The optic nerve sheath on MRI in acute optic neuritis

Optic nerve sheath dilatation or gadolinium-enhancement on magnetic resonance imaging in acute optic neuritis have been previously reported but have been thought to be rare occurrences. This study recruited 33 patients with acute unilateral optic neuritis. All had their optic nerves imaged with fat-saturated fast spin-echo (FSE) imaging, and 28 had imaging before and after triple-dose gadolinium-enhanced fat-saturated T₁-weighted imaging. Follow-up imaging was performed on 20 patients (15 following gadolinium). A dilated subarachnoid space at the anterior end of the symptomatic optic nerve on FSE imaging was seen in 15/33 cases. In three of these cases, dilatation was visible on short-term follow-up. Optic nerve sheath enhancement was seen in 21/28 cases acutely: seven at the anterior end of the lesion only, five at the posterior end only and nine at both ends. Optic sheath enhancement was seen in 13 patients on follow-up. This study suggests that optic nerve sheath dilatation on FSE images and optic nerve sheath enhancement on triple-dose gadolinium-enhanced images are common findings in acute optic neuritis. Optic nerve sheath dilatation may be due to inflammation of the optic nerve, with its associated swelling, interrupting the communication between the subarachnoid space of the diseased optic nerve and the chiasmal cistern. Optic nerve sheath enhancement suggests that meningeal inflammation occurs in optic neuritis, in agreement with pathological studies of both optic neuritis and multiple sclerosis.     

Intrathecal metrizamide enhancement of the optic nerve sheath

The subarachnoid space continues into the orbit as part of the optic nerve sheath. This space varies in size but is usually tiny. Occasionally, prominent (one case in our experience) enhancement of the optic nerve as part of metrizamide computed tomography (CT) cisternography is seen on transverse and coronal scans presumably because of a patulous optic subarachnoid space. In five cases, we have appreciated minimal enhancement of optic nerves with metrizamide only by close comparison of CT numbers with base-line scans. One of these patients had a tiny meningioma removed successfully from the optic sheath, with return to normal vision of a previously blind eye.     

视神经鞘脑膜瘤影像学研究

目的研究视神经鞘脑膜瘤的CT和MRI表现，并探讨双轨征的显示情况及其价值。方法35例经手术病理证实的视神经鞘脑膜瘤患者，年龄6-71岁，女20例，男15例。28例行CT扫描，其中25例行增强扫描；27例行MR扫描，其中25例行增强扫描。结果35例视神经鞘脑膜瘤中12例呈梭形，7例呈管形增粗，1例呈椭圆形，8例为偏心性生长的肿块，7例弥漫累及整个眼眶。35例均累及眶内段，其中22例同时累及管内段，13例同时累及颅内段，4例同时累及视交叉，1例同时累及视束。行CT扫描的28例中，20例呈等密度，8例为含有钙化的肿块。行CT增强扫描的25例全部强化，其中6例清楚显示双轨征。行MR扫描的27例中，16例T，WI和T2WI均为低信号，3例呈长T1、长T2信号，8例呈等T1、等T2信号。行MR增强扫描的25例均呈明显强化，17例清楚显示双轨征。经统计学处理，MRI显示双轨征明显优于CT(P=0．001)。结论CT和MRI都可显示视神经鞘脑膜瘤的部位、形态和内部特征，M砌在定位诊断和定性诊断方面明显优于CT。     

Decreased diameter of the optic nerve sheath associated with CSF hypovolemia

The subarachnoid space around the optic nerve can be detected by fat-saturated T2-weighted MR imaging of the orbit, and dilation of this space reflects increased intracranial pressure. We examined 3 patients with CSF hypovolemia with MR imaging of the orbit and measured the optic nerve sheath diameter before and after treatment. We showed that the subarachnoid space is decreased in patients with CSF hypovolemia and the usefulness of this finding.     

Creation of an optic nerve sheath diameter ultrasound model for NeuroICU education

Background:Using ultrasound to measure optic nerve sheath diameter(ONSD)is an emerging bedside technique to noninvasively assess intracranial pressure(ICP)in patients with brain injury.This technique is unique among bedside ultrasonography and is often performed by providers who have no formal ultrasound training.We sought to create a low-cost,3D,reusable ONSD model to train neurology,neurosurgery,and critical care providers in measuring ICP.Results:We identified 253 articles,of which 15 were associated with models and 2 with simulation.One gelatin model was reported,upon which we based our initial design.We could not validate the visual findings of this model;however,after constructing multiple beta models,the design most representative of human eye anatomy was a globe made of ballistics gel and either a 3 mm,5 mm,or 7 mmx50 mm 3D-printed optic nerve inserted into a platform composed of ballistics gel,all of which sat inside a 3D-printed skull.This model was used to teach ONSD measurements with ultrasound at a continuing medical education event prior to training on a live human model.Conclusions:A simple 3D ballistic ONSD model allows learners to practice proper hand placement and pressure,basic landmarks,and ONSD measurement prior to operating on a human eye.This model is replicable and sustainable given that the globe and platform are composed of ballistics gel.     

低分割立体定向放射治疗原发性视神经鞘脑膜瘤的疗效分析

 目的 评价在4 Gy×10次的剂量分割模式下,采用低分割立体定向放射治疗原发性视神经鞘脑膜瘤的近期疗效.方法 2004-8至2010-3本院收治的15例原发性视神经鞘脑膜瘤患者采用SGS-Ⅰ型超级伽玛刀进行低分割立体定向放射治疗,靶区处方剂量为40 Gy/4 Gy×10次,放疗结束后6个月进行随访,观察患者肿瘤控制率,临床症状改善情况及视力保存率.结果 经过中位时间23个月的随访,肿瘤控制率100%(15例),肿瘤最大径缩小超过50%的患者有4例.突眼症状改善率100%,治疗前后突眼度分别为(17.3±0.8) mm及(14.5±0.3) mm,P<0.01.全组视力保存率为73.3%(11/15),其中改善2例,稳定9例,下降2例,失明2例.有10例出现轻度的治疗相关反应,对症治疗后缓解.结论 原发性视神经鞘脑膜瘤接受处方剂量为40 Gy/4 Gy×10次低分割立体定向治疗,疗效确切,但视力改善率较低,甚至出现失明患者,对于剂量分割模式尚需进一步研究.     

The MRI appearance of the optic nerve sheath following fenestration for benign intracranial hypertension

Optic nerve fenestration is carried out in cases of severe benign intracranial hypertension. This study aimed to monitor the optic nerve sheath appearances and orbital changes that occur following this procedure. The eight patients were all female with an average age of 37.3 years and a range of 20–58 years. The duration of symptoms was 2–6 years. Symptoms included headaches, diplopia and visual obscurations. Examination revealed severe papilledema. All investigations, including MRI, biochemical and immunological tests, were negative. Patients had fenestration of a 2 mm × 3 mm segment of the medial aspect of the optic nerve sheath. Imaging was obtained with a 1 T MRI machine using a head coil. Coronal, axial and sagittal 3 mm contiguous sections using STIR sequences with TR 4900 ms, IT 150 ms and TE 60 ms were obtained. Five patients showed clinical improvement. The post-operative MRI findings in four of these included a decreased volume of cerebrospinal fluid (CSF) around the optic nerve sheaths and a localized collection of fluid within the orbit. There were no MRI changes in the three patients with no clinical improvement. Decreased CSF volume around the optic nerve and a fluid collection within the orbit may indicate a favorable outcome in optic nerve fenestration. Received 23 June 1997; Revision received 16 January 1998; Accepted 18 March 1998     

视神经损伤鼻内镜减压术疗效观察

 目的 观察视神经损伤患者鼻内镜减压术治疗效果。方法 回顾性分析武警总医院耳鼻咽喉头颈外科2012-08至2014-04收治的28例(28只眼)视神经损伤患者的临床资料。所有患者均实施经鼻内镜视神经减压术,观察患者的临床治疗效果,并对患者的术后视力进行分析评价。结果 15例术后视力有所改善;24例术前无光感患者中,12例术后恢复光感;3例术前视力下降患者术后视力均有不同程度恢复。结论 针对视神经损伤患者行经鼻内镜视神经减压术进行治疗,并根据患者视神经损伤的程度和类型给予针对性的手术治疗,可帮助改善患者视力,并且具有手术创伤小、术后恢复快、并发症少等优点,有较好的临床疗效。     

MR imaging of the optic nerve and sheath: correcting the chemical shift misregistration effect

The interface between soft-tissue structures and adipose tissue may be obscured by the chemical shift misregistration effect on MR images. In the orbit, this effect occurs at the edges at the optic nerve, even on high-resolution local coil images. In both phantom and clinical studies with a 1.5 T local coil imaging system, it was found that the chemical shift misregistration effect can be minimized by positioning the patient so that the optic nerve is parallel to the frequency encoding gradient. Alternatively, the effect can be corrected by using a computer program to combine "lipid" and "water" proton images. The sensitivity of MR for optic nerve lesions should be improved by these technical modifications.     

A unique method for estimating the reliability learning curve of optic nerve sheath diameter ultrasound measurement

Background

Optic nerve sheath diameter (ONSD) measurement using ultrasound has been proposed as a rapid, non-invasive, point of care technique to estimate intra-cranial pressure (ICP). Ultrasonic measurement of the optic nerve sheath can be quite challenging and there is limited literature surrounding learning curves for this technique. We attempted to develop a method to estimate the reliability learning curve for ONSD measurement utilizing a unique definition of reliability: a plateau in within-subject variability with unchanged between-subject variability.

Methods

As part of a previously published study, a single operator measured the ONSD in 120 healthy volunteers over a 6-month period. Utilizing the assumption that the four measurements made on each subject during this study should be equal, the relationship of within-subject variance was described using a quadratic-plateau model as assessed by segmental polynomial (knot) regression.

Results

Segmental polynomial (knot) regression revealed a plateau in within-subject variance after the 21st subject. However, there was no difference in overall mean values [3.69 vs 3.68 mm (p = 0.884)] or between-subject variance [14.49 vs 11.92 (p = 0.54)] above or below this cutoff.

Conclusions

This study suggests a significant finite learning curve associated with ONSD measurements. It also offers a unique method of calculating the learning curve associated with ONSD measurement.

     

兔视神经间接损伤的视神经组织压观察

目的　通过观察兔视神经间接损伤后视神经组织压的变化 ,探讨视神经间接损伤后继发性损伤机制。　方法　一侧视神经致伤后 2 4h ,采用微穿刺法分别记录损伤侧及对侧球后 2mm处视神经组织压的变化 ,并取测压开始后 40～ 6 0min的平均压力值进行分析比较。　结果　视神经间接损伤后 2 4h ,损伤侧视神经组织压 (0 .315± 0 .334 )kPa(1kPa =7.5mmHg)显著高于对侧 (- 0 .0 85± 0 .2 13)kPa (P <0 .0 1)。　结论　视神经间接损伤后视神经组织压显著增高 ,提示有必要实施视神经减压术。