connectivity from the left V1 showed mostly de‐activation in the corpus callosum and activation if the eye is stimulated from the contralateral central area of the visual field. Callosal activity is associated stronger with stimulation of the temporal central retina and right eye fixation. The stronger trigger from the right eye is likely due to ocular dominance: during central stimulation of the temporal retina of the RE, activation in the left V1 is associated with de‐activation in the corpus callosum.

A very rare, petro-clival, neurothekeoma tumor. Case Report

Abstract Known as nerve sheath myxoma too, neurothekeoma are benign tumors, usually arise in the skin of the head, neck region and upper extremities, in young females. Cerebral neurothekeoma are very rare, a few cases were already described in the parasellar area, in the middle cranial and posterior fossa. We present a petro-clival neurotekoma. A 78-year-old male was admitted for two years left fronto-temporal headache completed in the last 6 months with left trigeminal V1 neuralgia, left facial hypoesthesia, diplopia, swallowing disorders for liquid foods, balance disorders. From his medical records we noticed: stage 2 chronic kidney disease, hypertension, prostate adenoma, dyslipidemia hypercholesterolemia. The MRI showed a macronodular petroclival mass in hiper T2, hipo T1, flair iso signal; normal cerebral angiography. The patient was operated on using a left retrosigmoid, retromastoidian approach. A 4/3/3 cm tumor, gray, encapsulated, soft consistency, partially cystic, less bleeding, attached to the dura, displacing the basilar artery and brain stem controlateral, encasing the trigeminal nerve. The tumor was totally removed with a good postop evolution. Six months follow up he had no more facial pain, but only persistant left facial hypoesthesia. Histologically the tumor had lobular appearance with spindle or stellate cells embedded in abundant myxoid background. The tumor cells were diffusely positive for S100, PGP9.5’, CD 34” positive in vessels, Ki67’positive in 5%. Cranial MRI performed one month after surgery did not show any residual tumor. Also known as nerve sheath myxomas, neurothekoma are rare benign tumors. For intracranial neurothekoma surgical indication is mandatory

E-094 an elusive case of iatrogenic bow hunter's syndrome, lessons learned

Purpose Bow Hunter’s syndrome (BHS), also known as rotational occlusion of the vertebral artery, contributes to posterior circulation ischemia secondary to dynamic compression of the dominant vertebral artery. This entity is most commonly attributed to cervical spondylosis or atlantoaxial hypermobility. The purpose of this case report is to illustrate an iatrogenic cause of BHS following cervical spine surgery. In addition, we emphasize the importance of using provocative DSA in diagnosing this condition in the setting of posterior circulation ischemia. Materials and methods 74 year old male presented in 2011 with a complaint of right upper extremity weakness and imaging findings of C1–2 instability and myelomalacia of the cervical spinal cord. The patient subsequently underwent C1–6 posterior fusion by orthopedic surgery and recovered uneventfully with initial postoperative radiographs demonstrating intact hardware. Routine 9 month follow-up radiographs revealed a fractured left C1 pedicle screw. 11 months post-op, patient developed transient visual symptoms prompting MRI of the brain, which was normal. The patient had a fall in early 2012 and the next cervical spine radiographs demonstrated fractures of both C1 screws, 14 months post-fusion. Over the next year, the patient presented to the ED multiple times for falls and eventually developed slurred speech and an unsteady gait. MRI brain revealed multiple posterior circulation infarcts of varying ages. CTA and MRA of the neck revealed a focal area of 30% stenosis of the left V3 segment. Conventional angiography without provocative maneuvers demonstrated a chronically occluded right vertebral artery and 30% stenosis of the distal left vertebral artery, interpreted as atherosclerotic. Despite maximal medical therapy including aspirin and plavix, in January 2015 he again developed new symptoms with decreased responsiveness, blurred vision, and right sided weakness. CTA of the neck demonstrated extrinsic compression of the left V3 segment due to adjacent fractured screw fragment. MRI revealed progression of the posterior circulation ischemic changes with no lesions in the carotid territories. Given the concern for extrinsic compression by the adjacent screw fragment, repeat DSA was requested. Results Right subclavian arteriogram with blood pressure cuff inflated again demonstrated chronic occlusion of the right vertebral artery. Left vertebral artery injection performed with the patient’s head in neutral position revealed 50% stenosis of the left vertebral artery V3 segment adjacent to the fractured screw, as seen on CTA. A provocative maneuver was then performed by having the patient turn his head to the left. Angiogram showed complete occlusion of the left vertebral artery confirming the diagnosis of BHS. Final angiogram with his head in neutral position showed flow had been restored. Conclusion We have demonstrated an elusive case of iatrogenic BHS. CTA and MRA are the primary imaging modalities for vascular assessment in the setting of cerebral ischemia. However, DSA with provocative maneuvers is an essential tool and may have led to an earlier diagnosis in this patient if performed on the initial angiogram. There should be an increased index of suspicion for BHS in patients with history of cervical spine surgery and infarcts confined to the posterior circulation. Disclosures P. Gulotta: None. G. Bennett: None. J. Milburn: 3; C; Penumbra.

Progressive thinning of visual cortex in primary open-angle glaucoma of varying severity.

The aim of this study was to investigate possible changes of cortical thickness in the visual cortex in primary open-angle glaucoma (POAG) of varying severity. Twenty normal controls (NC), 20 mild (MP) and 17 severe (SP) POAG patients were recruited and scanned using magnetic resonance imaging. Cortical thickness analyses with regions of interest (V1, V2, ventral V3, V4 and V5/MT+) were used to assess the cortical changes among the three groups. Furthermore, the associations of cortical thickness with retinal nerve fiber layer (RNFL) thickness and mean deviation of visual field were analyzed. Compared with the NC group, decreased cortical thickness was detected in the bilateral V5/MT+ areas in the MP group and the left V1, bilateral V2 and V5/MT+ areas in the SP group. Cortical thinning of the bilateral V2 areas was detected in the SP group compared with the MP group. In addition, cortical thinning of these visual areas was related to the ophthalmologic measurements. In conclusion, POAG patients exhibit cortical thinning in the bilateral V5/MT+ in the early stage of disease. The cortical degeneration in visual areas is discrepant with disease progressing and the dorsal pathway might be selectively damaged in POAG. Therefore, the cortical thinning of these visual areas may play a key role in the progression of POAG and can serve as a novel biomarker for accurately evaluating the severity of POAG.

Peak frequency of induced gamma-band response to simple stimulus predicts individual switch rate for perceptual rivalry tasks.

The peak frequency of an induced gamma-band response to a simple stimulus is known to vary across individuals (Muthukumaraswamy et al., 2010) and is thought to be shaped by differences in the extent of inhibitory connections in visual cortex (Brunel & Wang, 2003). In support of this, peak gamma frequency has been found to predict individual levels of resting state GABA in visual cortex (Edden et al., 2009; Muthukumaraswamy eta l., 2009). Also varying reliably across normal populations is the rate of alternation for perceptual rivalry tasks including binocular rivalry and monocular pattern rivalry (Carter & Pettigrew, 2003; Miller et al., 2010). Models of perceptual rivalry include mutual inhibition as a constraint on switching dynamics (e.g., Wilson 2003), but do the differences in switch rate reflect individual differences in cortical inhibition? If so, individual switch rate should be inversely correlated with peak gamma frequency, yet this prediction has not been tested. We used magnetoencephalography (MEG) to compare the peak gamma-band frequency of neuromagnetic responses of 12 healthy adults (6 female) to the onset of simple grating stimuli with their individual switch rates for binocular and monocular rivalry tasks. We computed Morlet wavelet analyses for left and right V1, V2, and MT+ of individual source data based on minimum norm estimates for each participant. Peak frequency was determined for three latency ranges: evoked (10-150ms), early induced (200-450ms) and late induced (500-800ms). Results show significant inverse correlations between peak frequency of early induced gamma in V1 and switch rate for both rivalry tasks, compatible with models that propose inhibitory connections in visual cortex are crucial for tuning gamma-band frequency as well as perceptual alternation rate. Our study suggests that subtle variations of behavior in a normal population can directly advance our understanding of visual function by encouraging models at increasingly finer scales. Meeting abstract presented at VSS 2014

Functional Connectivity Density in Congenitally and Late Blind Subjects

Visual deprivation during different developmental periods leads to different structural and functional alterations in the brain; however, the effects of visual deprivation on the spontaneous functional organization of the brain remain largely unknown. In this study, we used voxel-based functional connectivity density (FCD) analyses to investigate the effects of visual deprivation during different developmental periods on the spontaneous functional organization of the brain. Compared with the sighted controls (SC), both the congenitally blind (CB) and the late blind (LB) exhibited decreased short- and long-range FCDs in the primary visual cortex (V1) and decreased long-range FCDs in the primary somatosensory and auditory cortices. Although both the CB and LB exhibited increased short-range FCD in the dorsal visual stream, the CB exhibited greater increases in the short- and long-range FCDs in the ventral visual stream and hippocampal complex compared with the LB. Moreover, the short-range FCD of the left V1 exhibited a significant positive correlation with the duration of blindness in the LB. Our findings suggest that visual deprivation before the developmental sensitive period can induce more extensive brain functional reorganization than does visual deprivation after the sensitive period, which may underlie an enhanced capacity for processing nonvisual information in the CB.

The surface area of early visual cortex predicts the amplitude of the visual evoked potential

The extensive and increasing use of structural neuroimaging in the neurosciences rests on the assumption of an intimate relationship between structure and function in the human brain. However, few studies have examined the relationship between advanced magnetic resonance imaging (MRI) indices of cerebral structure and conventional measures of cerebral functioning in humans. Here we examined whether MRI-based morphometric measures of early visual cortex-estimated using a probabilistic anatomical mask of primary visual cortex (V1)-can predict the amplitude of the visual evoked potential (VEP), i.e., an electroencephalogram signal that primarily reflects postsynaptic potentials in early visual cortical areas. We found that left, right, and total V1 surface area positively predicted the VEP amplitude. In addition, we showed, using whole brain analysis of local surface areal expansion/contraction, that the association between VEP amplitude and surface area was highly specific for regions within bilateral V1. Together, these findings indicate a strong, selective relationship between MRI-based structural measures and functional properties of the human cerebral cortex.

Stenosis and Dissection in the Same Vertebral Artery

In the current report, we present a case of a 59-year-old patient with arterial hypertension, diabetes and dislipidemia, which is presented by severe bilateral atherosclerotic lesions of the extracranial part of the vertebral arteries, thrombosis of the right and high-grade stenosis of the V1 segment of the left vertebral artery (VA). Despite the presence of the prominent atherosclerotic VA pathology, the patient develops asymptomatic VA dissection of the left V1 segment. The b rain c omputed tomography was without data for brain infarction . The patient was without neurological deficit . Treatment with stent placement was performed. J Med Cases. 2014;5(6):337-340 doi: http://dx.doi.o rg/ 10.14740 /jmc1774 w