Magnetic resonance imaging and ultrasound measurements of extraocular muscles in thyroid-associated ophthalmopathy at different stages of the disease

Application of Quantitative MRI in Thyroid Eye Disease: Imaging Techniques and Clinical Practices

Thyroid eye disease (TED) is a complex autoimmune disorder that impairs various orbital structures, leading to cosmetic damage and vision loss. Magnetic resonance imaging (MRI) is a fundamental diagnostic tool utilized in clinical settings of TED, for its accurate demonstration of orbital lesions and indication of disease conditions. The application of quantitative MRI has brought a new prospect to the management and research of TED, offering more detailed information on morphological and functional changes in the orbit. Therefore, many researchers concentrated on the implementation of different quantitative MRI techniques on TED for the exploration of clinical practices. Despite the abundance of studies utilizing quantitative MRI in TED, there remain considerable barriers and disputes on the best exploitation of this tool. This could possibly be attributed to the complexity of TED and the fast development of MRI techniques. It is necessary that clinical and radiological aspects of quantitative MRI in TED be better integrated into comprehensive insights. Hence, this review traces back 30 years of publications regarding quantitative MRI utilized in TED and elucidates this promising application in the facets of imaging techniques and clinical practices. We believe that a deeper understanding of the application of quantitative MRI in TED will enhance the efficacy of the multidisciplinary management of TED. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 3.

Subclinical Ocular Motility Dysfunction and Extraocular Muscle Changes in Inactive Graves' Orbitopathy

This study aimed to investigate the presence of structural and functional changes in extraocular muscles (EMs) among patients with inactive Graves' orbitopathy (GO) classified according to the Clinical Activity Score (CAS). Sixty-seven patients with Graves' disease (GD) and inactive GO were included. The data collected included clinical parameters, thyroid function, autoantibody levels, EOM morphology via orbital ultrasound (US), and ocular motility. Patients were stratified into Red Filter Test (RFT)-positive or RFT-negative groups based on the presence or absence of latent diplopia during the RFT examination. Thirty-three patients (49.25%) exhibited latent diplopia on the RFT, despite not reporting double vision during standard ocular motility tests. Significant differences were observed between the two groups in terms of age, disease duration, intraocular pressure (IOP) elevation in up-gaze, and medial rectus muscle thickness (p < 0.05). No significant differences were found in thyroid status, TRAb and ATA levels, CASs, exophthalmos, or lateral rectus thickness between the two groups. This study revealed that in inactive GO, subclinical EM dysfunction and morphological changes may be present, which might not be apparent through routine ocular examinations. The RFT is effective in detecting latent diplopia, highlighting its utility in identifying subtle ocular motility issues and subclinical muscle involvement. Comprehensive evaluations combining functional tests like the RFT and imaging are essential for early detection of GO-related abnormalities, enabling tailored and prompt management and improving patient outcomes.

Correlation of clinical and radiological scores for evaluation of activity in patients having thyroid-associated orbitopathy: A prospective observational study

PURPOSE

To find a correlation between the clinical (vision-inflammation-strabismus-appearance [VISA] score) and radiological (apparent diffusion coefficient [ADC] values) scores for evaluating disease activity in patients with thyroid-associated orbitopathy.

DESIGN

A prospective comparative study.

METHODS

Our study was performed for consecutively diagnosed thyroid-associated orbitopathy (TAO) patients. Clinical evaluation included the VISA classification system with the basic thyroid workup. An inflammatory score of <4/8 was considered inactive and ≥4/8 as an active disease. Every included patient underwent a diffusion-weighted magnetic resonance imaging (DW-MRI) scan of the orbits. The orbital parameters evaluated on imaging included the proptosis, thickness, as well as the ADC values of extraocular muscles.

RESULTS

We studied 33 consecutive patients (23 females, 69.7%) with a mean age of 41.8 years. The majority (n = 27, 81.8%) were hyperthyroid, four were hypothyroid, and two were euthyroid. In the VISA classification, nine patients had active TAO (≥4/8 inflammation score), while 24 had inactive disease. There was a positive correlation between the inflammation score and ADC values of medial rectus (MR), inferior rectus (IR) and lateral rectus (LR). We had nine patients with inflammation scores ≥4. With receiver operating characteristic (ROC) curve analysis, we found that the ADC value of IR can predict disease activity with 68% sensitivity and MR-ADC can predict active TAO with 87% sensitivity.

CONCLUSION

The ADC parameters of DW-MRI are objective and less operator dependent than the clinical TAO activity scores like VISA classification. A randomized control trial may provide robust data on this correlation.

Echographic characterization of extraocular muscles in pediatric patients with thyroid dysfunction

PURPOSE

To characterize the size of extraocular muscles (EOMs) in a pediatric population with thyroid dysfunction using orbital echography.

METHODS

Patients under age 18 with thyroid dysfunction who presented to an academic ophthalmology department from 2009 to 2020 and received orbital echography were included in this IRB-approved retrospective study. Data collected included age, clinical activity score (CAS), thyroid stimulating immunoglobulin (TSI), and extraocular recti muscle thickness on echography. Patients were organized into three age cohorts, after which statistical analysis compared recti measurements to previously reported normal ranges.

RESULTS

Twenty patients with thyroid dysfunction were included. When comparing average recti muscle thicknesses of study patients to those of previously published normal children in similar age ranges, the levator-superior rectus complex was significantly increased in all age groups of children with thyroid dysfunction (p-values = <.004), and the levator-superior rectus complex was most frequently enlarged compared to published normal values (78% of eyes). CAS was not correlated with EOM size in the youngest group (5-10 years old, p-values >.315) but was significantly correlated in older groups (11-17 years old, p-values <.027). TSI was not correlated with EOM size in any group (p-values >.206).

CONCLUSIONS

Echographic reference ranges for EOMs in children with thyroid dysfunction were established. There are increased rates of levator-superior rectus complex enlargement in children with TED compared to adults with TED, and EOM size is correlated with CAS in children older than 10 years. Though limited, these findings may serve as an additional tool for ophthalmologists to ascertain disease activity in pediatric patients with thyroid dysfunction.

Computed tomography and magnetic resonance imaging approaches to Graves' ophthalmopathy: a narrative review

Graves' ophthalmopathy (GO) affects up to 50% of patients with Graves' disease (GD) ranging from mild ocular irritation to vision loss. The initial diagnosis is based on clinical findings and laboratory tests. Orbital imaging, such as magnetic resonance imaging (MRI) and computed tomography (CT), is an important tool to assess orbital changes, being also useful for understanding disease progression and surgical planning. In this narrative review, we included 92 studies published from 1979 to 2020 that used either MRI and/or CT to diagnose and investigate GO, proposing new methods and techniques. Most of the methods used still need to be corroborated and validated, and, despite the different methods and approaches for thyroid eye disease (TED) evaluation, there is still a lack of standardization of measurements and outcome reports; therefore, additional studies should be performed to include these methods in clinical practice, facilitating the diagnosis and approach for the treatment of TED.

Changes in Clinical Activity, Serum Autoantibody Levels, and Chorioretinal Vessels After Systemic Glucocorticoid Therapy in Thyroid Eye Disease

INTRODUCTION

The aim of this study was to investigate changes in the Clinical Activity Score, serum thyroid-stimulating hormone receptor antibody and thyroid-stimulating immunoglobulin levels, chorioretinal blood vessels, and extraocular muscle thickness in patients with thyroid eye disease following systemic steroid treatment.

METHODS

This prospective observational study enrolled 57 patients with active thyroid eye disease who received systemic intravenous glucocorticoids for 12 weeks. Demographics, clinical activity scores, optical coherence tomography images, and serum thyroid-stimulating immunoglobulin and thyroid-stimulating hormone receptor antibody levels were assessed at baseline, at 6 and 12 weeks after intravenous (IV) GC therapy initiation, and 2 months after IV GC therapy termination. The extraocular muscle thickness, choroidal thickness, and choroidal vascularity index were measured.

RESULTS

The clinical activity scores showed a significant decrease. Serum thyroid-stimulating immunoglobulin levels dropped continuously for 2 months. The thyroid-stimulating hormone receptor antibody level decreased until 12 weeks after treatment but returned to within the normal range in 75% of patients after 77 and 126 days, respectively. The choroidal thickness decreased at all time points. The thickness of the medial and inferior rectus muscles decreased at 2 months after treatment. The clinical activity score decreased to < 3 points in 50% of patients after 78 days.

CONCLUSION

Intravenous glucocorticoid therapy improved the clinical activity score, chorioretinal blood flow, and extraocular muscle thickness. The serum autoantibody levels were normalized in patients with active thyroid eye disease 2 months after IV GC termination. The serum thyroid-stimulating immunoglobulin and thyroid-stimulating hormone receptor antibody levels correlated with restoration of chorioretinal capillary perfusion and improved clinical symptoms and muscle thickness. Non-invasive optical coherence tomography findings and serologic factors predict the response to intravenous glucocorticoid therapy.

Eye Muscle MRI in Myasthenia Gravis and Other Neuromuscular Disorders

INTRODUCTION

MRI of extra-ocular muscles (EOM) in patients with myasthenia gravis (MG) could aid in diagnosis and provide insights in therapy-resistant ophthalmoplegia. We used quantitative MRI to study the EOM in MG, healthy and disease controls, including Graves' ophthalmopathy (GO), oculopharyngeal muscular dystrophy (OPMD) and chronic progressive external ophthalmoplegia (CPEO).

METHODS

Twenty recently diagnosed MG (59±19yrs), nineteen chronic MG (51±16yrs), fourteen seronegative MG (57±9yrs) and sixteen healthy controls (54±13yrs) were included. Six CPEO (49±14yrs), OPMD (62±10yrs) and GO patients (44±12yrs) served as disease controls. We quantified muscle fat fraction (FF), T2water and volume. Eye ductions and gaze deviations were assessed by synoptophore and Hess-charting.

RESULTS

Chronic, but not recent onset, MG patients showed volume increases (e.g. superior rectus and levator palpebrae [SR+LPS] 985±155 mm3 compared to 884±269 mm3 for healthy controls, p < 0.05). As expected, in CPEO volume was decreased (e.g. SR+LPS 602±193 mm3, p < 0.0001), and in GO volume was increased (e.g. SR+LPS 1419±457 mm3, p < 0.0001). FF was increased in chronic MG (e.g. medial rectus increased 0.017, p < 0.05). In CPEO and OPMD the FF was more severely increased. The severity of ophthalmoplegia did not correlate with EOM volume in MG, but did in CPEO and OPMD. No differences in T2water were found.

INTERPRETATION

We observed small increases in EOM volume and FF in chronic MG compared to healthy controls. Surprisingly, we found no atrophy in MG, even in patients with long-term ophthalmoplegia. This implies that even long-term ophthalmoplegia in MG does not lead to secondary structural myopathic changes precluding functional recovery.

Clinical and imaging clues to the diagnosis and follow-up of ptosis and ophthalmoparesis

Ophthalmoparesis and ptosis can be caused by a wide range of rare or more prevalent diseases, several of which can be successfully treated. In this review, we provide clues to aid in the diagnosis of these diseases, based on the clinical symptoms, the involvement pattern and imaging features of extra-ocular muscles (EOM). Dysfunction of EOM including the levator palpebrae can be due to muscle weakness, anatomical restrictions or pathology affecting the innervation. A comprehensive literature review was performed to find clinical and imaging clues for the diagnosis and follow-up of ptosis and ophthalmoparesis. We used five patterns as a framework for differential diagnostic reasoning and for pattern recognition in symptomatology, EOM involvement and imaging results of individual patients. The five patterns were characterized by the presence of combination of ptosis, ophthalmoparesis, diplopia, pain, proptosis, nystagmus, extra-orbital symptoms, symmetry or fluctuations in symptoms. Each pattern was linked to anatomical locations and either hereditary or acquired diseases. Hereditary muscle diseases often lead to ophthalmoparesis without diplopia as a predominant feature, while in acquired eye muscle diseases ophthalmoparesis is often asymmetrical and can be accompanied by proptosis and pain. Fluctuation is a hallmark of an acquired synaptic disease like myasthenia gravis. Nystagmus is indicative of a central nervous system lesion. Second, specific EOM involvement patterns can also provide valuable diagnostic clues. In hereditary muscle diseases like chronic progressive external ophthalmoplegia (CPEO) and oculo-pharyngeal muscular dystrophy (OPMD) the superior rectus is often involved. In neuropathic disease, the pattern of involvement of the EOM can be linked to specific cranial nerves. In myasthenia gravis this pattern is variable within patients over time. Lastly, orbital imaging can aid in the diagnosis. Fat replacement of the EOM is commonly observed in hereditary myopathic diseases, such as CPEO. In contrast, inflammation and volume increases are often observed in acquired muscle diseases such as Graves' orbitopathy. In diseases with ophthalmoparesis and ptosis specific patterns of clinical symptoms, the EOM involvement pattern and orbital imaging provide valuable information for diagnosis and could prove valuable in the follow-up of disease progression and the understanding of disease pathophysiology.

Ocular hypertension in patients with active thyroid-associated orbitopathy: a predictor of disease severity, particularly of extraocular muscle enlargement

The purpose was to ascertain if any relation exists between the elevated intraocular pressure (IOP) in patients with thyroid-associated orbitopathy (TAO) in active stage and the severity of extraocular muscle involvement and the extent of exophthalmos.

METHODS

A total of 96 eyes and orbits of 48 adult patients with active TAO were investigated. All patients underwent magnetic resonance imaging of the orbit and measurement of all extraocular recti muscles (EOM). The obtained data was divided into two groups according to the IOP value: normal IOP ≤ 21 mmHg; n = 47 and elevated IOP with IOP > 21 mmHg; n = 49, and analyszed.

RESULTS

A significant difference was found in the short diameter of medial rectus and inferior rectus muscles and in the sum of short parameters of all EOM. All these parameters were significantly higher in the elevated IOP group. Motility restriction in at least one gaze direction was also significantly more frequent (p < 0.0001) in the elevated IOP group. A positive moderate correlation was found between IOP and the sum of short parameters of EOM (r = 0.496). No correlation was found between the IOP and exophthalmos values (r = 0.267). During the follow-up, the frequency of strabismus surgery and orbital decompression was significantly higher in the elevated IOP group (p = 0.003; p = 0.002).

CONCLUSION

Elevated IOP in the active TAO stage particularly correlates with extraocular muscle involvement. These patients are also more likely to require orbital decompression and strabismus surgery.

Advances in the Treatment of Thyroid Eye Disease Associated Extraocular Muscle Myopathy and Optic Neuropathy

PURPOSE OF REVIEW

To review emerging treatments for thyroid eye disease (TED) associated extraocular muscle myopathy and dysthyroid optic neuropathy (DON).

RECENT FINDINGS

Emerging targeted biologic therapies may alter the disease course in TED. Teprotumumab, a type I insulin-like growth factor receptor inhibitor, is the most recent addition to the treatments available for TED-associated extraocular muscle myopathy causing diplopia. Small studies also suggest a potential therapeutic benefit for DON. Various recent studies have also expanded our knowledge on conventional TED therapies. The therapeutic landscape of TED and its sequelae has evolved in recent years. New targeted therapies have the potential to reduce the extraocular muscle and orbital volume expansion which can lead to diplopia and vision loss from optic nerve compression. Longer term efficacy and durability data is needed to determine the role biologics, such as teprotumumab, should play in the treatment of TED patients compared to the current standard of care.

Correlation between extent of lacrimal gland prolapse and clinical features of thyroid-associated ophthalmopathy: a retrospective observational study

Background

Studies on the factors related to lacrimal gland prolapse (LGP) in patients with thyroid-associated ophthalmopathy (TAO) are limited. This study aimed to assess the factors associated with LGP on magnetic resonance imaging (MRI) and its relation to TAO activity .

Methods

Thirty-six patients (72 orbits) with inactive TAO (43 orbits, Clinical Activity Score [CAS] < 3) or active TAO (29 orbits, CAS ≥3) were investigated retrospectively. All patients underwent ophthalmic evaluation and orbital magnetic resonance imaging. The severity of LGP and proptosis and the extraocular muscle (EOM) volume were measured. LGP and related factors were assessed by correlational and linear regression analyses. The value of LGP for discriminating the activity of TAO was evaluated by receiver-operating characteristic curve analysis.

Results

The mean LGP was significantly higher in the active TAO group than in the inactive TAO group (P < 0.001). There were significant positive correlations between LGP severity and the CAS (r = 0.51, P < 0.001), proptosis (r = 0.72, P < 0.001), and EOM volume (superior rectus [r = 0.49, P < 0.001], inferior rectus [r = 0.47, P < 0.001], lateral rectus [r = 0.59, P < 0.001], medial rectus [r = 0.62, P < 0.001], superior oblique [r = 0.48, P < 0.001], and all EOMs [r = 0.59, P < 0.001]). Receiver-operating characteristic curve analysis revealed an LGP of 13.65 mm (area under the curve, 0.824; sensitivity, 79.3%; specificity, 81.4%) to be the cut-off value that differentiated active and inactive TAO.

Conclusions

LGP measurements obtained from orbital magnetic resonance images were positively correlated with CAS, proptosis and EOM volume. The extent of LGP appears to be a good indicator of disease activity in patients with TAO.

Correlation between Thyroid-stimulating Antibody Level Change and Extraocular Muscle Thickness Change in Thyroid Eye Disease

Purpose: To investigate the changes in extraocular muscle thicknesses by variations in the thyroid stimulating antibody (TSAb) level in patients with thyroid eye disease (TED).Methods: A total of 67 TED patients were enrolled. They were divided into two groups: an experimental group with clinically significant elevated TSAb levels (≥140 IU/L) and a control group (TSAb <140 IU/L). All of the lateral, medial, superior, and inferior rectus muscle thicknesses were measured with the aid of anterior segment optical coherence tomography (OCT). The average thicknesses for both eyes were recorded for each patient based on the values measured at the ends of the muscles (which become vertically thinner from the points of tendon attachment). We measured changes in TSAb levels and extraocular muscle thicknesses after two follow-up periods and sought correlations among these parameters.Results: At the initial visits, the inferior rectus muscle thickness was positively correlated with the TSAb level in the experimental group (p = 0.045, r = 0.478). None of the medial, superior, or lateral rectus muscle thicknesses were so correlated. On follow-up, the variation in TSAb level correlated negatively with changes in lateral rectus muscle thickness (p = 0.038, r = -0.357). The superior rectus muscle thickness tended to be negatively correlated with the TSAb level, but statistical significance was not attained (p = 0.146, r = -0.669). The thicknesses of the inferior and superior rectus muscles did not change over time.Conclusions: In TED patients, TSAb variations seem to reflect the extent of periorbital tissue edema, thus correlating negatively with especially lateral rectus muscle thickness changes.

Age-related difference in extraocular muscles and its relation to clinical manifestations in an ethnically homogenous group of patients with Graves' orbitopathy

PURPOSE

To evaluate the age-related difference in EOMs and its relation to clinical manifestations by computed tomography (CT) measurement of EOMs.

METHODS

The medical records and CT image review of 40 patients (80 orbits) with moderate-to-severe Graves' orbitopathy were performed. The patients were divided into two age groups, group 1 (≤ 40 years) and group 2 (> 40 years). CT scans of 30 gender- and age-matched normal controls were also obtained. The maximal cross-sectional area (MCA) and its position (pMCA) of each EOM were measured.

RESULTS

Group 1 presented with more severe proptosis (p < 0.001), while group 2 had a higher risk of diplopia (p < 0.001). Motility restriction in supraduction was more likely to occur in Group 2 (p = 0.027) with even higher severity (p = 0.047). The pMCA was higher in the inferior (p = 0.001), medial (p = 0.021), and lateral rectus (p = 0.013) in group 1. Proptosis was positively correlated to pMCA while diplopia was correlated to MCA in both groups. Significant correlation was noted between restrictions levels and MCA (superior, r = 0.467, p < 0.001; inferior, r = 0.358, p = 0.007; medial, r = 0.314, p = 0.018; lateral, r = 0.308, p = 0.021) or pMCA (inferior, r =  - 0.534, p < 0.001) only in group 2.

CONCLUSIONS

The muscle enlargement patterns are significantly different between younger and older patients. Older patients tended to have enlarged muscle bellies more posterior in the orbit, which is responsible for more diplopia and motility restriction. Proptosis is more likely to be affected by the most enlarged position than muscle size. So younger patients tended to develop more proptosis and be less bothered by motility restriction even with enlarged muscles.

A novel needle electrode for intraoperative fourth cranial nerve neurophysiological mapping

OBJECTIVES

Trochlear nerve (CN-IV) mapping method has not been confirmed to date. The compound muscle action potential (CMAP) of CN-IV cannot be recorded because of the low mapping sensitivity and anatomical characteristics of the superior oblique muscle (SOM). The aim of this study was to evaluate the effectiveness of a novel needle electrode (NNE), for the intraoperative mapping of CN-IV.

MATERIALS AND METHODS

The NNEs were inserted in the target extraocular muscles in 19 patients. We compared the CMAP amplitude of the NNE with that of the conventional needle electrode (CNE). Furthermore, we investigated the dissimilarity between the CMAP of the CN-IV and other extraocular cranial nerves (ECNs) and the correlation between the readings of the CN-IV mapping and its postoperative functional outcome.

RESULTS

The CMAP of CN-IV has been measured in nine patients (47.4%). The CMAP of CN-IV was distinguishable from other ECNs. The CMAP of the NNE was found to be three times higher than that of the CNE. Although the NNE has shown the potential to record the CN-IV's CMAP, 4 cases ended up having a CN-IV postoperative dysfunction.

CONCLUSIONS

For the first time, we confirmed the possibility of intraoperative mapping the CN-IV using an NNE inserted into the SOM. The NNE can also be useful for other neurophysiological monitoring methods.

Extraocular muscle biopsy during surgery for strabismus of unknown etiology

Most cases of strabismus have a chronic and stable or known etiologic diagnosis prior to surgery. In some cases, however, surgery is undertaken to correct a stable ocular misalignment without a definitive etiology. We present 2 cases, one with euthyroid Graves' orbitopathy and the other with amyloid light-chain amyloidosis, in which extraocular muscle biopsy performed intraoperatively allowed histopathologic confirmation of a clinical diagnosis.

Treatment with bimatoprost for exophthalmos in patients with inactive thyroid-associated ophthalmopathy

Purpose

This study was performed to observe changes prospectively in exophthalmos and orbital fat in patients with inactive thyroid-associated ophthalmopathy (TAO) treated with bimatoprost.

Methods

In this 12-month single-treatment pilot observational study, 13 patients with inactive-phase TAO were administered bimatoprost to treat exophthalmos due to TAO. Exophthalmos values and orbital tissue volumes were measured on MRI by technicians in a masked fashion.

Results

Nine orbits of nine patients (eight women, one man) were treated with bimatoprost for 12 months. Mean exophthalmos values before and after treatment were 21.7±2.2 and 21.7±2.0 mm, respectively. The mean value after 12 months of treatment was not significantly different from before treatment (P=0.82). Mean orbital fat volume before and after 12 months of treatment was 17.2±2.5 and 17.0±3.0 cm³, respectively. The corresponding total extraocular muscle volume was 4.0±0.7 and 3.8±0.9 cm³, respectively. Mean volume in each tissue type after 12 months of treatment was not significantly different from before treatment (orbital fat, P=0.70; extraocular muscles, P=0.32).

Conclusion

Topical bimatoprost treatment did not reduce exophthalmos or orbital fat in this cohort of patients with inactive TAO.

Relationship between magnetic resonance imaging signal intensity and volume of extraocular muscles in thyroid-associated ophthalmopathy with methylprednisolone pulse therapy

Purpose

To characterize the relationship between inflammation and swelling of extraocular muscles in thyroid-associated ophthalmopathy before and after methylprednisolone pulse therapy.

Methods

The signal intensities and volumes of the superior rectus (SR), inferior rectus (IR), lateral rectus (LR), medial rectus (MR), and superior oblique (SO) muscles were measured with magnetic resonance imaging in 25 eyes of 25 patients with thyroid-associated ophthalmopathy in the acute inflammatory phase before and after methylprednisolone pulse therapy. The signal intensity ratios (SIRs) of muscles and brain white matter were calculated.

Result

The mean SIRs before treatment were 2.28±0.74 in SR, 2.66±0.57 in IR, 2.03±0.42 in LR, 2.45±0.49 in MR, and 1.98±0.48 in SO muscles. The mean SIRs after treatment were 1.82±0.62, 1.84±0.52, 1.70±0.35, 1.95±0.46, and 1.60±0.36, respectively. The mean volumes (cm³) before treatment were 1.35±0.67 in SR, 1.21±0.39 in IR, 0.66±0.13 in LR, 0.94±0.31 in MR, and 0.58±0.14 in SO muscles. Those after treatment were 1.12±0.45, 0.91±0.31, 0.61±0.12, 0.85±0.28, and 0.49±0.11, respectively. The SIRs showed significantly positive correlations with volumes both before and after treatment in SR muscles (before, r=0.77; after, r=0.69), IR muscles (before, r=0.65; after, r=0.60), MR muscles (before, r=0.69; after, r=0.73), and SO muscles (before, r=0.52; after, r=0.50) (P<0.01 for all correlations).

Conclusion

Swelling reflected the inflammation in extraocular muscles of thyroid-associated ophthalmopathy both before and after treatment.

Morphometric parameters of extraocular rectus muscles evaluated by dynamic-multipositional magnetic resonance

PURPOSE

To establish normal values of morphologic parameters of extraocular rectus muscles visualized in different gaze positions by means of an accessible method of dynamic-multipositional magnetic resonance imaging (dmMRI).

METHODS

Twenty eyes of 10 healthy, orthotropic subjects were examined. A 1.5T scanner (Avanto) with standard head coil was used. The protocol of dmMRI included 6 gaze positions in 10° intervals in which 13-second, orbital, T2 sequences were performed in quasi-coronal plane. The measurements of extraocular rectus muscles shape, sectional area, and volume were obtained with use of ImageJ 1.38x (NIH) software.

RESULTS

Relative change in cross-sectional area between position of rest and gaze of action of each muscle appears to be significant just in the medial and posterior parts of their belly. The maximal cross-section area increases significantly when the muscle contracts (21% to 32% depending on the muscle). The superior rectus must be assessed along with levator palpebrae as the distinction between their bellies is difficult. Relative change in partial muscle volume on contraction ranged from 12.3% to 21.6% depending on the muscle. Muscle contraction results in more circular shape of its belly while relaxation is more of an ellipse.

CONCLUSIONS

Dynamic-multipositional MRI performed in the proposed manner is an accessible and repeatable method for visualization of extraocular rectus muscles. Assessment of morphometric parameters such as muscle shape, maximal cross-section area, and partial muscle volume is easy with digital imaging software.

Predictors of the Dose-Effect Relationship regarding Unilateral Inferior Rectus Muscle Recession in Patients with Thyroid Eye Disease

Purpose. To evaluate whether inferior rectus muscle (IRM) thickness, the degree of adipose change in the IRM, smoking status, and the previous history of orbital radiotherapy can predict the dose-effect relationship regarding unilateral IRM recession in thyroid eye disease (TED). Methods. Twenty-five patients were retrospectively reviewed. We calculated the largest IRM cross-sectional area and evaluated the degree of adipose change in the IRM using magnetic resonance imaging. The degree of adipose change and smoking status were classified using grading scales (0-3); previous orbital radiotherapy was graded as 0 when a history was not available and 1 when it was available. The correlation between the dose-effect relationship and the hypothesized predictive factors was evaluated using stepwise multiple regression analysis. Results. The multiple regression model, with the exception of the history of the previous orbital radiotherapy, estimated a significant dose-effect relationship for the parameters evaluated (Y DOSE-EFFECT = 0.013X IRM AREA  - 0.222X ADIPOSE  - 0.102X SMOKING + 1.694; r = 0.668; adjusted r (2) = 0.367; P = 0.005). Conclusions. The dose-effect relationship regarding unilateral IRM recession in TED could be predicted using IRM thickness, degree of intramuscular adipose change, and smoking status but could not be predicted using the previous orbital radiotherapy history.

Diagnostic neuroimaging in neuro-ophthalmic disorders

PURPOSE OF REVIEW

Neuroimaging studies are a valuable diagnostic tool in the evaluation of a patient with neuro-ophthalmic disease. This review provides an approach to selecting an appropriate imaging study and interpreting the results.

RECENT FINDINGS

MRI and CT are the imaging studies most commonly employed in neuro-ophthalmology. Each modality has unique strengths that make it particularly suitable in certain clinical situations.

SUMMARY

In the current practice of neuro-ophthalmology, the clinician must be familiar with the uses and limitations of neuroimaging studies so they can be used appropriately to improve diagnostic accuracy.

Diagnostic accuracy of short-time inversion recovery sequence in Graves' Ophthalmopathy before and after prednisone treatment

INTRODUCTION

In Graves' Ophthalmopathy, it is important to distinguish active inflammatory phase, responsive to immunosuppressive treatment, from fibrotic unresponsive inactive one. The purpose of this study is, first, to identify the relevant orbital magnetic resonance imaging signal intensities before treatment, so to classify patients according to their clinical activity score (CAS), discriminating inactive (CAS < 3) from active Graves' Ophthalmopathy (GO) (CAS > 3) subjects and, second, to follow post-steroid treatment disease.

METHODS

An observational study was executed on 32 GO consecutive patients in different phases of disease, based on clinical and orbital Magnetic Resonance Imaging parameters, compared to 32 healthy volunteers. Orbital Magnetic Resonance Imaging was performed on a 1.5 tesla Magnetic Resonance Unit by an experienced neuroradiologist blinded to the clinical examinations.

RESULTS

In pre-therapy patients, compared to controls, a medial rectus muscle statistically significant signal intensity ratio (SIR) in short-time inversion recovery (STIR) (long TR/TE) sequence was found, as well as when comparing patients before and after treatment, both medial and inferior rectus muscle SIR resulted significantly statistically different in STIR. These increased outcomes explain the inflammation oedematous phase of disease, moreover after steroid administration, compared to controls; patients presented lack of that statistically significant difference, thus suggesting treatment effectiveness.

CONCLUSION

In our study, we proved STIR signal intensities increase in inflammation oedematous phase, confirming STIR sequence to define active phase of disease with more sensibility and reproducibility than CAS alone and to evaluate post-therapy involvement.

Correlation between magnetic resonance imaging and ultrasound measurements of eye muscle thickness in thyroid-associated orbitopathy

AIMS

To compare ultrasound (US) and magnetic resonance imaging (MRI) measurements of horizontal eye muscle thickness in patients with thyroid-associated orbitopathy (TAO) and to compare these measurements according to the phase of the disease, the severity of exophthalmos, and the experience of the investigator.

METHODS

A total of 180 orbits of adult patients with TAO were investigated from May 2007 to December 2012. In addition to their general ophthalmic examination, all patients underwent ultrasonographic measurement of horizontal eye muscle thickness with the B-scan technique and MRI examination of the orbit. Correlations between values obtained by US and MRI were determined for different subgroups according to disease activity (active, inactive), exophthalmos values (Hertel < 18 mm; Hertel 18-22 mm; Hertel > 22 mm), and the time period of examination (2007-2009; 2010-2012).

RESULTS

Positive moderate correlation between US and MRI values for the medial rectus muscle (MRM; r = 0.690) and for the lateral rectus muscle (LRM; r = 0.572) was found. Significantly higher correlation was found for the MRM (P < 0.0001) and the LRM (P = 0.0008) in the time period 2010-2012 than in that of 2007-2009. Increasing correlation was found for MRM with increasing values of exophthalmos but this increase was not statistically significant. In the active phase of the disease compared to the inactive phase, statistically significant increased correlation (P = 0.019) was found for the LRM.

CONCLUSIONS

Ultrasonographic measurement of horizontal eye muscles thickness in TAO moderately correlates with values obtained using MRI. The accuracy of ultrasonographic measurements in particular increases with the experience of the investigator.

Disease activity in Graves' ophthalmopathy: diagnosis with orbital MR imaging and correlation with clinical score

In Graves' ophthalmopathy (GO) it is important to distinguish acute inflammation at an early stage, responsive to immunosuppressive treatment, from inactive fibrotic end stage disease, unresponsive to the same treatment. The purpose of this study was to identify the most relevant signal intensities on orbital MR imaging with contrast administration both to classify patients according to their clinical activity score (defined by a cut-off value of 3) and to make a prediction of patient's CAS. Such threshold was considered as widely used in literature. Sixteen consecutive patients with a diagnosis of GO in different phases of thyroid disease based on clinical and orbital MR imaging signs, and six normal volunteers were examined. Orbital MR imaging was performed on a 1.5 Tesla MR Unit. MR scans were assessed by an experienced neuroradiologist, blinded to the clinical examinations. We found a statistical correlation between CAS and both STIR and contrast enhanced T1-weighted sequences. There was also a statistically significant correlation between STIR and contrast-enhanced T1 images disclosing the possibility of avoiding the injection of contrast medium. Our study proved that signal intensity values on STIR sequence increase in the inflammatory oedematous phase of disease. We confirmed the correlation between signal intensities on this sequence and CAS, showing an increase in signal intensity proportional to the CAS value. So we validated MRI use to establish the activity phase of disease more sensitively than CAS alone.

Signal intensity and T2 time of extraocular muscles in assessment of their physiological status in MR imaging in healthy subjects

Background:

Lack of standardised orbital MR protocols leads to a situation, when each institution/centre may arbitrarily choose sequence parameters. Therefore, the results obtained and published by the authors may not be compared freely, and what is most important may not be considered fully reliable. Signal intensity (IS) and T2 time (T2) are important parameters in estimation of inflammatory processes of extraocular muscles in the clinical practice.

The aim of this study was to determine the reference values (i.e. cut-off values) for absolute signal intensity and T2 relaxation time in healthy subjects, their relativised values to white matter (WM) and temporal muscles (TM) and to evaluate the correlation between those parameters.

Material/Methods:

The orbital examination was performed in healthy volunteers according to the protocol prepared in the Radiology-Imaging Diagnostic Department of the Medical University of Lodz for patients with suspected/diagnosed thyroid orbitopathy. Using two of the standard sequences IS and T2 time were calculated for the muscles and two relativisation tissues in realtion to WM and TM. Subsequently cut-off values for healthy volunteers were calculated.

Results:

The differences between muscles for IS, IS MAX, IS/TM, IS/WM, IS MAX/TM, IS MAX/WM and T2 MAX/WM were not statistically significant. Therefore one cut-off value of these parameters for all the rectus muscles was calculated. T2-relaxation time and T2 relativised to white matter had to be calculated separately for each muscle.

Conclusions:

No statistical correlation was found between IS and T2-time for extraocular muscles in healthy volunteers. We calculated the reference ranges (cut-off values) for absolute IS and T2-time values and relativised parameters. In the clinical practice the objectification of IS and T2-time values should be done to WM, than to IS or T2 of the temporal muscle. The T2 MAX/WM seems to have the highest clinical utility for the assessment of the pathophysiological status of extraocular muscles.

Changes of saccadic eye movements in thyroid-associated ophthalmopathy

PURPOSE

To establish whether or not the dynamics of saccadic eye movements are significantly changed in patients with different stages of thyroid-associated ophthalmopathy (TAO) and, subsequently, if analysis of saccades could serve as an additional diagnostic tool for early detection of inflammatory activity in TAO.

METHODS

Thirty-seven patients with TAO and 10 age- and gender-matched control subjects were investigated. The patients were divided into four groups according to the stage of the disease: (i) early mild disease (n = 10), (ii) early severe disease (n = 11), (iii) long-standing restrictive disease (n = 10) and (iv) proven auto-immune hyperthyroidism without any signs of TAO (n = 6). Horizontal and vertical saccades with amplitudes of 10°, 20°, 30° and 40° were recorded binocularly using the induction scleral search coil technique. The two main sequence constants V(max) and C were calculated for each eye. Repeated measurement analysis of variance was carried out to test for differences between different gaze directions, eyes and groups.

RESULTS

In horizontal saccades, significant differences were found between groups but not between abduction and adduction. In vertical saccades, differences between groups and the interaction between groups and up- and down-gaze saccades were significant. Compared with the control group, analysis of the main sequence curves revealed larger differences in patients of group 3 and 4 than in those of group 1 and 2. Whereas in the control group down-gaze saccades were faster than up-gaze saccades, the opposite behaviour was found in all patient groups. The largest differences were detected among those patients who had no signs of TAO (group 4).

CONCLUSIONS

In this study, significant saccade differences were detected in all patients with TAO. In contrast to our earlier studies where evaluation of multiple individual saccade parameters did not reveal significant differences, analysis of the main sequence constants and mathematical reconstruction of the main sequence curves turned out to be a sensitive technique for reliable detection of subtle ocular motility changes. Significant differences were detected even in patients with auto-immune thyroiditis where no clinical signs of TAO were apparent.

Ultrasonography compared to magnetic resonance imaging in thyroid-associated Graves' ophthalmopathy

OBJECTIVE

To compare ultrasonography (US) to magnetic resonance imaging (MRI) and the clinical activity score (CAS) in Graves' ophthalmopathy.

SUBJECTS AND METHODS

Nineteen patients underwent extraocular muscle thickness measurements by US and MRI, reflectivity by US and signal-intensity ratio by MRI. There were also twelve US control subjects.

RESULTS

US median thicknesses were greater than in controls. Correlation was found between US and MRI in the median thickness of the left eye rectus medial muscle as well as between signal-intensity ratio (SIR) and thickness by US. An inverse correlation was found between reflectivity and SIR in the inferior and lateral rectus. On associating the tests for detecting activity the best results were obtained with CAS plus MRI (sensitivity 75%), and US and MRI (positive predictive value 77% and specificity 80%).

CONCLUSION

CAS and US results showed poor correlation with MRI results suggesting that they cannot replace each other but when combined these methods can improve the evaluation of thyroid-associated ophthalmopathy.

Predictability of visual function and nerve fiber layer thickness by cross-sectional areas of extraocular muscles in graves ophthalmopathy

PURPOSE

To evaluate the predictability of visual function and peripapillary nerve fiber layer thickness by cross-sectional areas of extraocular muscles in patients with Graves ophthalmopathy.

DESIGN

Interventional case series.

METHODS

The data on a total of 76 patients with Graves ophthalmopathy were collected, and the cross-sectional areas of 4 rectus muscles were calculated using computed tomographic images. This study measured the correlation between the cross-sectional area of all rectus muscles and the Hertel value, logarithm of the minimal angle of resolution (logMAR), mean deviation of retinal sensitivity, P(100) value of visual evoked potential, total error of the Farnsworth-Munsell 100-hue color sensation test, and total thickness of the peripapillary nerve fiber layer thickness by optical coherence tomography.

RESULTS

The cross-sectional area of all rectus muscles was significantly correlated with the mean deviation of retinal sensitivity (Pc = .08), the P(100) value of visual evoked potential (Pc < .01), and the total error of the 100-hue color sensation test (Pc < .01). However, the cross-sectional area of all rectus muscles was not significantly correlated with logMAR or proptosis, nor with the total thickness of the peripapillary nerve fiber layer.

CONCLUSIONS

For patients with Graves ophthalmopathy, the cross-sectional area of all rectus muscles was significantly correlated with visual function. The enlargement of extraocular muscles can be an early sign of optic neuropathy prior to perceived clinical symptoms. Furthermore, it is possible to predict visual function change using the cross-sectional area of all rectus muscles.

Treatment of idiopathic sclerosing inflammation of the orbit (myositis) with infliximab

PURPOSE

We report the successful use of infliximab in a young patient with idiopathic sclerosing orbital inflammation (myositis).

METHODS

We describe the patient's medical records and review the literature.

RESULTS

Idiopathic myositis in this patient could not be satisfactorily treated with corticosteroids or chemotherapy. Biopsy showed sclerosing orbital inflammation. The patient had a prompt and sustained response with infliximab and methotrexate treatment.

CONCLUSIONS

Infliximab and methotrexate might be considered in patients with idiopathic sclerosing orbital inflammation (myositis).

Oftalmopatia tireoidea revisitada

A oftalmopatia tireoidea é doença orbitária autoimune intimamente associada com o hipertireoidismo, porém podendo existir separadamente. Pode preceder, coincidir ou suceder o início da disfunção tireoidea, raramente ocorrendo em eutireoideos ou hipotireoideos. Os músculos extraoculares são os principais alvos acometidos e tornam-se aumentados de volume, determinando oftalmoplegia e proptose. Outros sinais importantes incluem retração palpebral, hiperemia conjuntival e edema periorbitário. Perda visual pode ocorrer se há compressão do nervo óptico no ápice orbitário. A oftalmopatia tireoidea é caracterizada por inflamação, congestão, hipertrofia e fibrose da gordura e músculos orbitários. A atividade da doença é dividida em fase aguda ou inflamatória, seguida pela fase inativa associada com alterações fibróticas e infiltração gordurosa. O diagnóstico é clínico, e quando este é difícil ou se suspeita de neuropatia óptica os métodos de imagem são indicados. A tomografia computadorizada e a ressonância magnética podem confirmar o diagnóstico e avaliar a área crítica do ápice orbitário. A ressonância magnética é superior, em virtude da resolução tecidual e da sua capacidade de avaliar a atividade da doença (mediante sequências com TR longo) e detectar alterações inflamatórias, auxiliando o planejamento terapêutico no momento certo, melhorando o prognóstico.

Repeated peribulbar injections of triamcinolone acetonide: a successful and safe treatment for moderate to severe Graves' ophthalmopathy

PURPOSE

In this study, we aimed to evaluate the efficacy of peribulbar triamcinolone injections to treat inflammatory signs of Graves' ophthalmopathy (GO) in patients with moderate to severe GO and associated optic neuropathy (ON).

METHODS

Twenty-one patients with active GO [clinical activity score (CAS) > or = 4] and systemic thyroid disease under control were enrolled in this prospective pilot study. Peribulbar triamcinolone acetonide was injected in each orbit (42 eyes), in four doses of 20 mg at 2-week intervals. Ophthalmological examination including CAS evaluation, visual field, computerized tomography (CT) scan and digital photography were performed before and after treatment.

RESULTS

Twenty-one patients (11 with moderate disease, 10 with ON) were enrolled in this study and followed for at least 14 months. Initial mean CAS was 6.38 +/- 1.49, which dropped to 1.8 +/- 1.12 after 6 months of treatment (P = 0.01; mean difference of 4.57 +/- 1.56; range 1-8 score points). ON was diagnosed in 10 patients. Of these, 66% improved with peribulbar triamcinolone exclusively. A transitory increase in intraocular pressure in two patients was controlled with topic medication.

CONCLUSION

Peribulbar triamcinolone injections reduce the inflammatory signs of moderate GO, as measured by the CAS, and could also be used as an alternative treatment for ON. Randomized clinical trials are needed to compare the results of triamcinolone peribulbar injections to those of other treatment modalities.

Inferior oblique muscle thickness in Asians

The purpose of this study was to examine the inferior oblique muscle (IOM) thickness in Asians by the quasi-sagittal plane of the orbits. Specimens were examined from 23 orbits of 18 Asians (9 orbits in males, 14 in females), aged 63 to 97 years at death. All specimens were fixed in 10% buffered formalin before use. The orbital contents were incised parallel to the optic nerve, after which the lengths of both short and long axes of the IOM were measured and the ratio of short to long axes was calculated. The mean lengths of each short or long axis of the IOM were 2.27 ± 0.49 mm and 7.23 ± 0.97 mm, respectively. The average ratio was 0.32 ± 0.07. There were no significant differences in laterality or gender. This study determined the normal IOM thickness in Asian cadavers, the outcome of which could be useful for detection of IOM involvement in Graves’ orbitopathy.

Strabismus and eye muscle function

Studies of external eye muscle morphology and physiology are reviewed, with respect to both motor and sensory functions in concomitant strabismus. The eye muscles have a more complex fibre composition than other striated muscle, and they are among the fastest and most fatigue-resistant muscles in the body. However, it is not generally believed that concomitant strabismus is due to a primary abnormality of the eye muscles or the ocular motor system. The gross anatomy of eye muscles, including the shape and position of the eye muscle pulleys, was not changed in strabismus. The histology of the eye muscle fibres was also basically the same, but changes have been observed in the cellular and biochemical machinery of the fibres, most notably in the singly innervated orbital fibres. Functionally, this was seen as slower contractions and reduced fatigue resistance of eye muscles in animals with strabismus and defects of binocular vision. Most likely the changes represented an adaptation to modified visual demands on the ocular motor control, because of the defects of binocular vision in strabismus from an early age. Adaptation of eye muscle function to visual demands could be seen also in the adult human ocular motor system, but here the effects could be reversed with treatment in some conditions. External eye muscles in the human have sensory organs, muscle spindles and tendon organs, responding to changes in muscle force and length. It is not known how these proprioceptors are used more specifically in ocular motor control, and there is no stretch reflex in the external eye muscles. However, a clear influence on space localization and eye position can be demonstrated with vibratory stimulation of the eye muscles, presumably activating muscle spindles. Different effects were observed in normal subjects and in adult patients with strabismus, which would indicate that the proprioceptive input from one eye of strabismic patients could be suppressed by the other eye, similar to visual suppression in concomitant strabismus. Such an interaction would most likely occur in the visual cortex, and not in the ocular motor system. Further studies of proprioceptive mechanisms, during the postnatal developmental stage and in adult concomitant strabismus may shed light on the mechanisms of childhood strabismus and may, in this respect, be a more fruitful avenue for further research than eye motor studies.