Ocular myasthenia: a protean disorder

Pediatric Ocular Myasthenia Gravis: A Review

Pediatric ocular myasthenia gravis (OMG) is difficult to diagnose and manage, owing to its rarity and low index of suspicion in the early stage of the disease. Also, many other conditions having similar presentation cause a further delay in diagnosis. In this review, we highlighted various pointers in history and described bedside clinical tests that can aid in its timely diagnosis. The antibody spectrum in myasthenia is ever increasing and includes anti-muscle specific kinase and low-density lipoprotein-receptor related protein 4 antibodies in addition to acetylcholine receptor antibodies besides many others. However, pediatric OMG patients often test negative for all three antibodies, making the diagnosis even more difficult in triple seronegative patients. Edrophonium and electrophysiological tests, which help in confirming myasthenia in adults, have a limited utility in diagnosing pediatric ocular myasthenia cases. Various practical difficulties are encountered like nonavailability of edrophonium, risk of bradycardia associated with neostigmine use and its lower sensitivity, noncooperative children, and limited technical expertise in performing electrophysiological tests in children. In this article, we described a pragmatic approach to diagnose pediatric OMG along with the important aspects of its management.

Disorders of the Fourth Cranial Nerve

ABSTRACT

This review of disorders of the fourth cranial nerve includes discussion on anatomy, examination techniques, congenital and acquired etiologies, differential diagnosis, and management options. The findings of the superior oblique muscle on orbital MRI in patients with fourth nerve palsy have had a major impact on our understanding of this cranial neuropathy. In addition, briefly reviewed are rare disorders of the fourth nerve: superior oblique myokymia, Brown syndrome, and ocular neuromyotonia. It behooves the clinician to have a clear understanding of the role that the fourth cranial nerve plays in a variety of neuro-ophthalmic conditions.

Pediatric Autoimmune Ocular Myasthenia Gravis: Evaluation of Presentation and Treatment Outcomes in a Large Cohort

BACKGROUND

In autoimmune myasthenia gravis (MG), autoantibodies target the neuromuscular junction. Ocular myasthenia gravis (OMG) is localized, affecting only extraocular and/or levator palpebrae muscles. OMG presents across all ages, varying in presentation, treatment modalities, and outcomes. Recently, there have been advances in MG/OMG treatment; their utilization and effectiveness are an important part of optimal disease management.

METHODS

We completed a retrospective chart review of children aged 18 years or younger with a confirmed diagnosis of OMG presenting from 2002 to 2019.

RESULTS

Forty-two patients were included with mean age at presentation of 8.5 years (2 to 18 years). Twenty-one patients (50%) had positive antibodies; 90% had acetylcholine receptor antibodies. Ten patients developed generalized symptoms with mean time to generalization of 13.6 months. Multiple logistic regression showed that older age of onset was a trend predictive factor (P = 0.054; odds ratio 1.17) for generalized disease. All patients were treated with pyridostigmine. Immunomodulating agents included steroids (15), mycophenolate mofetil (four), and intravenous immunoglobulin (one). Three patients underwent thymectomy. Twenty patients reached minimal manifestation status, and 12 achieved remission. Gender, race, and positive antibody status were not statistically significant predictors for advanced immunosuppressive therapy.

CONCLUSIONS

We summarize one of the largest cohorts of pediatric patients with OMG who have undergone up-to-date diagnostic and therapeutic regimens. The predictors of outcome and treatment pathway for OMG patients suggested by this report may be further elucidated by future prospective studies.

Quantification of Cover Test Prior and Post Pyridostigmine in Diagnosis of Myasthenia Gravis

Objective: To assess the value of measuring diplopia before and after pyridostigmine intake to differentiate myasthenia gravis from sagging eye syndrome.To establish a threshold for a positive response to pyridostigmine in the diagnosis of myasthenia gravis.Methods: 15 patients with myasthenia gravis and 15 with sagging eye syndrome diplopia were evaluated. Diplopia was measured in five positions (upgaze, downgaze, right gaze, left gaze, and primary position). After baseline measurements, the patient received a single dose (60 mg) of pyridostigmine. After 60 minutes the prism measure was performed again in five positions. Horizontal deviation, vertical deviation at distance was compared before and after a single dose of pyridostigmine in each gaze. Ocular deviations were compared between the two groups to identify the threshold with the highest sensitivity and specificity.Results: Differences between pretest deviations and posttest deviations in any gaze were found to be statistically significant only in the MG group. The optimum threshold for a positive response to pyridostigmine was a reduction of 2 prism diopters in any component in any gaze. Sensitivity for the detection of myasthenia diplopia was 80.00% and specificity was 86.67%.Conclusions: Our results suggest that measuring diplopia with prisms before and after pyridostigmine administration can help to detect patients with suspected myasthenia.

Challenges in diagnosing coexisting ocular myasthenia gravis and thyroid eye disease

Ocular myasthenia gravis (OMG) and thyroid eye disease are two autoimmune conditions that have several overlapping clinical features, and these coexist with a small but not insignificant frequency. Segregating these diagnoses is typically straightforward, but, when the two diseases co-occur in the same individual, making a diagnosis of OMG can be very challenging. In this review we address what is known about the coexistence of OMG and thyroid eye disease and we highlight the clinical features that are suggestive of overlapping conditions. We also describe the major testing approaches used in the diagnosis of these two entities, with special emphasis on the potential shortcomings of individual tests in patients with overlapping disease. In patients with thyroid eye disease, securing a diagnosis of OMG may not be possible on the basis of a single positive test. A multimodal approach using clinical, serologic, imaging, and electrodiagnostic data, is typically required.

Algorithm of objective examination of a patient with blepharoptosis

Meticulous objective examination of a patient with blepharoptosis allows determining the tactics of surgical treatment. It depends on many factors, but main ones are blepharoptosis etiology, upper eyelids levator function, and ptosis degree. The estimation algorithm of objective examination of a patient with blepharoptosis is presented in this article.

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.

Ocular myasthenia gravis: an update on diagnosis and treatment

PURPOSE OF REVIEW

Myasthenia gravis is an autoimmune disease that commonly affects the palpebral and extraocular muscles. Ocular myasthenia gravis (OMG) is a variant of the disease that is confined to the ocular muscles but frequently becomes generalized over time. The diagnosis of OMG is often challenging but both clinical and laboratory findings are helpful in confirming the clinical suspicion. This review provides an update on the diagnostic approach and therapeutic options for OMG.

RECENT FINDINGS

Antimuscle-specific tyrosine kinase and LDL-related receptor-related protein 4 are newly available serologic testing for myasthenia gravis that can help in increasing the diagnostic sensitivity of OMG. They should be included to the diagnostic algorithm of OMG in appropriate clinical situations.

SUMMARY

OMG remains a primarily clinical diagnosis, but recent advances in laboratory testing can improve the diagnostic accuracy and should be used in appropriate clinical settings. The mainstay of treatment for OMG has not significantly changed over the past years, but the increasing availability of steroid-sparing agents improved the disease control while minimizing steroid-induced complications.

Juvenile Ocular Myasthenia Gravis: Presentation and Outcome of a Large Cohort

BACKGROUND

Isolated ocular myasthenia gravis (MG) is sparingly common in children relative to adults, ranging from 71% to 93% of all children with MG.

PURPOSE

We aimed to characterize the ocular manifestations and outcomes in children with isolated ocular MG.

METHODS

Medical records of consecutive 62 subjects less than 15 years of age with ocular MG, were retrospectively reviewed. Demographic data, presenting ocular features, types and variabilities of duction limitation, MG confirmatory tests, types of and responses to treatment, and generalized MG conversion were reviewed.

RESULTS

Mean age at onset and follow-up time were 49 months (range, one to 173 months) and 95 months (range, six to 226 months), respectively. Female-to-male ratio was 1.5:1. Initially, ptosis was found in 60 subjects (96.8%), while duction limitation was observed in 28 subjects (45.2%). Total ophthalmoparesis was the most common type of duction limitation. Variability of duction limitation was found in 68% of subjects during the follow-up. Pyridostigmine alone was the most common medication used (48.4%); ptosis was more responsive to therapy than duction limitation. Conversion to generalized MG occurred in 19.4% of subjects, with a mean interval to conversion of nine months after symptom onset. Most conversions (91.7%) occurred in the first two years.

CONCLUSIONS

Ptosis was more responsive to treatment than duction limitation. Thus other treatment modalities, as well as strabismic amblyopia screening, should be considered in children with prolonged duction limitation that is refractory to medication. In contrast with adults, a much lower proportion of children converted to generalized MG. This may explain the higher prevalence of isolated ocular MG among the juvenile population.

Generalization after ocular onset in myasthenia gravis: a case series in Germany

BACKGROUND AND PURPOSE

Approximately, 50% of myasthenia gravis (MG) patients initially present with purely ocular symptoms. Of these, about 60% will develop secondary generalized MG, typically within 2 years. Risk factors for secondary generalization are still controversial. In this study, we reviewed clinical parameters, thymic pathologies and medical treatments of MG patients with purely ocular symptoms at onset to investigate risk factors for secondary generalization.

METHODS

In this monocentric retrospective study, we reviewed consecutive patients who underwent robotic thymectomy between January 2003 and October 2017 in Charite Universitaetsmedizin Berlin. We used univariate and multivariate Cox proportional hazards regression models to identify factors associated with secondary generalization. Survival curves were plotted using Kaplan-Meier method and log-rank tests were performed to analyze the association between corticosteroids use and secondary generalization in subgroups defined by anti-AChR antibody status and thymic pathology.

RESULTS

One hundred and eighty of 572 MG patients who underwent robotic thymectomy were eligible for inclusion, of whom 110 (61.1%) developed a secondary generalized MG over a mean follow-up time of 23.6 months. The presence of a thymoma (HR 1.659, 95% CI (1.52-2.617), P = 0.029) was the only risk factor for secondary generalization in our series. Treating with corticosteroids was associated with a lower conversion rate in ocular myasthenia patients with thymic hyperplasia (n = 55, P = 0.028), but not with other thymic pathologies including thymoma and normal or atrophic thymus.

CONCLUSIONS

The conversion rate in ocular myasthenia was high in our series, predicted by the presence of a thymoma. Our findings suggest that corticosteroids can prevent secondary generalization in ocular myasthenia patients with thymic hyperplasia, which requires further research.

Efficacy of Gaze Photographs in Diagnosing Ocular Myasthenia Gravis

Background and Purpose

The various tests that are routinely used to diagnose generalized myasthenia gravis, such as the edrophonium test, serum anti-acetylcholine-receptor antibodies (AChR-Ab), and repetitive nerve stimulation (RNS) tests, have lower diagnostic sensitivity in ocular myasthenia gravis (OMG). Diagnosing OMG becomes even more difficult when the clinical symptoms are subtle. There is no gold-standard diagnostic test available for OMG patients, and so this study compared the diagnostic sensitivity of gaze photographs with conventional tests in OMG.

Methods

Records of gaze photographs were available for 25 of 31 consecutive patients diagnosed with OMG. Each patient underwent a neuro-ophthalmologic examination, serum AChR-Ab, RNS, edrophonium test, ice tests, and the acquisition of gaze photographs. The margin reflex distance 1 (MRD1) was measured on each of the gaze photographs, with MRD1 <2 mm or an interlid MRD1 difference of ≥2 mm on any of the gaze photographs defined as a positive sign of OMG. The diagnostic sensitivities of the tests were assessed.

Results

The mean age at onset was 38.5 years (range, 2–76 years), and 13 patients (52%) were men. The diagnostic sensitivities of the RNS test, AChR-Ab test, gaze photographs, and ice test were 56%, 64%, 80%, and 73%, respectively.

Conclusions

The diagnostic sensitivity was higher for gaze photographs than for the other tests applied to OMG patients.

[Ocular myasthenia gravis]

Ocular myasthenia gravis, although clinically often characterized by typical classical features, can cause considerable diagnostic problems. This article aims to provide a pragmatic approach to the pathogenesis, clinical features, diagnostics and therapeutic strategies in the clinical routine.

Overview of myasthenia gravis

Myasthenia gravis is an antibody-mediated disorder of neuromuscular transmission that is characterized by weakness and fatigue of voluntary muscles. Weakness may be ocular, bulbar, or generalized. Diagnostic evaluation of patients consists of bedside assessment, antibody testing, and electrophysiologic studies. Various therapeutic options are available, which consist of anticholinesterase inhibitors for symptomatic management, immunosuppressive agents as maintenance therapy, and thymectomy. Plasmapheresis and intravenous immunoglobulin are used in patients in crisis or those with rapidly worsening or refractory symptoms. In our article, we elaborate on key aspects of the epidemiology, pathogenesis, diagnostic evaluation, and therapeutic options for patients with myasthenia gravis.

Ocular myasthenia gravis

PURPOSE OF REVIEW

To review ocular myasthenia gravis (OMG), a localized form of myasthenia gravis clinically involving only the extraocular, levator palpebrae superioris, and orbicularis oculi muscles.

RECENT FINDINGS

Ocular manifestations can masquerade as a variety of ocular motility disorders, including central nervous system disorders and peripheral cranial nerve palsies. While sparing the pupils, the diagnosis and management can be challenging.

SUMMARY

Because several diagnostic and treatment options are available for OMG, clinicians must decide the sequence and combination based on the level of disease activity and patient disability.

Myasthenia mimicking monocular elevation deficiency

Monocular elevation deficiency is the inability to elevate the eye in abduction and adduction. Myasthenia gravis could mimic any pattern of ophthalmoplegia. However, myasthenia gravis mimicking monocular elevation deficiency appears to be very rare. A 12-month-old girl presented with the inability to elevate the left eye and blepharoptosis from 3 months of age. A neostigmine test showed a weakly positive response. Repetitive stimulation of the left orbicularis oculi produced no decremental response. Three assays for acetylcholine receptor antibodies were negative. Placing ice over the lids definitely improved left blepharoptosis. In conclusion, myasthenia gravis could mimic elevation deficiency. An ice test could be very helpful in making the diagnosis. Myasthenia gravis should be included in the differential diagnosis of monocular elevation deficiency even at a young age.

Treatment for diplopia in patients with myasthenia gravis

BACKGROUND

The purpose of this study was to describe the treatment experiences and outcomes of patients with myasthenia gravis (MG) whose initial presenting symptom was diplopia

METHODS

A retrospective review was performed on a group of patients with MG whose initial presenting symptom was diplopia.

RESULTS

The mean age of onset was 45.5 ± 16.9 years, and the mean follow-up period was 45.4 ± 39.7 months. Exotropia with vertical heterotropia was the most common type of deviation. The mean horizontal deviation was 20.1 ± 17.9 prism diopters, and the mean vertical deviation was 14.8 ± 11.1 prism diopters. Limitation of eye movement was found in 20 patients (71.4 %) during the follow-up period. After conventional treatment for MG, six patients (21.4 %) showed a good response with resolution of diplopia. Four patients (14.3 %) showed a partial response to treatment. Eighteen patients (64.3 %) showed minimal or no response; among them, ten (35.7 %) had an angle of deviation of 15 prism diopters or more. Six patients underwent strabismus surgery. Four were symptom free, and satisfactorily aligned after surgical treatment. One patient had intermittent diplopia despite the small amount of deviation, and one patient experienced recurrence of exotropia with diplopia during the 10-year follow-up. In multivariable analysis, the only factor associated with the need for strabismus surgery was the initial angle of deviation (p = 0.016).

CONCLUSIONS

Patients with MG who have a larger angle of deviation at presentation tend to require strabismus surgery after stabilization of the disease. Strabismus surgery is one treatment option for patients with MG who have a large angle of deviation and respond poorly to conventional treatment.

Pediatric neuro-ophthalmology

PURPOSE OF REVIEW

This review will update the ophthalmologist on recent developments in pediatric neuro-ophthalmology.

RECENT FINDINGS

Research into the genetics of congenital strabismus syndromes has brought new insights into the development of the ocular motor system. There is also new literature on childhood ocular myasthenia gravis and childhood neurosarcoidosis. The results of three different surgical treatments for congenital nystagmus are described. Reviews on cortical visual impairment, dyslexia, Aicardi syndrome, and neuronal ceroid lipofuscinosis are presented.

SUMMARY

Pediatric neuro-ophthalmology is a diverse and challenging field. As we strive to provide excellent care to these patients, we will use the results of basic science, genetic, and neurobiological research.

The effect of prednisone on the progression from ocular to generalized myasthenia gravis

Fifty percent of ocular myasthenia gravis (OMG) patients will progress to generalized myasthenia, 90% within 3 years from the onset of ocular symptoms. This study was performed to determine whether treatment with oral prednisone initiated and completed within 2 years from the onset of ocular symptoms would affect the progression of ocular myasthenia to generalized myasthenia gravis (GMG). Fifty-six patients were included in this review, with 27 patients in the prednisone-treated group and 29 patients in the untreated group. The treated group was initiated on 60 mg of prednisone daily with a slow taper over 3-6 months. At 2 years, significantly fewer patients in the treated group (3 of 27) progressed to generalized myasthenia when compared to the untreated group (10 of 29) (chi(2), p=0.04). Our results suggest that the early use of steroids may decrease progression of ocular to generalized myasthenia gravis. The decision to use steroids should be considered early in the course of patients diagnosed with ocular myasthenia gravis. This study should be considered preliminary and a prospective trial is warranted to confirm our observations.

Immunotherapy of ocular myasthenia gravis reduces conversion to generalized myasthenia gravis

BACKGROUND

Several retrospective studies have suggested that immunotherapy, including prednisolone, azathioprine and thymectomy, reduces progression of ocular myasthenia gravis to generalized myasthenia gravis. This study examines the effect of immunotherapy on generalization rates in ocular myasthenia patients who are acetylcholine receptor (AChR) antibody-positive.

METHODS

Retrospective record review of 34 patients from three university-based hospitals with neurology and neuro-ophthalmology services in Australia. In all patients, positive AChR antibodies were recorded, the initial symptoms were purely ocular, and all had at least 2 years of follow-up. The patients who developed generalized myasthenia gravis were compared with those who remained purely ocular.

RESULTS

There were 21 patients who developed generalized myasthenia gravis. Of these 21, only 2 (9.5%) had received prior immunotherapy. Among the 13 patients whose symptoms remained purely ocular, 10 (76.9%) had received prior immunotherapy.

CONCLUSIONS

In this study, most of the patients who progressed from ocular myasthenia to generalized myasthenia had not received prior immunotherapy. This study adds weight to the call for a prospective trial of early immunotherapy in patients with ocular myasthenia.

Childhood ocular myasthenia gravis

PURPOSE

To investigate the clinical manifestations and ocular findings in children with ocular myasthenia gravis (MG) that rarely have been reported in the literature.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Twenty-four consecutive patients less than 15 years of age with ocular MG treated between June 1988 and July 2001.

METHODS

The medical records of 6 boys and 18 girls with ocular MG were reviewed retrospectively.

MAIN OUTCOME MEASURES

Alternate prism cover and uncover test, examination of ductions and versions, and visual acuity.

RESULTS

Mean age at onset was 38 months. Ptosis was found in 23 patients (96%), strabismus in 21 patients (88%), and amblyopia in 5 patients (21%). Exotropia combined with vertical heterotropia was the most frequent type of strabismus. Ductions were limited in 17 patients (71%), among whom supraduction or infraduction limitations were most frequently observed. Contrary to previous reports, medial rectus underaction was less common than lateral rectus underaction. Manifestations of strabismus and limitation of duction were variable and changed frequently during the follow-up period. The combined use of prednisone and pyridostigmine was found to be the predominant form of maintenance therapy, and ptosis was more responsive to drug therapy than limited ocular motility.

CONCLUSIONS

Children with ocular MG were found to have a high incidence of ptosis (96%) and exotropia and vertical hyperdeviation. Limitation on adduction was less common than that on abduction. First reported incidence of amblyopia (21%) and a relative nonresponsiveness of the limitation of eye movement to treatment were also noted.

Double trouble

A 78-year-old woman presented with vertical double vision. The Bielschowsky-Parks' three-step test suggested a left inferior rectus muscle paresis. Diagnostic testing confirmed the diagnosis of myasthenia gravis. Despite treatment with pyridostigmine bromide (mestinon) the diplopia persisted. She refused corticosteroid treatment and sought a second opinion, resulting in three unsuccessful strabismus surgeries to correct her ocular misalignment. The evaluation and management of ocular myasthenia gravis is reviewed and the appropriate timing of strabismus surgery is discussed.

Myasthenia gravis

BACKGROUND

In myasthenia gravis (MG), the prototypic autoimmune disease, antibodies against acetylcholine receptors impair neuromuscular transmission and produce weakness. Although recognized for several hundred years, it has only been over the last three decades that effective treatments have become available for MG.

REVIEW SUMMARY

This review summarizes the principles of normal neuromuscular transmission, the clinical features of MG, and the tests available for its diagnosis. The current treatments for MG are discussed, including possible mechanisms of action and a discussion of potential adverse effects. When available, evidence-based justification for individual treatment options is given, and areas of controversy identified.

CONCLUSIONS

Significant improvements in the diagnosis and management of MG have been made over the last several decades. The available treatments either improve neuromuscular transmission directly, or suppress or modulate the pathogenic immune response in MG. Treatment is highly individualized and must take into account the severity of disease, the presence of other diseases, and the kinetics of response for the available treatments. This requires detailed knowledge of the mechanisms of action and possible adverse effects for each treatment. However, despite an optimistic outlook with modern treatment, the management of MG continues to be plagued by lack of efficacy in some, and significant adverse effects in most MG patients.

Tensilon and the diagnosis of myasthenia gravis: are we using the Tensilon test too much?

BACKGROUND

Tensilon (edrophonium chloride) is a reversible acetylcholinesterase inhibitor used in the diagnosis of myasthenia gravis, diagnosis and treatment of arrhythmias, detection of early digitalis toxicity, reversal of neuromuscular blockade, and other medical conditions. Toxicity associated with Tensilon use has appeared in the literature for decades.

REVIEW SUMMARY

This review discusses the risks of Tensilon and the information practitioners should know before administering the drug. We review the literature regarding serious toxicity of this drug and offer recommendations for its safe use.

CONCLUSIONS

A careful medication history should be taken before the administration of Tensilon. Additionally, physicians should be aware of appropriate alternative methods of diagnosis before choosing to administer Tensilon. Physicians should be aware of the clinical situations where the Tensilon test no longer is indicated.

Discrimination between normal and glaucomatous eyes with visual field and scanning laser polarimetry measurements

AIM

To evaluate the ability of structural parameters (as determined by retinal nerve fibre layer (RNFL) measurements obtained with the scanning laser polarimeter (SLP-NFA/GDx)) and functional parameters (as determined by automated perimetry) to discriminate between normal and glaucomatous eyes.

METHODS

In a case-control study, a total of 91 normal subjects and 94 patients with glaucoma underwent automated perimetry and RNFL measurements obtained with the SLP. Three independent scans of each eye were obtained and a mean image was created and used for further analysis. Only one eye per individual was randomly included in the study. The sensitivity (Se) and specificity (Sp) of 12 RNFL parameters were calculated according to the SLP internal normative database. The Se and Sp of the visual field (VF) global indices and the glaucoma hemifield test (GHT) were also calculated according to the instrument's normative database. Receiver operator characteristic (ROC) curves were built for each SLP parameter and VF index. Fisher's linear discriminant formulas (LDFs) were developed for VF indices (VF LDF), SLP measurements (SLP LDF), and both examinations (combined LDF).

RESULTS

According to the SLP internal database, the parameters with better Se and Sp were: superior/nasal ratio (Se = 58.5%; Sp = 86.8%), and GDx the number (Se = 43.3%; Sp = 96.7%). The construction of an ROC curve for the number resulted in Se = 84% and Sp = 79%. The creation of LDFs improved both the sensitivities and specificities when compared with isolated parameters SLP LDF (Se = 90.4%; Sp = 82.4%), VF LDF (Se = 89.4%; Sp = 89.0%), and combined LDF (Se = 93.0%; Sp = 90.1%). The sensitivity to diagnose early and moderate glaucomatous damage observed with the GHT was lower than that obtained with the number (p < 0.01).

CONCLUSIONS

Creation of LDFs enhanced the Se and Sp for both VF and SLP. Integration of SLP and VF in a combined LDF reached the highest Se/Sp relation, suggesting that these examinations may be additive concerning the diagnosis of glaucoma. The SLP parameter the number may be more sensitive than the GHT in diagnosing early and moderate glaucomatous damage.

Therapeutic options in ocular myasthenia gravis

The term ocular myasthenia gravis refers to the disease clinically restricted to extrinsic ocular muscles. It can be disabling as ptosis, and to a greater extent diplopia, both interfere with daily activities. Although ocular disturbances are the most frequent initial complaints in myasthenic patients, symptoms usually progress to generalized disease and only 15% of patients complain of purely ocular weakness for the entire course of their illness. Secondary generalization occurs with the highest frequency in the first 2 years from the onset. Both the severity of symptoms and the risk of generalization should be taken into account when devising a therapeutic plan for these patients. Anticholinesterases are of limited efficacy and a considerable proportion of patients require additional therapy. Corticosteroid therapy, generally prednisone on an alternate-day schedule, is very effective, but a reason for concern is represented by the frequent need for long-term administration with increased risk of severe complications. In patients unresponsive to prednisone or requiring too high dosages, immunosuppressive drugs like azathioprine should be used with the same criteria applied in generalized myasthenia. As corticosteroids and immunosuppressants reduce the chance of generalization, their use is justified in patients with recent-onset disabling disease. In long-standing cases with low risk of generalization, treatment is aimed at the relief of symptoms and pharmacological therapy should be reduced to the minimum effective dosage. The indication for thymectomy in ocular myasthenia remains highly controversial and should be reserved for disabled patients in the early stages of the disease.

New onset of crossed eyes in an adult

A 77-year-old woman presents with a seven-year history of an isolated slowly progressive esotropia with bilateral abduction defects. The only potential cause discovered was dolichoectasia of the intracavernous carotid arteries.

Extraocular muscle responses to orbital cooling (ice test) for ocular myasthenia gravis diagnosis

BACKGROUND

As a result of clinical and laboratory investigations of temperature correlates of myasthenia gravis, orbital cooling (ice test) has been developed as a reliable test for ocular myasthenia diagnosis through blepharoptosis response. The test has not been utilized in a prospective manner for myasthenia diagnosis through extraocular muscle responses.

METHODS

Fifteen patients with acquired motility disorders were studied with the use of orbital cooling and other tests for myasthenia gravis. Orbital cooling was performed in a standard fashion for all patients. In 14 of 15 patients, the diagnosis of myasthenia was not established at the time the ice test was performed. Fifteen non-myasthenic patients with acquired motility disorders were also studied with use of the ice test. Temperatures during orbital cooling were measured in the superior cul-de-sac of one patient and between the lateral rectus muscle and globe in 3 patients.

RESULTS

All patients subsequently proven to have myasthenia gravis by other tests and by response to myasthenia therapy had a positive (diagnostic of myasthenia) response to the ice test. No patient had a false-positive or a paradoxical response to the ice test. No control patient had a positive blepharoptosis or motility response to orbital cooling. Temperature measurements demonstrated significant cooling effects in the superotemporal cul-de-sac and beneath the lateral rectus muscles after orbital cooling for 5 minutes.

CONCLUSIONS

Orbital cooling, within certain parameters, can be a useful clinical test for myasthenia diagnosis through motility response, as well as blepharoptosis response.

The complication rate of edrophonium testing for suspected myasthenia gravis

BACKGROUND

The incidence of life-threatening complications from edrophonium chloride (Tensilon) testing for suspected myasthenia gravis is thought to be extremely low. We carried out a survey to determine the rate of serious complications from such testing.

METHODS

In April 1998, 357 physicians listed in the 1998 roster of the North American Neuro-ophthalmology Society were mailed a questionnaire for anonymous completion. Questions asked included the number of years the clinician had practised neuro-ophthalmology, the estimated number of edrophonium tests performed since completion of training, the number and nature of major complications from edrophonium, and whether the clinician preferred the sleep test or ice test to edrophonium testing.

RESULTS

The response rate was 56% (199/357). Of the 199 respondents, 105 (53%) had practised neuro-ophthalmology for at least 10 years. The group estimated that they had performed at least 23,111 edrophonium tests, of which 37 (0.16%) were associated with a serious complication, mostly attributed to brady-arrythmias and syncope. Respiratory failure, seizure, severe vomiting and transient ischemic attack were also reported. Thirty-one respondents (16%) preferred the sleep test or ice test to the edrophonium test; one-third of this group reported a serious complication with edrophonium.

INTERPRETATION

The rate of significant complications of edrophonium testing is low, but the complications can be potentially life threatening. Clinicians should know the nature and incidence of these complications when obtaining informed consent for edrophonium testing.

Acquired binocular horizontal diplopia

Binocular horizontal diplopia is an important symptom that may foretell or help localize and characterize various neurologic and neuromuscular disorders. An appropriate evaluation requires a careful and complete neuro-ophthalmic history and examination. This review focuses on the differential diagnosis of binocular horizontal diplopia.

Pseudo-myasthenia gravis and thymic hyperplasia in Graves' disease

BACKGROUND

Diagnostic confusion between thyroid disease and myasthenia gravis (MG) can arise because the two may have similar clinical features, and also because of the more frequent coexistence of these autoimmune disorders in the same individual. In MG, autoantibodies directed against the acetylcholine receptor result in muscle weakness. Thymic pathology is well recognized in MG, with thymic hyperplasia frequent in early onset MG and thymoma more common in later onset MG. In Graves' disease, autoantibodies against thyroid antigens result in hyperthyroidism. A seldom-recognized feature of Grave's disease is the occurrence of an enlarged thymus (thymic hyperplasia) on chest CT, or of thymic lymphoid hyperplasia pathologically.

CASE STUDY

This report describes a case in which the discovery of a mediastinal mass during imaging of the thyroid, and the presence of myasthenic-like symptoms, in a patient with Graves' disease prompted investigations into whether the patient also had MG.

RESULTS

Despite symptoms which strongly suggested MG, subsequent investigations did not confirm the diagnosis, and treatment of Grave's lead to a resolution of the symptoms and regression of the thymic enlargement seen on CT.

CONCLUSIONS

The case study highlighted clinical similarities between Grave's disease and myasthenia gravis which might cause diagnostic confusion, and also the investigations which are useful in order to differentiate the two diseases. In addition to common clinical features, the autoimmune diseases Grave's disease and myasthenia gravis may both produce radiological thymic enlargement.

An ice test for the diagnosis of myasthenia gravis

OBJECTIVE

To determine whether ice application to a ptotic eyelid can differentiate myasthenic from nonmyasthenic ptosis.

DESIGN

Prospective, multicenter, nonrandomized, comparative trial.

PARTICIPANTS

Twenty patients with myasthenia gravis (MG) and ptosis were evaluated in the neuro-ophthalmology service. CONTROL SUBJECTS: Twenty patients with nonmyasthenic ptosis evaluated in the same locale.

METHODS

Palpebral fissures were measured before and immediately after a 2-minute application of ice to the ptotic eyelid.

MAIN OUTCOME MEASURES

The difference in palpebral fissures in millimeters before and after ice application. Two or more millimeters of improvement after ice application was considered a positive ice test result.

RESULTS

A positive ice test result was noted in 16 of the 20 (80%) patients with MG and in none of the 20 patients without MG (P < 0.001). Of the 4 patients with MG and complete ptosis, 3 had a negative ice test result.

CONCLUSIONS

The ice test is a simple, short, specific, and relatively sensitive test for the diagnosis of myasthenic ptosis. The sensitivity of the ice test in patients with complete ptosis decreases considerably.

Quantitative ocular tests for myasthenia gravis: a comparative review with detection theory analysis

Many reports in the literature describe a variety of ocular signs in myasthenia gravis. To determine the utility of laboratory recordings of ocular signs in the evaluation for myasthenia, we reviewed all previous studies of quantitative measures of eye movements or intra-ocular pressures. We selected those studies with data presented for both myasthenic and non-myasthenic ocular palsies. Signal detection theory was used to evaluate the discriminative power of each variable. The characteristics of saccades and quick phases of optokinetic nystagmus at the start of recording were poor at distinguishing between myasthenic and non-myasthenic palsies, except when the comparison was solely between myasthenia and chronic progressive external ophthalmoplegia. The effects of fatigue on saccadic parameters were also not discriminative, though there was insufficient data to evaluate this adequately. Changes induced by edrophonium in the amplitude or peak velocity of saccades or optokinetic quick phases were good diagnostic tests, retaining high sensitivities when criteria were set to yield a specificity of 95%. Most of these parameters were less efficient as screening tests, with modest specificities when criteria were set to yield a sensitivity of 95%. The change in optokinetic quick phase amplitude recorded by infrared oculography was the best test, with ideal characteristics of 97% specificity and sensitivity at a criterion of zero change. This analysis suggests that eye movement recordings of saccades or optokinetic nystagmus have potential as useful and inexpensive tests for myasthenia, and warrant further study.

Transient ptosis and miosis after rugby injury

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