Inferior oblique muscle paresis as a sign of myasthenia gravis

A protocol to quantify cross-sectional and longitudinal differences in duction patterns

Currently, there is no established system for quantifying patterns of ocular ductions. This poses challenges in tracking the onset and evolution of ocular motility disorders, as current clinical methodologies rely on subjective observations of individual movements. We propose a protocol that integrates image processing, a statistical framework of summary indices, and criteria for evaluating both cross-sectional and longitudinal differences in ductions to address this methodological gap. We demonstrate that our protocol reliably transforms objective estimates of ocular rotations into normative patterns of total movement area and movement symmetry. This is a critical step towards clinical application in which our protocol could first diagnose and then track the progression and resolution of ocular motility disorders over time.

Oculomotor fatigability with decrements of saccade and smooth pursuit for diagnosis of myasthenia gravis

BACKGROUND AND OBJECTIVES

As the efficacy of current diagnostic methods for myasthenia gravis (MG) remains suboptimal, there is ongoing interest in developing more effective diagnostic models. As oculomotor fatigability is one of the most common and diagnostic symptoms in MG, we aimed to investigate whether quantitative saccadic and smooth-pursuit fatigability analyses with video-oculography (VOG) are useful for diagnosis of MG.

METHODS

A convenience cohort of 46 MG patients was recruited prospectively, including 35 with ocular and 11 with generalized MG (mean age, 50.9 ± 14.5 years; 17 females); 24 healthy controls (HCs) (mean age, 50.6 ± 16.3 years; 13 females) also were enrolled. Seventy-five repetitive saccades and smooth pursuits were recorded in ranges of 20° (horizontal plane) and 15° (vertical plane) using a three-dimensional VOG system. Based on the oculomotor range of the second saccade and smooth pursuit and the mean ranges of the last five of each, the estimated decrements (%) reflecting oculomotor fatigability were calculated.

RESULTS

The baseline oculomotor ranges did not show significant difference between the MG and HCs groups. However, following repetitive saccades and pursuits, the oculomotor ranges were decreased substantially during the last five cycles compared to baseline in the MG group. No such decrements were observed in the HC group (p < 0.01, Mann-Whitney U test). Receiver operating characteristic (ROC) analysis revealed that repetitive vertical saccades yielded the best differentiation between the MG and HC groups, with a sensitivity of 78.3% and specificity of 95.8% when using a decrement with an amplitude of 6.4% as the cutoff.

CONCLUSION

This study presents an objective and reproducible method for measuring decrements of oculomotor ranges after repetitive saccadic and pursuit movements. Quantification of oculomotor fatigability using VOG could be a sensitive and specific diagnostic tool for MG and allows easy, cost-effective, accurate, and non-invasive measurements.

CLASSIFICATION OF EVIDENCE

This study provides class III evidence that VOG-based quantification of saccadic and pursuit fatigability accurately identifies patients with MG.

Diagnosing myasthenia gravis using orthoptic measurements: assessing extraocular muscle fatiguability

INTRODUCTION

Diagnosing ocular myasthenia gravis (MG) can be challenging because serum antibodies are often not detected. We aimed to explore whether determining extraocular muscle (EOM) weakness using orthoptic measures, including an adapted Hess chart examination, can aid in diagnosing MG.

METHODS

We conducted a prospective study among patients with acetylcholine receptor antibody positive MG (20 recently diagnosed, 19 chronic) and 14 seronegative MG patients. We compared orthoptic measures to 19 healthy and 18 disease controls with Graves orbitopathy, chronic progressive external ophthalmoplegia or oculopharyngeal muscular dystrophy. Maximal eye duction angles were measured using a synoptophore. Gaze deviations between eyes were measured using standard Hess chart examination with addition of 1 min persistent gaze to assess MG-associated fatiguability. Receiver operating characteristics curve analysis was performed.

RESULTS

For duction angles, the area under the curve (AUC) was 0.73 comparing MG to healthy, and 0.69 comparing to patient controls. For the outer field of the Hess chart, the AUC was 0.89 comparing to healthy and 0.54 to patient controls. For drift, the AUC was 0.93 comparing to healthy and 0.93 to patient controls. The sensitivity and specificity of the presence of drift was 81% and 100%.

DISCUSSION

Orthoptic measurements can be used to diagnose MG by quantifying EOM weakness and fatiguability. Drift during persistent gaze on a Hess chart is specific for MG and could be used for diagnostic purposes. The Hess chart examination is widely available, inexpensive and fast. Moreover, orthoptic measurements may be a clinically relevant outcome measure for clinical trials.

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.

Isolated inferior oblique pareses

PURPOSE

To describe etiology, clinical characteristics, radiological features and management of isolated inferior oblique pareses.

METHODS

A diagnosis of inferior oblique paresis was made after a thorough strabismus examination and neuroimaging. The patients were managed surgically with adjustable strabismus surgery, or conservatively. Surgical success was defined as average horizontal deviation within ≤ 10 prism diopters [PD] post-operatively and for vertical deviation, it was ≤ 5 PD, at last follow-up.

RESULTS

Seven cases were congenital, 6 cases were bilateral, with esotropia in 6 cases; 'A' pattern in 7 cases and hypotropia in 3 cases. The mean preoperative horizontal deviation was 52.5 PD, and the mean postoperative horizontal deviation was 2.37 PD (p = 0.028). The pre-operative vertical deviation was 18 PD and post-operative vertical deviation was 5 PD. MRI showed reduced IO muscle size; average area being 11.27 mm² in the affected eyes, with normal sized inferior recti (average: 24.63 mm²) and medial recti muscles (average: 30.08 mm²). Surgical success was seen in all six cases. Average follow-up was 265 days. The Parks' three step test was not valid, except for one acquired unilateral case.

CONCLUSION

Isolated pareses of inferior oblique muscle exhibit defective elevation in adduction of the affected eye, 'A' pattern and fundus intorsion, and is confirmed by neuroimaging. These can be successfully managed surgically to correct the deviation.

Clinical characteristics and surgical outcomes of isolated inferior rectus palsy

Aim

As isolated inferior rectus muscle (IRM) palsy represents a rare clinical entity, very limited information is available on this condition. The aim of this report was to elucidate the etiology, clinical characteristics and surgical outcomes of isolated IRM palsy.

Methods

Isolated IRM palsy cases who underwent surgical treatments at the Zhongshan Ophthalmic Center, Sun Yat-sen University, China over the period from January 2008 to June 2019 were reviewed retrospectively. Data evaluated from these cases included their etiology, ocular alignment, ocular motility, surgical procedures and surgical outcomes.

Results

A total of 61 patients (40 males, 21 females) were included in this review. Their mean ± SD age was 27.21 ± 16.03 years (range: 2 to 73 years). In these cases, 32 (52.5%) involved traumatic injury, 28 (45.9%) congenital hypoplasia or absence of inferior rectus and 1 (1.6%) with thyroid ophthalmopathy. The right eye was affected in 33 patients (54.1%), the left in 24 patients (39.3%), and both eyes in 4 patients (6.6%). The main clinical presentations consisted of hypertropia of the affected eye, motility limitation in abduction and depression and incyclotropia. After treatment consisting of various surgical approaches, including muscle repair or resection of the affected inferior rectus, recession of ipsilateral superior rectus, elongation of contralateral superior oblique and partial transposition of the horizontal rectus, the isolated IRM palsy was rectified in 49 patients (80.4%) with one surgery, while 11 cases (18.0%) required two surgeries and 1 case (1.6%) needed three surgeries. Finally, 52 patients (85.2%) showed a complete recovery, 6 (9.9%) improved and 3 (4.9%) experienced a surgical failure.

Conclusion

The main etiologies of isolated IRM palsy involved traumatic injury and developmental events. Overall, surgical outcomes of the various approaches employed were quite effective.

Ophthalmologic manifestations in myasthenia gravis: presentation and prognosis

We investigated the ophthalmologic manifestations and factors that influence outcomes in patients with myasthenia gravis (MG). We retrospectively analyzed the prevalence of neuro-ophthalmologic findings and clinical and outcome measures of 100 consecutive patients (53 males, 47 females), aged 55.7 ± 17.5 (range 15-85) years with an established diagnosis of MG. Forty-eight patients had purely ocular symptoms at the onset of disease (OMG) and 52 patients presented with generalized symptoms (GMG). Overall, 21 patients presented with extraocular muscle (EOM) weakness. Bilateral EOM weakness was seen in 12 patients, and unilateral EOM weakness was seen in nine patients. Diplopia responded partially to immunosuppressive treatments in 60% of patients with ophthalmoparesis. Twenty-five (52.1%) patients with ocular-onset MG converted to secondary GMG at a mean time of 14.5 months. Patients who developed secondary GMG were younger and had an earlier age of disease onset when compared with patients with pure OMG (p < 0.05). Patients with secondary GMG presented more frequently with ptosis and diplopia (72% vs. 28%) compared with patients with pure ocular MG who presented more frequently with isolated ptosis (66.7% vs. 33.3%) (p = 0.02). Remission and minimal manifestation status were achieved in 50 (79.3%) of all patients with a clinical follow-up ≥ 3 years. Poor outcome was associated with the presence of thymoma (p < 0.05). Myasthenic ophthalmoparesis is bilateral and heterogeneous and partly responds to treatment with immunotherapy. Younger patients with ptosis and diplopia at disease onset had an increased risk of secondary GMG. The presence of thymoma increases the risk for poor prognosis.

Diagnosis and surgical management of isolated inferior oblique palsy

AIM

To describe the etiology, clinical characteristics, surgical options and surgical outcomes of isolated inferior oblique palsy (IOP).

METHODS

A retrospective review was performed on patients with isolated IOP who were seen between January 2010 and June 2017. The following clinical data were obtained from the patients' charts: visual acuity, ocular alignment, ocular motility, cyclotorsion, stereoacuity, Parks three-step test, surgical methods, surgical outcomes and complications. Surgical success was defined as horizontal deviation ≤10 prism diopters (PD) and a vertical deviation ≤5 PD in primary gaze at both near and distant vision as assessed at last follow-up.

RESULTS

The records from a total of 18 patients (8 males and 10 females) with an average age of 27.56y were included in this study. The right eye was affected in 11 patients, the left in 6 patients and both eyes in 1 patient. Twelve cases (66.7%) were congenital and 6 (33.3%) were acquired IOP. The 6 acquired cases involved 2 resulting from orbital trauma/surgery, 2 from midbrain microvascular ischemia, 1 from myasthenia gravis and 1 of unknown etiology. Strabismus surgery was performed in 13 cases. Surgical techniques included weakening of superior oblique and vertical rectus recession and resection. After a mean follow-up of 15.11mo, the corrected vertical deviation in primary position was 19.92±8.52 PD (P=0.000) and the corrected horizontal deviation was 14.31±12.68 PD (P=0.002). The surgical success rate was 61.5% and no surgical complications were present.

CONCLUSION

Isolated IOP represents a rare condition, with most cases (66.7%) involving a congenital basis. The acquired cases included vascular, orbital trauma/surgery and myasthenia gravis. Weakening of the ipsilateral superior oblique muscle and/or contralateral superior rectus recession often resulted in favorable surgical outcomes with a surgical success rate of 61.5%.

Ocular Weakness in Myasthenia Gravis: Changes in Affected Muscles are a Distinct Clinical Feature

Introduction:

In this study we quantitatively describe ocular weakness patterns in myasthenia gravis (MG) to help neurologists in making the clinical diagnosis and to investigate how the current outcome measures reflect ocular weakness in MG.

Methods:

We investigated ptosis and diplopia patterns in a retro- and prospective cohort of 306 MG patients. Diplopia was systematically examined by testing extra-ocular muscle (EOM) fatigability in two horizontal and four oblique directions for 60 seconds.

Results:

Of patients with initial symmetric ptosis, 40% developed asymmetric ptosis at the second visit. Changes in form of ptosis occurred less often in seronegative MG patients (50%) than in patients with acetylcholine receptor (AChR) antibodies (70%) or muscle-specific kinase (MuSK) antibodies (69%) (p = 0.038). Of patients with diplopia on the first visit, double vision contained both a vertical and horizontal component in 95%. At the second visit, 83% manifested diplopia in other gaze directions. The mean time (in seconds) to diplopia was 11.6±14.0 and the mean time to ptosis was 27.6±19.8. Diplopia or ptosis manifested within 30 seconds in 87% and 58%, respectively. Patients who manifested diplopia after 30 seconds, reported no limitations due to diplopia.

Discussion:

Changes in the gaze directions in which diplopia occurs or ptosis side occur frequently in MG. In diagnostically challenging cases, we recommend testing ptosis and diplopia in multiple gaze directions for 30–60 seconds during at least two follow-up visits to maximize the chance of observing changes in ocular weakness patterns.

Causes and surgical treatment of diplopia and strabismus secondary to myasthenia gravis

OBJECTIVE

To present a report of the ocular motility disorders, treatment and outcomes of myasthenia gravis (MG).

MATERIAL AND METHOD

A retrospective study was performed on the data of patients with MG. An evaluation was made using mean age, gender, initial diagnosis, ocular deviation, time of onset of clinical characteristics, treatment and results. Resolution of diplopia and/or ocular deviation in primary and reading gaze was considered a good outcome at the end of follow-up.

RESULTS

A total of 14 cases were included. The mean age of the sample was 55.64 years, of which 9 were women, and 10 cases were bilateral. The diagnosis was made by ophthalmologists in 4 cases. The initial diagnoses were diverse: bilateral cranial third nerve palsy in 3, unilateral third nerve palsy in 1, superior or inferior rectus palsy in 3, sixth nerve palsy in 2, fourth nerve palsy in 1, exotropia in 3 and esotropia in 1. Diplopia was presented in 14 cases and 9 associated ptosis. The different types of strabismus were horizontal ocular deviation in 11 cases: 8 with exotropia, and 4 with vertical deviation. Strabismus surgery was performed in 4 cases that did not respond to medical treatment, with a good final outcome. Pharmacological treatment resolved diplopia in 6 cases, and prisms in one. Ptosis surgery was only necessary in one patient. Outcome was favourable in 78.57% at the end of follow-up.

CONCLUSION

Acute onset diplopia caused by strabismus with variable angle or oculomotor palsy, associated or not with a ptosis can indicate MG. There were favourable outcomes with strabismus surgery. Pharmacological treatment did not resolve the diplopia in all cases.

Electrophysiology of Extraocular Cranial Nerves: Oculomotor, Trochlear, and Abducens Nerve

The utility of extraocular cranial nerve electrophysiologic recordings lies primarily in the operating room during skull base surgeries. Surgical manipulation during skull base surgeries poses a risk of injury to multiple cranial nerves, including those innervating extraocular muscles. Because tumors distort normal anatomic relationships, it becomes particularly challenging to identify cranial nerve structures. Studies have reported the benefits of using intraoperative spontaneous electromyographic recordings and compound muscle action potentials evoked by electrical stimulation in preventing postoperative neurologic deficits. Apart from surgical applications, electromyography of extraocular muscles has also been used to guide botulinum toxin injections in patients with strabismus and as an adjuvant diagnostic test in myasthenia gravis. In this article, we briefly review the rationale, current available techniques to monitor extraocular cranial nerves, technical difficulties, clinical and surgical applications, as well as future directions for research.

Fixation stability of the upward gaze in patients with myasthenia gravis: an eye-tracker study

Objective

To quantify fixation stability of the upward gaze in patients with myasthenia gravis (MG) using an eye tracker.

Methods and analysis

In this study, 21 normal subjects, 5 patients with MG with diplopia, 5 patients with MG without diplopia and 6 patients with superior oblique (SO) palsy were included. Subjects fixated on a target in the upward direction for 1 min. The horizontal (X) and vertical (Y) eye positions were recorded using an eye tracker. Fixation stability was first quantified using the bivariate contour ellipse areas (BCEA) of fixation points as an index of whole stability. Then, the SDs of the X and Y eye positions (SDX and SDY, respectively) were quantified as indices of directional stability, with the data divided into three 20 s fractions to detect temporal fixation fluctuation.

Results

BCEAs were larger in patients with MG (both with and without diplopia) than normal subjects and patients with SO palsy, without significant differences among the three 20 s fractions. Compared with normal subjects, SDXs were larger only in patients with MG with diplopia; SDYs were larger in both patients with MG with and without diplopia. In addition, SDYs in patients with MG with diplopia were larger than those in patients with MG without diplopia and patients with SO palsy. Furthermore, a significant difference among the three 20 s fractions was detected for SDYs in patients with MG with diplopia.

Conclusion

Patients with MG, especially those with diplopia, exhibit fixation instability in the upward gaze. Non-invasive quantification of fixation stability with an eye tracker is useful for precisely identifying MG-specific fatigue characteristics.

Trial registration number

UMIN000023468; pre-results.