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.     

特发性颅内高压的影像学研究

目的研究特发性颅内高压（IIH）的可靠影像学征象及与临床症状的关系,提高对该病的认识。方法研究2008年7月～2012年12月有完整临床、影像学资料的20例IIH患者,并以同期20例正常志愿者作为对照组。由2位有经验的神经放射医生共同评价影像学异常,包括垂体及蝶鞍形态、脑室形态及视神经鞘形态。结果空蝶鞍/部分空蝶鞍和视神经鞘扩张都具有较高的敏感性（分别为75％、80％和75％）和特异性（分别为95％、75％和80％）;2组之间Evans指数、双侧麦氏腔长宽比及OND均无统计学差异（P〉O．05）,垂体腺高度及深度、双侧ONSD均有统计学显著性差异（Pd0．01）。结论空蝶鞍和视神经鞘扩张是IIH的可靠影像学征象。正确认识IIH的影像学表现对其早期诊断和治疗具有重要价值。     

MRI of the optic nerve in benign intracranial hypertension

We investigated the MRI appearance of the optic nerve and its cerebrospinal-fluid-containing sheath in 17 patients with benign intracranial hypertension (BIH) and 15 normal controls. Using phased-array local coils, 3-mm coronal T2-weighted fat-suppressed fast spin-echo images were obtained with an in-plane resolution of < 0.39 mm. The optic nerve and its sheath were clearly differentiated. An enlarged, elongated subarachnoid space around the optic nerve was demonstrated in patients with BIH. High-resolution MRI of the optic nerve offers additional information which may be of value for diagnosis and in planning and monitoring treatment. Received: 12 February 1996 Accepted: 2 March 1996     

Lesion discrimination in optic neuritis using high-resolution fat-suppressed fast spin-echo MRI

Fast spin-echo (FSE) is a new sequence with acquisition times currently down to one-sixteenth of those obtained with conventional spin-echo sequences, which allows high-resolution (512×512 matrix) images to be acquired in an acceptable time. We compared the higher resolution of FSE with the medium resolution of a short inversion-time inversion-recovery (STIR) sequence in depicting the optic nerves of healthy controls and patients with optic neuritis. Optic nerve MRI examinations were performed in 18 patients with optic neuritis and 10 normal controls. Two sequences were obtained coronally: fat-suppressed FSE (FSE TR 3250 ms/TEef 68 ms, echo-train length 16, 4 excitations, 24 cm rectangular field of view, 3 mm interleaved contiguous slices, in-plane resolution 0.5×0.5 mm) and STIR (TR 2000 ms/TE 50 ms/TI 175 ms, inplane resolution 0.8×0.8 mm, slice thickness 5 mm). FSE demonstrated much more anatomical detail than STIR, e. g. distinction of optic nerve and sheath. Lesions were seen in 20 of 21 symptomatic nerves using FSE and in 18 of 21 using STIR. Nerve swelling or partial cross-sectional lesions of the optic nerve were each seen only on FSE in 3 cases. Fatsuppressed FSE imaging of the optic nerve improves anatomical definition and increases lesion detection in optic neuritis.     

颅脑外伤后视神经蛛网膜下腔扩张与颅内压增高的MRI相关性研究

目的:探讨颅脑外伤患者眶内段视神经蛛网膜下腔扩张与颅内压增高的关系。方法:14例颅脑外伤并颅内压增高及蛛网膜下腔出血患者,在伤后2d内进行MRI检查,并在斜冠状位重T2加权图像上测量视神经球后4mm、10mm、16mm处蛛网膜下腔的外径,MRI检查结束后4h内进行腰穿,在施放脑脊液前测量脑脊液压力。经保守治疗6～14d,临床症状明显好转后,再重复一次MRI检查及腰穿脑脊液压力测定,对所得数据进行统计分析。结果:14例颅脑外伤并急性颅内压增高患者,首次检查脑脊液压力为2.31±0.24kPa,视神经眶内段前、中、后各测量点蛛网膜下腔的外径(左右侧平均值)分别为6.5±0.5mm、5.5±0.5mm、4.9±0.5mm,由前向后逐渐变窄(P<0.01)。经保守治疗好转后,脑脊液压力降低为1.75±0.21kPa,此时各测量点蛛网膜下腔外径分别为4.2±1.0mm、3.6±0.9mm、3.2±0.7mm,较首次检查明显变窄(P<0.01)。前、中、后各测量点的蛛网膜下腔的外径与脑脊液压力的相关系数分别为0.864、0.858、0.837(P<0.01)。结论:眶内段视神经蛛网膜下腔扩张程度与颅内压呈显著的正相关关系,可作为临床评价颅脑损伤患者颅内压增高程度的定量指标。     

眼眶磁共振成像技术的研究

目的探讨眼眶磁共振扫描成像技术。方法采用GE1.5TsignaEchospeed或GE1.5TsignaTwinspeed,对30例患者做眼眶磁共振成像(MagneticResonanceImaging)。脉冲序列:SET1加权(weightedImagingWI),FSET2加权(weightedImagingWI),T2WI采用脂肪抑制技术或SET1flair,FRFSET2WIT2WI采用脂肪抑制技术。扫描方位:横轴位(Axial)、冠状位(Coronal)、矢状斜位(ObliqueSagittal)和横轴俯卧位(prone)等。扫描参数:Fov18cm×18cm,SET1WI:TR440msTE11ms,FSET2WI:TR3000msTE98ms或T1flair:TR2143ms,TE11ms,TI750ms,FRFSET2WI:TR3500msTE80ms,矩阵256×256,接收带宽15.63MHz,平均激励次数4次,层厚3～4mm,无间隔。增强对比剂用GdDTPA0.1mmolkg。结果横轴位可清晰显示视神经全长及眼内外直肌及与病变的关系。冠状位在同一层面可清晰显示视神经、眼内外直肌、眼上下直肌的断面及与病变的关系。矢状斜位可清晰显示视神经全长、眼上下直肌及与病变的关系。结论磁共振扫描参数的优化组合和选择正确的扫描方位,及T2WI脂肪抑制技术等的应用更有助于显示正常眼眶解剖结构及眼眶病变的定位和诊断。     

Fast and quantitative high-resolution magnetic resonance imaging of the optic nerve at 3.0 tesla

A novel and fast magnetic resonance imaging approach for imaging the optic nerve and the surrounding cerebrospinal fluid sheath is presented. The method provides high contrast between the nerve and cerebrospinal fluid and allows for accurate quantification of the optic nerve and its cerebrospinal fluid sheath diameter within 1.5 seconds scan time. Results of a volunteer study illustrate that measurements can reliably be performed even in the distal part of the intraorbital optic nerve track. Accuracy of quantification of the new technique is demonstrated by the assessment of changes in the optic nerve and CSF sheath diameter between straight gaze and 30 degrees abduction.     

Tuberculous infection of the wrist: MRI features

OBJECTIVE: The objective of our study was to define the MRI features of tuberculous infection of the wrist. MATERIALS AND METHODS: We present the MRI findings of eight patients with tuberculous infection of the wrist. Spin-echo T1-weighted, gradient-echo T2(*)-weighted, and fast spin-echo T2-weighted sequences were performed for all patients. Gadolinium-enhanced MR images were obtained in seven patients. All images were evaluated for the characteristics of tuberculous infection of the wrist, including the presence of synovial thickening around the joints and tendons, signal intensity of the thickened tenosynovium and synovium on the T2-weighted images, synovial fluid collection in the tendon sheath, small low-signal and nonenhanced foci in the synovial fluid, bone erosion, osteomyelitis, and encasement of the median nerve. RESULTS: The tuberculous infection involved the right (n = 6) and left (n = 2) wrists. All patients had synovial thickening around the flexor and extensor tendons with synovial fluid collection in the tendon sheath. The thickened tenosynovium and synovium revealed low signal intensity on T1-weighted images, intermediate to low signal intensity on T2- and T2(*)-weighted images, and enhancement on contrast-enhanced MR images. The synovial fluid showed intermediate to low signal on T1-weighted images and homogeneous or heterogeneous high signal intensity on T2- and T2(*)-weighted images. Multiple small foci of low signal intensity and nonenhancement scattered in the synovial fluid were present in seven patients. Bone erosion occurred in seven patients, osteomyelitis was seen in six patients, and encasement of the median nerve was found in three patients. CONCLUSION: Characteristic MRI findings of tuberculous infection of the wrist include synovial thickening around the flexor and extensor tendons and synovial fluid collection that contains small low-signal and nonenhanced foci in the tendon sheath. Bone erosion, osteomyelitis, and median nerve encasement are also frequently present. These characteristic manifestations are helpful in diagnosing this disease entity.     

Can preoperative MR imaging predict optic nerve invasion of retinoblastoma?

Purpose

To evaluate the accuracy of pre-operative MRI for the detection of optic nerve invasion in retinoblastoma.

Materials and methods

Institutional review board approval and informed consent were waived for this retrospective study. A total of 41 patients were included. Inclusion criteria were histologically proven retinoblastoma, availability of diagnostic-quality preoperative MR images acquired during the 4 weeks before surgery, unilateral retinoblastoma, and normal-sized optic nerve. Two radiologists retrospectively reviewed the MR images independently. Five imaging findings (diffuse mild optic nerve enhancement, focal strong optic nerve enhancement, optic sheath enhancement, tumor location, and tumor size) were evaluated against optic nerve invasion of retinoblastoma. The predictive performance of all MR imaging findings for optic nerve invasion was also evaluated by the receiver operating characteristic curve analysis.

Results

Optic nerve invasion was histopathologically confirmed in 24% of study population (10/41). The differences in diffuse mild enhancement, focal strong enhancement, optic sheath enhancement, and tumor location between patients with optic nerve invasion and patients without optic nerve invasion were not significant. Tumor sizes were 16.1 mm (SD: 2.2 mm) and 14.9 mm (SD: 3.6 mm) in patients with and without optic nerve involvement, respectively (P = 0.444). P-Values from binary logistic regression indicated that all five imaging findings were not significant predictors of tumor invasion of optic nerve. The AUC values of all MR imaging findings for the prediction of optic nerve invasion were 0.689 (95% confidence interval: 0.499–0.879) and 0.653 (95% confidence interval: 0.445–0.861) for observer 1 and observer 2, respectively.

Conclusion

Findings of MRI in patients with normal-sized optic nerves have limited usefulness in preoperatively predicting the presence of optic nerve invasion in retinoblastoma.     

Meta-Analysis of CSF Diversion Procedures and Dural Venous Sinus Stenting in the Setting of Medically Refractory Idiopathic Intracranial Hypertension

BACKGROUND AND PURPOSE:In medically refractory idiopathic intracranial hypertension, optic nerve sheath fenestration or CSF shunting is considered the next line of management. Venous sinus stenosis has been increasingly recognized as a treatable cause of elevated intracranial pressure in a subset of patients. In this article, we present the results of the largest meta-analysis of optic nerve sheath fenestration, CSF shunting, and dural venous sinus stenting. This is the only article that compares these procedures, to our knowledge.MATERIALS AND METHODS:We performed a PubMed search of all peer-reviewed articles from 1988 to 2014 for patients who underwent a procedure for medically refractory idiopathic intracranial hypertension.RESULTS:Optic nerve sheath fenestration analysis included 712 patients. Postprocedure, there was improvement of vision in 59%, headache in 44%, and papilledema in 80%; 14.8% of patients required a repeat procedure with major and minor complication rates of 1.5% and 16.4%, respectively. The CSF diversion procedure analysis included 435 patients. Postprocedure, there was improvement of vision in 54%, headache in 80%, and papilledema in 70%; 43% of patients required at least 1 additional surgery. The major and minor complication rates were 7.6% and 32.9%, respectively. The dural venous sinus stenting analysis included 136 patients. After intervention, there was improvement of vision in 78%, headache in 83%, and papilledema in 97% of patients. The major and minor complication rates were 2.9% and 4.4%, respectively. Fourteen additional procedures were performed with a repeat procedure rate of 10.3%. Three patients had contralateral stent placement, while 8 had ipsilateral stent placement within or adjacent to the original stent. Only 3 patients required conversion to CSF diversion or 2.2% of patients with stents.CONCLUSIONS:Patients with medically refractory idiopathic intracranial hypertension have traditionally undergone a CSF diversion procedure as the first intervention. This paradigm may need to be re-examined, given the high technical and clinical success and low complication rates with dural venous sinus stenting.

Idiopathic intracranial hypertension (IIH), previously referred to as pseudotumor cerebri and benign intracranial hypertension, is a syndrome defined by elevated intracranial hypertension without radiographic evidence of a mass lesion in the brain.¹ The overall prevalence of IIH in North America has been estimated to be 0.9–1.07/100,000^2,3; however, in women with obesity between 20 and 44 years of age, the prevalence rises to 15–19/100,000.²Although headache is the most common presenting symptom, seen in 92%–94% of patients,^4,5 IIH also represents a significant cause of chronic headaches. In some patients, there may be vision changes,^6–9 which, if not corrected, may progress to permanent visual loss.^10,11The standard medical treatment includes weight loss, acetazolamide, diuretics, and repeat high-volume lumbar punctures. In patients with medically refractory IIH or progressive visual loss, a CSF-diversion procedure (lumboperitoneal shunt, ventriculoperitoneal shunts, or optic nerve sheath fenestration) is considered the next line of management.^9,12CSF diversion procedures in the setting of medically refractory IIH have been described in the literature dating back to 1955, by Jackson and Snodgrass.^13,14 These studies are level 3 evidence, comprising case series and individual case reports. There are no prospective randomized controlled studies on lumboperitoneal shunt, ventriculoperitoneal shunts, or optic nerve sheath fenestration, to our knowledge.Venous sinus stenosis has been increasingly recognized as a treatable cause of elevated intracranial pressure. Venous sinus stent placement was first described by Higgins et al.¹⁵ During the past 20 years, an increasing number of case reports and larger case series have described dural venous sinus stent placement, and reported high rates of technical success and favorable clinical outcomes.^6,7,16–21In this article, we present the results of the largest meta-analysis of optic nerve sheath fenestration, CSF diversion procedure, and venous sinus stent placement for medically refractory IIH from 1988 to present. We then compare these interventions with a focus on symptom improvement, complications, and the need for repeat procedures.     

CT evaluation of perineural orbital lesions: evaluation of the "tram-track" sign

Cranial computed tomographic scans of 225 patients with orbital mass lesions were reviewed. In 11 patients, the optic nerve was seen as a linear defect through the orbital mass. These 11 cases comprised three optic nerve sheath meningiomas, three hemangiomas, two cases of pseudotumor, and one case each of Erdheim-Chester disease, optic neuritis, and metastatic disease. Optic nerve sheath meningiomas could be further differentiated from the other mass lesions by showing the entire length of the optic nerve through the lesion, smooth margins, a fusiform shape, and parallel enhancement of the periphery of the optic nerve even greater than that of the surrounding mass. These features may aid in differentiating optic nerve sheath meningiomas from other mass lesions in the orbit.     

脑脊液鼻漏的CT及MRI的检查技术和表现

目的 探讨联合冠状薄层CT及磁共振3D重T2水成像在评价脑脊液鼻漏的价值.方法收集临床确诊自发性脑脊液鼻漏的病人4例.男2例,女2例.所有病人均行CT检查,采集层厚0.625 mm,采用骨算法、无间隔采集.4例行MRI检查前颅凹底冠状薄层 3D FSE 重T2WI,TR/TE 5000 ms/119 ms.结果 4例自发性脑脊液鼻漏病人均行手术修补治疗.CT显示骨质缺损,MRI显示颅腔内脑脊液直接与鼻腔相通,其中1例MRI还显示垂体膨出至蝶窦.结论对自发性脑脊液鼻漏,CT可显示有无骨质缺损或骨折线,MRI可清晰显示漏口的位置.     

"Papilledema": neuroradiologic evaluation of optic disk protrusion with dynamic orbital CT

Current-generation CT scanners enable the visualization in vivo of structures and substructures that were previously unobservable. Certainly the orbit and optic nerve/sheath complex have demonstrated a great number of pathologic and normal anatomic variations. It has been found in patients with elevated intracranial pressure that what was previously thought to be simple papilledema in fact masks a surprisingly large component of optic papilla protrusion. There may be a variable amount of increased intercellular/axonal fluid within the optic disk in patients with increased intracranial pressure; however, a significant factor in the "swollen disk" is the simple transmission of pressure along the optic nerve sheath to the papilla, causing it to bulge. Further investigations with dynamic CT reveal that there is decreased perfusion of the optic disk in the active phase of severe increased intracranial pressure in patients with papilledema and/or protrusion as compared with normal control subjects. This depressed flow pattern seems to originate subacutely and appears to resolve in certain patients after normalization of the elevated pressure. These findings apparently indicate that clinical intervention in cases of intracranial hypertension to restore the hemodynamic status of the optic disk would be timely, and thereby avert irreversible damage. This suggests and supports the theory that increased intracranial pressure may lead to rapid vision loss by the mechanical mechanism of pressure projected directly to the junction of the optic nerve and optic nerve head, leading to decreased perfusion, ischemia, axonal flow stasis, and resultant optic nerve atrophy.     

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.     

Serial magnetic resonance imaging of the donor site after harvesting the central third of the patellar tendon A prospective study of 37 patients after arthroscopic anterior cruciate ligament reconstruction

The aim of this prospective study was to follow the development of repair tissue in the donor-site area using serial magnetic resonance imaging (MRI) evaluation and to assess whether the MRI findings were correlated with donor-site morbidity. Thirty-seven consecutive patients with unilateral anterior cruciate ligament injuries undergoing elective reconstruction of the ligament were included in the study. They were aged 27 (range 14–50) years. The graft was harvested through two 25-mm vertical incisions with the aim of protecting the infrapatellar nerve and sparing the paratenon. The tendon defect was left open. The patients underwent MRI evaluation at 6 weeks, 6 months and 27 months postoperatively. A final clinical follow-up was made 25 (range 23–29) months postoperatively. MRI demonstrated that the donor-site gap, i.e. the area corresponding to a pathological non-tendinous-like tissue signal, was 9 (range 4–18) mm at 6 weeks, 5 (range 2–14) mm at 6 months and 2 (range 0–5) mm at 27 months. The size of the donor-site gap had significantly decreased at 6 months compared with 6 weeks (P = 0.0001), as well as at 27 months compared with 6 months (P = 0.0001). We conclude that the patellar tendon at the donor site healed gradually, as expressed by a decrease in the area of non-tendinous-like tissue signal on the serial MRI evaluations. Received: 3 March 1998 Accepted: 28 May 1998     

Orbital and optic pathway sarcoidosis: MR findings.

PURPOSETo identify and characterize the MR findings of sarcoidosis when it involves the orbit and visual pathways.METHODSThe MR scans of 15 patients, 3 with presumed and 12 with proved orbital or optic pathway sarcoidosis were retrospectively reviewed.RESULTSEight patients had MR evidence of optic nerve involvement by sarcoid granuloma. Perineural enhancement was seen in four cases, optic atrophy in one. Three who had had unenhanced scans showed optic nerve enlargement. Nine patients had optic chiasmal involvement. One patient had increased T2 signal in the optic radiations. Three patients had orbital masses that had MR signal characteristics similar to pseudotumor. Five patients had periventricular white matter abnormalities closely resembling multiple sclerosis.CONCLUSIONSSarcoidosis should be considered in the differential diagnosis of optic nerve or nerve sheath enhancement on MR. Orbital sarcoidosis has MR characteristics very similar to pseudotumor.     

MRI of the intraorbital optic nerve in patients with autosomal dominant optic atrophy

Measurements of the intraorbital optic nerve were made using high-resolution coronal MRI in 10 adults with autosomal dominant optic atrophy. Comparisons were made with previous studies of 10 normal adult subjects. The cross-sectional diameters of the optic nerve and the perineural subarachnoid space were measured and a ratio of there diameters at anterior, mid and posterior positions along the optic nerve was determined. We found a statistically significant difference in the mean optic nerve: sheath ratio between the control group and patients with autosomal dominant optic atrophy. At anterior, mid and posterior locations along the optic nerve it is significantly smaller in patients with optic atrophy. We have demonstrated that the loss of ganglion cells, previously documented in dominant optic atrophy, is associated with a significant loss of optic nerve tissue and thinning of the nerve along its length. Received: 6 July 1999/Accepted: 22 July 1999     

眶颅沟通性病变的CT和MRI研究

目的 研究、探讨眶颅沟通性病变的沟通路径、CT和MRI表现及其影像学特征。方法 51例患者,男28例,女23例,年龄2－68岁,平均41岁,为手术病理和随访结果证实。51例均行 CT扫描,45例行MR扫描,CT和MR增强扫描各44例。结果 通过眶上裂或视神经管沟通的颅眶沟通笥病变31例,占60.8％。其中9例通过视神经管沟通,包括4例视神经和视交叉胶质瘤、3例视神经鞘脑膜瘤,以及2例视网膜母细胞瘤侵犯视神经和视交叉;通过眶上裂沟通者,包括5例脑膜瘤、4例神经源性肿瘤、2例Tolosa-Hunt综合征、3例炎性假瘤、1例眼眶和海绵窦皮样囊肿,以及7例鼻咽癌同时侵犯海绵窦和眼眶,通过眶骨穿支血管间隙沟通的病变或骨质破坏缺损区沟通的眶颅沟通性病变20例,占39.2％,包括5例眶骨扁平性脑膜瘤、10例眶壁转移瘤、1例眶壁软骨肉瘤侵犯筛窦、额窦和额叶、3例泪腺囊腺癌侵犯颅内和1例额底脑膜瘤侵犯眼眶。结论 CT和MRI,尤其是使用脂肪抑制技术和增强扫描的T1WI能明确显示眶颅沟通性病变的沟通路径和病变特征,为制订治疗方案和手术入路提供重要和直接的依据。     

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.