Neurometabolic and Brain Functional Alterations Associated with Cognitive Impairment in Patients with Myasthenia Gravis: A Combined 1H-MRS and fMRI Study

Whether patients with myasthenia gravis (MG) exhibit cognitive impairment is controversial. Also the underlying mechanisms are unknown. We aimed to investigate alterations in cognitive function, neurometabolite levels, and brain function in patients with MG and to explore the associations between abnormal regional brain functional activity, neurometabolite concentrations in the MPFC and left thalamus, and cognitive activity in patients with MG. Neuropsychological tests, proton magnetic resonance spectroscopy, and resting-state functional magnetic resonance imaging were performed on 41 patients with MG and 45 race-, sex-, age-, and education-matched healthy controls (HCs). The results suggest that MG is accompanied by cognitive decline, as indicated by global cognitive function, visual-spatial function, language, memory, abnormalities in regional brain functional activity, and neurometabolite alterations (including GABA, NAA, and Cho) in the medial prefrontal cortex (MPFC) and left thalamus. Cognitive impairment in patients with MG may be related to abnormal regional brain functional activity and changes in neurometabolites, and regional brain functional activity may be modulated by specific neurometabolites.

Contrast-enhanced CT-based radiomics differentiate anterior mediastinum lymphoma from thymoma without myasthenia gravis and calcification

AIM

To explore the value of a radiomics model based on enhanced computed tomography (CT) in differentiating anterior mediastinal lymphoma (AML) and thymoma without myasthenia gravis (MG) and calcification.

MATERIALS AND METHODS

The present study analysed patients who were diagnosed histologically with AML and thymoma in three independent institutions. All pre-treatment patients underwent enhanced CT. In the training group of patients from institutions 1 (the First Affiliated Hospital of Kunming Medical University) and 3 (the Yunnan Cancer Hospital), two radiologists independently analysed the enhanced CT images and performed manual segmentation of each tumour. Radiomics features were screened using interobserver interclass coefficient (ICC) analysis, feature correlation analysis, and L1 regularisation. The discriminative efficacy of the logistic regression model was evaluated using receiver operating characteristic (ROC) analysis. Validation group of patients from institution 2 (the Second Affiliated Hospital of Zhejiang University School of Medicine) was used to validate the proposed models.

RESULTS

A total of 114 patients were enrolled in this study and 1,743 radiomics features were extracted from the enhanced CT images. After feature screening, the remaining 37 robust radiomics features were used to construct the model. In the training group, the AUC of the model was 0.987 (95% confidence interval [CI]: 0.976-0.999), the sensitivity, specificity, and accuracy were 0.912, 0.946, and 0.924, respectively. In the validation group, the AUC of the model was 0.798 (95% CI: 0.683-0.913), the sensitivity, specificity, and accuracy were 0.760, 0.700, and 0.743, respectively.

CONCLUSION

The radiomics model created provided effective information to assist in the selection of clinical strategies, thus reducing unnecessary procedures in patients with AML and guiding direct surgery in patients with thymoma to avoid biopsy.

Diaphragmatic ultrasonography as a predictor of respiratory muscle fatigue in myasthenia gravis

INTRODUCTION/AIMS

Easy fatigability, the clinical hallmark of generalized myasthenia gravis (GMG), cannot be detected in a dynamic way. The aim of this study was to assess respiratory function dynamically through diaphragmatic ultrasonography (DUS) in GMG patients.

METHODS

GMG patients and controls were recruited in a 1:1 ratio. DUS was performed during one quiet breath and 15 consecutive deep breaths. The diaphragm thicknesses were measured at different positions. Diaphragm thickening fraction (TFdi) and the maximal change in diaphragm thickness (Tmax) during 15 consecutive deep breaths were calculated and transformed to normality, named N-TFdi and N-Tmax, respectively. The percentages of changes in TFdi and Tmax compared with baseline were named ΔTFdi and ΔTmax, respectively. The diagnostic parameter for respiratory muscle fatigue was chosen from ΔTFdi and ΔTmax at different deep breath times according to their ability to distinguish GMG patients from controls and the interrater reliability of TFdi and Tmax.

RESULTS

Thirty-four GMG patients and 30 healthy controls were enrolled. N-TFdi and N-Tmax significantly changed as the number of deep breaths increased (p < .001) in GMG patients, but not in controls. ΔTmax of the 15th deep breath (ΔTmax15) was selected as the diagnostic parameter for respiratory muscle fatigue. There were no significant differences in percentage of predicted values of forced vital capacity and arterial partial pressure of carbon dioxide between patients with normal and abnormal ΔTmax15.

DISCUSSION

DUS could identify diaphragm fatiguability in GMG patients, which may be more reliable and sensitive in assessment of diaphragm fatigue than conventional methods.

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.

The efficiency of chemical-shift MRI for the evaluation of thymoma in patients with myasthenia gravis

PURPOSES

This research aimed to evaluate the efficiency of using chemical-shift magnetic resonance imaging (MRI) to differentiate thy-moma from non-thymoma in patients with myasthenia gravis (MG).

METHODS

A total of 137 subjects were split into thymoma and non-thymoma groups. The qualitative parameters and the chemical-shift ratio (CSR) were compared between the two groups, using the Chi-square test and the Student's t-test, respectively. Logistic regression was performed to investigate the significant factors associated with both the qualitative parameters and CSR values that can be used to predict thymoma. The discriminative capability of CSR was defined by the area under the receiver operating characteristic (ROC) curve (AUROC), which was used to compute an optimal cut-off point for thymoma distinction.

RESULTS

Although significant differences between groups were identified by univariate analyses for most of the qualitative parameters, during the multivariate logistic regression, only CSR was significant for the distinction between two groups, with an odds ratio (OR) of 9.700 [95% confidence interval (CI): 1.874-50.200, p = 0.007). The CSR values for the thymoma and non-thymoma groups were 1.020 ± 0.073 and 0.604 ± 0.126, respectively. With an optimal cut-off point defined at 0.825, the AUROC of CSR was 0.982. When applying this cut-off point, the sensitivity and specificity of chemical-shift MRI for the detection of thymoma were 100% and 97.22%, respectively.

CONCLUSIONS

CSR values, calculated from chemical-shift MRI, was exceedingly valuable for distinguishing thymoma from non-thymoma in patients with MG.

Computed tomography radiomics for the prediction of thymic epithelial tumor histology, TNM stage and myasthenia gravis

Objectives

To evaluate CT-derived radiomics for machine learning-based classification of thymic epithelial tumor (TET) stage (TNM classification), histology (WHO classification) and the presence of myasthenia gravis (MG).

Methods

Patients with histologically confirmed TET in the years 2000–2018 were retrospectively included, excluding patients with incompatible imaging or other tumors. CT scans were reformatted uniformly, gray values were normalized and discretized. Tumors were segmented manually; 15 scans were re-segmented after 2 weeks by two readers. 1316 radiomic features were calculated (pyRadiomics). Features with low intra-/inter-reader agreement (ICC<0.75) were excluded. Repeated nested cross-validation was used for feature selection (Boruta algorithm), model training, and evaluation (out-of-fold predictions). Shapley additive explanation (SHAP) values were calculated to assess feature importance.

Results

105 patients undergoing surgery for TET were identified. After applying exclusion criteria, 62 patients (28 female; mean age, 57±14 years; range, 22–82 years) with 34 low-risk TET (LRT; WHO types A/AB/B1), 28 high-risk TET (HRT; WHO B2/B3/C) in early stage (49, TNM stage I-II) or advanced stage (13, TNM III-IV) were included. 14(23%) of the patients had MG. 334(25%) features were excluded after intra-/inter-reader analysis. Discriminatory performance of the random forest classifiers was good for histology(AUC, 87.6%; 95% confidence interval, 76.3–94.3) and TNM stage(AUC, 83.8%; 95%CI, 66.9–93.4) but poor for the prediction of MG (AUC, 63.9%; 95%CI, 44.8–79.5).

Conclusions

CT-derived radiomic features may be a useful imaging biomarker for TET histology and TNM stage.

The feasibility of quantitative MRI of extra-ocular muscles in myasthenia gravis and Graves' orbitopathy

Although quantitative MRI can be instrumental in the diagnosis and assessment of disease progression in orbital diseases involving the extra-ocular muscles (EOM), acquisition can be challenging as EOM are small and prone to eye-motion artefacts. We explored the feasibility of assessing fat fractions (FF), muscle volumes and water T2 (T2_water ) of EOM in healthy controls (HC), myasthenia gravis (MG) and Graves' orbitopathy (GO) patients. FF, EOM volumes and T2_water values were determined in 12 HC (aged 22-65 years), 11 MG (aged 28-71 years) and six GO (aged 28-64 years) patients at 7 T using Dixon and multi-echo spin-echo sequences. The EOM were semi-automatically 3D-segmented by two independent observers. MANOVA and t-tests were used to assess differences in FF, T2_water and volume of EOM between groups (P < .05). Bland-Altman limits of agreement (LoA) were used to assess the reproducibility of segmentations and Dixon scans. The scans were well tolerated by all subjects. The bias in FF between the repeated Dixon scans was -0.7% (LoA: ±2.1%) for the different observers; the bias in FF was -0.3% (LoA: ±2.8%) and 0.03 cm³ (LoA: ± 0.36 cm³ ) for volume. Mean FF of EOM in MG (14.1% ± 1.6%) was higher than in HC (10.4% ± 2.5%). Mean muscle volume was higher in both GO (1.2 ± 0.4 cm³ ) and MG (0.8 ± 0.2 cm³ ) compared with HC (0.6 ± 0.2 cm³ ). The average T2_water for all EOM was 24.6 ± 4.0 ms for HC, 24.0 ± 4.7 ms for MG patients and 27.4 ± 4.2 ms for the GO patient. Quantitative MRI at 7 T is feasible for measuring FF and muscle volumes of EOM in HC, MG and GO patients. The measured T2_water was on average comparable with skeletal muscle, although with higher variation between subjects. The increased FF in the EOM in MG patients suggests that EOM involvement in MG is accompanied by fat replacement. The unexpected EOM volume increase in MG may provide novel insights into underlying pathophysiological processes.

Paraneoplastic pemphigus and myasthenia gravis as the first manifestations of a rare case of pancreatic follicular dendritic cell sarcoma: CT findings and review of literature

BACKGROUND

Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm that originates from follicular dendritic cells in lymphoid tissue while paraneoplastic pemphigus (PNP) is an autoimmune blistering disease associated with neoplasms. Pancreatic FDCS associated with PNP and myasthenia gravis (MG) is even rarer and highly malignant. We present the clinical data, pathological materials and computed tomography (CT) features of a rare case of this disease.

CASE PRESENTATION

A 49-year-old woman presented with repeated ptosis of both eyelids, oral ulcers and erosions. Her laboratory results showed a slight elevation of CA125 and positivity of some autoimmune antibodies. CT revealed a round solid mass with central necrosis in the pancreatic tail. The solid component of the mass showed slight enhancement and serpentine feeding arteries in the arterial phase, moderate enhancement with a draining vein around the tumor in the portal venous phase and persistent enhancement in the delayed phase. Surgical resection was performed, and the pathological diagnosis was FDCS. However, the patient died of inability to excrete sputum and occlusion of the respiratory tract.

CONCLUSIONS

Pancreatic FDCS manifested as PNP and MG is very rare. Its CT features are not specific, and the disease should be differentiated from neuroendocrine tumors, solid pseudopapillary neoplasms and acinar cell carcinoma.

[Concomitant Operations for Thoracic Aortic Aneurysm and Myasthenia Gravis;Report of a Case]

A 77-year-old man, who had been under medical treatment for myasthenia gravis without thymoma, was diagnosed with aortic arch aneurysm. He underwent total aortic arch replacement and total resection of the thymus through median sternotomy. His symptoms relating to myasthenia gravis dramatically disappeared after the surgery. The serum anti-acetyl chorine receptor antibody decreased from 2.7 to 0.7 nmol/l (N<0.2) with the reduction of oral predonisolone from 12.5 to 5 mg/day at 4 years after the surgery. The concomitant operations significantly improved his quality of life.

[Intractable Myasthenia Gravis Accompanied with Thymoma;Report of a Case]

A 46-year-old female visited a hospital due to pelvic inflammatory disease (PID) and then her chest computed tomography revealed an abnormal shadow in the upper mediastinum. Four months later,she complained muscle weakness with her limbs, dysphagia, and ptosis of her eyelids. Total thymectomy was performed through a median sternotomy for mass lesion, which was pathologically proven to be type B1 thymoma. Postoperative myasthenia gravis (MG) crisis, which led to respiratory failure requiring intubation and mechanical ventilation, developed and laboratory tests showed elevated serum anti-AChR Ab(130 nmol/l), antinuclear antibody( ×640 serum dilution, speckled pattern) and anti-RNP Ab(129.2 U/ml). For MG crisis, steroid pulse therapy, immunosuppressive therapy and immuno absorption were performed, and she successfully weaned from mechanical ventilaton on 41 post operative day (POD). Some factors such as inapparent mixed connective tissue disease (MCTD) and Anti RNP antibody were thought to be a cause for having any difficulty in MG treatment in the present case.

Impact of screening with thyroid ultrasonography in myasthenia gravis patients

OBJECTIVES

This study was conducted to screen thyroid abnormality evaluated with ultrasonography (US) in patients with myasthenia gravis (MG) and investigate further when malignancy is suspected.

METHODS

Thyroid screening using US was conducted in 162 patients with MG. In cases where malignancy was suspected, further investigations were performed.

RESULTS

Abnormal US findings were detected in 125 of 162 patients with MG (72 patients with nodules, 74 patients with cysts, 27 patients with diffuse findings such as enlargement, atrophy, a hypoechoic pattern or a heterogenous echoic pattern, and 28 patients with calcification). From among these 125 subjects, 30 patients underwent further examinations such as needle aspiration cytology. As a result, six patients (3.7% of 162 cases) were positive for papillary carcinoma. The size of the carcinoma in three patients was <10 mm, yet the stage of thyroid carcinomas was high (stage III or IVa) in all six cases.

CONCLUSIONS

Our data suggest that the prevalence of thyroid carcinoma in cases of MG may be higher than that of the general population. Furthermore, in patients with MG, there is a possibility that the stage of the carcinoma is higher even when the carcinoma is of a very small size. Patients with MG, when diagnosed, should be advised to undergo US screening of the thyroid because most cases of thyroid carcinoma are highly curable.

Acquired myasthenia gravis in a poodle

An 11-year-old, spayed female, teacup poodle was evaluated for a chronic cough, lethargy, hindlimb weakness, and reluctance to exercise. Thoracic radiographs revealed megaesophagus and aspiration pneumonia. Serum antibodies against acetylcholine receptors confirmed the diagnosis of myasthenia gravis. The unusual clinical history and case outcome are discussed.

Rare association of Hodgkin lymphoma, Graves' disease and myasthenia gravis complicated by post-radiation neurofibrosarcoma: coincidence or genetic susceptibility?

With Hodgkin lymphoma (HL), other (autoimmune) diseases may occasionally occur or associate, whereas as a late treatment-complication, second tumour may develop. In our patient HL was diagnosed in 1996 and consequently received COPP/ABV and mantle irradiation. Due to the residual mediastinal tumour CRu was declared but later on no progression/relapse could be proved by PET. In 2000 Graves's disease, in 2001 myasthenia gravis was diagnosed, which showed resistance for immunosuppressant drugs, thus plasmapheresis, intravenous immunoglobulin treatments were applied. In 2005, the residual mediastinal tumour started progressive growth, which leads to thoracotomy in which the tumour was removed, it was malignant peripheral nerve sheath tumour. The disease showed progression despite the chemotherapy applied and the patient died in 2007 due to respiratory failure. Not even the postmortem histopathologic examination revealed the relapse of HL. Association of Hodgkin lymphoma, and two antibody-mediated autoimmune diseases, Graves' disease and myasthenia gravis, is rare and has not yet been reported in the literature. The etiologic role of genetic predisposition and immune regulatory disorder must definitely be thought of, as the possibility of mere coincidence is extremely small. Malignant peripheral nerve sheath tumour is a rare complication of irradiation, which underlines the importance of the risk or/and response adapted therapy of HL.

[Myasthenia gravis]

Myasthenia gravis is a rare, auto-immune neuromuscular junction disorder. Prevalence rates is about 50/1,000000. The disease results from circulating auto-antibody attacks against post-synaptic targets (acetylcholine receptor [AChR] in 80% cases) on the endplate region of the postsynaptic membrane. The diagnosis is supported clinically by transient weakness, increased by activity that can affect eye movements, swallowing, speech, upper and lower limbs, and trunk. There are generalized or focalized forms (as ocular myasthenia). The course is variable and evolved either with attacks or more chronically. Helpful tests for diagnosis are serologic antibodies detection against AChR, decrement of muscle action potential after repetitive nerve stimulations, identification of thymus gland abnormality (frequently associated with myasthenia) by chest computed tomography. Myasthenia gravis treatment is based on oral form of cholinesterase inhibitors, corticosteroids and other immunosuppressive drugs in severe forms. During myasthenia crisis, intraveinous immune globulines or plasma exchanges can be used. Thymectomy is proposed in case of thymus abnormality.

Somatostatin receptor scintigraphy in the follow-up of myasthenia gravis

To evaluate the potential value of somatostatin receptor scintigraphy (SRS) using 111In-DTPA (diethylenetriaminepenta acetic acid)-D-Phe1-octreotide (111In-pentetreotide) in patients with recurring or persisting symptoms of myasthenia gravis (MG), 14 consecutive cases with such supplemental receptor imaging during neurological routine follow-up were retrospectively evaluated in this study. All 14 patients underwent SRS in addition to chest computed tomography (CT). Mean follow-up after imaging was 34 months. Eight patients had previous thymectomy, and three patients were referred to surgery after scintigraphy and chest CT. SRS was positive in one of the 14 patients with local recurrence of thymoma and pleural invasion, and negative in the remaining 13 patients. CT was positive for thymoma in three patients, inconclusive in four patients and negative in seven patients. In conclusion, while SRS may be able to detect thymoma lesions including metastases, it seems of limited value in patients with inconspicuous CT findings. Our initial experience fails to point out a benefit of SRS in the management of persisting or recurring MG (with regard to detection of thymic disorders) compared to CT. Whether SRS is useful for differentiating thymoma from non-neoplastic thymic disease may be investigated by larger series. A predominant proportion of patients with unsatisfactory treatment response, however, continue to suffer an unfavourable clinical course despite absent evidence for thymic pathology.

Preoperative assessment of thymic veins on multidetector row CT: optimization of contrast material volume

PURPOSE

Preoperative localization of the thymic veins is considered important to prevent intraoperative severe bleeding prior to video-assisted thoracoscopic thymectomy. The purpose of this study was to determine the optimal dose of contrast material for preoperative CT imaging for the detection of thymic veins on the basis of patient weight.

MATERIALS AND METHODS

The records of 31 patients who underwent thymectomy were examined retrospectively. All patients were scanned using an eight-channel multidetector-row computed tomography (CT) scanner at 1.25 mm collimation and a 0.625-mm reconstruction interval. CT scans were obtained after injection of 300 mg I/ml nonionic contrast material at a rate of 2 ml/s. A 90-ml contrast bolus was used for the first 16 consecutive patients (group I), and a 150-ml bolus was used for the following 15 patients (group II). The scan delay was 60 s and 90 s in groups I and II respectively. Two independent radiologists who were blinded to the surgical results evaluated the number of thymic veins observed on preoperative CT, which was later correlated with the actual number of thymic veins clipped during surgery. The responses were analyzed with respect to contrast amount by single bolus and per kilogram of body weight.

RESULTS

Thymic veins were correctly detected in 9 of 16 (56%) patients in group I and 14 of 15 (93%) patients in group II. Thymic vein detection was significantly better in patients who received the >or=2.0 ml/kg contrast medium compared to those who received the 1.00-1.99 ml/kg medium (P < 0.05).

CONCLUSION

An intravenous contrast material volume of 2 ml/kg (300 mg I/ml) is appropriate for the identification of thymic veins on prethymectomy CT.

Role of flourine-18 fluorodeoxyglucose positron emission tomography in thymic pathology

OBJECTIVE

To evaluate the utilization of positron emission tomography (PET) scan with fluorine-18 fluorodeoxyglucose (FDG) in thymic pathology.

METHODS

Twenty-five consecutive patients with thymic pathology underwent FDG-PET after being evaluated by computed tomography (CT). The indication for CT was myasthenia gravis in 10, anterior mediastinal mass in 7, and recurrent thymic tumor after surgical excision in 8 patients. The results of PET were compared with results obtained by CT, and histopathologic examination of the surgical specimens.

RESULTS

All mediastinal abnormal thymic tissue showed FDG uptakes. FDG-PET managed to differentiate between thymic hyperplasia and thymoma in myasthenia gravis group (n=10) in which CT images were questionable in two patients. There was one case of ectopic thymic tissue which was not diagnosed preoperatively. There were no false-negative results for both CT and FDG-PET in seven patients with thymoma presented as anterior mediastinal mass. However, PET scan predicted thymic carcinoma in one patient. PET was superior to CT scan in localization of recurrent thymoma in two patients, and equal to CT in detecting metastatic lesions in six patients during the follow-up after thymoma excision.

CONCLUSIONS

In myasthenia gravis, selective use of FDG-PET is useful in differentiating thymoma from hyperplasia, especially when CT scan is controversial, but fails to recognize ectopic thymic tissue. FDG-PET may differentiate thymoma from thymic carcinoma. FDG-PET is also useful in follow-up patients, who underwent thymoma excision, when there is suspicion of recurrence or metastasis.

[Thymus CT scan and thymoma associated antibodies in myasthenia gravis with thymoma]

OBJECTIVE

To investigate the clinical significance of the serum anti-titin, anti-ryanodine receptor (RyR) antibody level and thymus CT scan in the diagnosis of myasthenia gravis with thymoma.

METHODS

Totally 32 patients with myasthenia gravis who had received thymectomy were included in the study. Abnormalities were shown under CT scan of thymus in all these patients. The relationships were studied among the pathological diagnosis, CT findings, and serum level of thymoma associated antibodies: anti-titin and anti-RyR antibodies.

RESULTS

The pathological diagnosis of thymoma was made in 21 patients and thymus hyperplasia in 11 patients after operation. The sensitivity of CT scan in the diagnosis of thymomas was 90.5%, the specificity of serum thymoma associated antibodies in the diagnosis of thymoma was 100%.

CONCLUSION

The thymoma-associated antibodies test is helpful in the differential diagnosis of thymomas and thymus hyperplasia; when combined with CT scan, it may achieve high sensitivity in the diagnosis of the thymoma.

Use of radiographic measurements in distinguishing myasthenia gravis from other causes of canine megaoesophagus

OBJECTIVES

To evaluate whether dogs with megaoesophagus due to myasthenia gravis display less oesophageal dilatation radiographically than dogs with other causes of megaoesophagus.

METHODS

Thoracic radiographs of 66 dogs with megaoesophagus in which concurrent acetylcholine receptor antibody titre was known were analysed retrospectively. Maximum oesophageal diameter was transformed to a "relative oesophageal diameter" using a ratio with thoracic inlet diameter. Dogs were divided into two groups according to "MG" or "non-MG" antibody status and median relative oesophageal diameter values were compared between groups and with age, weight and sex. A receiver operating characteristic plot was used to evaluate a suitable relative oesophageal diameter cut-off.

RESULTS

Twenty dogs were diagnosed with myasthenia gravis and 46 with other causes of megaoesophagus. Thoracic inlet size correlated significantly with bodyweight and surface area (r(2)=0.627 and 0.669, respectively). Median values of relative oesophageal diameter for the MG group and non-MG group were 0.58 and 0.66, respectively, and these showed a small, but significant, difference (P=0.029), although there was complete overlap in the range of relative oesophageal diameter values between groups. There was no significant association between relative oesophageal diameter and sex, age or weight or significant difference in age, sex or weight between the two groups. An increased odds ratio for myasthenia gravis existed in golden retrievers and German shepherd dogs.

CLINICAL SIGNIFICANCE

Relative oesophageal diameter appears to be of limited diagnostic utility in distinguishing dogs with megaoesophagus due to myasthenia gravis from those with megaoesophagus due to other causes.

Clinical utility of videofluorography with concomitant Tensilon administration in the diagnosis of bulbar myasthenia gravis

Myasthenia gravis (MG) classically presents with ocular, bulbar, and predominantly proximal muscle weakness. Isolated bulbar symptoms occur in less than 25% of cases and can mimic stroke (1-3). If left untreated, MG can lead to significant morbidity and mortality, including myasthenic crisis and recurrent aspiration pneumonia. We describe a case of a 68-year-old man who presented with isolated bulbar symptoms. We used a novel approach to diagnosis which included a videofluorographic swallow study with concomitant Tensilon (edrophonium) injection.

[Our strategy in the therapy of myasthenia gravis]

Surgical treatment of myasthenia gravis has at the 3 (rd) Department of Surgery, 1 (st) Medicine Faculty of Charles University in Prague a multiyear tradition which has originated in the 60's of the 20 (th) century. Since that time we carried out over 1 000 operations on the thymus, especially thymectomy for myasthenia gravis (MG) and with lesser frequency for thymomas. Thymectomy combined with exenteration of fatty tissue from the front mediastinum belongs to basic MG surgery. According to our experience an optimal approach to the thymus is given by partial sternotomy. A jugular approach is not regarded as enough radical. Videothoracoscopic approach and operation are possible but take more time, however they are the method of choice at some workplaces. The combined conservative and surgical treatment brings in 80 % of the cases an obvious improvement or deletion of the symptoms of the disease.

CT-guided percutaneous ethanol injection of the thymus for treatment of myasthenia gravis

OBJECTIVE

This study was designed to validate the therapeutic effectiveness of CT-guided percutaneous ethanol injection of the thymus for the treatment of myasthenia gravis.

SUBJECTS AND METHODS

The subjects were 45 patients with myasthenia gravis. The diagnosis was determined by the patients' histories, physical findings, neostigmine tests, and morphologic changes. According to the Osserman classification, the 45 patients with myasthenia gravis were classified as stage I (n = 26), stage III (n = 13), and stage IV (n = 6). A 21- or 22-gauge needle was inserted into the thymus under CT guidance, and then ethanol was injected step by step until it was distributed throughout the whole thymoma, the hyperplasia of the thymus, or the normal thymus. The amount of ethanol injected ranged from 2 to 13 mL, with a mean of 7 mL.

RESULTS

CT follow-up at 3-4 weeks showed that the thymus or thymoma was completely or mostly necrotized. CT follow-up at 3 months showed that the vertical, transverse, and anteroposterior dimensions of the thymus in all 45 myasthenia gravis patients decreased by 59.2%, 68.6%, and 73.2%, respectively, compared with those before percutaneous ethanol injection treatment. The therapeutic effect was observable clinically 2 days after treatment in 44 patients, including 36 patients who were able to open their eyes after treatment. A 5-year follow-up study showed that the condition markedly improved in 35 patients, improved in nine patients, and failed to improve in one patient who did not respond to the treatment. After treatment, 37 patients presented with low-grade fever (range, 37.3-37.7 degrees C; mean, 37.5 degrees C), which resolved 3 days later without treatment; all 45 patients complained of mild retrosternal pain after ethanol injection.

CONCLUSION

The therapeutic effect of CT-guided percutaneous ethanol injection into the thymus of patients with myasthenia gravis is definite. This procedure is safe and has low morbidity. CT-guided percutaneous ethanol injection is a minimally invasive alternative treatment for myasthenia gravis.

Assessment of esophageal function in patients with myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) is an autoimmune disease in which impairment of neuromuscular transmission results in a pathological fatigability of striated muscles. Dysphagia is a common symptom in MG. It is caused by a weakness of the striated muscles in the pharynx and esophagus. The purpose of our study was to evaluate the role of esophageal scintigraphy in the assessment of esophageal function in MG.

METHODS

In 15 patients with clinically proven MG (oculopharyngeal manifestation in 6/15 patients, generalized weakness in 9/15 patients) esophageal transit was investigated scintigraphically with a multiple swallow test protocol. 10/15 patients had a history of dysphagia. Patients were studied twice: under baseline conditions, and immediately after pharmacological stimulation with 10 mg of edrophonium chloride (EC), a short-acting acetylcholinesterase inhibitor.

RESULTS

Under baseline conditions all patients showed an impaired esophageal function (emptying [%]= 58 % +/- 21; normal range > 85 %). In 14/15 individuals esophageal transit improved after administration of EC (emptying [%]= 75 % +/- 18; p < 0.01), reaching the normal range in 6 patients. One patient showed no effect attributable to EC.

CONCLUSIONS

Esophageal transit is often compromised in MG. Functional abnormalities may be also present in patients without a history of dysphagia. Inhibition of cholinesterase positively affects striated muscles in the pharynx and upper esophagus, thus improving esophageal transit. Esophageal scintigraphy may be considered as a simple, non-invasive method for diagnosing impairment of esophageal function in MG and to monitor the changes under pharmacological stimulation.

Thymic lesions and myasthenia gravis. Diagnosis based on mediastinal imaging and pathological findings

PURPOSE

To achieve a better understanding of the role of CT and MR imaging in the study of the mediastinum in patients with myasthenia gravis (MG).

MATERIAL AND METHODS

Mediastinal CT and MR findings were correlated with the histopathological results in 104 thymectomized MG patients.

RESULTS

CT was performed in 104 patients; in 11 of them, MR was also carried out. 44 patients had hyperplasia at histology. On CT, thymic hyperplasia was confirmed in 16 cases, thymoma was diagnosed in 10 and a normal thymus in 18 (sensitivity 36%, specificity 95%). Of 52 patients with thymoma at histology, CT showed thymoma in 46, hyperplasia in 1, and normal thymus in 5. CT showed 88.5% sensitivity and 77% specificity for thymoma. In 10 patients with invasive thymoma, CT was indiscriminate, while invasiveness was detected in 7 cases at MR (70% sensitivity) and at CT in 1 case. Both CT and MR detected tumor recurrence in 5 cases, but the exact localization and degree of invasion were best defined by MR.

CONCLUSION

In MG patients CT is a sensitive, specific and efficient modality for detecting thymoma, but is less so for detecting thymic hyperplasia. MR was shown to be accurate in detecting invasive thymoma both preoperatively and in postoperative follow-up.

[Myasthenia and thymoma in a seven year old girl]

INTRODUCTION

Myasthenia is an autoimmune disease, being generalized muscular weakness, with important participation of facial muscles, a prominent feature. Signs of muscular fatigue arise, worsened by exercise and alleviated by rest. Clinical symptoms are less marked before noon, and get worse as the day advances, through the afternoon and evening. A clear relationship between myasthenia and thymic abnormalities does exist, being glandular hyperplasia and tumours the commonest underlying pathologic findings. Initial treatment is based on anticholinesterase drugs and steroids. Non respondents should be treated with immunoglobulins, immunosuppresses, plasmapheresis and surgical removal of the thymus, according to the symptoms control.

CASE REPORT

We present the case of a seven years old girl with generalized muscular weakness, worsening through the day, being the diagnosis of myasthenia confirmed by the high level of acetylcholine antireceptors antibodies and the neurophysiologic study. Imaging study of the mediastinum showed a thymic mass located in the right lobe.

CONCLUSION

It is therefore most important to rule out these conditions when myasthenia is suspected.

Pseudomyasthenia resulting from a posterior carotid artery wall aneurysm: a novel presentation: case report

OBJECTIVE AND IMPORTANCE

Painful oculomotor palsy can result from enlargement or rupture of intracranial aneurysms. The IIIrd cranial nerve dysfunction in this setting, whether partial or complete, is usually fixed or progressive and is sometimes reversible with surgery. We report an unusual oculomotor manifestation of a posterior carotid artery wall aneurysm, which mimicked ocular myasthenia gravis.

CLINICAL PRESENTATION

A 47-year-old woman developed painless, intermittent, partial IIIrd cranial nerve palsy. She presented with isolated episodic left-sided ptosis, which initially suggested a metabolic or neuromuscular disorder. However, digital subtraction angiography revealed a left posterior carotid artery wall aneurysm, just proximal to the origin of the posterior communicating artery.

INTERVENTION

The aneurysm was successfully clipped via a pterional craniotomy. During surgery, the aneurysm was observed to be compressing the oculomotor nerve. The patient's symptoms resolved after the operation.

CONCLUSION

The variability of incomplete IIIrd cranial nerve deficits can present a diagnostic challenge, and the approach for patients with isolated IIIrd cranial nerve palsies remains controversial. Although intracranial aneurysms compressing the oculomotor nerve classically produce fixed or progressive IIIrd cranial nerve palsies with pupillary involvement, anatomic variations may result in atypical presentations. With the exception of patients who present with pupil-sparing but otherwise complete IIIrd cranial nerve palsy, clinicians should always consider an intracranial aneurysm when confronted with even subtle dysfunction of the oculomotor nerve.

Expanded indications for transcervical thymectomy in the management of anterior mediastinal masses

BACKGROUND

Transcervical thymectomy (TCT) is an accepted though controversial approach for thymectomy in myasthenia gravis (MG). The suggestion of thymoma on computed tomography (CT) has been considered a contraindication to TCT. We sought to determine whether the indications for TCT could be safely expanded to include selected patients with thymomas as well as other types of anterior mediastinal masses.

METHODS

Between January 1992 and September 1999, we performed 121 TCTs: 98 in patients with MG and 23 in patients without MG. The patients' records were retrospectively reviewed.

RESULTS

Among the 98 MG patients, 28 had CT scans suspicious for thymoma. Of these, 14 had a thymoma pathologically. These were classified as stage I (5), stage II (8), and stage III (1). Five patients required extension of the incision for completion of the procedure. There have been no thymoma recurrences to date with a mean follow-up of 48 months (range 3 to 96 months). In the 23 patients without MG, 12 had new anterior mediastinal masses, 4 had a history of treated lymphoma, 1 had a history of treated germ cell tumor, and 6 had suspected mediastinal parathyroid adenoma. Diagnostic tissue was obtained in all patients undergoing the procedure for diagnosis, and in 4 of 6 patients, a parathyroid adenoma was successfully resected.

CONCLUSIONS

Transcervical exploration and thymectomy offers a less invasive approach to the diagnosis and/or definitive treatment of selected anterior mediastinal masses. We suggest that it is appropriate to expand its use to several clinical scenarios beyond the typical indication of thymectomy in MG patients without thymoma.

In vivo and in vitro expression of somatostatin receptors in two human thymomas with similar clinical presentation and different histological features

[(111)In-DTPA0]octreotide scintigraphy allows the in vivo visualization of several types of SS receptor (SSR)-expressing tumors. Among these, thymomas have been recently detected. Here we report on 2 patients admitted for myasthenia gravis and radiological evidence of thymic mass. Although these patients had similar clinical presentation, in vivo SSR scintigraphy displayed a difference in the degree of the [(111)In-DTPA0]octreotide uptake. Considering that both thymic masses had comparable volume, [(111)In-DTPA0]octreotide level was significantly higher in one of the 2 tumors (tumor/background ratio of 5.7 vs 2.6). The SSR subtype expression pattern was studied in vitro on the surgically resected specimens by ligand binding techniques, quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. According to the recent World Health Organization classification, the 2 tumors were classified A and B2 thymomas respectively. In membrane homogenates, we found a higher number of high affinity [125I-Tyr11]-SS-14 binding sites in the B2 thymomas (23.5+/-2.5 vs 12.0+/-0.4 fmol/mg membrane protein; p<0.05). RT-PCR analysis showed sst1, sst2A and sst3 mRNA in the 2 thymoma tissues, whereas SS mRNA was detectable only in the A thymoma. Quantitative evaluation of RT-PCR data showed a comparable expression of the relative amount of sst2A mRNA in both tumors, whereas a significant higher expression of sst3 mRNA in the B2 thymoma. Sst2A immunoreactivity was localized mainly on the endothelium of intratumoral vessels, whereas sst3 was present on either tumoral epithelial cells or normal reactive thymocytes. The expression of sst2A receptors in these tumors is in line with the in vivo visualization by [(111)In-DTPA0]octreotide, which is considered a sst2-preferring ligand. However, since radioligand uptake was significantly higher in the B2 thymoma, which expressed the largest sst3 mRNA levels, it might be possible that this subtype is involved in determining the tumor visualization during SSR scintigraphy. Apart from the affinity of the radioligand for the receptor, also the efficacy of the internalization of the radioligand-receptor complex might play a role in radioactivity accumulation during in vivo SSR scintigraphy. In fact, although octreotide binds with lower affinity to sst3 receptors, this subtype displayed the highest amount of agonist-dependent receptor internalization compared to the other SSR subtypes. Moreover, sst3 was localized on both tumor cells and reactive thymocytes, and these latter cells are characterized by a very active turnover of membrane molecules. Finally, although more cases need to be evaluated, the lack of detection of SS mRNA in the tumor presenting a more aggressive phenotype (B2 thymoma) might have physiopathological or prognostic significance.

A study of myasthenia gravis in patients with and without thymoma

This study was undertaken to compare the clinical, neurophysiological, radiological and prognostic features of myasthenia gravis with and without thymoma. 37 patients with myasthenia gravis (27 males, 10 females), with age range of 4.5 to 72 (mean 39) years, were managed at a tertiary care centre in India. Four patients were below 15 years of age and 6 above 55 years. Most of the patients were in stage II (34). There were 2 patients in stage III and 1 in stage I. 27 patients underwent thymectomy. Thymoma was detected in 10 cases. The decrement in patients with thymoma ranged between 11 and 62% (mean 27.9%) and nonthymoma group 10-75% (mean 28%). CT scan of thorax revealed mediastinal mass in 5 out of 10 cases of thymoma and 2 out of 27 patients without thymoma. Outcome of myasthenia gravis with thymoma was worse than without thymoma at 1 year followup. Severity of illness, extent of decrement, lack of facilitation, duration of illness and age of the patients were not related to the outcome. It is concluded the clinical and neurophysiological changes in myasthenia gravis with and without thymoma do not differ. However, patients with thymoma have a worse outcome.

Extended thymectomy for myasthenia gravis in an octogenarian. A case report

An 86-year-old woman with myasthenia gravis successfully underwent an extended thymectomy. The patient had a 2-year history of generalized myasthenia and had limited response to anticholinesterases and steroids. An extended thymectomy was successfully performed in the usual fashion. The postoperative course was uneventful except for an episode of psychosis probably due to postoperative steroid therapy. The steroid dosage was gradually reduced to 5 mg/day over seven months after the operation, during which she became fully asymptomatic. No symptoms due to myasthenia have surfaced for over 2 years after surgery. Although elderly patients are usually considered to be less responsive to an operation, thymectomy may sometimes be the treatment of choice for myasthenia gravis even in octogenarians.

Thymectomy in the integrated management of myasthenia gravis

Since the early days of Sauerbruch and Blalock, thymectomy has been used with increasing success in the management of myasthenia gravis. Several principles of management have emerged from this experience: the patient clearly benefits from care by a coordinated team, including a neurologist, intensivist, anesthesiologist, and surgeon in an institution familiar with the routine care of the myasthenic patient. Thymectomy is indicated early in the routine management of most patients with generalized myasthenia gravis, as well as those with purely ocular involvement uncontrolled by anticholinesterase medication. Patients should not undergo thymectomy while in crisis, but their medical condition should be optimally controlled prior to surgery, even if this requires the use of immunosuppressive agents. Because of the proven benefit in patient pain management and postoperative respiratory function, epidural adjuvant analgesia should be administered, unless contraindicated. Furthermore, the data from multiple series indicate that some form of "maximal" thymectomy should be used to try to remove all thymic tissue and induce patient clinical improvement or remission. Finally, long-term patient follow-up using an objective grading system should be maintained to optimize maximal functional status with as few medications as possible. When it is possible, there is little question that patients do better without long-term immunosuppression with steroids or other agents.

Myasthenia gravis presenting with dysphagia and postoperative ventilatory failure

We report a case of myasthenia gravis presenting to the department of otolaryngology with acute dysphagia on two separate occasions over a one-year period. Diagnosis of myasthenia gravis was made when the patient developed ventilatory failure after his second general anaesthetic for rigid oesophagoscopy. Our patient required emergency transfer to the intensive therapy unit for ventilation. He improved after treatment with corticosteroids, anticholinesterase and immunosuppressive medications. Our case was unusual in that cricopharyngeal spasm causing dysphagia and significant aspiration was demonstrated by a barium swallow and this was completely resolved after treatment of the myasthenia gravis.

Thymus in myasthenia gravis: comparison of CT and pathologic findings and clinical outcome after thymectomy

PURPOSE

To correlate computed tomographic (CT) appearance of the thymus with results from histologic examination of thymic tissue and clinical outcome in patients with generalized myasthenia gravis who underwent thymectomy.

MATERIALS AND METHODS

Forty-five patients with myasthenia gravis underwent CT of the thorax and thymectomy. Findings at clinical follow-up were available in all patients.

RESULTS

Twenty-six patients had normal CT findings, seven had a diffusely enlarged thymus, and 12 had a focal mass. The results of histologic examination showed that 16 of 26 patients with normal CT findings had normal thymic tissue and 10 had lymphoid follicular hyperplasia; all seven patients with an enlarged thymus had lymphoid hyperplasia. Five of 12 patients with a focal mass at CT had lymphoid hyperplasia, and seven had thymoma. Clinical improvement following thymectomy was observed in 27 (93%) of 29 patients with lymphoid hyperplasia or thymoma and 11 (69%) of 16 patients with normal histologic examination (P < .03, chi(2) test).

CONCLUSION

The presence of an enlarged thymus or a focal mass in patients with myasthenia gravis indicates lymphoid hyperplasia or thymoma. However, CT is of limited value in distinguishing lymphoid follicular hyperplasia from a normal thymus or thymoma and in predicting clinical outcome.

[Correlation of computer tomography findings with surgical findings in patients with myasthenia gravis]

A group of patients with myasthenia gravis operated at the Third Surgical Clinic, Faculty Hospital had in 20.5% a thymoma. Before operation CT did not detect the thymoma in 13.8% of the thymomas detected during operation and verified by histological examination. This fact must be taken into account when indicating conservative treatment in a myasthenic patient.

Myasthenia gravis presenting with stridor

The case is described of a 72 year old woman who presented with a two year history of exertional stridor in whom the diagnosis of myasthenia gravis was delayed. Although an uncommon cause, myasthenia gravis should be included in the differential diagnosis of stridor.

[Imaging of the thymus gland in myasthenia gravis (computerized tomography and magnetic resonance)]

Since thymectomy is nearly always indicated as a possible treatment of myasthenia gravis, we examined with Magnetic Resonance (MRI) and Computed Tomography (CT) 22 patients (21-62 years old) to identify the best methodological approach. MR images were obtained with a 1.5 T superconducting unit with slice thickness ranging from 6 to 8 mm and an interslice gap of 0.6 and 0.8 mm. Spin-echo images were acquired with repetition time (TR) < 700 ms and echo time (TE) of 20 ms and T2-weighted images with TR > 1800 ms and TE of 80 ms. The sections were obtained, with cardiac gating, on transverse and sagittal planes. CT was performed with contiguous 5-mm slice thickness, after intravenous bolus injection of contrast medium. All the patients underwent surgery of anterior mediastinum and histologic diagnosis was made. Both CT and MRI correctly identified the patterns of normal thymus or hyperplasia not associated with gland enlargement, the only two cases of hyperplasia with thymic enlargement and clearly demonstrated thymomas. MRI appears to be more accurate in the evaluation of the relationship between thymus and contiguous structures. If pericardial infiltration is suspected, sagittal MR scans yield accurate information on tumor spread. We recommend MRI of anterior mediastinum to rule out the presence of a thymoma and the possible involvement of contiguous structures.

Single fiber electromyography of extraocular muscles: a sensitive method for the diagnosis of ocular myasthenia gravis

We performed single fiber electromyography (SFEMG) in the superior rectus and levator palpebralis (SR-LP) muscles of 17 patients with pure ocular myasthenia gravis (MG) and 9 controls. Thirteen patients were also assessed with SFEMG in the orbicularis oculi (OO) muscle. All the MG patients but none of the control subjects showed abnormal SFEMG jitter in the SR-LP muscles. On the other hand, only 62% of the MG patients had abnormal SFEMG jitter in the OO muscle. The procedure was well tolerated by the patients, and complications were minor. We conclude that SFEMG of the SR-LP muscles is a safe and highly sensitive technique for the diagnosis of ocular MG.

A case of myasthenia gravis complicated with hyperthyroidism and thymic hyperplasia in childhood

We report here a case of myasthenia gravis complicated with hyperthyroidism and thymic hyperplasia. The patient was a 13-year-old girl with struma and hyperthyroidism which began at age 12. Two weeks following the initiation of treatment against hyperthyroidism she developed left blepharoptosis, diplopia, and dysphagia, which responded promptly to edrophonium administration. An increase of the anti-acetylcholine receptor antibody was found in the serum. A chest CT showed a large soft tissue mass in front of the ascending aorta, which was proven histopathologically as thymic hyperplasia. The patient underwent an extensive thymectomy and was placed on combination therapy with an anti-thyroid drug, glucocorticosteroid, and an anti-cholinesterase drug. Her symptoms and signs have been well controlled by this treatment. Coexistence of myasthenia gravis, hyperthyroidism, and thymic hyperplasia in childhood have never been documented in literature.

Prenatal diagnosis of congenital myasthenia with arthrogryposis in a myasthenic mother

We studied two children born to a myasthenic mother. The first child, a female, had multiple flexion contractures. She died 1 h after birth. In the second pregnancy, 3 years later, ultrasonographic examination at 20 weeks showed decreased fetal movements and multiple flexion contractures. The pregnancy was interrupted. Eight other cases of congenital myasthenia with arthrogryposis are known; four of them are siblings. The recurrence risk may be as high as 100 per cent. Our second case demonstrates that prenatal diagnosis is possible early enough to allow termination of pregnancy.

Computerized tomography in the evaluation of myasthenia gravis

Thymomas occur in 10% to 15% of patients with myasthenia gravis. Since not all patients are referred for thymectomy, a test that could reliably predict the presence or absence of a thymoma would be of great assistance in the management of these patients. We studied all patients referred for thymectomy at Walter Reed Army Medical Center from 1983 to 1989. Complete records were available for 13 patients. Computerized tomography (CT) correctly predicted the presence of a thymoma in one patient and falsely predicted a thymoma in a patient with a thymic cyst; it accurately predicted the absence of a thymoma in the remaining 11 patients. The sensitivity of CT scanning was 100%, the specificity was 92%, and the accuracy was 92%, results that are in agreement with previously published data. Compared to conventional chest roentgenography, CT scanning provided a more precise anatomic localization, and accurately predicted local invasion. We recommend a CT scan of the mediastinum in all patients with myasthenia gravis to avoid delayed diagnosis of thymoma in patients who normally would not be referred for thymectomy.

[Radiological examination and diagnosis of thymus in myasthenia gravis (report of 61 cases)]

Chest radiological plane films and traditional tomographic and CT scans of the mediastinum were correlated with pathological findings of the thymus following thymectomy in 61 cases with myasthenia gravis. The authors suggest that since it is difficult to differentiate the normal thymus or thymic hyperplasia from thymoma, thymoma can be more easily diagnosed in older than in younger patients.