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Clinical profile of myasthenia gravis in the Sultanate of Oman.

OBJECTIVE: Clinical study and follow up of myasthenia gravis patients in Oman. METHODS: Follow up of 50 consecutive myasthenia gravis patients referred to the Sultan Qaboos University Hospital, Oman for a median period of 3 years from 1997 to 2000. We based the diagnosis on the clinical picture, repetitive nerve stimulation tests and edrophonium test. We performed a computerized tomography scan of the chest and anti-acetylcholine receptor antibodies. We reviewed the results of immuno modulatory treatment including thymectomy and compared these with other studies. RESULTS: Of 50 patients, 6 had purely ocular myasthenia. Of the 44 with generalized myasthenia, 28 had bulbar involvement and 12 required ventilatory support. Eight out of 29 thymectomized patients had drug free remission after 2 years. There was worsening of myasthenic symptoms in only one out of 8 pregnancies and deliveries. CONCLUSION: Bulbar and ventilatory involvement are more common in our series as compared with western data. Pregnancy and delivery were well tolerated.

Adolescent↗

Management of myasthenia gravis by extended thymectomy with anterior mediastinal dissection.

BACKGROUND: Thymectomy has continued to gain acceptance as definitive treatment for myasthenia gravis. Because of the nature of thymic embryology with scattered rests throughout the anterior mediastinum, we advocate a transsternal thymectomy with extended anterior mediastinal dissection. METHODS: A series of 48 patients with myasthenia gravis treated by thymectomy between 1979 and 1991 were reviewed. RESULTS: The mean length of duration of disease from onset to operation was 48.7 +/- 11.3 months, and the mean length of follow-up was 51.6 +/- 6.5 months. The operation was associated with a 21% morbidity rate (4% major morbidity) with no deaths. Forty-five patients (94%) have improved, requiring decreased medication. The overall drug-free remission rate was 42%. Of the 20 patients in remission, three had thymomas and four had hyperplastic glands. All of the patients who achieved drug-free remission were classified as Osserman's I or II. CONCLUSIONS: An aggressive surgical approach to myasthenia gravis can result in a high percentage of overall improvements and drug-free remissions. The best results are achieved in patients with lower-stage disease. Therefore transsternal extended thymectomy for myasthenia gravis appears to be the procedure of choice and should be advocated as soon as the diagnosis is made and the patient stabilized.

Adult↗

The effect of use of pyridostigmine and requirement of vecuronium in patients with myasthenia gravis.

CONTEXT: Patients with myasthenia gravis receive pyridostigmine, an anticholinesterase agent, as a part of therapy. These patients demonstrate a heightened sensitivity towards non-depolarising muscle relaxants. Continuing pyridostigmine till the day of the surgery or omitting it on the night before surgery could provide variable results with regards to the effect of vecuronium. AIMS: Myographic evaluation of a dose of vecuronium in patients with myasthenia gravis on pyridostigmine therapy. SETTING AND DESIGN: A randomised, double-blind, clinical study conducted in a teaching hospital. SUBJECTS AND METHODS: Medically (oral pyridostigmine) well-controlled adult patients with myasthenia gravis who were posted for thymectomy, were randomly divided into two groups. Patients in Group 1 received their last dose of pyridostigmine on the night before surgery while those in Group 2 received even the morning dose of the drug on the day of surgery. Neostigmine (1-2 mg) intravenously was used as rescue medication. Vecuronium (0.01 mg/kg) was used for intubation and muscle relaxation during trans-sternal thymectomy and its effect was reversed using neostigmine and atropine. RESULTS: Fourteen patients (7 in each group) belonging to both sexes were enrolled in the study. The intubating dose of vecuronium showed quicker onset time (155 sec or 2.7 min approx.) and peak effect (99% T1 suppression) in patients belonging to Group 1, and 3/7 (43%) complained of respiratory discomfort while waiting for surgery. By giving the morning dose of pyridostigmine (Group 2), an identical intubating dose of vecuronium showed relative resistance (peak effect-97% T1 suppression) and delayed onset time (198 sec approx.). However, the reversal was complete at the end of surgery in both the regimens. CONCLUSIONS: Omission of the pyridostigmine dose on the day of surgery predisposed patients with myasthenia gravis to the possibility of respiratory discomfort and sensitivity to vecuronium. Continued administration significantly prolonged the onset time of vecuronium and the patients required a higher dose of vecuronium.

Adult↗

[Experience in the treatment of acute fulminating myasthenia gravis].

During past 15 years, 188 myasthenia gravis (MG) patients underwent thymomectomy or thymectomy with extended resection of the adipose tissue around the thymus in our institution. Four of 188 patients (2%) had to be given respiratory support within 2 months after the onset of MG. We defined this MG as the acute fulminating type. There were 2 male and 2 female patients, ranging in age from 22 to 44 years (average, 32.5 years). Three of these patients had thymoma. One of these patients was post-thymomectomy myasthenia gravis and another patient was d-penicillamine induced myasthenia gravis. Two patients admitted on respirator for respiratory crisis. All patients underwent operation within 2 weeks after admission. The duration of respiratory support ranged from 10 to 120 days (mean 44) after operation. The period of the hospital stay ranged from 8 months to 2 years 1 month (mean 1 year 5 months). During acute stage after operation, the patients needed ACTH, steroid, immunosuppressants (azathioprine, Bredinin) and plasma pheresis depending on their severity of myasthenic symptoms. In 2 patients dose of steroid could be reduced without deterioration of the symptoms. They are doing well with small dose of steroid. In one patient plasma pheresis was performed 6 years after thymectomy. Various symptoms due to myasthenia gravis and rheumatoid arthritis has recurred 10 years after thymectomy. The titer of acetylcholine receptor antibody of this patient has been continuing in high level.

Acute Disease↗

Myasthenia gravis: how to treat?

Myasthenia Gravis is an acquired autoimmune disorder caused by a neuromuscular transmission defect which is clinically characterized by fluctuating weakness of voluntary muscles and fatigability. It can be diagnosed by clinical features, clinical, pharmacological and electrophysiological tests and serological evaluation. Treatment modalities include symptomatic treatment in the form of cholinesterase inhibitors and plasmapheresis and immunotherapy in the form of immunosuppressant medications, immunomodulating therapy and thymectomy. No single regimen is appropriate for all patients and up to now no mode of therapy has been proven to be clearly superior. The response to any form of treatment is difficult to assess because the severity of symptoms fluctuate. We retrospectively analyzed the clinical records of 33 myasthenia gravis patients which were managed at our clinic between 1995-2003. All patients were treated with anticholinesterase medications sometime during their treatment. Most patients recieved immunosupressant and/or immunomodulator therapy. Patients were referred for thymectomy when indicated. We evaluated the outcome with different treatment modalities, focusing on the role of thymectomy. We also investigated the possible correlations between clinicopathological features and clinical outcome. We conclude that as for the medical treatment of myasthenia gravis azathioprine plus steroid improves the outcome; and for the surgical treatment, early thymectomy should be performed in all generalize myasthenia patients.

Adolescent↗

Interferon system and natural killer cell activity in myasthenia gravis.

The autoimmune response in myasthenia gravis is well characterized, but little is known about the mechanisms initiating it. We have studied the interferon system and natural killer cell activity in 25 patients with myasthenia gravis and compared them to 68 healthy subjects and 96 patients with acute viral infections. Forty-four per cent of patients had circulating interferon (greater than 16 mu/ml), and in a similar proportion their peripheral blood mononuclear cells were in an antiviral state, i.e., showed low levels of viral replication when infected by vesicular stomatitis virus. Spontaneous in vitro interferon production by patients' peripheral blood mononuclear cells was also common (greater than 10 mu/ml, 32 per cent), while the response to the alpha-interferon inducer poly I:C was lower than expected, possibly reflecting the already high state of activation of the interferon system. These results were essentially similar to those obtained in patients with viral illnesses and differed significantly from healthy controls. In many myasthenia gravis patients (16 of 22, 73 per cent), a markedly deficient natural killer cell activity was found, with a median cytotoxicity of 6.5 per cent compared to 29 per cent in healthy subjects (p less than 0.005). Thus, many patients with myasthenia gravis have evidence of an activated interferon system and defective natural killer cell activity, suggesting an occult viral infection or reflecting nonspecific stimulation which may nevertheless contribute to the pathogenesis of the autoimmune response.

Acute Disease↗

Treatment of antenatal myasthenia gravis.

Maternal myasthenia gravis has been associated with the presence of neonatal myasthenia and sometimes fatal congenital anomalies. As a result, antenatal therapy directed at fetal sequelae may be indicated. We present the case of a pregnant myasthenic woman whose two previous pregnancies had ended in neonatal deaths from fetal deformations that were presumably due to maternal myasthenia. Serial plasmaphereses and oral prednisone therapy were used in an attempt to depress maternal anti-acetylcholine receptor antibody titers. As anti-acetylcholine receptor antibody titers fell, fetal breathing movements became apparent by ultrasound, and as these titers rose, no fetal breathing movements were apparent. Our patient delivered an infant with transient neonatal myasthenia but normal pulmonary development and no deformations. We suggest that the therapy given may have improved the outcome of this pregnancy compared with her two previous pregnancies.

Administration, Oral↗

[Myasthenia gravis and pregnancy: review of the literature and report of 2 cases].

Two cases of women with myasthenia gravis are presented. These women had three pregnancies followed by the authors, and description is made of clinical follow-up, therapeutic complications, termination of pregnancy, puerperal and perinatal outcome. A review of the literature is made due to the rarity of this condition and emphasis is given to the specialized knowledge required to adequately manage these cases. Myasthenia gravis, when associated to pregnancy, presents aspects that make it a high risk disease, decompensations of myasthenia being more common. Aspects relative to diagnosis and therapy of myasthenia in pregnancy and in the newly-born are reviewed, and considerations about anesthesia in the myasthenic pregnant woman.

Adult↗

[Acetylcholine receptor antibody titer, sensitivity to curare electromyogram and disease severity in myasthenia gravis].

All of 39 rabbits immunized with acetylcholine receptors invariably formed anti-AChR Abs and some of them developed muscular weakness or flaccid paralysis. Pharmacological, physiological and ultrastructural studies indicated that the pathology of experimental autoimmune myasthenia gravis in rabbits resembled that of human myasthenia gravis. The titer of anti-AChR Abs correlated poorly with disease severity and did not simply predicted the muscular weakness. The results ruled out the possibility that antigenic modulation of AChR was sufficient to account for the induction of myasthenia gravis. There was a close relationship between the sensitivity to curare and disease severity, but only part of immunized animals appeared electromyogram change. This led us to conclude that serum anti-AChR concentration would not be the single pathological factor in myasthenia gravis and disease severity may correlate with amount of normal AChR.

Animals↗

[A case report of extended thymectomy in an elderly patient with myasthenia gravis associated with Hashimoto's disease].

We experienced a case of late-onset myasthenia gravis associated with Hashimoto's disease. A 74-year-old female with chief complaints of extremities acratia and hypohidrosis was diagnosed as having myasthenia gravis by the Tensilon test. In addition severe hypothyroidism was noted, and histological examination of a thyroid biopsy revealed Hashimoto's thyroiditis. Extended thymectomy was carried out, and the postoperative course was uneventful due to administration of an anti-ChE drug and a thyroid hormone. This case is extremely rare because only 10 patients with late-onset (over 70 years old) myasthenia gravis have been reported in the literature in Japan, and only three of them were associated with Hashimoto's disease. It was suggested that, in cases of myasthenia gravis in elderly patients, we should take into consideration radical therapy including thymectomy as a positive approach to treatment.

Aged↗

[Tactical and technical errors in surgical treatment of patients with generalized myasthenia gravis].

From experience in surgical treatment of 1,800 patients with generalized myasthenia as well as from literature data, the authors analyse the main tactical and technical errors in the treatment of this category of patients. A complex approach and a program of improving the results of treatment of patients with myasthenia were elaborated. Compulsory examination of the mediastinum for revealing possible affection of the thymus is indicated in myasthenia. Median sternotomy with ++extra-fascial removal of the whole thymus is considered the optimal approach in thymectomy. Thymomthymectomy with extensive removal of the areolar tissue of the anterior mediastinum is believed to be the operation of ++choice in tumors of the thymus. Thymus tissue which is not removed during the operation is one of the causes of recurrent myasthenia, while unjustified extension of the volume of the operation in nonneoplastic affection of the thymus is also inadvisable. Preoperative radiotherapy is not recommended. The principles elaborated in the clinic enabled the authors to reduce the frequency of assisted ventilation sevenfold and the incidence of infectious complications, pneumonia among others, to 0.6%.

Adult↗

[Congenital myasthenia gravis. Presentation of a case with dysphagia as the only clinical manifestation].

Myasthenia gravis is an infrequent disease seen at the neonatal stage. Two main groups are identified: a) one with a genetic origin which can be secondary to pre- or postsynaptic defects and b) of an acquired origin, as transitory neonatal myasthenia seen in 10-15% of those children with myasthenic mothers. Few cases with a genetic origin have been reported in the literature; the most common symptoms being bilateral eyelid ptosis, ophtalmoparesis, easy fatigability, respiratory and feeding difficulties. This is a report of a genetic neonatal case of myasthenia gravis with dysphagia as the only clinical manifestation seen since the first days of the child's life, confirming the diagnosis using a repetitive supramaximal stimulation test and obtaining excellent results with pyridostigmine. We conclude that, although this a rare form of the disease, genetic neonatal myasthenia gravis should be considered in the differential diagnosis of newborns with difficulties to swallow. The repetitive supramaximal stimulation test is the diagnostic procedure of first choice to be used in the neonatal period.

Deglutition Disorders↗

Pseudoselectivity of the neuromuscular block in ocular myasthenia: a SFEMG study.

The patients with pure ocular myasthenia presenting no signs of neuromuscular transmission defect on classical supramaximal repetitive stimulation were studied using SFMG method. Only those patients were selected to the study in whom the diagnosis of the ocular myasthenia was confirmed by the clinical criteria arranged so as to exclude ophthalmoplegia of the other nature. The series comprises 20 patients in whom the results of the supramaximal repetitive stimulation with the recording from the proximal muscles and with the evaluation of posttetanic phenomena were normal. SFEMG examination was performed in the clinically intact EDC muscle and in 17 patients an elongated jitter, sometimes with blocking was found. Among those three patients with normal results two were in full clinical remission, so there was only one patient presenting the symptoms of ocular myasthenia in whom the neuromuscular transmission defect was absent in the EDC. The results justify an admission that the neuromuscular block in ocular myasthenia is only apparently selective; in fact it concerns all the muscles with a different severity and may be detected if properly sensitive diagnostic methods are applied.

Adolescent↗

[Thymus gland pathology in myasthenia gravis: cause or consequence?].

Analysis of the literature data and of the findings of histologic and immunohistochemical studies of operation biopsy specimens of the thymus obtained from 92 patients with myasthenia has demonstrated that abnormalities of the thymus are characteristic of myasthenia patients. In nontumor involvement of the thymus (84.7 percent of the examinees) these abnormalities present as thymic parenchyma involution of varying gravity, combined (in 54.3 percent of patients) with hyperplasia of intralobular perivascular cavities, this simulating the so-called thymic hyperplasia with lymphoid follicles. Furthermore, impaired expression of certain epitheliocytic antigens is detectable and changed counts of these cells subpopulations; thymic hormones hyperproduction occurs in young patients. In thymomas (15.3 percent of the examined myasthenia patients) the tumor epithelial cell subcortical and/or cortical antigens are intact, thymic hormones production is not always excessive, and disorders in some antigens expression are similar to those observed in nontumor involvement of the thymus. Thymic dysfunction appears to play the key role in the pathogenesis of autoimmune disturbances in myasthenia, and disordered activity of the epithelial cells and lymphoepithelial interactions may be the major factors here.

Adolescent↗

Possible evidence for a variant of myasthenia gravis based on HLA and acetylcholine receptor antibody in Chinese patients.

A comprehensive study of 194 Chinese patients with myasthenia gravis in Hong Kong has shown distinct differences from the patterns of disease seen in Caucasians. Restricted ocular myasthenia is the predominant disease type in patients presenting in the first two decades of life and is associated with absence or low titres of acetylcholine receptor antibody. Predisposition to this type of disease is strongly associated with HLA-DRw9. Generalized myasthenia gravis occurs predominantly in patients presenting after the age of 20 years and is accompanied by high titres of acetylcholine receptor antibody but is less strongly associated with HLA-DRw9. It is suggested that myasthenia gravis occurring within the first two decades of life and characterized by affected ocular muscles and absence or low titre of acetylcholine receptor antibody is a genetically determined variant of the disease which occurs commonly in Orientals.

Adult↗

Myasthenia gravis complicating Charcot-Marie-Tooth disease: report of a case.

Generalized myasthenia gravis developed in a 61 year old man with the hypertrophic form of Charcot-Marie-Tooth disease (CMT). While ocular abnormalities mimicking myasthenia gravis have been reported in CMT, and two patients with atypical CMT have had features consistent with ocular myasthenia, this is the first report of generalized myasthenia gravis complicating CMT. The estimated prevalence for the concurrence of these two disorders suggests that it is an extremely rare event.

Adult↗

Exacerbation of a case of myasthenia gravis during therapeutic electric stimulation.

In patients with myasthenia gravis, vigorous exercise and electric stimulation produce weakness that is usually reversed by rest. We describe a case of persistent weakness in a 31-year-old woman with myasthenia gravis following therapeutic electric stimulation. She was injured in an automobile accident, with cervical and lumbar muscle strain diagnosed by a local emergency room physician. She consulted a chiropractor two days later because her symptoms had not abated. The chiropractic treatment of short-wave diathermy, high-voltage electric stimulation and spinal manipulation continued thrice weekly for six weeks. She then presented to her neurologist, complaining of persistent fatigue, weakness, increased diplopia, cervical and occipital pain, and disrupted sleep. Neck weakness had developed since her last visit. She was admitted to the hospital for evaluation. Neurologic exam showed no other abnormality of strength, sensation, or reflexes. The exacerbation of myasthenia responded to prednisone and increased pyridostigmine. After two months she required only her preinjury dose of pyridostigmine (60 mg q.d. p.r.n.) to prevent diplopia or fatigue, and her strength was normal. Repeated electrically induced muscle contraction is suspected of causing this exacerbation of myasthenia gravis.

Adult↗

Familial myasthenia gravis: a study of three families.

Six patients suffering from familial myasthenia gravis belonging to three different families are described. Three brothers are classified as having familial limb-girdle myasthenia and the other three patients, belonging to two other families, are classified as having familial congenital myasthenia. The clinical features, HLA antigen typing, autoantibody screening and anti-acetylcholine receptor antibodies were analysed. The variability of this condition from family to family is exemplified in this series and confirms the heterogeneous nature of familial myasthenia gravis.

Adult↗