Imaging studies for diagnosing Graves' orbitopathy and dysthyroid optic neuropathy

Graves-Basedow ophthalmopathy surgical approaches: Open vs Endoscopic

Graves-Basedow's disease (GBD) is an autoimmune pathology that affects the thyroid and is characterized by the presence of goiter, hyperthyroidism, ophthalmopathy, and dermopathy. Graves-Basedow ophthalmopathy (GBO) is a set of inflammatory and infiltrative alterations of the orbital tissue that affects 40-90% of subjects suffering from GBD. Our study aims to investigate the differences in the clinical outcomes of patients treated with two different techniques: the classic open and the more modern endoscopic. A retrospective clinical study was carried out from the year 2011 until the year 2020 to evaluate the clinical outcomes of two different surgical techniques for the treatment of GBO. Eighteen patients were given surgical indications, 12 males and 6 females aged between 37 and 69 years (average age 48.5 years), for a total of 36 orbits. From the year 2011 to the year 2014, all patients were treated with the open orbital decompression technique; from 2015 onwards, patients were subjected to orbital decompression with the endoscopic transnasal approach. Pre- and postoperative ophthalmometry, reduction of proptosis, and reduction of oculo-orbital index were compared for the two techniques. As evidenced by the statistical analysis carried out on the sample before and after surgical treatment, there is a statistically significant difference between ophthalmometry and the Oculo-Orbital Index (IOO) values; this indicates that surgical orbital decompression with two walls (floor and medial wall) is effective in reducing exophthalmos. The positive result is also confirmed by the reduction of proptosis, measured in millimeters, averaging 1.7 mm. In the analysis of data relating to the two different patient groups, treated respectively with endoscopic orbital decompression (Technique 1) and classical open orbital decompression (Technique 2), the results obtained show that there is no statistically significant difference between the results of the two techniques. Therefore, the choice of surgical approach is at the discretion of the surgeon. It is our opinion that orbital decompression with the endoscopic transnasal technique should be an absolute indication in all patients who have clinical and radiographic signs of involvement of the optic nerve at the orbital apex (crowded apex syndrome) thanks to the ability of this technique to add and decompress the optical channel at the apex. For all other patients with GBO, the endoscopic technique of orbital decompression can be indicated as a first-line surgical approach considering the absence of skin scars and the best aesthetic results.

Impact of sphenoid trigone size and extraocular muscle thickness on the outcome of lateral wall orbital decompression for thyroid eye disease

BACKGROUND

To retrospectively review lateral wall orbital decompression for thyroid eye disease (TED) and to evaluate pre-operative CT scans to analyse the variation in proptosis reduction.

METHODS

Consecutive lateral wall orbital decompressions performed by a single surgeon were retrospectively reviewed. Pre-operative CT scan features and post-operative proptosis reduction were analysed. The sphenoid trigone cross-sectional areas were summed and multiplied by the slice thickness to yield bone volume. Cumulative extraocular muscle thickness was calculated by combining the maximum thickness of the four recti. "Trigone volume" and "cumulative muscle thickness" were correlated with proptosis reduction at 3 months post-surgery.

RESULTS

Out of 73 consecutive lateral wall orbital decompressions, 17 orbits had prior endonasal medial wall orbital decompression. In the remaining 56 orbits, the mean pre-operative and post-operative proptosis were 24.3 ± 1.6 mm and 20.9 ± 2.3 mm respectively. The proptosis reduction ranged from 1 to 7 mm (mean of 3.5 mm ± 1.3 (p < 0.001)). Mean sphenoid trigone volume was 895 ± 434.4 mm3. The mean cumulative muscle thickness was 20.4 ± 5 mm. The correlation coefficient between muscle thickness and proptosis reduction was - 0.3 and was statistically significant (p = 0.043). The correlation coefficient between sphenoidal trigone volume and proptosis reduction was 0.2 (p = 0.068). With a multivariate analysis, the coefficient of efficient of regression for muscle thickness was - 0.007 (p = 0.42) and the coefficient of regression for trigone volume was 0.0 (p = 0.046).

CONCLUSION

Proptosis reduction following lateral wall orbital decompression can be variable. Extraocular muscle thickness had a significant correlation with the outcome, with greater proptosis reduction in orbits with thin muscles. The sphenoidal trigone size had a weak correlation with decompression outcome.

Application of quantitative orbital analysis to assess the activity of Graves' ophthalmopathy

This study aimed to evaluate the diagnostic value of uptake ratios in the extraocular muscles (EOMs), lacrimal glands, and optic nerves to detect the inflammation activity of Graves' ophthalmopathy (GO) using quantitative analysis of 99m technetium (99mTc)-labeled diethylene triamine pentaacetic acid (DTPA) orbital single-photon emission computed tomography/computed tomography (SPECT/CT) images. The patients were categorized into an active stage (clinical activity score ≥ 3/7, n=23) or an inactive stage (clinical activity score < 3/7, n=38), based on their clinical activity score. The uptake ratio was manually determined by placing a region of interest within the area of highest uptake, as agreed upon by consensus, in the EOMs, lacrimal gland, and optic nerve on SPECT images corrected for CT attenuation. Patients with active GO exhibited significantly higher uptake ratios in the EOMs, lacrimal glands, and optic nerves compared to patients with inactive GO (all P < 0.01). These parameters have been proven effective in differentiating between active and inactive disease.

Dysthyroid Optic Neuropathy

PURPOSE

Dysthyroid optic neuropathy (DON) is a sight-threatening complication of thyroid eye disease (TED). This review provides an overview of the epidemiology, pathogenesis, diagnosis, and current therapeutic options for DON.

METHODS

A literature review.

RESULTS

DON occurs in about 5% to 8% of TED patients. Compression of the optic nerve at the apex is the most widely accepted pathogenic mechanism. Excessive stretching of the nerve might play a role in a minority of cases. Increasing age, male gender, smoking, and diabetes mellitus have been identified as risk factors. Diagnosis of DON is based on a combination of ≥2 clinical findings, including decreased visual acuity, decreased color vision, relative afferent pupillary defect, visual field defects, or optic disc edema. Orbital imaging supports the diagnosis by confirming apical crowding or optic nerve stretching. DON should be promptly treated with high-dose intravenous glucocorticoids. Decompression surgery should be performed, but the response is incomplete. Radiotherapy might play a role in the prevention of DON development and may delay or avoid the need for surgery. The advent of new biologic-targeted agents provides an exciting new array of therapeutic options, though more research is needed to clarify the role of these medications in the management of DON.

CONCLUSIONS

Even with appropriate management, DON can result in irreversible loss of visual function. Prompt diagnosis and management are pivotal and require a multidisciplinary approach. Methylprednisolone infusions still represent first-line therapy, and surgical decompression is performed in cases of treatment failure. Biologics may play a role in the future.

Current imaging methods for assessing Graves` orbitopathy activity with particular emphasis on FDG-PET

The most frequent extrathyroidal Graves' disease manifestation is Graves' orbitopathy (GO). The treatment of GO is determined by its severity and activity. There is currently no reliable, impartial method for assessing it clinically or distinguishing fibrosis from active inflammatory disorders. Today, imaging methods including orbital ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) are frequently employed to show pathological abnormalities in the ocular adnexa of GO patients. In addition, a not widely accepted technique - 99mTc-DTPA SPECT - has some potential to evaluate retrobulbar inflammation in GO patients. However, FDG-PET/CT is possibly superior to other imaging modalities in detecting inflammation in GO and it may be useful in assessing disease activity in case of clinical or serological uncertainty. It might also act as an early indicator of GO development and its aggravation before irreversible tissue alterations take place and may be used in the differential diagnosis of inflammatory disorders of the orbit. However, before FDG-PET/CT could be applied in daily clinical practice, the methodology of GO activity assessment with defined cut-off values for radionuclide concentration - standardized units of value (SUV) have to be established and validated. In addition, the limitations of this technique have to be recognized.

A Comparison of Observational Studies on Subfoveal Choroidal Thickness Measured with OCT according to the Level of Thyroid Eye Disease Activity-Systematic Review and Meta-Analysis

This study aims to systematise subfoveal choroidal thickness (SFCT) measured using optical coherence tomography (OCT) in patients with different severities of thyroid eye disease (TED) compared with healthy subjects. The PubMed, Web of Science and Scopus databases were searched for the following terms: ((Graves' ophthalmopathy) OR (thyroid eye disease) OR (Graves' orbitopathy) OR (thyroid-associated orbitopathy)) AND (choroidal thickness) AND ((optical coherence tomography) OR (OCT)). The pool of papers was narrowed down to articles published until 31 January 2023 (26, 26 and 96 papers, respectively). Twenty-five (25) articles were taken into consideration, which were original papers and included the choroidal thickness measurements among TED patients in their results. Finally, eight papers were included in the comparative analysis of the SFCT parameter in TED patients and a group of healthy controls, and seven papers in the comparative analysis of the same parameter between active and inactive TED patients. The mean value of the difference between the TED group and the healthy group was 38.79 μm, with a confidence interval (CI) from 0.09 to 77.49 μm (p = 0.0495). The mean difference between the active TED group and inactive TED group was 38.02 μm, with a CI from 8.62 to 67.42 μm (p = 0.0113). All the results were statistically significant.

The significance of ophthalmological features in diagnosis of thyroid-associated ophthalmopathy

BACKGROUND

Thyroid-associated ophthalmopathy (TAO) is an autoimmune disorder. It has discriminable appearance. This study was conducted to dig the clinical significance of demographic characteristics and ophthalmologic diagram features in TAO diagnosis and stage/severity evaluation.

RESULTS

We included 320 males and 633 females, with an average age of 41.75 ± 13.75. A majority of TAO patients had hyperthyroidism, and most of them were in the inactive stage and at the moderate level. The thyroid function type, stage and severity were closely associated with hypopsia, eyelid congestion, conjunctival congestion, corneal ulcer, ocular motility disorder, best corrected visual acuity, and extraocular muscle thickening. Using these features, we established different logistic regression models to predict thyroid function subtypes, abnormal thyroid function, stage, and severity, in which the AUC of the ROC curve and accuracies were satisfactory.

CONCLUSION

Together, TAO subtype, stage and severity can be diagnosed by auxiliary references including demographic factors, symptoms from complains, and image features. These non-invasive indices can be applied in a timely manner in clinical estimating TAO status.

Detection of abnormal extraocular muscles in small datasets of computed tomography images using a three-dimensional variational autoencoder

We sought to establish an unsupervised algorithm with a three-dimensional (3D) variational autoencoder model (VAE) for the detection of abnormal extraocular muscles in small datasets of orbital computed tomography (CT) images. 334 CT images of normal orbits and 96 of abnormal orbits diagnosed as thyroid eye disease were used for training and validation; 24 normal and 11 abnormal orbits were used for the test. A 3D VAE was developed and trained. All images were preprocessed to emphasize extraocular muscles and to suppress background noise (e.g., high signal intensity from bones). The optimal cut-off value was identified through receiver operating characteristic (ROC) curve analysis. The ability of the model to detect muscles of abnormal size was assessed by visualization. The model achieved a sensitivity of 79.2%, specificity of 72.7%, accuracy of 77.1%, F1-score of 0.667, and AUROC of 0.801. Abnormal CT images correctly identified by the model showed differences in the reconstruction of extraocular muscles. The proposed model showed potential to detect abnormalities in extraocular muscles using a small dataset, similar to the diagnostic approach used by physicians. Unsupervised learning could serve as an alternative detection method for medical imaging studies in which annotation is difficult or impossible to perform.

A Survey on the Management of Thyroid Eye Disease Among American and European Thyroid Association Members

Background: The thyroid eye disease (TED) treatment landscape is rapidly evolving. How new treatment options have impacted practice is unknown. Methods: We conducted a cross-sectional electronic survey of American and European Thyroid Association members between June 2 and June 30, 2021. The survey included TED questions about resources for its management, index cases for different severities and presentations of TED, barriers for the management of TED, and participants' concerns about TED. We classified respondents into three geographic categories: North America, Europe, or other regions. Results: Two hundred fifty-two eligible participants started the survey (15% response rate), and 227 completed it. Participants were mostly men (50.2%, 114/227), white (79.7%, 181/227), endocrinologists with a thyroid focus (66.1%, 150/227), practicing in a tertiary academic center (46.7%, 106/227), caring for 10 or more TED patients over the last 12 months (40.5%, 92/227), and reported not having a multidisciplinary TED clinic in their institution (52.8%, 120/227). The majority reported that new TED cases per annum have not changed in the past 10 years (47.5%, 108/227), and that TED patients are found in practice during the management of hyperthyroidism (41.8%, 95/227). For mild active TED, participants from Europe reported a higher use of selenium (73%[96/132] vs. 32%[20/62] of respondents from North America and 24%[8/33] of respondents from other regions). For moderate-to-severe active TED, there was a modest preference for teprotumumab as first-line therapy (37%, 23/62) among North American participants and intravenous (IV) steroids (73%[96/132], and 42%[14/33]) for participants from Europe and other regions, respectively. These treatment preferences did not change in patients with moderate-to-severe active TED with poorly controlled diabetes. In contrast, participants from the three geographic categories preferred IV steroids for optic neuropathy and women planning pregnancy. The three top "very important" concerns about TED management according to participants were: the cost of TED treatment (31.3%, 71/227), lack of effective TED treatments (19.8%, 45/227), and difficulty in predicting whether TED will develop (18.9%, 43/227). Conclusions: There is a marked geographic practice variation in the management of TED. Clinicians' concerns about TED management demand ongoing research on more effective treatment, TED predictive tools, and policy changes to improve the affordability of new TED therapies.

Dysthyroid optic neuropathy: Demographics, risk factors, investigations, and management outcomes

Purpose

To analyze the clinical presentations, risk factors, and management outcomes in patients presenting with dysthyroid optic neuropathy (DON).

Methods

This is a retrospective, single-center study carried out on consecutive patients presenting with DON over a period of 4 years (2013-2016). The VISA classification was used at the first visit and subsequent follow-ups. The diagnosis was based on optic nerve function tests and imaging features. Demographic profiles, clinical features, risk factors, and management outcomes were analyzed.

Results

Thirty-seven eyes of 26 patients diagnosed with DON were included in the study. A significant male preponderance was noted (20, 76.92%). Twenty patients (76.9%, P = 0.011) had hyperthyroidism, and 15 (57.69%, P = 0.02) were smokers. Decreased visual acuity was noted in 28 eyes (75.6%). Abnormal color vision and relative afferent pupillary defects were seen in 24 (64.86%) eyes, and visual field defects were seen in 30 (81.01%) eyes. The visual evoked potential (VEP) showed a reduced amplitude in 30 (96.77%, P = 0.001) of 31 eyes and delayed latency in 20 (64.51%, P = 0.0289) eyes. Twenty-six (70.27%) patients were treated with intravenous methyl prednisolone (IVMP) alone, whereas 11 (29.72%) needed surgical decompression. The overall best-corrected visual acuity improved by 0.2 l logMARunits. There was no statistically significant difference in outcome between medically and surgically treated groups. Four patients developed recurrent DON, and all of them were diabetics.

Conclusion

Male gender, hyperthyroid state, and smoking are risk factors for developing DON. VEP, apical crowding, and optic nerve compression are sensitive indicators for diagnosing DON. Diabetics may have a more defiant course and are prone to develop recurrent DON.

Automated detection of enlarged extraocular muscle in Graves' ophthalmopathy with computed tomography and deep neural network

This study aimed to develop a diagnostic software system to evaluate the enlarged extraocular muscles (EEM) in patients with Graves’ ophthalmopathy (GO) by a deep neural network.This prospective observational study involved 371 participants (199 EEM patients with GO and 172 controls with normal extraocular muscles) whose extraocular muscles were examined with orbital coronal computed tomography. When at least one rectus muscle (right or left superior, inferior, medial, or lateral) in the patients was 4.0 mm or larger, it was classified as an EEM patient with GO. We used 222 images of the data from patients as the training data, 74 images as the validation test data, and 75 images as the test data to “train” the deep neural network to judge the thickness of the extraocular muscles on computed tomography. We then validated the performance of the network. In the test data, the area under the curve was 0.946 (95% confidence interval (CI) 0.894–0.998), and receiver operating characteristic analysis demonstrated 92.5% (95% CI 0.796–0.984) sensitivity and 88.6% (95% CI 0.733–0.968) specificity. The results suggest that the deep learning system with the deep neural network can detect EEM in patients with GO.

Diagnostic Ability of Barrett’s Index and Presence of Intracranial Fat Prolapse in Dysthyroid Optic Neuropathy

Background

Dysthyroid optic neuropathy (DON) is one of the most serious visual loss threats for patients with Graves’ ophthalmopathy (GO). Barrett’s index (BI) and intracranial-fat prolapse have been used in diagnosing DON. However, these parameters are rarely used in Southeast Asian populations with a variety of cut-off values.

Objective

To evaluate the performance of BI and fat prolapse in diagnosing of DON, and to study the correlation between their parametric values with visual acuity (VA) and visual field defect (VF).

Methods

Between January 2011 and December 2020, orbits affected by GO were retrospectively reviewed and classified into 2 groups based on the presence or absence of DON. All orbital-computed-tomography (CT) scans were measured for BI and fat prolapse. Diagnostic performance of BI and fat prolapse was analyzed and evaluated in relation to visual outcome.

Results

We included orbits with DON (23 orbits) and the absence of DON (61 orbits). BI was significantly higher in patients in the DON group (47.68 ± 12.52%) compared to the absence of DON (37.55 ± 10.88%), p < 0.001. The presence of fat prolapse was significantly higher in the DON group (p = 0.003). BI at 40% provided best diagnostic performance with sensitivity of 78.3%/specificity of 63.9%. The presence of fat prolapse 4.5 mm via the superior-ophthalmic-fissure (SOF) had a lower sensitivity compared with fat prolapse 2.5 mm. Comparison between area under the curve (AUC) of BI and fat prolapse revealed no statistically significant difference (AUC 0.742 and 0.705 in BI and fat prolapse, respectively, p = 0.607). A negative correlation between the BI and fat prolapse with VA and VF was observed (p < 0.001).

Conclusion

Measurement of BI is a simple diagnostic method for detecting DON in Thai populations. The presence of fat prolapse (2.5 mm) provides a lower sensitivity compared with a BI at 40%. A slightly larger BI or fat prolapse should be suspected of DON for early treatment.

2022 Update on Clinical Management of Graves Disease and Thyroid Eye Disease

The management of hyperthyroidism and extrathyroidal manifestations of Graves disease remains complex. Considerations that include patient preference, age, comorbidity, pregnancy, tobacco smoking, and social determinants of health must all be weaved into a cohesive management plan. A multidisciplinary team is required to manage all aspects of Graves disease, particularly thyroid eye disease, for which new therapeutic options are now available.

Optic Nerve Head Vessel Density Changes from Graves' Disease without TED to TED Dysthyroid Optic Neuropathy: Does Optic Nerve Head Ischemia Play a Role?

PURPOSE

To compare the retinal peripapillary capillary (RPC) vessel density (VD) between 5 groups of patients on the spectrum of thyroid eye disease (TED).

METHOD

This is a prospective comparative study looking at 5 groups of patients who were consecutively included from January 2018 to March 2021. They were composed of: Healthy volunteers (39 eyes and 20 subjects), patients with Graves' disease without TED (26 eyes and 13 patients), mild TED (28 eyes and 14 patients), moderate-severe TED (30 eyes and 17 patients), and TED with dysthyroid optic neuropathy (DON) (21 eyes and 12 patients). Ocular and periocular examination, visual field indices, RPC-VD (with optical coherence tomography angiography), and retinal nerve fiber layer, and macular ganglion cell complex thickness were recorded.

RESULT

An initial insignificant (0.5 < p < 0.9) rise in the peripapillary-VD (pp-VD) and whole image-VD (wi-VD) from the healthy subject to the Graves' disease without TED was followed by a significant (p = 0.001) fall in RPC-VD in different severity grades of the TED. Paired comparison between the 5 groups showed that the statistically significant fall from the Graves' disease group occurred in the moderate-severe and DON groups (0.001 ≤ p ≤ 0.04). No variable significantly affected the VD (0.08 ≤ p ≤ 0.9). A lower wi-VD and pp-VD were significantly (0.001 ≤ p ≤ 0.009) correlated with the impaired optic nerve functional and structural tests. The sensitivity and specificity of wi-VD (81% and 76%) and pp-VD (69% and 71%) for detecting the DON were statistically significant (p < 0.001).

CONCLUSION

Despite an insignificant rise in the wi- and pp-VD from the healthy volunteers to the patients with Graves' disease without TED, VD showed a declining trend in the course of patients with TED, which was statistically significant in the moderate-severe TED and DON groups.

Orbital Muscle Enlargement: What if It’s Not Graves’ Disease?

Purpose of Review

To provide the radiologist with tools to recognize findings atypical for Graves’ ophthalmopathy and differentiate between the most important and common alternative causes of extraocular muscle enlargement on CT and MR imaging.

Recent findings

We introduce five ‘red flags’ representing features that are atypical for Graves’ ophthalmopathy: unilateral disease, atypical pattern of muscle involvement, adjacent structure involvement, restricted diffusion, and absence of pain.

Summary

About 95% of the cases with extraocular enlargement are due to Graves’ ophthalmopathy, other causes are less well known and recognized. The ‘red flags’ may aid in recognizing and suggesting alternative diagnoses.

Old Bottle, New Wine: Diplopia Sans Proptosis as the Sole Presentation of Thyroid Orbitopathy

Thyroid orbitopathy holds a dominant place in the list of causes for external ophthalmoplegia and is commonly accompanied by eye surface signs such as congestion, lacrimation, and proptosis. An elderly male presented to us with painless diplopia in the absence of proptosis, conjunctival congestion, tearing or irritative symptoms. He had bilateral complete external ophthalmoplegia. He was evaluated to have hypothyroidism with elevated anti-thyroid peroxidase antibodies. MRI revealed bulky extraocular muscles in a pattern of sparing of tendinous insertions, highly suggestive of thyroid orbitopathy. He was managed with IV steroid pulse and thyroxine supplementation with minimal improvement. Through this case report, we highlight an unusual presentation of thyroid eye disease in the form of isolated diplopia, in the absence of other usual eye signs. We also emphasize the characteristic typical neuroimaging signs, such as the 'Coca Cola bottle' sign, which strongly augments the diagnosis in an atypical setting.

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.

Evaluation of Retinal Neurodegeneration and Choroidal Thickness in Patients with Inactive Graves' Ophthalmopathy

PURPOSE

The study was conducted for the assessment of the retinal nerve fiber layer, ganglion cell layer, and subfoveal choroidal thickness changes in patients with inactive Graves' ophthalmopathy (GO) using swept-source optical coherence tomography (SS-OCT) before the development of active GO findings.

MATERIALS AND METHODS

The cross-sectional designed study consisted of patients with inactive Graves' ophthalmopathy (study group) and healthy subjects (control group). The thicknesses of the retinal ganglion cell layer, retinal nerve fiber layer, and subfoveal choroid (SFCT) were measured using SS-OCT with deep range imaging technology to compare these parameters between the study and control groups.

RESULT

Patients with inactive Graves' ophthalmopathy had higher values of intraocular pressure but similar best-corrected visual acuity (p = 0.001, p = 0.232, respectively). The retinal nerve fiber layer was thinner only in the superior zone of the study group (p = 0.039), whereas similar values were noted in the temporal, nasal, and inferior areas as well as the average thickness. We did not observe any statistically significant difference in any sector of the ganglion cell layer between the study and control groups. A thicker mean subfoveal choroidal thickness value was measured in patients with inactive Graves' ophthalmopathy than in healthy subjects (p = 0.013) in correlation with a clinical activity score (p = 0.046).

CONCLUSION

SS-OCT showed minimal retinal neurodegenerative alteration and significant choroidal thickening in inactive GO. Thus, SS-OCT might be a beneficial technique to detect retinal neurodegenerative and choroidal changes earlier in the stage of inactive GO before the development of active GO signs, which may affect the time and type of treatment modalities to prevent further ocular or systemic complications. Additionally, SFCT may be a good indicator for assessment of the severity of Graves' disease.

Thyroid-Associated Ophthalmopathy: Preliminary Study Using T2 Mapping to Characterize Intraorbital Optic Nerve Changes Before Dysthyroid Optic Neuropathy

OBJECTIVE

To evaluate the performance of T2 mapping in detecting intraorbital optic nerve (ON) changes in patients with thyroid-associated ophthalmopathy (TAO) before the onset of dysthyroid optic neuropathy (DON).

METHODS

Thirty-five patients with TAO and without DON (21 active, 14 inactive) and 21 healthy controls (HCs) were enrolled. Magnetic resonance imaging-derived parameters of T2 relaxation time (T2RT) at the intraorbital ON, extraocular muscle (EOM), orbital fat, exophthalmos, summed thickness of EOMs, orbital fat thickness, and clinical variables were compared. Correlations between T2RT at the ON and other variables were assessed.

RESULTS

Patients with TAO showed significantly higher T2RTs at the intraorbital ON than HCs (P < .001). Patients with active TAO had significantly higher T2RTs than those with inactive TAO and HCs (P < .001). Differences between patients with inactive TAO and HCs were insignificant (P > .05/3). T2RT at the intraorbital ON was positively correlated with clinical activity score, modified NOSPECS score, T2RT at EOM, exophthalmos, and summed thickness of EOMs in the TAO group (P ≤ .003) and negatively correlated with visual acuity (P = .033) and visual field indices (P = .030) in patients with active TAO. A T2RT cutoff of 82.9 ms for the intraorbital ON distinguished active TAO and healthy eyes optimally (area under the curve, 0.800; sensitivity, 85.7%; specificity, 64.3%).

CONCLUSION

T2RT detects disturbance in the intraorbital ON in patients with TAO, especially active TAO, before DON develops. T2 mapping has a potential for noninvasive evaluation of ON changes in patients with TAO.

Evaluation of Proptosis: A Primer

Collapse

Current Knowledge on Graves' Orbitopathy

(1) Background: Graves' orbitopathy (GO) is an autoimmune inflammation of the orbital tissues and the most common extra-thyroid symptom of Graves' disease (GD). Mild cases of GO are often misdiagnosed, which prolongs the diagnostic and therapeutic process, leading to exacerbation of the disease. A severe course of GO may cause permanent vision loss. (2) Methods: The article presents an analysis of GO-its etiopathogenesis, diagnostics, current treatment and potential future therapeutic options based on a review of the currently available literature of the subject. (3) Results: Current treatment of the active GO consists predominantly in intravenous glucocorticoids (GCs) administration in combination with orbital radiotherapy. The growing knowledge on the pathogenesis of the disease has contributed to multiple trials of the use of immunosuppressive drugs and monoclonal antibodies which may be potentially effective in the treatment of GO. Immunosuppressive treatment is not effective in patients in whom a chronic inflammatory process has caused fibrous changes in the orbits. In such cases surgical treatment is performed-including orbital decompression, adipose tissue removal, oculomotor muscle surgery, eyelid alignment and blepharoplasty. (4) Conclusions: Management of GO is difficult and requires interdisciplinary cooperation in endocrinology; ophthalmology, radiation oncology and surgery. The possibilities of undertaking a reliable assessment and comparison of the efficacy and safety of the therapeutic strategies are limited due to the heterogeneity of the available studies conducted mostly on small group of patients, with no comparison with classic systemic steroid therapy. The registration by FDA of Teprotumumab, an IGF1-R antagonist, in January 2020 may be a milestone in future management of active GO. However, many clinical questions require to be investigated first.

Thyroid-Associated Orbitopathy: Evaluating Microstructural Changes of Extraocular Muscles and Optic Nerves Using Readout-Segmented Echo-Planar Imaging-Based Diffusion Tensor Imaging

Objective

We aimed to investigate the ability of readout-segmented echo-planar imaging (rs-EPI)-based diffusion tensor imaging (DTI) in assessing the microstructural change of extraocular muscles (EOMs) and optic nerves in patients with thyroid-associated orbitopathy (TAO) as well as in evaluating disease activity.

Materials and Methods

We enrolled 35 TAO patients and 22 healthy controls (HCs) who underwent pre-treatment rs-EPI-based DTI. Mean, axial, and radial diffusivity (MD, AD, and RD) and fractional anisotropy (FA) of the medial and lateral EOMs and optic nerve for each orbit were calculated and compared between TAO and HC groups and between active and inactive TAO groups. Factors such as age, sex, disease duration, mediation, and smoking history between groups were also compared. Logistic regression analysis was used to evaluate the predictive value of significant variables for disease activity.

Results

Disease duration was significantly shorter in active TAOs than in inactive ones (p < 0.001). TAO patients showed significantly lower FA and higher MD, AD, and RD than HCs for both medial and lateral EOMs (p < 0.001), but not the AD value of lateral EOMs (p = 0.619). Active patients had significantly higher FA, MD, and AD than inactive patients for medial EOMs (p < 0.005), whereas only FA differed significantly in the lateral EOMs (p = 0.018). The MD, AD, and RD of optic nerves were significantly lower in TAO patients than HCs (p < 0.05), except for FA (p = 0.129). Multivariate analysis showed that the MD of medial EOMs and disease duration were significant predictors for disease activity. The combination of these two parameters showed optimal diagnostic efficiency for disease activity (area under the curve, 0.855; sensitivity, 68.4%; specificity, 96.9%).

Conclusion

rs-EPI-based DTI is promising in assessing microstructural changes of EOMs and optic nerves and can help to indicate the disease activity of TAO, especially through the MD of medial EOMs.

Predictive parameters on CT scan for dysthyroid optic neuropathy

AIM

To evaluate the value of parameters on CT scan in predicting dysthyroid optic neuropathy (DON) and to provide guidance for early diagnosis of DON accordingly.

METHODS

A total of 67 eyes of 35 patients with thyroid-associated ophthalmopathy (TAO) were included in this study. Patients were divided into 2 groups (DON group and non-DON group). Parameters were measured on high resolution CT, including muscle index (MI), superior ophthalmic vein (SOV) dilatation, extraocular muscle volume/orbit volume (MV/OV), and intracranial fat prolapsed, and be compared between these 2 groups. The relation between those parameters and visual function [visual acuity (VA) and visual field defect (VF defect)] were also evaluated.

RESULTS

MI and MV/OV were significantly higher in DON group (P=0.00035 and P=0.00026). No significant difference was detected regarding intracranial fat prolapse existence and SOV dilatation (P=0.37 and P=0.15). MV/OV was found to have significant negative correlation with both VF defect (R=-0.332, P=0.0273) and VA (R=-0.635, P=0.00) while MI was found to have negative linear correlation with VA only (R=-0.456, P=0.00017). The area under receiver operating characteristic curves was 0.82 for MV/OV and 0.75 for MI. The best performance in detecting DON was achieved when MV/OV is set at 0.20 with 72% sensitivity and 87% specificity and MI is set at 0.52 with 64% sensitivity and 80% specificity.

CONCLUSION

MI and MV/OV are predictive parameters for DON. Together with clinical manifestations, MV/OV≥0.2 can be used as a good indicator for DON in TAO patients.

Semi-automatic magnetic resonance imaging based orbital fat volumetry: reliability and correlation with computed tomography

Post-processing analysis can provide valuable information for diagnosis and planning of orbital disorders. This cross-sectional study aims to evaluate the reliability of semi-automatic, orbital fat volumetry using magnetic resonance imaging (MRI). Two observers assessed the orbital fat volume using a standard MRI protocol (3T, T1w sequence) in 12 orbits diagnosed with Graves' orbitopathy (GO) and 10 healthy control orbits. MRI and computed tomography (CT) based analysis were compared. Intra-observer variability was good (intraclass correlation coefficient (ICC) 0.88; 95% confidence interval (CI) [0.70, 0.95]) and interobserver agreement was moderate (ICC 0.55; 95% CI [-0.09, 0.81]), which corresponds to a mean percentage difference of 1.3% and 17.9% of the total orbital fat volume. Mean differences between MRI and CT measurements were, respectively, 1.1 cm³ (P= 0.064, 95% CI [-0.20, 2.43]) and 1.4 cm³ (P=0.016, 95% CI [0.21, 2.56]) for the control and the GO group. MRI volumetry was strongly correlated with CT (Pearson's r= 0.7, P<0.001). We conclude that orbital fat volumetry is feasible with a semi-automatic segmentation procedure and standard MRI protocol. Correlation with CT volumetry is good, but considerable bias may derive from observer variability and these errors should be taken into account for the purpose of volumetric analysis. Better definition of error sources may increase measurement accuracy.

Analysis of Foveal and Parafoveal Microvascular Density and Retinal Vessel Caliber Alteration in Inactive Graves' Ophthalmopathy

Purpose

We aimed to evaluate foveal and parafoveal density using optical coherence tomography angiography and the alteration on the retinal vessel diameter in patients with inactive Graves' ophthalmopathy compared to age-matched normal population. Materials and Methods. Patients with inactive Graves' ophthalmopathy (study group) and healthy individuals (control group) were enrolled in the cross sectionally designed study. The optical coherence tomography angiography parameters and retinal vessel diameter measurements were assessed between the study and control groups. Foveal and parafoveal microvascular density in the retina was measured using optical coherence tomography angiography. Retinal artery and vein diameter and artery/vein ratio were assessed for retinal vessel caliber changes.

Results

Patients with inactive Graves' ophthalmopathy had higher values of intraocular pressure, proptosis, and axial length (P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001,

Conclusion

Optical coherence tomography angiography could be a novel and promising noninvasive diagnostic technique in patients with inactive Graves' ophthalmopathy to detect foveal and parafoveal vessel density changes compared to healthy subjects. The decrease of retinal vessel diameter might be observed in patients with inactive graves ophthalmopathy.

Cranial Nerve Imaging and Pathology

This review provides a symptom-driven approach to neuroimaging of disease processes affecting the cranial nerves. In addition to describing characteristic imaging appearances of a disease, the authors emphasize exceptions to the rules and neuroimaging pearls. The focus is on adult neurology although some important pediatric conditions are included. On reviewing this material, the reader should be able to (1) differentiate intra- and extra-axial causes of cranial nerve dysfunction and (2) appropriately use neuroimaging to investigate abnormalities of cranial nerve function.

Real-time ultrasound elastographic evaluation of extraocular muscle involvement in Graves' ophthalmopathy

Purpose: To evaluate the affected extraocular muscles (EOMs) of patients with Graves' ophthalmopathy (GO) using real-time ultrasound elastography (UE) and to compare these results with those of healthy subjects.Methods: This prospective, comparative case series included 70 eyes of 35 patients with moderate-to-severe GO with type 2 orbitopathy (myogenic variant) according to their computed tomography (CT) scans. Forty-six eyes of 23 healthy subjects were evaluated as the control group. The strain ratio of orbital fat to medial rectus was calculated as the ratio of the medial rectus to orbital fat tissue, and the strain ratio of orbital fat to lateral rectus was calculated as the ratio of lateral rectus to orbital fat tissue.Results: The strain ratio of orbital fat to medial rectus was 3.03 ± 1.25 (range: 1.05-5.07) in the GO group, and 0.54 ± 0.20 (range: 0.14-1.08) in the control group (p = .0001). The strain ratio of orbital fat to lateral rectus was 0.97 ± 0.29 (range: 0.56-1.55) in the GO group, and 0.63 ± 0.23 (range: 0.18-1.09) in the control group (p = .0001).Conclusion: By using real-time UE, we found the medial and the lateral recti of GO patients to be stiffer compared to those of healthy subjects.

Value of Infrared Thermography Camera Attached to a Smartphone for Evaluation and Follow-up of Patients with Graves' Ophthalmopathy

PURPOSE

Graves' ophthalmopathy (GO) is the most common extra-thyroid manifestation of Graves' disease (GD). The Clinical Activity Score (CAS) has been widely used to evaluate GO inflammation severity and response to treatment; however, it is quite subjective. Infrared thermography (IRT) is a portable and low-cost device to evaluate local temperature and assess inflammation. The aim was to evaluate ocular temperature by IRT as an instrument for measuring inflammatory activity in GO and its correlation with CAS.

METHODS

This is a cross-sectional study involving 136 consecutive GD patients (12 with CAS ≥ 3/7, 62 with CAS < 3 and 62 without apparent GO) with 62 healthy controls. Patients with active ophthalmopathy were prospectively evaluated. Exophthalmometry, CAS, and thermal images from caruncles and upper eyelids were acquired from all subjects.

RESULTS

All eye areas of thermal evaluation had higher temperatures in GD patients with active ophthalmopathy (caruncles, p<0.0001; upper eyelids, p<0.0001), and it was positively correlated with CAS (r=0.60 and p<0.0001 at caruncles; r=0.58 and p<0.0001 at upper eyelids). No difference in temperature was found between other groups. Patients with active ophthalmopathy were prospectively evaluated after 6 or 12 months of the treatment and a significant difference was found in ophthalmometry (p=0.0188), CAS (p=0.0205), temperature of caruncles (p=0.0120), and upper eyelids (p=0.0066).

CONCLUSIONS

IRT was an objective and simple tool for evaluation and follow-up of inflammation in GO, allowed evidencing patients with significant inflammatory activity, and had a good correlation with the CAS score.

Dysthyroid Optic Neuropathy

PURPOSE

Dysthyroid optic neuropathy (DON) is a serious complication of Graves orbitopathy that can result in irreversible and profound visual loss. Controversy exists regarding the pathogenesis and management of the disease. The authors provide an overview of the current understanding of DON and present a therapeutic guideline.

METHODS

A review of the literature.

RESULTS

The mechanism of DON appears to be multifactorial: direct compression of the optic nerve by enlarged extraocular muscles, stretching of the optic nerve by proptosis, orbital pressure, vascular insufficiency, and inflammation. Some or all of these factors may be involved in an individual patient. There has only been one controlled trial comparing high-dose intravenous methylprednisolone to bony orbital decompression for DON. Both 2-wall and 3-wall decompression techniques successfully improve visual functions of patients with DON. There are few case reports/case series that suggest biologic agents may improve visual function in DON.

CONCLUSIONS

DON is a serious complication of Graves orbitopathy, the diagnosis and management of which is complex and requires a multidisciplinary approach. There is little evidence regarding the optimum management strategy. Based on the current literature, the first line of treatment is intravenous methylprednisolone, with the exact timing and indication of bony orbital decompression still to be determined. In addition, there may be a role for the use of biologic agents that will require a systematic program to determine efficacy.

Management of graves myopathy: Orbital imaging in thyroid-related orbitopathy

A broad understanding of the different imaging modalities used to assess the physiologic changes seen in Graves' orbitopathy complement clinical examination. Subtle applications of radiographic imaging techniques allow for a better understanding of the overall physiology of the orbit, quantify progression of disease, and differentiate it from orbital diseases with overlapping features. A nuanced approach to interpreting imaging features may allow us to delineate inactive from active thyroid eye disease, and advances within this field may arm clinicians with the ability to better predict and prevent dysthyroid optic neuropathy.

Characterizing Intraorbital Optic Nerve Changes on Diffusion Tensor Imaging in Thyroid Eye Disease Before Dysthyroid Optic Neuropathy

OBJECTIVE

The aim of this study was to determine whether the optic nerve is affected by thyroid eye disease (TED) before the development of dysthyroid optic neuropathy with diffusion-tensor imaging (DTI).

METHODS

Twenty TED patients and 20 controls were included. The mean, axial, and radial diffusivities and fractional anisotropy (FA) value were measured at the optic nerves in DTI. Extraocular muscle diameters were measured on computed tomography. The diffusivities and FA of the optic nerves were compared between TED and controls and between active and inactive stages of TED. The correlations between these DTI parameters and the clinical features were determined.

RESULTS

The mean, axial, and radial diffusivities were lower in TED compared with the controls (P < 0.05). In contrast, FA was higher in TED (P = 0.001). Radial diffusivity was lower in the active stage of TED than the inactive stage (P = 0.035). The FA was higher in the TED group than in the control group (P = 0.021) and was positively correlated with clinical activity score (r = 0.364, P = 0.021), modified NOSPECS score (r = 0.469, P = 0.002), and extraocular muscle thickness (r = 0.325, P = 0.041) in the TED group. Radial diffusivity was negatively correlated with modified NOSPECS score (r = -0.384, P = 0.014), and axial diffusivity was positively correlated with exophthalmos degree (r = 0.363, P = 0.025).

CONCLUSIONS

The diffusivities and FA reflected changes in the optic nerve before dysthyroid optic neuropathy in TED. The FA, in particular, reflected TED activity and severity.

Thyroid-Associated Orbitopathy and Biomarkers: Where We Are and What We Can Hope for the Future

Background

Thyroid-associated orbitopathy (TAO) is the most common autoimmune disease of the orbit. It occurs more often in patients presenting with hyperthyroidism, characteristic of Graves' disease, but may be associated with hypothyroidism or euthyroidism. The diagnosis of TAO is based on clinical orbital features, radiological criteria, and the potential association with thyroid disease. To date, there is no specific marker of the orbital disease, making the early diagnosis difficult, especially if the orbital involvement precedes the thyroid dysfunction.

Summary

The goal of this review is to present the disease and combine the available data in the literature concerning investigation of TAO biomarkers.

Conclusions

Despite the progress done in the understanding of TAO disease, some important pieces are still missing. Typically, for the future, major efforts have to be done in the discovery of new biomarkers, validation of the suspected candidates on multicenter cohorts with standardized methodologies, and establishment of their clinical performances on the specific clinical application fields in order to improve not only the management of the TAO patients but also the therapeutic options and follow-up.

Changes in peripapillary blood vessel density in Graves' orbitopathy after orbital decompression surgery as measured by optical coherence tomography angiography

The purpose is to evaluate the utility of optical coherence tomography (OCT) angiography in the evaluation of Graves' orbitopathy (GO) and response to orbital decompression in patients with and without dysthyroid optic neuropathy (DON). This was a single-center, prospective case series in a cohort of 12 patients (24 orbits) with GO and ±DON, (6 orbits) who underwent bilateral orbital decompression. All patients underwent pre- and postoperative OCT angiography of the peripapillary area. Vessel density indices were calculated in a 4.5 mm × 4.5 mm ellipsoid centered on the optic disk using split-spectrum amplitude decorrelation angiography algorithm, producing the vessel density measurements. Mean change in vessel density indices was compared between pre- and postoperative sessions and between patients with and without DON. Patient 1, a 34-year-old male with GO and unilateral DON OD, showed a significant reduction in blood vessel density indices oculus dexter (OD) (DON eye) after decompression while a more modest reduction was found oculus sinister (OS) with the greatest change noted intrapapillary. Patient 2, a 50-year-old male with DON OU, showed worsening neuropathy following decompression OD that was confirmed by angiographic density indices. Patient 3, a 55-year-female with DON, showed a reduction in blood vessel density OD and increased density OS. Patients without DON showed overall less impressive changes in indices as compared to those with DON. Using OCT angiography, response to surgical treatment in GO orbits, more so in orbits with DON, can be demonstrated and quantified using vessel density indices with reproducibility.

Multimodal assessment of orbital immune cell infiltration and tissue remodeling during development of graves disease by 1 H19 F MRI

PURPOSE

To evaluate key molecular and cellular features of Graves orbitopathy (GO) by simultaneous monitoring of alterations in morphology, inflammatory patterns, and tissue remodeling.

METHODS

To this end, we utilized a murine model of GO induced by immunization with a human thyroid-stimulating hormone receptor A-subunit plasmid. Altogether, 52 mice were used: 27 GOs and 25 controls (Ctrl) immunized with β-galactasidose plasmid. From these, 17 GO and 12 Ctrl mice were subjected to multimodal MRI at 9.4T, whereas 23 mice only underwent histology. Beyond anatomical hydrogen-1 (¹ H) MRI, we employed transverse relaxation time (T₂ ) mapping for visualization of edema, chemical exchange saturation transfer (CEST) for detection of hyaluronan, and fluorine-19 (¹⁹ F) MRI for tracking of in situ-labeled immune cells after intravenous injection of perfluorcarbons (PFCs).

RESULTS

¹ H/¹⁹ F MRI demonstrated substantial infiltration of PFC-loaded immune cells in peri and retro-orbital regions of GO mice, whereas healthy Ctrls showed only minor ¹⁹ F signals. In parallel, T₂ mapping indicated onset of edema in periorbital tissue and adjacent ocular glands (P = 0.038/0.017), which were associated with enhanced orbital CEST signals in GO mice (P = 0.031). Concomitantly, a moderate expansion of retrobulbar fat (P = 0.029) was apparent; however, no signs for extraocular myopathy were detectable. ¹⁹ F MRI-based visualization of orbital inflammation exhibited the highest significance level to discriminate between GO and Ctrl mice (P = 0.006) and showed the best correlation with the clinical score (P = 0.0007).

CONCLUSION

The present approach permits the comprehensive characterization of orbital tissue and holds the potential for accurate GO diagnosis in the clinical setting. Magn Reson Med 80:711-718, 2018. © 2018 International Society for Magnetic Resonance in Medicine.

Diagnostic imaging in neuro-ophthalmology

Neuro-ophthalmology is a field combining neurology and ophthalmology that studies diseases that affect the visual system and the mechanisms that control eye movement and pupil function. Imaging tests make it possible to thoroughly assess the relevant anatomy and disease of the structures that make up the visual pathway, the nerves that control eye and pupil movement, and the orbital structures themselves. This article is divided into three sections (review of the anatomy, appropriate imaging techniques, and evaluation of disease according to clinical symptoms), with the aim of providing useful tools that will enable radiologists to choose the best imaging technique for the differential diagnosis of patients' problems to reach the correct diagnosis of their disease.

Signs in Neuroradiology: A Pictorial Review

One of the major problems radiologists face in everyday practice is to decide the correct diagnosis, or at least narrow down the list of possibilities. In this context, indicative evidences (signs) are useful to recognize pathologies, and also to narrow the list of differential diagnoses. Despite classically being described for a single disease, or a closely related family of disorders, most indications are not restricted exclusively to their traditional definition. Therefore, using signs for prognosis requires knowledge of the mechanism of their appearance, and which pathologies they are observed in. In this study, we demonstrate some of the more common and useful neuroradiologic signs with relevant images, and discuss their use in differential diagnosis.

Isolated primary amyloidosis of the inferior rectus muscle mimicking Graves' orbitopathy

The diagnosis of Graves’ orbitopathy is usually straightforward. However, orbital diseases that mimick some clinical signs of Graves’ orbitopathy may cause diagnostic confusion, particularly when associated to some form of thyroid dysfunction. This report describes the rare occurrence of localized inferior rectus muscle amyloidosis in a patient with autoimmune hypothyroidism, who was misdiagnosed as Graves’ orbitopathy. A 48-year-old man complained of painless progressive proptosis on the left side and intermittent vertical diplopia for 6 months. The diagnosis of Graves’ orbitopathy was entertained after magnetic resonance imaging revealing a markedly enlarged, tendon-sparing inferior rectus enlargement on the left side, and an autoimmune hypothyroidism was disclosed on systemic medical workup. After no clinical improvement with treatment, the patient was referred to an ophthalmologist and further investigation was performed. The presence of calcification in the inferior rectus muscle on computed tomography, associated with the clinical findings led to a diagnostic biopsy, which revealed amyloid deposition. This report emphasizes that a careful evaluation of atypical forms of Graves’ orbitopathy may be crucial and should include, yet with rare occurrence, amyloidosis in its differential diagnosis.

Performance of apparent diffusion coefficient of medial and lateral rectus muscles in Graves' orbitopathy

Objective The purpose of this study was to determine the performance of the apparent diffusion coefficient in the detection of involvement of the medial and lateral rectus muscles in patients with Graves' orbitopathy. Methods and materials This prospective study was conducted on 33 consecutive patients (16 males, 17 females with a mean age of 36 years) with Graves' orbitopathy and 18 age- and sex-matched volunteers. The patients and volunteers underwent diffusion-weighted magnetic resonance imaging of the orbit in the axial plane using echo-planar imaging. The apparent diffusion coefficient of the medial and lateral rectus muscles was calculated. Results The medial rectus muscle was more affected than the lateral rectus muscle. The mean apparent diffusion coefficient value of the medial and lateral rectus muscles was 1.81 ± 0.19 and 1.72 ± 0.07 × 10^-3mm²/s in patients with Graves' orbitopathy and 1.59 ± 0.06 and 1.51 ± 0.06 × 10^-3 mm²/s in volunteers, respectively. There was a significant difference in apparent diffusion coefficient values of the medial and lateral rectus muscles between patients with Graves' orbitopathy and volunteers ( p = 0.001). The classification performance as measured with area under the receiver operator characteristic curve was 0.89 (95% confidence interval: 0.732-0.904). The best performing threshold of the apparent diffusion coefficient value of the medial rectus muscle was 1.69 × 10^-3 mm²/s and associated efficiency was 86%, sensitivity was 97%, and specificity was 97%. Conclusion We concluded that the apparent diffusion coefficient of the medial rectus muscle can be used for diagnosis of Graves' orbitopathy.

Dysthyroid optic neuropathy: update on pathogenesis, diagnosis, and management

INTRODUCTION

Dysthyroid optic neuropathy (DON) is a severe manifestation of thyroid eye disease (TED) that can result in permanent vision loss. Management is complex, multidisciplinary, and involves medical and/or surgical therapies. This review describes current concepts in the epidemiology, pathophysiology, diagnosis, and treatment of DON.

AREAS COVERED

An extensive review of the literature was performed to detail current concepts on the diagnosis and management of DON. This includes utilization of various medical and surgical modalities for disease management.

EXPERT COMMENTARY

DON can result in permanent blindness and often requires the use of corticosteroids and surgical decompression. We favor the use of intravenous corticosteroids and a transcaruncular approach when surgical decompression is indicated. The use of orbital radiation for DON is often reserved for patients that are poor surgical candidates and/or patients with refractory disease.

Fractional anisotropy and diffusivity changes in thyroid-associated orbitopathy

INTRODUCTION

To investigate the extraocular muscle (EOM) changes in thyroid-associated orbitopathy (TAO) on DTI and the correlations between DTI parameters and clinical features.

METHODS

Twenty TAO patients and 20 age- and sex-matched controls provided informed consent and were enrolled. Ten-directional DTI was acquired in orbit. Fractional anisotropy (FA), mean, axial, and radial diffusivities were obtained at medial and lateral EOMs in both orbits. EOM thickness was measured in patients using axial CT images. FA and diffusivities were compared between patients and controls. The relationships between DTI values and muscle thickness and exophthalmos were evaluated. DTI values compared between patients in active and inactive phases by clinical activity score of TAO. DTI values were also compared between acute and chronic stages by the duration of disease.

RESULTS

In medial EOM, FA was significantly lower in patients (p < 0.001) and negatively correlated with muscle thickness (r = -0.604, p < 0.001). Radial diffusivity was significantly higher in patients (p = 0.010) and correlated with muscle thickness (r = 0.349, p = 0.027). In lateral EOM, DTI values did not differ between patients and controls. In the acute stage, the diffusivities of the medial rectus EOM were increased compared with the chronic stage. DTI values of the medial and lateral rectus EOM did not differ significantly between active and inactive phases.

CONCLUSION

DTI can be used to diagnose TAO with FA and radial diffusivity change in EOM. Diffusivities can be used to differentiate acute and chronic stage of TAO. However, DTI values showed limitation in reflecting TAO activity according to the CAS.

Magnetic resonance imaging of optic nerve

Optic nerves are the second pair of cranial nerves and are unique as they represent an extension of the central nervous system. Apart from clinical and ophthalmoscopic evaluation, imaging, especially magnetic resonance imaging (MRI), plays an important role in the complete evaluation of optic nerve and the entire visual pathway. In this pictorial essay, the authors describe segmental anatomy of the optic nerve and review the imaging findings of various conditions affecting the optic nerves. MRI allows excellent depiction of the intricate anatomy of optic nerves due to its excellent soft tissue contrast without exposure to ionizing radiation, better delineation of the entire visual pathway, and accurate evaluation of associated intracranial pathologies.