Intraorbital Segment Research Articles

Diabetic Oculomotor Nerve Palsy Displaying Enhancement of the Oculomotor Nerve in the Orbit and Cavernous Sinus on MRI

Introduction: Imaging data were scarce on diabetic oculomotor nerve palsy (ONP). Our study explored the MRI features and their clinical implications for diabetic ONP. Methods: Fifty-nine patients with a clinical diagnosis of diabetic ONP were recruited from our department between January 2015 and December 2019. Orbital MRI was retrospectively analyzed, and follow-up scans were obtained for 5 patients. Based on the ocular motor nerve palsy scale, the difference in the scores on the first and last hospital days was defined as the improvement score and was used to assess the treatment effects in all. Results: Thirty-eight (64.41%) patients presented thickening and enhancement of the cavernous segment and inferior division of the intraorbital segment of the ipsilateral oculomotor nerve, with the cisternal segment spared in all. After complete resolution of symptoms, follow-up MRI in 5 patients revealed that the enhancement was less obvious compared with the previous images. 6 patients in the enhancement group and 4 patients in the nonenhancement group were treated with 80 mg of methylprednisolone. Significant differences were not detected in the median improvement scores between patients with and those without corticosteroid use (p = 0.240). Conclusion: Thickening and enhancement of the unilateral oculomotor nerve were common imaging findings in diabetic ONP, and they persisted after complete resolution of symptoms in some patients. The cavernous segment and the inferior division of the intraorbital segment were simultaneously involved, and the cisternal segment was often spared. Refraining from corticosteroids was recommended even with nerve enhancement.

Chronic methanol toxicity through topical and inhalational routes presenting as vision loss and restricted diffusion of the optic nerves on MRI: A case report and literature review.

Methanol intoxication can cause irreversible neurologic sequelae if unrecognized and untreated. Ingestion is the most common form of toxicity; however, dermal and inhalational exposures likewise occur but are documented rarely. While acute intoxication is commonly encountered, chronic exposure to methanol should also be highlighted. We report a case of a 57-year old female presenting in the emergency room with progressive dyspnea, metabolic acidosis with high anion gap, and metabolic encephalopathy. After emergency hemodialysis, the patient complained of vision loss on both eyes. Initial non-contrast cranial magnetic resonance imaging (MRI) revealed restricted diffusion of the intraorbital segment of both optic nerves. A thorough history revealed that she was applying a clear colorless liquid bought online all over her body for alleged pruritus for more than a year. The syndrome of metabolic acidosis with high anion gap, metabolic encephalopathy, vision loss, and laboratory findings led us to suspect a diagnosis of chronic methanol poisoning with an acute component. The liquid in question was sent for chemical analysis and result showed that it consisted of 95.5% Methanol. This case highlights the need for high index of clinical suspicion for methanol toxicity in the absence of oral consumption, the complications of chronic form of methanol intoxication, and the uncommon radiologic finding seen in diffusion-weighted imaging (DWI).

Changing the paradigm of intracranial hypertension in brain tumor patients: a study based on non-invasive ICP measurements

BackgroundThe ultrasound based non-invasive ICP measurement method has been recently validated. Correlation of symptoms and signs of intracranial hypertension with actual ICP measurements in patients with large intracranial tumors is controversial. The purpose of this study was to assess ICP in patients with brain tumors, presenting with neurological signs and symptoms of elevated ICP and to further evaluate the value and utility of non-invasive ICP monitoring.MethodsTwenty patients underwent non-invasive ICP measurement using a two-depth transcranial Doppler ultrasound designed to simultaneously compare pulse dynamics in the proximal (intracranial), and the distal (extracranial) intraorbital segments of the ophthalmic artery through the closed eyelid.ResultsForty-eight measurements were analyzed. Radiological characteristics included tumor volume (range = 5.45–220.27cm3, mean = 48.81 cm3), perilesional edema (range = 0–238.27cm3, mean = 74.40 cm3), and midline shift (mean = 3.99 mm). All ICP measurements were in the normal range of 7–16 mmHg (ICPmean: 9.19 mmHg). The correlation of demographics, clinical and radiological variables in a bivariate association, showed a statistically significant correlation with neurological deficits and ICPmax (p = 0.02) as well as ICPmean (p = 0.01). The correlation between ICP and neurological deficits, showed a negative value of the estimate. The ICP was not increased in all cases, whether ipsilateral nor contralateral to the tumor. The multivariate model analysis demonstrated that neurological deficits were associated with lower ICPmax values, whereas maximum tumor diameter was associated with larger ICPmax values.ConclusionsThis study demonstrated that ICP in patients with intracranial tumors and mass effect is not necessarily increased. Therefore, clinical signs of intracranial hypertension do not necessarily reflect increased ICP.

A case report of optic neuropathy following dacryocystorhinostomy in a 57-year-old female patient with May-Hegglin anomaly

BackgroundWe report a rare case of optic neuropathy following dacryocystorhinostomy (DCR) in a 57-year-old female patient with May-Hegglin anomaly.Case presentationThe patient was presented with sudden onset of vision loss for the left eye after DCR under general anesthesia. Her best corrected visual acuity was light perception in the left eye. Relative afferent pupillary defect was detected in her left eye. Magnetic resonance imaging of the orbit revealed an hyperintensity at the intra-orbital segment of the left optic nerve on T2-weighted image and Flair image. The patient was diagnosed with acute postoperative optic neuropathy and treated with methylprednisolone. Although her vision partially improved, she was left with a visual field defect in the left eye.ConclusionsIn patients with hematologic diseases, postoperative vision loss can occur following even minor surgery under general anesthesia, such as DCR. Therefore, preoperative counseling regarding the risk of visual loss should be given to high-risk patients.

En-Bloc Resection Versus Resection After Evacuation and Suction of the Content for Orbital Optic Nerve Glioma Causing Visual Loss and Disfiguring Proptosis.

To evaluate the surgical outcomes of two different techniques of resection for optic nerve gliomas confined to the intra-orbital segment. This prospective, comparable, clinical interventional case series was conducted at the orbital clinic of Assiut University Hospital, the referral centre of Upper Egypt in the period between 2006 and 2018. The study included 10 children with optic nerve gliomas confined to the intra-orbital part without intracanalicular or intracranial extension and causing severe visual loss and disfiguring proptosis. In all cases, lateral orbitotomy was performed to expose the mass. In 5 cases (group A), the glioma was resected en-bloc. In 5 cases (group B), a new technique of resection was introduced. The wall of the glioma was incised, the content was evacuated and suctioned and followed by resection under good visualization of the markedly reduced mass in size. In the 2 groups, no tumour regrowth was reported during the follow-up period of 3-12 years. In group A, the 5 cases developed postoperative third nerve damage with paralytic ptosis and one case had severe neurotrophic keratitis ended by dense corneal opacity. In group B, a healthy ipsilateral eye was preserved in all cases and no one case developed postoperative paralytic ptosis. Reduction of size of an intra-orbital optic nerve glioma by evacuation and suction of the content before resection is highly recommended. This makes the surgical field during resection more visible and minimizes the possibility of third or other nerves damage.

The accuracy of standard multiple sclerosis MRI brain sequences for the diagnosis of optic neuropathy

BackgroundDetection of optic neuropathy on MRI has potential implications for the diagnosis and management of Multiple Sclerosis (MS). ObjectiveThis study assessed the accuracy of T2 sagittal MRI brain for detection of optic neuropathy, compared to coronal STIR orbit. Methods and materialsRetrospective single-center blinded diagnostic accuracy study of 100 consecutive patients who underwent both T2 sagittal brain and coronal STIR orbit MRI. All were performed on 1.5T scanners. T2 sagittal slice thickness was 4 mm for the first 50 patients (group1) and 3 mm for the second 50 (group2). The MRIs were reviewed in a blinded fashion to determine the presence of optic neuropathy. Coronal STIR orbit sequences were considered the diagnostic reference standard. ResultsThe sensitivity of T2 sagittal brain imaging for ON was 44% in group 1 and 85% in group 2 (p = 0.007). The specificities were 98% and 97% respectively (p = 0.9). Sensitivity was poorest for evaluation of the intraorbital nerve segment (56% grp1, 69% grp2, p = 0.4). ConclusionT2 sagittal MRI brain has high specificity for the detection of optic neuropathy when compared to coronal STIR orbit. Sensitivity is increased when slice thickness is reduced, but remains poor for evaluation of the intraorbital segment.

An Anatomical Feasibility Study for Revascularization of the Ophthalmic Artery. Part II: Intraorbital Segment

Distal ophthalmic artery (OpA) aneurysms are a rare subset of vascular lesions with lack of optimal treatment. The management of these aneurysms may require complete occlusion of the parent vessel, carrying a risk of permanent visual impairment due to individual variations of extracranial collateral flow to the intraorbital ophthalmic artery (iOpA). To test the feasibility of a superficial temporal artery (STA) to iOpA bypass to prevent acute ischemic retinal injury. Two different transorbital corridors (superomedial and posterolateral approaches) for this bypass were evaluated. Each approach was carried out in 10 specimens each (n= 20). The corridors were compared to achieve the optimal exposure of the iOpA until the central retinal artery origin was visualized. An end-to-end anastomosis was performed from STA-to-iOpA. The arterial caliber and length at the anastomotic sites, required donor artery length, and intraorbital surgical area were measured. STA-iOpA bypasses were performed in all specimens. For the posterolateral transorbital approach, the mean caliber of STA was 1.8 ± 0.2 mm, and that of iOpA was 1.7 ± 0.5 mm. The required STA graft length was 78.3 ± 1 mm with lateral iOpA transposition of 8.2 ± 1.1 mm. For the superomedial approach, the average STA length required for an intraorbital bypass was 130.8 ± 14.0 mm. The mean calibers of iOpA and STA were 1.5 ± 0.1 mm and 1.5 ± 0.1 mm, respectively. This study demonstrates the feasibility of a novel revascularization technique of the iOpA using 2 different transorbital approaches. These techniques can be used in the management of intraorbital lesions such as OpA aneurysms, tumoral infiltrations, or intraoperative injuries.

Analysis of clinical characteristics of optic nerve metastases

Objective To explore the clinical features, primary lesions and prognosis of optic nerve metastases. Methods Seven patients (11 eyes) with optic nerve metastatic tumor diagnosed by the examinations of ophthalmology, laboratory and pathology in Chinese PLA General Hospital from April 2015 to September 2017 were included in this study. All patients underwent BCVA, flash VEP, OCT, orbital MRI, serum tumor marker, cerebral spinal fluid detection and PET-CT. Histopathological examination of primary or near superficial metastases was performed. The follow-up period was ranged from 16 to 44 months, with the mean of 23.0±10.9 months. The clinical characteristics, primary tumor, imaging features, treatment and clinical prognosis in the patients were analyzed. Results Among 7 patients, there were 5 males and 2 females, with the mean age of 53.90±14.99 years; 3 patients with unilateral optic nerve involvement, 4 patients with bilateral optic nerve involvement; 5 patients (71.4%) first diagnosed in ophthalmology. Five patients (45.5%) were misdiagnosed as optic neuritis, optic disc edema in 6 eyes (54.5%). All of them appear loss of visual acuity, including 8 eyes (72.7%) with BCVA 0.5. MRI results show that 1 patient with intraorbital segment, 1 patient with internal segment of optic canal, 4 patients with intracranial segment, 1 patient with intracranial segment and optic chiasma involved simultaneously, 4 patients involving surrounding tissue. There were 4 patients (57.1 %) with lung cancer, 2 patients (28.6%) with kidney cancer, 1 patient (14.3%) with gastric cance; 6 patients (85.7%) with metastasis from other sites, 2 patients with brain metastasis (1 patient with meningitis carcinomatosa). There were 2 patients(28.6%) with previous primary cancer surgery. After diagnosis, 1 patient received chemotherapy, 1 patient received radiotherapy, 5 patients gave up treatment. At the end of follow-up, 1 patient (1 eye) of chemotherapy with BCVA increased by 2 line; 1 patient (2 eyes) of radiotherapy with no change in BCVA; of the 5 patients who gave up treatment, 1 patient died of disease, 1 patient lost follow-up, and 3 patients (4 eyes) had no change in BCVA. Conclusions With atypically clinical manifestations, the optic nerve metastases easily misdiagnosed as optic neuritis, and with poor therapeutic effect. Primary lesions are mostly found in lung cancer. Key words: Optic nerve neoplasms; Neoplasm metastasis; Lung neoplasms; Disease attributes

Optical coherence tomography angiography in optic nerve sheath meningioma

Abstract This study describes Spectral Domain-Optical Coherence Tomography (SD-OCT) and Optical Coherence Tomography Angiography (OCTA) features of Optic Nerve Sheath Meningioma (ONSM). A 22-year-old woman, diagnosed with meningioma encircling the right optic nerve inside the intraorbital segment optic canal at the magnetic resonance imaging, showed a normal fundus examination. Instead, SD-OCT and OCTA revealed alterations in the neurostructure and microvascular network of the optic nerve. Despite fundoscopy and fluorescein angiography, SD-OCT and OCTA represent valid, non-invasive and reliable methods to evaluate neurostructural and vascular irregularities in this benign tumor of the optic nerve.

Neurolin expression in the optic nerve and immunoreactivity of Pax6-positive niches in the brain of rainbow trout (Oncorhynchus mykiss) after unilateral eye injury.

In contrast to astrocytes in mammals, fish astrocytes promote axon regeneration after brain injury and actively participate in the regeneration process. Neurolin, a regeneration-associated, Zn8-labeled protein, is involved in the repair of damaged optic nerve in goldfish. At 1 week after unilateral eye injury, the expression of neurolin in the optic nerve and chiasm, and the expression of Pax6 that influences nervous system development in various brain regions in the rainbow trout (Oncorhynchus mykiss) were detected. Immunohistochemical staining revealed that the number of Zn8+ cells in the optic nerve head and intraorbital segment was obviously increased, and the increase in Zn8+ cells was also observed in the proximal and distal parts of injured optic nerve. This suggests that Zn8+ astrocytes participate in optic nerve regeneration. ELISA results revealed that Pax6 protein increased obviously at 1 week post-injury. Immunohistochemical staining revealed the appearance of Pax6+ neurogenic niches and a larger number of neural precursor cells, which are mainly from Pax6+ radial glia cells, in the nuclei of the diencephalon and optic tectum of rainbow trout (Oncorhynchus mykiss). Taken together, unilateral eye injury can cause optic nerve reaction, and the formation of neurogenic niches is likely a compensation phenomenon during the repair process of optic nerve injury in rainbow trout (Oncorhynchus mykiss).

Characteristics of perioptic and intraoptic arterial vascularization of extracranial segment of optic nerve

<p>Introduction. The optic nerve is supplied by the arterial branches of the supericial pial plexus and direct intraneural branches. The aim of the study was to study the morphological characteristics (origin, number of arteries, calibers, and branching pattern) of perioptic arterial vascularization and intraoptic vascular network of the extracranial sections of the optic nerve: canalicular and intraorbital. Methods. The study included 18 pairs of the optic nerves of both sexes (11 males and 7 females), aged 51 to 78 years, with no signs of changes in the structures of the nervous system. The vasculature of the optic nerves was microdissected and examined under the stereoscopic microscope, after injecting their arteries with 10% mixture of India ink and gelatin, and 5% formaline ixation. Results. The intracanalicular part of the optic nerve received ine blood vessels from the ophthalmic artery, usually in two branches in 29 (82.9%) cases, while in 6 (17.1%) specimens there was only one branch for the nerve. The intraorbital segment of the optic nerve was supplied by two interconnected systems of blood vessels, peripheral and axial, both coming from the central retinal artery. Conclusion. On the basis of the obtained results, it has been conirmed that both segments of the optic nerve have a rich and very delicate vascular network. The supericial pial arterial plexus of the intracanalicular segment of the optic nerve has been identiied as the only source of its vascular supply. The intraorbital part of the optic nerve has two interconnected systems of blood vessels: peripheral and axial.</p>

Antibodies to myelin oligodendrocyte glycoprotein in chronic relapsing inflammatory optic neuropathy

Background/aimsTo evaluate the status of myelin oligodendrocyte glycoprotein antibodies (MOG-IgG) in chronic relapsing inflammatory optic neuropathy (CRION) and investigate its different clinical characteristics and prognosis.MethodsPatients diagnosed with CRION were recruited...

Modern Management of Meningiomas Compressing the Optic Nerve: A Systematic Review

Meningiomas that compress the optic nerve (ON) can lead to different visual outcomes depending on the segment of ON affected (intraorbital, canalicular, and intracranial). In this study, we performed a comprehensive comparison of the management options (surgery, radiation, or observation alone) for meningiomas compressing the ON, categorized by location and relation to the ON. MEDLINE, EMBASE, Web of Science, and the Cochrane Database of Systematic reviews databases were searched according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. Data were extracted from the articles regarding anatomic location, initial visual impairment, surgical procedure, visual outcome, morbidity and mortality, gross total removal, and requirement for postoperative radiotherapy. Of the 47 articles eligible for full-text reading, 9 surgical studies met our inclusion criteria. Data from 317 patient cases were extracted. In patients in whom the intracranial segment of the ON was impaired in isolation, 49% experienced visual improvement after surgery. When the meningioma affected the canalicular segment or intraorbital segment, visual improvement after surgery was 31% and 11%, respectively. Of patients who underwent surgery for the intraorbital segment of the ON, 56% experienced a decline in visual outcome. When a neurosurgeon deals with a meningioma compressing the ON, opening the optic canal is suggested if invasion is suspected on the preoperative imaging. Extra caution should be used when operating on meningiomas with ON sheath adhesion, given the higher evidence of postoperative visual worsening.

Perioptic Cerebrospinal Fluid Dynamics in Idiopathic Intracranial Hypertension.

Purpose: To examine the cerebrospinal fluid (CSF) dynamics along the entire optic nerve in patients with idiopathic intracranial hypertension (IIH) and papilledema by computed tomographic (CT) cisternography.Methods: Retrospective analysis of CT cisternographies in 16 patients with a history of IIH and papilledema (14 females and 2 males, mean age: 49 ± 16 years). Contrast loaded CSF (CLCSF) was measured in Hounsfield Units (HU) at three defined regions of interest (ROI) along the optic nerve (orbital optic nerve portion: bulbar and mid-orbital segment, intracranial optic nerve portion) and additionally in the basal cistern. The density measurements in ROI 1, ROI 2, and ROI 3 consist of measurements of the optic nerve complex: optic nerve sheath, CLCSF filled SAS and optic nerve tissue. As controls served a group of patients (mean age: 60 ± 19 years) without elevated intracranial pressure and without papilledema.Results: In IIH patients the mean CLCSF density in the bulbar segment measured 65 ± 53 HU on the right and 63 ± 35 HU on the left side, in the mid-orbital segment 68 ± 37 HU right and 60 ± 21 HU left. In the intracranial optic nerve portion 303 ± 137 HU right and 323 ± 169 HU left and in the basal cistern 623 ± 188 HU. Within the optic nerve the difference of CLCSF density showed a highly statistical difference (p < 0.001) between the intracranial optic nerve portion and the mid-orbital segment. CLCSF density was statistically significantly (p < 0.001) reduced in both intraorbital optic nerve segments in patients with IIH compared to controls.Conclusions: The current study demonstrates reduced CLCSF density within the orbital optic nerve segments in patients with IIH and papilledema compared to 12 controls without elevated intracranial pressure and without papilledema. Impaired CSF dynamics could be involved in the pathophysiology of optic nerve damage in PE in IIH.

Impaired cerebrospinal fluid dynamics along the entire optic nerve in normal-tension glaucoma.

To investigate the cerebrospinal fluid (CSF) dynamics along the entire optic nerve (ON) in patients with normal-tension glaucoma (NTG). Retrospective analysis of computed tomographic (CT) cisternographies in Caucasian patients with NTG. Fifty-six patients (99 of 112 eyes) fulfilled the diagnostic criteria of NTG and underwent CT-cisternography. Twelve subjects without NTG (24 eyes) served as controls. Contrast-loaded cerebrospinal fluid (CLCSF) density measurements in Hounsfield units (HU) were performed at four defined regions along the ON and in the basal cistern. In NTG patients, the mean density CLCSF in the bulbar segment measured 76±49HU right and 88±74HU left, in the mid-orbital segment 117±92HU right and 119±73HU left, in the intracanalicular ON portion 209±88HU right and 216±101HU left, in the intracranial ON portion 290±106HU right and 286±118HU left and in the basal cistern 517±213HU. The distribution of CLCSF along the ON showed a statistically significant reduction in the intraorbital ON segments in NTG patients compared to controls without NTG with the far largest difference within the retrobulbar segment (-150HU right and -117HU left; right: p<0.001, left: p<0.001). This study demonstrates a gradual reduction in CLCSF towards the retrobulbar segment in NTG, while in controls without NTG, no reduction in CLCSF was measured within the orbital segments. Impaired CSF dynamics along the ON may contribute to the pathophysiology of NTG.

Advanced diffusion-weighted imaging in patients with optic neuritis deficit - value of reduced field of view DWI and readout-segmented DWI.

Objective The objective of this article is to evaluate advanced techniques of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) measurements of the optic nerve in patients with optic neuritis. Methods In this prospective and institutional review board-approved trial, we examined 15 patients with acute visual loss and clinical signs of optic neuritis including thin-slice multi-shot segmented readout of long variable echo trains (rs-EPI, RESOLVE) DWI and reduced field-of view DWI using a parallel transmit system (rFOV-EPI). Conventional single-shot echo-planar DWI (ss-EPI) of the whole brain was available in 13 patients. Subjective image quality was compared using a four-point scale and objective ADC measurements were performed in comparison with the non-affected side. Results In the intraorbital segment, subjective image quality was significantly higher in rFOV-EPI (score 3.3 ± 0.8) compared with rs-EPI (score 2.1 ± 0.8) and ss-EPI (score 0.9 ± 0.8). Diagnosis was hampered in the canalicular segment ( n = 3) and the intracranial segment ( n = 1) in all applied DWI techniques. ADC measurements of the affected side differed significantly in all DWI sequences ss-EPI (sensitivity 54%, accuracy 77%), rs-EPI (sensitivity 71%, accuracy 86%), and rFOV-EPI (sensitivity 73%, accuracy 87%). Conclusion Optic neuritis in the intraorbital segment can be detected with high sensitivity without the need for contrast application. Using rFOV-EPI improves subjective image quality compared with rs-EPI and ss-EPI. Due to its higher spatial resolution, rFOV-EPI was the preferred technique in our study and can ensure the diagnosis in the intraorbital segment. However, artefacts occur in the canalicular and intracranial segment of the optic nerve, therefore contrast-enhanced T1-weighted images must still be considered as the gold standard.

Clinical features of chronic relapsing inflammatory optic neuropathy

Objective: To explore the clinical characteristics and prognosis of chronic relapsing inflammatory optic neuropathy (CRION). Methods: A retrospective analysis was conducted. Clinical features, disease course, prognosis and magnetic resonance imaging (MRI) of patients with CRION who were admitted to Department of Neurology between 2014 and 2016 were reviewed and analyzed. Results: Totally, there were 27 patients (10 males and 17 females), with an age range of 17-59 years. The disease duration was between 40 days and 8 years. There were 2 to 9 CRION episodes. The mean frequency of CRION episodes was 3.30±1.56. The outcome of visual acuity showed that the more episodes frequency was, the worse outcome became. There was 25 abnormal optic nerve signals in MRI. And in 22 cases, the abnormal signals were in intraorbital segment or inner pipe section. The antinuclear antibodies (ANA) titers were elevated in 5 patients. Five cases relapsed during reduction or withdrawal of steroids, but steroids was not added in time. The final outcome of these 5 patients was poor. Conclusions: CRION was more common in female than male patients. Most patients were companied by pain, and the lesions were more common in the intraorbital segment of optic nerve. The more episode frequency was, the worse prognosis became. If a relapse happened, steroids or other immunosuppressive agents should be used.

Diffusion-Weighted Imaging and Post-contrast Enhancement in Differentiating Optic Neuritis and Non-arteritic Anterior Optic Neuropathy

ABSTRACTNon-arteritic anterior ischaemic optic neuropathy (NAION) and optic neuritis (ON) may be difficult to distinguish early in their disease courses. Our goal was to determine if specific magnetic resonance imaging characteristics differentiate acute NAION from ON. Neuroradiologists, masked to diagnosis, reviewed the diffusion-weighted imaging (DWI) and post-contrast enhancement (PCE) characteristics of the optic nerve in 140 eyes. PCE and DWI signals of the optic disc alone did not discriminate between NAION and ON. After taking age and sex into consideration, only DWI and PCE of the intraorbital segment of the optic nerve differentiated the two, with ON having the increased likelihood of these findings. Isolated PCE without DWI signal at the optic disc, however, was 100% specific for NAION. This may be the most specific way to radiographically differentiate between NAION and ON in the acute setting.

SU‐E‐J‐187: Management of Optic Organ Motion in Fractionated Stereotactic Radiotherapy

Purpose:Fractionated stereotactic radiotherapy (FSRT) for optic nerve tumors can potentially use planning target volume (PTV) expansions as small as 1–5 mm. However, the motion of the intraorbital segment of the optic nerve has not been studied.Methods:A subject with a right optic nerve sheath meningioma underwent CT simulation in three fixed gaze positions: right, left, and fixed forward at a marker. The gross tumor volume (GTV) and the organs‐at‐risk (OAR) were contoured on all three scans. An IMRT plan using 10 static non‐coplanar fields to 50.4 Gy in 28 fractions was designed to treat the fixed‐forward gazing GTV with a 1 mm PTV, then resulting coverage was evaluated for the GTV in the three positions. As an alternative, the composite structures were computed to generate the internal target volume (ITV), 1 mm expansion free‐gazing PTV, and planning organat‐risk volumes (PRVs) for free‐gazing treatment. A comparable IMRT plan was created for the free‐gazing PTV.Results:If the patient were treated using the fixed forward gaze plan looking straight, right, and left, the V100% for the GTV was 100.0%, 33.1%, and 0.1%, respectively. The volumes of the PTVs for fixed gaze and free‐gazing plans were 0.79 and 2.21 cc, respectively, increasing the PTV by a factor of 2.6. The V100% for the fixed gaze and free‐gazing plans were 0.85 cc and 2.8 cc, respectively increasing the treated volume by a factor of 3.3.Conclusion:Fixed gaze treatment appears to provide greater organ sparing than free‐gazing. However unanticipated intrafraction right or left gaze can produce a geometric miss. Further study of optic nerve motion appears to be warranted in areas such as intrafraction optical confirmation of fixed gaze and optimized gaze directions to minimize lens and other normal organ dose in cranial radiotherapy.

Assessment of Optic Nerve Impairment in Patients with Neuromyelitis Optica by MR Diffusion Tensor Imaging.

BackgroundDiffusion tensor imaging (DTI) has been used for the evaluation of the white matter integrity. In this study, we evaluated optic nerve impairment in patients with neuromyelitis optica (NMO) using DTI.Methodology/Principal FindingsOptic nerve DTI were performed on 28 NMO patients and 38 normal controls. Fractional anisotropy (FA) values were measured in the anterior, middle, and posterior parts of the intraorbital optic nerve segment. For the posterior intraorbital optic nerve, FA values of BI (0.20±0.07), MI (0.24±0.16), and NA (0.25±0.14) decreased significantly compared with that of NC (0.43±0.07) (P<0.05), and ROC analysis demonstrated that the area under the curve (AUC) measurements for BI vs. NC, MI vs. NC, NA vs. NC, and NMO (including BI, MI, and NA) vs. NC were 0.99, 0.93, 0.88, and 0.96, respectively. The corresponding diagnostic sensitivities of ROC analysis were 100%, 80%, 80%, and 91%; and the specificities were 93%, 97%, 91%, and 93%.Conclusions/SignificanceDecreased FA value in the intraorbital optic nerve, especially in the posterior part of the nerve, was demonstrated as a characteristic MR feature for NMO-related optic nerve impairment.