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Ann Thorac Surg 1996;62:242-245
© 1996 The Society of Thoracic Surgeons
Division of Cardiothoracic Surgery, Department of Surgery, and Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, North CarolinaUSA
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Abstract |
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 TopFootnotes Abstract IntroductionPatients and MethodsResultsCommentReferences |
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Methods. A consistent, planned protocol involving preoperative, intraoperative, and postoperative care was followed. All thymectomies were performed through a median sternotomy with removal of all visible thymus and perithymic fat in the anterior mediastinum.
Results. There was no perioperative mortality or long-term morbidity. Mean postoperative hospital stay was 6.3 days (range, 3 to 18 days). Ninety-six percent of the patients were extubated the day of the operation, and all patients were extubated within 24 hours. Mean postoperative intensive care unit stay was 1.2 days (range, 1 to 4 days). After a mean follow-up of 65 months (range, 1 to 199 months), 78% of all patients are improved by at least one modified Osserman classification when their current status is compared with their worst preoperative disease severity. In fact, 69% of patients with mild disease preoperatively (class I, II, or III maximal severity) are in pharmacologic remission (asymptomatic without regular medication), whereas 29% of patients with severe disease (class IV or V) are in remission (p = 0.0001).
Conclusions. Our programmatic approach to thymectomy through a sternotomy has shown minimal morbidity and mortality. It is beneficial to myasthenics at both ends of the age and severity spectrum.
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Introduction |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Myasthenia gravis is an autoimmune disease of disordered neuromuscular transmission resulting in exertional fatigue and weakness of voluntary muscles, due to a specific antibody directed against the acetylcholine receptor complex of the motor end plate [1]. The role of thymectomy in myasthenia began in 1912 when Sauerbruch noted significant improvement in a myasthenic patient after removal of an enlarged thymus [2]. Since that time, published series have shown improvement in the majority of patients after thymectomy [3–10]. However, several series have reported a sizeable proportion of patients who have required prolonged ventilatory assistance postoperatively [7–9].
A large number of patients with myasthenia gravis have undergone thymectomy at the University of North Carolina, and long-term follow-up data are available for most patients. We have reviewed our experience retrospectively, with particular attention to morbidity, mortality, need for ventilatory assistance, and relief of myasthenia.
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Patients and Methods |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Follow-up data were available for 99 patients. The mean follow-up was 64 months, with a range of 1 to 199 months. Seventy-four patients have current follow-up, defined as occurring within 2 years of the closure of the study. Four patients in the study are dead, none of them of complications of myasthenia gravis. The remaining 21 files are inactive, primarily because of patients having moved to another state. This review was carried out under the guidelines of the Human Investigation Committee at the University of North Carolina at Chapel Hill.
All patients were followed up and referred for operation by a single neurologist (J.F.H.). Thymectomy was recommended in patients who had a thymoma, had generalized symptoms of myasthenia gravis with a life expectancy of at least 10 years, or had ocular symptoms refractory to medical management. A consistent protocol of perioperative care was used, encompassing preoperative preparation, anesthetic and operative technique, and postoperative medical and nursing care.
Plasma exchange was used preoperatively in 60 patients with generalized symptoms. Patients receiving steroids at the time of operation had perioperative stress dose coverage, after which they were weaned off steroids as quickly as possible. Anticholinesterase medications were not routinely restarted postoperatively unless required by symptoms. Negative inspiratory force and forced vital capacity were measured every 8 hours postoperatively for several days. Narcotics were used routinely for pain medication, and potassium and magnesium levels were maintained in the normal range.
The use of neuromuscular blockers during anesthesia was avoided if at all possible. The operative technique was similar in all patients. The thymus was approached through a median sternotomy, and all visible fatty tissue was removed from the anterior mediastinum down to the diaphragm, including the upper poles of the thymus in the neck. Dissection was carried out laterally to within 1 cm of the phrenic nerves. Tissue posterior to the phrenic nerves or underneath the subclavian vein was not excised. The anterior pericardium was left intact, except in cases of infiltrating tumor.
The modified Osserman (University of Virginia) scale [11] was used to describe disease severity (Table 1
). Maximum disease severity is defined as the worst condition of the patient preoperatively either with or without medication. Disease severity at time of operation is defined as the modified Osserman classification at the time of admission for operation. It should be noted that patients frequently underwent plasma exchange during this admission as part of their preoperative preparation. Improvement is defined as an improvement in symptoms by at least one modified Osserman classification. Pharmacologic remission is defined as the absence of any myasthenic symptoms and no routine use of anticholinergic medications or steroids. Patients who used medications occasionally, but not regularly, were included in the pharmacologic remission group. Statistical comparisons were done using the 
2 analysis.
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Results |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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The majority of the patients (67%) were extubated in the operating room. An additional 17% of patients were extubated within 1 hour and another 12% within 10 hours. Therefore, 84% of patients were extubated in the operating room or within 1 hour, and 96% were extubated within 10 hours. The remaining 4 patients were extubated on the first postoperative day. No patients required reintubation. Eight patients received short-acting neuromuscular blockers as part of their anesthetic. There was no correlation between the use of these medications and prolonged intubation.
A report of the pathologic findings was available in the hospital chart for 99 patients. The mean weight of the thymic specimens was 66 g (range, 5 to 205 g). The thymus was normal in 25% of patients, atrophic in 31%, and hyperplastic in 36%. Seven thymomas were found: one benign and six malignant (two spindle-cell, three epithelial cell, and one neuroendocrine tumor). None of the patients undergoing thymectomy at the University of North Carolina have required a repeat operation for retained thymus, and there was no instance where retained thymic tissue was suspected clinically. One patient who originally underwent transsternal thymectomy elsewhere underwent resection of retained thymus at the University of North Carolina, and was included in this series.
The severity of myasthenia at most recent follow-up is compared with the disease severity at time of operation in Figure 1A, and the maximal (preoperative) severity in Figure 1B. Improvement was obtained in 78% of all patients when most recent severity was compared with maximum severity and in 57% of patients when most recent disease severity was compared with disease severity at time of operation. No significant differences were seen in the rate of improvement when patients with mild disease (modified Osserman class I, II, III) were compared with those with generalized disease (class IV, V). However, pharmacologic remission was observed in 69% of patients with localized disease. The pharmacologic remission rate of the more severe group was significantly lower at 29% (p = 0.0001).
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Comment |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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The results with extensive thymectomy as performed in all of these patients compares favorably with published results using either a cervical thymectomy or a radical (``maximal'') thymectomy [2, 5, 12]. The morbidity and mortality are low, and the need for postoperative ventilation is low, as well. The improvement in the vast majority of patients suggests that adequate thymic tissue is removed with this operation. In our opinion, the theoretical advantage of an even more extensive resection as described by Jaretski and Wolff [12] is not supported by improved patient outcome data.
In this series, the majority of the patients were extubated in the operating room, and none were extubated any later than the first postoperative day. This compares very favorably with other series [8–10, 13, 14]. Even in a recent series, the average length of intubation was 9 hours [8]. Ventilatory support for an average of 1 to 2 days has been reported in 13% to 50% of patients undergoing transsternal thymectomy [9, 10, 14]. In one series of 92 transcervical thymectomies, 9% of patients required ventilation for up to 3 days postoperatively [13], although others have reported that all patients were extubated within 24 hours after transcervical thymectomy [2, 5].
The waxing and waning nature of myasthenia gravis makes it difficult to characterize results in an individual patient at any one time. However, the disease severity at most recent follow-up was, in fact, quite representative of patients' average severity of symptoms during follow-up. The overall improvement rate (79%) indicates that the vast majority of patients benefit from thymectomy. Patients with less severe disease are more likely to obtain a complete remission after thymectomy (69%). Nevertheless, 85% of patients with more severe disease are improved when maximum disease severity is compared with recent follow-up disease severity. No significant difference is seen when the patient cohort is stratified by age.
A consistent programmatic approach to thymectomy and perioperative management of myasthenia gravis has been used in 100 consecutive patients over a 16-year period. A sternotomy leading to an extensive thymectomy was the approach used in all patients. The incidence of major complications and the need for ventilatory support have been very low. There was no mortality. The vast majority of patients are improved at later follow-up, regardless of initial disease severity or patient age. We conclude that the approach to thymectomy in patients with myasthenia at the University of North Carolina has yielded excellent results.
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Footnotes |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Address reprint requests to Dr Detterbeck, University of North Carolina, 108 Burnett-Womack Building, CB 7065, Chapel Hill, NC 27599-7065.
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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