The optic nerve sheath on MRI in acute optic neuritis

Detecting optic nerve lesions in multiple sclerosis patients with a 1,5 T MRI: Evaluation of a 3D DIR sequence compared to a 2D STIR sequence

OBJECTIVES

Optic neuritis is a common clinical presentation in patients suffering from multiple sclerosis (MS). Even though optic neuritis is not part of the MS diagnostic criteria, the diagnosis and consideration of differential diagnoses are important in clinical routine. For the evaluation of the optic nerves with MRI, T2-weighted images with fat suppression, known as short tau inversion recovery sequences (STIR), are often used. Besides that, double inversion recovery (DIR) sequences are being used increasingly in MS patients, especially to determine cortical lesions. The Aim of this study was to evaluate the 3D-DIR for the detection of lesions in the optic nerves in MS patients.

METHODS

MR examinations of 45 MS-patients containing both STIR and DIR images were independently assessed by two neuroradiologic experienced radiologists, blinded to clinical data. A third neuroradiologic, an experienced radiologist, evaluated the images together, also considering clinical data. These results were considered ground truth and statistically compared to the results of the single readings. To objectify our findings, ROI measurements of affected and unaffected optic nerve segments were made, and a contrast ratio (CR) was calculated.

RESULT

DIR images are statistically equivalent to STIR images concerning the detection of lesions in the optic nerve (p < 0.001). The sensitivity of DIR images (84.7 %) and STIR images (77 %), as well as the specificity (92.2 % and 91.2 %), are comparable. The interrater reliability was substantial for both sequences (κ = 0,73) as well as separated for the STIR images (κ = 0.744) and the DIR images (κ = 0.707). The objective analysis revealed significantly higher CRs in DIR images (p < 0.001).

CONCLUSION

3D DIR images showed similar sensitivity and specificity for detecting optic nerve lesions in comparison to dedicated 2D images of the optic nerve. When 3D DIR images are part of the routine scan protocol for evaluating MS patients, additional 2D imaging of the optic nerve is no longer necessary.

Suspected intracranial hypertension in COVID-19 patients with severe respiratory failure

BACKGROUND

COVID-19 patients may exhibit neurological symptoms due to direct viral damage, systemic inflammatory syndrome, or treatment side effects. Mechanical ventilation in patients with severe respiratory failure often requires sedation and neuromuscular blockade, hindering thorough clinical examinations. This study aimed to investigate neurological involvement through clinical and noninvasive techniques and to detect signs of intracranial hypertension in these patients.

METHOD

We conducted a prospective observational study on mechanically ventilated COVID-19 adult patients admitted to our ICU, following standard of care protocols for ventilation and permissive hypercapnia. Data were collected at three time points: admission day (T1), day seven (T7), and day fourteen (T14). At each time point, patients underwent multimodal noninvasive neurological monitoring, including clinical examination, pupillary reactivity, transcranial color doppler of the middle cerebral artery (MCA), and optic nerve sheath diameter (ONSD) assessed via ultrasound (US). Head computer tomography (CT) was performed at T1 and T14. A limited subset of patients had a follow-up examination six months after ICU discharge.

RESULTS

Seventy-nine patients were recruited; most were under deep sedation and neuromuscular blockade at T1. Pupillary size, symmetry, and reactivity were normal, as was the MCA mean velocity. However, ONSD, assessed by both US and CT, appeared enlarged, suggesting raised intracranial pressure (ICP). In a subgroup of 12 patients, increased minute ventilation was associated with a significant decrease in US-ONSD, corresponding to a drop in paCO2. At follow-up, twelve patients showed no long-term neurological sequelae, and US-ONSD was decreased in all of them.

DISCUSSION AND CONCLUSIONS

In this cohort, enlarged ONSD was detected during non-invasive neurological monitoring, suggesting a raised ICP, with hypercapnia playing a prominent role. Further studies are needed to explore ONSD behavior in other samples of mechanically ventilated, hypercapnic patients.

Comparison between contrast-enhanced fat-suppressed 3D FLAIR brain MR images and T2-weighted orbital MR images at 3 Tesla for the diagnosis of acute optic neuritis

PURPOSE

The purpose of this study was to compare the capabilities of contrast-enhanced fat-suppressed (CE FS) three-dimensional fluid-attenuated inversion recovery (3D FLAIR) brain magnetic resonance imaging (MRI) with those of coronal T2-weighted orbital MRI obtained at 3 Tesla for the diagnosis of optic neuritis (ON).

MATERIALS AND METHODS

Patients who presented to our center with acute visual loss and underwent MRI examination of the orbits and the brain between November 2014 and February 2020 were retrospectively included. Three radiologists independently and blindly analyzed CE FS 3D FLAIR and coronal T2-weighted images. Disagreements in image interpretation were resolved by consensus with an independent neuroradiologist who was not involved in the initial reading sessions. The primary adjudication criterion for the diagnosis of ON was the presence of an optic nerve hypersignal. Sensitivity, specificity, and accuracy of CE 3D FLAIR brain images were compared with those of coronal T2-weighted orbital images using McNemar test. Artifacts were classified into three categories and compared between the two image sets.

RESULTS

A total of 1023 patients were included. There were 638 women and 385 men with a mean age of 42 ± 18.3 (standard deviation) years (age range: 6-92 years). Optic nerve hyperintensities were identified in 375/400 (94%) patients with ON using both 3D FLAIR and coronal T2-weighted images. Sensitivity, specificity, and accuracy of both sequences were 94% (95% CI: 91.3-96.1), 79% (95% CI: 75.5-82.2), and 89% (95% CI: 86.8-90.7), respectively. Optic disc hypersignal was detected in 120/400 patients (30%) using 3D FLAIR compared to 3/400 (0.75%) using coronal T2-weighted images (P < 0.001). Optic radiation hypersignal was observed in 2/400 (0.5%) patients using 3D FLAIR images. Significantly more artifacts (moderate or severe) were observed on coronal T2-weighted images (801/1023; 78%) by comparison with 3D FLAIR images (448/1023; 44%) (P < 0.001).

CONCLUSION

The performance of 3D FLAIR brain MRI for the diagnosis of ON is not different from that of coronal T2-weighted orbital MRI and its use for optic nerve analysis may be beneficial.

Characteristics of Optic Neuritis in South Korean Children and Adolescents: A Retrospective Multicenter Study

Purpose

To analyze the clinical characteristics and prognosis of optic neuritis (ON) in pediatric patients aged <19 years in South Korea.

Methods

This multicenter retrospective cohort study included 127 pediatric patients (median age: 10.3 (IQR: 7.3–14.2) years; female, 62.2%) who experienced ON for the first time between January 2004 and January 2018, with data obtained from five tertiary university-based hospitals in Korea. When ON was bilateral, the worse eye was selected for analysis. The baseline clinical characteristics and prognoses of patients, as well as the associations between these parameters, were analyzed.

Results

The baseline clinical characteristics of the patients were as follows: best-corrected visual acuity (BCVA) < 20/200, 65.9%; pain on eye movement, 47.2%; optic disc swelling, 66.9%; and bilateral involvement, 41.7%. Among 101 patients who were followed up for ≥6 months, 48 (47.5%), 12 (11.9%), 19 (18.8%), 13 (12.9%), and 9 (8.9%) had been diagnosed with isolated ON, recurrent ON, multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), and acute disseminated encephalomyelitis (ADEM)-related ON, respectively. At the latest visit, 81.9% and 71.1% had achieved BCVA of ≥20/40 and ≥ 20/25, respectively. Only disc swelling at presentation was associated with poor baseline BCVA (coefficient: 0.31, P=0.004) and greater improvement in BCVA (coefficient: 0.49, P = 0.001P=0.001); there were no significant associations between the baseline factors and final BCVA.

Conclusions

This study demonstrated pediatric ON-related clinical characteristics and visual outcomes in South Korea. Within this cohort, in about 40.6% of patients, ON was associated with other demyelinating diseases, namely, MS, NMOSD, and ADEM.

Improved detection of multiple sclerosis lesions with T2-prepared double inversion recovery at 3T

BACKGROUND AND PURPOSE

Double inversion recovery (DIR) imaging is used in multiple sclerosis (MS) clinical protocols to improve the detection of cortical and juxtacortical gray matter lesions by nulling confounding signals originating from the cerebrospinal fluid and white matter. Achieving a high isotropic spatial resolution, to depict the neocortex and its typically small lesions, is challenged by the reduced signal-to-noise ratio (SNR) determined by multiple tissue signal nulling. Here, we evaluate both conventional and optimized DIR implementations to improve tissue contrast (TC), SNR, and MS lesion conspicuity.

METHODS

DIR images were obtained from MS patients and healthy controls using both conventional and prototype implementations featuring a T2-preparation module (T2P), to improve SNR and TC, as well as an image reconstruction routine with iterative denoising (ID). We obtained quantitative measures of SNR and TC, and evaluated the visibility of MS cortical, cervical cord, and optic nerve lesions in the different DIR images.

RESULTS

DIR implementations adopting T2P and ID enabled improving the SNR and TC of conventional DIR. In MS patients, 34% of cortical, optic nerve, and cervical cord lesions were visible only in DIR images acquired with T2P, and not in conventional DIR images. In the studied cases, image reconstruction with ID did not improve lesion conspicuity.

CONCLUSIONS

DIR with T2P should be preferred to conventional DIR imaging in protocols studying MS patients, as it improves SNR and TC and determines an improvement in cortical, optic nerve, and cervical cord lesion conspicuity.

Can Optic Nerve Sheath Images on a Thin-Slice Brain Computed Tomography Reconstruction Predict the Neurological Outcomes in Cardiac Arrest Survivors?

We analyzed the prognostic performance of optic nerve sheath diameter (ONSD) on thin-slice (0.6 mm) brain computed tomography (CT) reconstruction images as compared to routine-slice (4 mm) images. We conducted a retrospective analysis of brain CT images taken within 2 h after cardiac arrest. The maximal ONSD (mONSD) and optic nerve sheath area (ONSA) were measured on thin-slice images, and the routine ONSD (rONSD) and gray-to-white matter ratio (GWR) were measured on routine-slice images. We analyzed their area under the receiver operator characteristic curve (AUC) and the cutoff values for predicting a poor 6-month neurological outcome (a cerebral performance category score of 3–5). Of the 159 patients analyzed, 113 patients had a poor outcome. There was no significant difference in rONSD between the outcome groups (p = 0.116). Compared to rONSD, mONSD (AUC 0.62, 95% CI: 0.54–0.70) and the ONSA (AUC 0.63, 95% CI: 0.55–0.70) showed better prognostic performance and had higher sensitivities to determine a poor outcome (mONSD, 20.4% [95% CI, 13.4–29.0]; ONSA, 16.8% [95% CI, 10.4–25.0]; rONSD, 7.1% [95% CI, 3.1–13.5]), with specificity of 95.7% (95% CI, 85.2–99.5). A combined cutoff value obtained by both the mONSD and GWR improved the sensitivity (31.0% [95% CI, 22.6–40.4]) of determining a poor outcome, while maintaining a high specificity. In conclusion, rONSD was clinically irrelevant, but the mONSD had an increased sensitivity in cutoff having acceptable specificity. Combination of the mONSD and GWR had an improved prognostic performance in these patients.

The diagnostic value of the IDEAL-T2WI sequence in dysthyroid optic neuropathy: a quantitative analysis of the optic nerve and cerebrospinal fluid in the optic nerve sheath

OBJECTIVES

To evaluate the optic nerve and CSF in the optic nerve sheath as imaging markers of dysthyroid optic neuropathy (DON).

METHODS

In this single-centre retrospective study, orbital images of 30 consecutive participants (54 orbits) with DON, 30 patients (60 orbits) with thyroid-associated ophthalmopathy (TAO) without DON, and 19 healthy controls (HCs; 38 orbits) were analysed. The diameter and cross-sectional area of the optic nerve and its sheath, water fraction of the optic nerve, and volume of the fluid in the optic nerve sheath were measured and compared. The associations between MR parameters and clinical measures were assessed using correlation analysis.

RESULTS

The diameter and water fraction of the optic nerve (3 mm and 6 mm behind the eyeball), optic nerve subarachnoid space (ONSS) (3 mm and 6 mm behind the eyeball), and subarachnoid fluid volume in the optic nerve sheath were significantly greater in the DON group than in the TAO group (p < 0.01) or HC group (p < 0.01). ROC analysis showed that ONSS 3 mm behind the eyeball (ONSS3) was a robust predictor of DON (AUC = 0.957, sensitivity = 0.907, specificity = 0.9). Water fraction of the optic nerve 3 mm behind the eyeball (water fraction3) had the best specificity (0.967). Water fraction3, fluid volume in the optic nerve sheath, and optic nerve diameter (3 mm behind the eyeball) were correlated with clinical measures (i.e. clinical activity score, mean defect, and pattern standard deviation).

CONCLUSIONS

Increased water fraction of the optic nerve and ONSS3 are promising and easily accessible radiological markers for diagnosing DON.

KEY POINTS

• The water fraction of the optic nerve and optic nerve subarachnoid space (ONSS) are greater in patients with dysthyroid optic neuropathy (DON) than in patients with thyroid-associated ophthalmopathy (TAO) without DON. • The optic nerve and the cerebrospinal fluid in the optic nerve sheath measures are associated with visual dysfunction. • The water fraction of the optic nerve and ONSS may be promising imaging markers for diagnosing DON.

Incorporating non-linear alignment and multi-compartmental modeling for improved human optic nerve diffusion imaging

In vivo human optic nerve diffusion magnetic resonance imaging (dMRI) is technically challenging with two outstanding issues not yet well addressed: (i) non-linear optic nerve movement, independent of head motion, and (ii) effect from partial-volumed cerebrospinal fluid or interstitial fluid such as in edema. In this work, we developed a non-linear optic nerve registration algorithm for improved volume alignment in axial high resolution optic nerve dMRI. During eyes-closed dMRI data acquisition, optic nerve dMRI measurements by diffusion tensor imaging (DTI) with and without free water elimination (FWE), and by diffusion basis spectrum imaging (DBSI), as well as optic nerve motion, were characterized in healthy adults at various locations along the posterior-to-anterior dimension. Optic nerve DTI results showed consistent trends in microstructural parametric measurements along the posterior-to-anterior direction of the entire intraorbital optic nerve, while the anterior portion of the intraorbital optic nerve exhibited the largest spatial displacement. Multi-compartmental dMRI modeling, such as DTI with FWE or DBSI, was less subject to spatially dependent biases in diffusivity and anisotropy measurements in the optic nerve which corresponded to similar spatial distributions of the estimated fraction of isotropic diffusion components. DBSI results derived from our clinically feasible (∼10 min) optic nerve dMRI protocol in this study are consistent with those from small animal studies, which provides the basis for evaluating the utility of multi-compartmental dMRI modeling in characterizing coexisting pathophysiology in human optic neuropathies.

Primary optic neuropathy in Behçet’s syndrome

Background:

Primary optic neuropathy in Behçet’s syndrome (PONBS) is limited to a few case reports.

Objective:

To investigate the clinical features, magnetic resonance imaging (MRI) changes, and visual prognosis of PONBS.

Methods:

Sixty-one patients who presented with first onset of optic neuritis and fulfilled the International Criteria for Behçet’s Disease (ICBD) were evaluated.

Results:

The female-to-male ratio was 1.7:1. No patient had other central nervous system (CNS) disease. In 67 eyes with optic nerve abnormalities on MRI scan, perineural enhancement around the orbital optic nerve (46 eyes, 68.7%) was significantly more frequent than was increased signal in the optic nerve itself (31 eyes, 46.3%; p = 0.000), typically with sunflower-like appearance on coronal view (33 eyes, 71.7%). Two patients (3.6%) relapsed during follow-up (median 12 months). Kaplan–Meier survival analysis estimated the cumulative risk of severe visual loss (⩽0.1) at 24 months was 14.7% in females versus 62.5% in males (hazard ratio (HR), 0.16; 95% confidence interval, 0.05–0.54).

Conclusion:

PONBS frequently presents with isolated optic neuropathy in females. The sunflower-like sign might be a distinctive MRI feature. Short-term recurrence is very rare. Males have a higher cumulative risk of severe visual loss.

Contrast-enhanced fat-suppressed FLAIR for the characterization of leptomeningeal inflammation in optic neuritis

BACKGROUND

Leptomeningeal contrast enhancement on fluid-attenuated inversion recovery (FLAIR) images has been reported in patients with multiple sclerosis and interpreted as a biomarker of inflammation. In this study, we sought to evaluate this phenomenon in patients with optic neuritis (ON).

METHODS

A total of 42 patients with suspected ON were included in this prospective study and underwent a dedicated study magnetic resonance imaging (MRI) protocol including native and contrast-enhanced fat-suppressed thin-section axial and coronal FLAIR images on an 1.5 T magnetic resonance (MR) system.

RESULTS

After diagnostic workup, 34 patients with final diagnosis of ON were analyzed in detail. On contrast-enhanced fat-suppressed FLAIR images, 25 (73.5%) patients with ON demonstrated perioptic leptomeningeal enhancement, and in 3 (8.8%) patients, this was even the only pathological MRI finding. In comparison, patients with perioptic leptomeningeal enhancement on contrast-enhanced fat-suppressed FLAIR images had a higher prevalence of additional hyperintense brain lesions ( p = 0.022) as well as cerebrospinal fluid (CSF)-specific oligoclonal bands ( p = 0.013) than patients without.

CONCLUSION

Perioptic leptomeningeal contrast enhancement on fat-suppressed FLAIR images is a novel marker in ON and possibly reflects a leptomeningeal inflammatory process preceding or accompanying ON. Thin-section contrast-enhanced fat-suppressed FLAIR images might be a useful addition in MRI protocols for patients with suspected ON.

Clinical Features of Toxocara-Seropositive Optic Neuritis in Korea

Purpose: This study was undertaken to analyze the characteristics of optic neuritis in Korean patients seropositive for Toxocara. Methods: We retrospectively reviewed data from patients diagnosed with optic neuritis and followed up for at least one month between 2012 and 2016. Patients were grouped according to Toxocara serological testing outcomes (positive or negative) and clinical characteristics were compared. Results: The seropositive and seronegative groups comprised 13 and 12 patients, respectively. The seropositive patients were older (56.8 years versus 34.5 years), reported ocular pain less frequently (30.8% versus 91.7%), and showed more frequent asymmetric optic disc swelling (72.7% versus 22.2%). During follow-up, visual acuity of all seronegative patients improved to 20/40 or better, compared with 38.5% of the seropositive group. Conclusion: Atypical features such as painless, older age, or asymmetric disc swelling in optic neuritis may be related to seropositivity for Toxocara, suggesting the possibility of undiagnosed Toxocara optic neuropathy.

How Common Is Signal-Intensity Increase in Optic Nerve Segments on 3D Double Inversion Recovery Sequences in Visually Asymptomatic Patients with Multiple Sclerosis?

BACKGROUND AND PURPOSE

In postmortem studies, subclinical optic nerve demyelination is very common in patients with MS but radiologic demonstration is difficult and mainly based on STIR T2WI. Our aim was to evaluate 3D double inversion recovery MR imaging for the detection of subclinical demyelinating lesions within optic nerve segments.

MATERIALS AND METHODS

The signal intensities in 4 different optic nerve segments (ie, retrobulbar, canalicular, prechiasmatic, and chiasm) were evaluated on 3D double inversion recovery MR imaging in 95 patients with MS without visual symptoms within the past 3 years and in 50 patients without optic nerve pathology. We compared the signal intensities with those of the adjacent lateral rectus muscle. The evaluation was performed by a student group and an expert neuroradiologist. Statistical evaluation (the Cohen κ test) was performed.

RESULTS

On the 3D double inversion recovery sequence, optic nerve segments in the comparison group were all hypointense, and an isointense nerve sheath surrounded the retrobulbar nerve segment. At least 1 optic nerve segment was isointense or hyperintense in 68 patients (72%) in the group with MS on the basis of the results of the expert neuroradiologist. Student raters were able to correctly identify optic nerve hypersignal in 97%.

CONCLUSIONS

A hypersignal in at least 1 optic nerve segment on the 3D double inversion recovery sequence compared with hyposignal in optic nerve segments in the comparison group was very common in visually asymptomatic patients with MS. The signal-intensity rating of optic nerve segments could also be performed by inexperienced student readers.

Initial Pattern of Optic Nerve Enhancement in Korean Patients with Unilateral Optic Neuritis

Purpose

The purpose of this study was to demonstrate whether the pattern of optic nerve enhancement in magnetic resonance imaging (MRI) can help to differentiate between idiopathic optic neuritis (ON), neuromyelitis optica (NMO), and multiple sclerosis (MS) in unilateral ON.

Methods

An MRI of the brain and orbits was obtained in patients with acute unilateral ON. Patients with ON were divided into three groups: NMO, MS, and idiopathic ON. The length and location of the abnormal optic nerve enhancement were compared for ON eyes with and without NMO or MS. The correlation between the pattern of optic nerve enhancement and the outcome of visual function was analyzed.

Results

Of the 36 patients with ON who underwent an MRI within 2 weeks of the onset, 19 were diagnosed with idiopathic ON, 9 with NMO, and 8 with MS. Enhancement of the optic nerve occurred in 21 patients (58.3%) and was limited to the orbital segment in 12 patients. Neither the length nor the location of the optic nerve enhancement was significantly correlated with visual functions other than contrast sensitivity or the diagnosis of idiopathic ON, MS, or NMO. Patients with greater extent of optic nerve sheath enhancement and more posterior segment involvement showed higher contrast sensitivity.

Conclusions

Our data revealed that the pattern of optic nerve enhancement was not associated with diagnosis of idiopathic ON, NMO, or MS in Korean patients with unilateral ON. We believe further studies that include different ethnic groups will lead to a more definitive answer on this subject.

Optic Perineuritis

Optic perineuritis (OPN) is now defined as "a form of idiopathic orbital inflammatory disease, in which the specific target tissue is the optic nerve sheath". It may be idiopathic or may occur as part of an underlying systemic inflammatory disease. It is a rare disorder and information regarding its presentation and management is only available in case reports and small case series. This review will discuss the contribution of these recent articles to what is known about idiopathic and secondary OPN. Suggestions will also be made as to how to investigate and treat a patient presenting with OPN.

Short Term Reproducibility of a High Contrast 3-D Isotropic Optic Nerve Imaging Sequence in Healthy Controls

The optic nerve (ON) plays a crucial role in human vision transporting all visual information from the retina to the brain for higher order processing. There are many diseases that affect the ON structure such as optic neuritis, anterior ischemic optic neuropathy and multiple sclerosis. Because the ON is the sole pathway for visual information from the retina to areas of higher level processing, measures of ON damage have been shown to correlate well with visual deficits. Increased intracranial pressure has been shown to correlate with the size of the cerebrospinal fluid (CSF) surrounding the ON. These measures are generally taken at an arbitrary point along the nerve and do not account for changes along the length of the ON. We propose a high contrast and high-resolution 3-D acquired isotropic imaging sequence optimized for ON imaging. We have acquired scan-rescan data using the optimized sequence and a current standard of care protocol for 10 subjects. We show that this sequence has superior contrast-to-noise ratio to the current standard of care while achieving a factor of 11 higher resolution. We apply a previously published automatic pipeline to segment the ON and CSF sheath and measure the size of each individually. We show that these measures of ON size have lower short-term reproducibility than the population variance and the variability along the length of the nerve. We find that the proposed imaging protocol is (1) useful in detecting population differences and local changes and (2) a promising tool for investigating biomarkers related to structural changes of the ON.

Cavernous malformation of the optic chiasm: Neuro-endoscopic removal

Cavernous malformations (CMs) arising from the optic nerve and chiasm are extremely rare. In large autopsy series, CMs were estimated to range from 0.02 to 0.13% in the general population. However, with introduction of MRI, these lesions were found more often than previously thought, ranging from 0.2% to 0.4%. Only 29 cases have been reported according to our knowledge. Most patients present with drop in visual acuity and visual field. Although MRI findings of cavernous malformations have been reported, they may not be diagnostic enough. Among the 29 reported, 16 underwent total resection with good results. In some, resection was complicated by damage to the surrounding neural tissue. Surgical removal is the recommended treatment to restore or preserve vision and to eliminate the risk of future hemorrhage. However, the anatomical location and eloquence of nearby neural structures can make these lesions difficult to access and remove. CMs appear to occur in every age group (range 4 months to 84 years mean-34.6 years) ith an approximately equal male to female ratio. They typically present with chiasmal apoplexy, characterized by sudden visual loss, acute headaches, retro orbital pain, and nausea

Diffusion-weighted imaging using readout-segmented echo-planar imaging, parallel imaging, and two-dimensional navigator-based reacquisition in detecting acute optic neuritis

PURPOSE

To evaluate the accuracy of diffusion-weighted imaging (DWI) in comparison to contrast-enhanced, fat-suppressed T1 -weighted imaging (CET1WI) in detecting acute optic neuritis (ON).

MATERIALS AND METHODS

The clinical data and magnetic resonance imaging (MRI) findings of 42 patients who presented with decreased vision were retrospectively reviewed. Both 3.0T MRI DWI and CET1WI orbital imaging studies were performed. Two neuroradiologists independently evaluated the DWI and CET1WI. The sensitivity, specificity, and accuracy of the DWI and CET1WI were individually calculated using the clinical diagnosis as the reference standard. The interobserver and intraobserver reliability of DWI and CET1WI were assessed by using a weighted Cohen's kappa (κ) test; a value of P < 0.05 was set as the threshold for statistical significance.

RESULTS

Of the 42 patients, 34 patients (41 nerves) had clinically confirmed acute ON, two had ischemic optic neuropathy, and three had chronic recurrent ON. The sensitivities of DWI and CET1WI for acute ON were 82.9-82.9% and 68.3-85.4%, respectively; the specificities were 81.4-83.7% and 79.1-93.0%, respectively; and the accuracies were 82.1-83.3% and 82.1-90.0%, respectively. The interobserver kappa values were 0.596-0.643 and 0.694-0.734 for DWI and CET1WI, respectively; the intraobserver kappa values were 0.809-0.905 and 0.834-0.924 for DWI and CET1WI, respectively (each P < 0.0001).

CONCLUSION

Given that its sensitivity and specificity are similar to those of dedicated CET1WI for acute ON, DWI can play an important complementary role in detecting acute ON, especially in atypical ON cases, and can provide a quantitative modality that can be used to evaluate axonal damage in the optic nerves.

Baseline magnetic resonance imaging of the optic nerve provides limited predictive information on short-term recovery after acute optic neuritis

Background

In acute optic neuritis, magnetic resonance imaging (MRI) may help to confirm the diagnosis as well as to exclude alternative diagnoses. Yet, little is known on the value of optic nerve imaging for predicting clinical symptoms or therapeutic outcome.

Purpose

To evaluate the benefit of optic nerve MRI for predicting response to appropriate therapy and recovery of visual acuity.

Methods

Clinical data as well as visual evoked potentials (VEP) and MRI results of 104 patients, who were treated at the Department of Neurology with clinically definite optic neuritis between December 2010 and September 2012 were retrospectively reviewed including a follow up within 14 days.

Results

Both length of the Gd enhancing lesion (r = -0.38; p = 0.001) and the T2 lesion (r = -0.25; p = 0.03) of the optic nerve in acute optic neuritis showed a medium correlation with visual acuity after treatment. Although visual acuity pre-treatment was little but nonsignificantly lower if Gd enhancement of the optic nerve was detected via orbital MRI, improvement of visual acuity after adequate therapy was significantly better (0.40 vs. 0.24; p = 0.04). Intraorbitally located Gd enhancing lesions were associated with worse visual improvement compared to canalicular, intracranial and chiasmal lesions (0.35 vs. 0.54; p = 0.02).

Conclusion

Orbital MRI is a broadly available, valuable tool for predicting the improvement of visual function. While the accurate individual prediction of long-term outcomes after appropriate therapy still remains difficult, lesion length of Gd enhancement and T2 lesion contribute to its prediction and a better short-term visual outcome may be associated with detection and localization of Gd enhancement along the optic nerve.

Improved diffusion tensor imaging of the optic nerve using multishot two-dimensional navigated acquisitions

PURPOSE

A diffusion-weighted multishot echo-planar imaging approach combined with SENSE and a two-dimensional (2D) navigated motion correction was investigated as an alternative to conventional single-shot counterpart to obtain optic nerve images at higher spatial resolution with reduced artifacts.

METHODS

Fifteen healthy subjects were enrolled in the study. Six of these subjects underwent a repeated acquisition at least 2 weeks after the initial scan session to address reproducibility. Both single-shot and multishot diffusion tensor imaging studies of the human optic nerve were performed with matched scan time. Effect of subject motions were corrected using 2D phase navigator during multishot image reconstruction. Tensor-derived indices from proposed multishot were compared against conventional single-shot approach. Image resolution difference, right-left optic nerve asymmetry, and test-retest reproducibility were also assessed.

RESULTS

In vivo results of acquired multishot images and quantitative maps of diffusion properties of the optic nerve showed significantly reduced image artifacts (e.g., distortions and blurring), and the derived diffusion indices were comparable to those from other studies. Single-shot scans presented larger variability between right and left optic nerves than multishot scans. Multishot scans also presented smaller variations across scans at different time points when compared with single-shot counterparts.

CONCLUSION

The multishot technique has considerable potential for providing improved information on optic nerve pathology and may also be translated to higher fields.

Transorbital sonography in acute optic neuritis: a case-control study

BACKGROUND AND PURPOSE

Acute unilateral optic neuritis is associated with a thickening of the retrobulbar portion of the optic nerve as revealed by transorbital sonography, but no comparison has been made between nerve sheath diameter and optic nerve diameter in patients with acute optic neuritis versus healthy controls. We evaluated optic nerve sheath diameter and optic nerve diameter in patients with acute optic neuritis and healthy controls and compared optic nerve sheath diameter and optic nerve diameter with visual-evoked potentials in patients.

MATERIALS AND METHODS

A case-control study was performed in 2 centers. Twenty-one consecutive patients with onset of visual loss during the prior 10 days and established acute noncompressive unilateral optic neuritis were compared with 21 healthy controls, matched for sex and age (±5 years). Two experienced vascular sonographers performed the study by using B-mode transorbital sonography. Visual-evoked potentials were performed on the same day as the transorbital sonography and were evaluated by an expert neurophysiologist. Sonographers and the neurophysiologist were blinded to the status of the patient or control and to clinical information, including the side of the affected eye.

RESULTS

The median optic nerve sheath diameter was thicker on the affected side (6.3 mm; interquartile range, 5.9-7.2 mm) compared with the nonaffected side (5.5 mm; interquartile range, 5.1-6.2 mm; P < .0001) and controls (5.2 mm; interquartile range, 4.8-5.5 mm; P < .0001). The median optic nerve diameter was 3.0 mm (range, 2.8-3.1 mm) on the affected side and 2.9 mm (range, 2.8-3.1 mm) on the nonaffected side (P = not significant.). Both sides were thicker than those in controls (2.7 mm; interquartile range, 2.5-2.8 mm; P = .001 and .009). No correlation was found between optic nerve sheath diameter and optic nerve diameter and amplitude and latency of visual-evoked potentials in patients with optic neuritis.

CONCLUSIONS

Transorbital sonography is a promising tool to support the clinical diagnosis of acute optic neuritis. Further studies are needed to define its specific role in the diagnosis and follow-up of optic neuritis.

Serial scans in healthy volunteers following intravenous administration of gadoteridol: time course of contrast enhancement in various cranial fluid spaces

PURPOSE

Heavily T2-weighted, 3-dimensional, fluid-attenuated inversion recovery (hT2W-3D-FLAIR) imaging has been reported to detect low concentrations of gadolinium-based contrast media (GBCM) in the anterior eye segment (AES), subarachnoid space (SAS), and labyrinthine perilymph as well as in the cerebrospinal fluid (CSF) of the internal auditory canal (IAC) 4 hours after intravenous administration of a single dose (IV-SD-GBCM) in patients with inner ear disorders. To elucidate the time course of contrast enhancement in healthy volunteers, we obtained hT2W-3D-FLAIR serially after IV-SD-GBCM.

MATERIALS AND METHODS

We obtained hT2W-3D-FLAIR before and 0.5, 1.5, 3, 4.5 and 6 hours after IV-SD-GBCM in 6 healthy volunteers and measured signal intensity of the AES, SAS surrounding the optic nerve (SAS-ON), SAS in Meckel's cave (SAS-MC), pontine parenchyma, CSF in the IAC (CSF-IAC), CSF in the ambient cistern (CSF-AC), CSF in the lateral ventricles (CSF-LV), perilymph (PL), and endolymph (EL) in the labyrinth. We then compared averaged values among all time points using analysis of variance (ANOVA).

RESULTS

After IV-SD-GBCM, we observed no change in signal intensity in the pontine parenchyma, CSF-LV, or EL and significant enhancement in all other structures. Maximum enhancement was most frequent at 4.5 hours after IV-SD-GBCM in the SAS-ON and PL, at 1.5 hours in the AES and SAS-MC, and at 3 hours in the CSF-IAC and CSF-AC.

CONCLUSIONS

Contrast enhancement can be detected by hT2W-3D-FLAIR in the AES, SAS-ON, SAS-MC, PL, CSF-IAC, and CSF-AC in healthy volunteers after IV-SD-GBCM. Timing of maximum enhancement differed among locations. These data might serve as basic knowledge for future clinical research.

Visual issues in multiple sclerosis

Multiple sclerosis has several ophthalmic manifestations, including optic neuritis, internuclear ophthalmoplegia, and nystagmus. The presentation, treatment, and prognosis of visual complaints secondary to multiple sclerosis are discussed. Additionally, the use of optical coherence tomography and complications related to the use of fingolimod are considered.

Treatment of steroid-unresponsive optic neuritis with plasma exchange

OBJECTIVES

Until now, the significance of plasma exchange (PE) as a treatment for steroid-unresponsive optic neuritis (ON) is still unclear because placebo-controlled and larger studies are missing. We report our experience with 23 patients treated by PE due to steroid-unresponsive ON.

MATERIALS AND METHODS

Patients were admitted to the University Medical Center Hamburg-Eppendorf between 2006 and 2010 with a visual acuity of <50% on the affected eye following steroid treatment. Ten patients suffered from RR-MS, one from neuromyelitis optica, and 12 patients developed ON as a clinically isolated syndrome. Routinely, they were treated with five cycles of PE. Visual acuity was measured before and directly after PE and during follow-up (first follow-up after 50 days, second follow-up after 174 days).

RESULTS

Altogether, 70% of our patients improved after PE, 69% of them showed a good or very good response to therapy. Patients who improved well after PE (n = 11) showed a mean visual acuity of 16% before PE compared to 45% immediately after PE and 60% at the first follow-up. No serious adverse events occurred.

CONCLUSIONS

To our knowledge, our study is the largest case series of patients with steroid-unresponsive ON treated with PE. Based on our experience, we conclude that PE is an important treatment option for patients with steroid-unresponsive ON although placebo-controlled studies are missing until now.

Reversible distension of the subarachnoid space around the optic nerves in a case of idiopathic hypertrophic pachymeningitis

Idiopathic hypertrophic pachymeningitis (IHP) is a chronic inflammatory disease of unknown cause. We report a case of IHP with bilateral distended subarachnoid space (SAS) of the optic nerves and unilateral visual disturbance. We observed marked amelioration of magnetic resonance (MR) imaging findings after initiation of treatment with prednisolone. This radiological finding implicates optic nerve sheath involvement that affects cerebrospinal fluid (CSF) dynamics around the optic nerve.

Diffusion-weighted imaging in optic neuritis

PURPOSE

To evaluate imaging characteristics of optic nerves by using magnetic resonance imaging, especially diffusion-weighted imaging (DWI) with apparent diffusion coefficient measurements in acute and chronic phases of optic neuritis (ON).

MATERIALS AND METHODS

A retrospective study was conducted by using records of 14 patients with clinically suspected acute ON (15 nerves), 5 chronic ON (7 nerves), and 11 normal volunteers with no eye symptoms were used as controls. Magnetic resonance imaging was performed by a 1.5T scanner. Affected nerves were evaluated for sizes, signal characteristics on DWI and T2-weighted imaging (T2WI), contrast enhancement, and apparent diffusion coefficient values. Visually assessed characteristics were compared between the acute and chronic, whereas apparent diffusion coefficient values were assessed among acute ON, chronic ON, and the control groups by using the Fisher exact test and Mann-Whitney U test.

RESULTS

There were significant differences in the diameter of the optic nerves, hyperintensity on DWI, and enhancement characteristics on post-enhanced images in acute and chronic phases of ON (P = .0001, P < .0001, and P = .0022, respectively), apparent diffusion coefficient values of the optic nerves in acute ON, chronic ON, and control groups also differed significantly from each other.

CONCLUSION

In conclusion, DWI can add valuable information in assessment of damage to nerve and neuronal barriers and thus in predicting recovery in cases of ON.

Diffusion tensor imaging of the optic nerve in subacute anterior ischemic optic neuropathy at 3T

BACKGROUND AND PURPOSE

DTI can provide in vivo information about the pathology of optic nerve disease, but there is no study of DTI in the setting of ION, the most frequent acute optic neuropathies in patients over 50 years of age. Our aim was to investigate the potential of DTI in the diagnosis of subacute AION at 3T.

MATERIALS AND METHODS

Twenty-six patients with unilateral AION and 15 healthy controls were enrolled in this study. DTI and pattern VEP were performed on the ONs of all subjects. The mean ADC, FA, and eigenvalue maps were obtained for quantitative analysis. Quantitative electrophysiology was also performed on all subjects.

RESULTS

The mean ADC and orthogonal eigenvalue λ(⊥) in affected nerves increased, and the mean FA was reduced compared with clinically unaffected contralateral nerves (P < .001) and control nerves (P < .001). However, no significant changes of the mean principal eigenvalue λ(‖) in affected nerves compared with unaffected contralateral nerves (P = .13) and control nerves (P = .14) were seen. There was a significant correlation of whole-field VEP amplitude with ADC (r = -0.63, P = .001) and λ(⊥) (r = -0.47, P = .015) but no correlation with FA (P = .06) and λ(‖) (P = .06).

CONCLUSIONS

DTI measurement of ischemic ONs provides in vivo information about pathology and may serve as a biomarker of axonal and myelin damage in AION.

Fat-saturated post gadolinium T1 imaging of the brain in multiple sclerosis

BACKGROUND

Magnetic resonance imaging (MRI) is of vital importance in the diagnosis and follow-up of patients with multiple sclerosis (MS). Imaging sequences better demonstrating enhancing lesions can help in detecting active MS plaques.

PURPOSE

To evaluate the role of fat-saturated gadolinium-enhanced T1-weighted (T1W) images of the brain in MS and to assess the benefit of performing this additional sequence in the detection of enhancing lesions.

MATERIAL AND METHODS

In a prospective study over a six-month period, 70 consecutive patients with clinically diagnosed MS were enrolled. These constituted 14 male and 56 female patients between the ages of 21 and 44 years. All the patients underwent brain MRIs on a 1.5 Tesla Magnet. Gadolinium-enhanced T1 images with and without fat saturation were compared and results were recorded and analyzed using a conspicuity score and McNemar test.

RESULTS

There were a total of 157 lesions detected in 70 patients on post-contrast T1W fat-saturated images compared with 139 lesions seen on the post-contrast T1W fast spin-echo (FSE) images. This was because 18 of the lesions (11.5%) were only seen on the fat-saturated images. In addition, 15 lesions were more conspicuous on the fat saturation sequence (9.5%). The total conspicuity score obtained, including all the lesions, was 2.24 +/-0.60 (SD). Using the two-tailed McNemar test for quantitative analysis, the P value obtained was <0.0001.

CONCLUSION

T1W fat-saturated gadolinium-enhanced images show better lesion enhancement than T1W images without fat saturation.

Directional diffusivity changes in the optic nerve and optic radiation in optic neuritis

OBJECTIVE

Optic neuritis (ON) is defined as an inflammation of the optic nerve and provides a useful model for studying the effects of inflammatory demyelination of white matter. The aim of this study was to assess the diffusion changes in both the optic nerve and optic radiation in patients with acute and chronic ON using diffusion tensor (DT) MRI.

METHODS

33 patients with idiopathic demyelinating optic neuritis (IDON) and 33 gender- and age-matched healthy controls were examined with DT-MRI and with T(1) and T(2) weighted MRI.

RESULTS

Compared with controls, both first-episode and recurrent patients with IDON in the acute stage showed significantly increased radial diffusivity (λ(⊥)) and decreased mean fractional anisotropy (FA) in the affected nerves. Reduced FA, increased λ(⊥), mean diffusivity (MD) and axial diffusivity (λ(∥)) were determined in patients with subacute IDON. We found no significant difference in the directional diffusivity of optic radiation in patients whose disease had lasted less than 1 year compared with healthy controls. However, significant changes in the FA and λ(⊥) of the optic radiation were detected in patients with disease duration of more than 1 year.

CONCLUSION

These results show the great potential and capacity of DT-MRI measures as useful biomarkers and indicators for the evaluation of myelin injury in the visual pathway.

MR imaging of optic neuropathy with extended echo-train acquisition fluid-attenuated inversion recovery

BACKGROUND AND PURPOSE

XETA, also known as Cube, is a relatively new 3D FSE sequence that can be used to perform whole-brain FLAIR T2-weighted imaging at isotropic high spatial resolution. This high-resolution volumetric imaging, coupled with both fat and fluid suppression, permits ideal evaluation of optic nerve anatomy and signal intensity; therefore, we hypothesized that XETA FLAIR would be useful for the detection of T2 signal-intensity abnormality in the optic nerve. Our purpose was to evaluate the sensitivity of XETA FLAIR for this abnormality and to compare it with the coronal FSE T2 FS.

MATERIALS AND METHODS

After obtaining approval of the institutional review board, 2 CAQ neuroradiologists retrospectively reviewed all patients with a clinical diagnosis of optic neuropathy who had undergone XETA FLAIR and standard orbital imaging from September 2006 to February 2009. Fifteen patients met these criteria and underwent the following sequences: XETA FLAIR, coronal FSE T2 FS, and T1-weighted postgadolinium sequences with FS.

RESULTS

Signal-intensity abnormality was identified on the correct side of the patient's vision loss in all 15 patients on XETA but in only 11/15 patients on the coronal FSE T2-weighted imaging. Reviewer 1 perceived the signal-intensity abnormality better on the XETA versus T2-weighted imaging in 10/15 patients, and reviewer 2, in 9/15 patients. Neither reviewer visualized any of the imaging better by using the conventional coronal FSE T2 FS sequence.

CONCLUSIONS

XETA FLAIR was more sensitive than coronal FSE T2 FS for identifying abnormal signal intensity within the optic nerves in patients with optic neuropathy.

Eye disorders in patients with multiple sclerosis: natural history and management

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system and leading cause of disability in young adults. Vision impairment is a common component of disability for this population of patients. Injury to the optic nerve, brainstem, and cerebellum leads to characteristic syndromes affecting both the afferent and efferent visual pathways. The objective of this review is to summarize the spectrum of eye disorders in patients with MS, their natural history, and current strategies for diagnosis and management. We emphasize the most common disorders including optic neuritis and internuclear ophthalmoparesis and include new techniques, such as optical coherence tomography, which promise to better our understanding of MS and its effects on the visual system.

Magnetic Resonance Imaging in Acute Optic Neuritis in Singapore

Introduction: The Optic Neuritis Treatment Trial (ONTT) has established that the magnetic resonance imaging (MRI) findings at the time of presentation of optic neuritis (ON) is the strongest indicator of the development of multiple sclerosis (MS). Reports from Singapore as well as other Asian countries have indicated that these abnormalities are less frequently encountered compared to that reported by the ONTT. This paper aims to describe systematically the brain MRI as well as the optic nerve abnormalities in patients after an episode of acute optic neuritis. Materials and Methods: Patients who presented with acute optic neuritis were retrieved from our prospective optic neuritis study and their MRI scans were reviewed and graded in accordance with the standardised classification employed in the ONTT. Results: Fifteen of 24 patients had MRI brain and optic nerves performed during the acute episode. In the evaluation of brain abnormalities, 40% were classified as grade 0, 20% grade I, 20% grade II, 6.7% grade III and 13.3% grade IV. Optic nerve abnormalities were observed in 80% of cases. At study entry, 10 patients had idiopathic (monosymptomatic) ON, 3 had multiple sclerosis (MS), one each with infective and autoimmune optic neuritis, respectively. The single patient who developed MS at study completion presented with grade II brain abnormalities at the initial MRI. For those with idiopathic ON, our study revealed a higher percentage of grade 0-I brain changes as well as a lower lesion load compared to the ONTT. Lesion load and grade was also lower in anterior optic neuritis compared with retrobulbar disease. Conclusion: Our study revealed a lower percentage of grade II-IV brain MRI abnormalities as well as less lesion load in idiopathic ON compared to the ONTT. This may be related to the lower prevalence of MS in our predominantly Asian population. As diagnostic tests and understanding of neuromyelitis optica or Devic’s disease improves, we may see more patients being diagnosed with this condition, which may also explain our findings. Our data also showed that MRI grade and lesion load in cases of anterior ON was lower than for retrobulbar disease. MRI in ON has an essential role in characterising the disease, evaluating for associated brain lesions, and assessing prognosis in retrobulbar disease but may be less useful in anterior disease. Key words: Multiple sclerosis, Optic nerve enhancement, Periventricular plaques

Assessing optic nerve pathology with diffusion MRI: from mouse to human

The optic nerve is often affected in patients with glaucoma and multiple sclerosis. Conventional MRI can detect nerve damage, but it does not accurately assess the underlying pathologies. Mean diffusivity and diffusion anisotropy indices derived from diffusion tensor imaging have been shown to be sensitive to a variety of central nervous system white matter pathologies. Despite being sensitive, the lack of specificity limits the ability of these measures to differentiate the underlying pathology. Directional (axial and radial) diffusivities, measuring water diffusion parallel and perpendicular to the axonal tracts, have been shown to be specific to axonal and myelin damage in mouse models of optic nerve injury, including retinal ischemia and experimental autoimmune encephalomyelitis. The progression of Wallerian degeneration has also been detected using directional diffusivities after retinal ischemia. However, translating these findings to human optic nerve is technically challenging. The current status of diffusion MRI of human optic nerve, including imaging sequences and protocols, is summarized herein. Despite the lack of a consensus among different groups on the optimal sequence or protocol, increased mean diffusivity and decreased diffusion anisotropy have been observed in injured optic nerve from patients with chronic optic neuritis. From different mouse models of optic nerve injuries to the emerging studies on patients with optic neuritis, directional diffusivities show great potential to be specific biomarkers for axonal and myelin injury.