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Treating Myasthenia Gravis With Thymectomy



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Am Fam Physician. 2000 Mar 15;61(6):1857-1858.

Myasthenia gravis is a rare autoimmune disorder characterized by increasing fatigue with exercise. Symptoms range from isolated ptosis, diplopia or mild proximal muscle weakness to severe generalized weakness. The thymus is thought to play a major role in the pathogenesis of myasthenia gravis. Auto-antibodies associated with myasthenia gravis are directed at the acetylcholine receptor in the neuromuscular junction, resulting in a decrease in acetylcholine receptors. Medical management consists of maintenance therapy with anticholinergic inhibitors such as pyridostigmine to relieve symptoms and steroids to treat the autoimmunity. Thymectomy as an adjunctive treatment is considered the standard of care, with the best results occurring in younger patients who have had myasthenia gravis for a short period of time. Calhoun and associates conducted a retrospective review of patients with myasthenia gravis who underwent transcervical thymectomy to identify outcomes and incidence of complications.

A total of 100 consecutive patient records was reviewed for the study. Preoperative Osserman grades were assigned by a neurologist for each patient, and postoperative grades were obtained by telephone interview with the patient. For a description of the Osserman classification system for myasthenia gravis, see the accompanying table. No transfusions, postoperative ventilator requirements or nerve injuries were documented postoperatively.

Osserman Classification in Myasthenia Gravis

0

Asymptomatic

1

Ocular signs and symptoms

2

Mild generalized weakness

3

Moderate generalized weakness, bulbar dysfunction, or both

4

Severe generalized weakness, respiratory dysfunction, or both


Information from Calhoun RF, Ritter JH, Guthrie TJ, Pestronk A, Meyers BF, Patterson GA, et al. Results of transcervical thymectomy for myasthenia gravis in 100 consecutive patients. Ann Surg 1999; 230:555–61.

Osserman Classification in Myasthenia Gravis

View Table

Osserman Classification in Myasthenia Gravis

0

Asymptomatic

1

Ocular signs and symptoms

2

Mild generalized weakness

3

Moderate generalized weakness, bulbar dysfunction, or both

4

Severe generalized weakness, respiratory dysfunction, or both


Information from Calhoun RF, Ritter JH, Guthrie TJ, Pestronk A, Meyers BF, Patterson GA, et al. Results of transcervical thymectomy for myasthenia gravis in 100 consecutive patients. Ann Surg 1999; 230:555–61.

Of the 100 patients, 88 had surgery. Six patients were lost to follow-up; two others died more than four years after surgery, one of cardiac arrest and the other of a cerebrovascular accident. A total of 78 patients was available for long-term follow-up. Almost all patients experienced an improvement in Osserman grade, with patients younger than 40 years of age demonstrating the greatest improvement. Ninety percent of the patients took pyridostigmine and 33 percent took prednisone preoperatively. Following thymectomy, only 46 percent took pyridostigmine, and 27 percent took prednisone. Patients who underwent surgery within nine months of the diagnosis of myasthenia gravis demonstrated a statistically significant improvement in postoperative Osserman grade.

The authors conclude that early thymectomy for nonthymoma–associated myasthenia gravis is a useful adjunct to medical management, especially in younger patients. In the authors' experience, the transcervical approach is associated with low morbidity and no mortality, making this approach safer than the transsternal approach or a combination approach. In addition, the transcervical approach has fewer associated side effects, decreased operative time and minimal postoperative hospitalization.

Calhoun RF, et al. Results of transcervical thymectomy for myasthenia gravis in 100 consecutive patients. Ann Surg. October 1999;230:555–61.



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