Outcome after thymectomy for myasthenia gravis: a retrospective review

Long-term evaluation of extended thymectomy with anterior mediastinal dissection for myasthenia gravis

BACKGROUND

Thymectomy for the treatment of myasthenia gravis (MG) is well established. The extent of resection, however, remains a source for debate. Outcomes for newer surgical techniques need to be compared to more extensive procedures.

METHODS

A retrospective review was done of 64 consecutive patients who underwent transsternal thymectomy with extended anterior mediastinal dissection for MG between 1979 and 2000 and who were operated on by a single surgeon.

RESULTS

Fifty-six patient charts were available, providing 58 operative procedures. Three patients had died of unrelated causes. The mean age of symptom onset was 36.0 +/- 2.5 years, with a mean duration of 3.3 +/- 0.5 years until surgery was undertaken. The mean length of follow-up was 6.8 +/- 0.8 years. Operative procedures were associated with a 10.3% major morbidity rate and no mortality. Drug-free remission was achieved in 50.0% of the patients, and symptoms were absent or improved in 76.8% of the patients. Patients followed up long-term (>10 years) achieved the greatest remission rate (71.4%) and symptomatic improvement (85.7%). After thymectomy, the mean dosages of prednisone and Mestinon decreased by 69.3% and 58.8%, respectively.

CONCLUSIONS

Extended thymectomy provides excellent overall symptom improvement, which is enhanced over time. This review provides a basis for long-term comparison with other less invasive and perhaps less extensive procedures.

Transcervical thymectomy

Transcervical thymectomy is appropriate for managing carefully selected patients with myasthenia gravis due to its noninvasive nature, good cosmetic results, and favorable long-term outcomes. Contraindications to its use include the presence of a thymoma and advanced age. In optimally prepared patients, the operative complication rate is negligible and the average length of hospital stay is 1 to 2 days. The ultimate results of therapy often are not evident for several years postoperatively, indicating that comprehensive preoperative and postoperative treatment by a qualified neurologist is essential in optimizing outcomes. A meta-analysis of long-term results shows that 90% of patients who undergo the operation are improved, 80% become asymptomatic, and 50% achieve a complete remission.

Effect of chronic treatment with piracetam and tacrine on some changes caused by thymectomy in the rat brain

Thymectomized rats, 5 weeks after surgery, showed a significant impairment in learning and memory as shown by deficits in passive avoidance and in the Morris water maze test. The behaviour of the thymectomized rats in the "open field" apparatus was largely unchanged. Following treatment for 20 days with either piracetam (500 mg/kg) or tacrine (3.0 mg/kg), the deficit in passive avoidance learning was largely reversed. Chronic treatment with tacrine also reversed the deficit in the behaviour of the thymectomized rats in the Morris water maze. The effects of thymectomy on the biogenic amines and some of their metabolites in the amygdaloid cortex, hypothalamus, striatum and olfactory bulbs were also determined. Relative to the sham-operated controls, thymectomy resulted in a reduction in the noradrenaline concentration in the amygdala, hypothalamus, and olfactory bulbs. This effect was reversed by chronic piracetam and tacrine treatments. The concentration of dopamine was also reduced in the olfactory bulbs after thymectomy whereas in the striatum the concentration of 5-hydroxytryptamine (5-HT; serotonin) was increased. The concentration of gamma amino butyric acid (GABA) was determined in amygdaloid cortex and hippocampus only. The only significant change occurred following chronic treatment of thymectomized rats with tacrine, when a significant elevation of GABA was found. Neither piracetam nor tacrine produced any change in the amines of their metabolites in the sham-operated controls. Tacrine, however, elevated the dopamine and reduced the 5-HT content of the hypothalamus and increased the 3,4-dihydroxylphenylacetic acid concentration of the striatum of thymectomized rats. Examination of the differential white blood cell count of the thymectomized rats showed that the percentage of lymphocytes was decreased, and the percentage of neutrophils increased, relative to the sham-operated controls. Chronic lacrine, but not piracetam, treatment reversed the lesion-induced changes.

Surgical treatment of myasthenia gravis in two major Middle East teaching hospitals: factors influencing outcome

BACKGROUND

The results of thymectomy on patients with generalised myasthenia gravis have been widely reported. However, there is no information on whether the experience of western countries can be generalised to the population of the Middle East. The purpose of this study was to evaluate the safety and efficacy of thymectomy in patients with myasthenia gravis in a Middle East patient population and to identify clinical and histopathological factors associated with improved long term outcome of surgery.

METHODS

In a prospective study, sixty three patients (aged 1.5-51 years) were treated in two university teaching hospitals between 1984 and 1991 and followed up for a mean of four years. Close communication was established with neurologists to obtain early referral. Radical anterior mediastinal dissection through a median sternotomy was performed in all patients. The response was evaluated by modified Osserman's classification.

RESULTS

Eighteen patients achieved complete remission and a further 39 improved, producing an overall response rate of 90.5%. Patients with milder disease (stage II) had a higher response rate (97%) than those with more advanced disease (78%). Patients operated on with less than three years of symptoms had a better outcome (94%) than those with longer duration of preoperative symptoms, especially in non-thymomatous patients. Age and sex had no effect on the outcome. There was no effect on response rate if patients had hyperplastic or non-specific thymic histological findings, but patients with thymoma fared worse.

CONCLUSIONS

These results are comparable with reports from the western world and represent the first prospective study from the Middle East. Thymectomy is indicated for all patients suffering from generalised myasthenia gravis soon after the diagnosis is made, regardless of age, stage, thymic pathology, and preoperative clinical status.