1. Results of 19 thymectomies in patients with myasthenia gravis, performed during the period from August 1961 to July 1964, were reported.
2. Based on the severity of symptoms, the cases were divided into the following three groups. Grade I included four cases of a localized myasthenia with ocular symptoms. Grade II included six cases of moderately advanced generalized myasthenia with not only ocular but also bulbar symptoms. Grade III included nine cases of far advanced generalized myasthenia with muscular weakness of neck, trunk, and extremities beside the ocular and bulbar symptoms.
3. Routine laboratory examination did not reveal any pathognomonic findings or confirm any difference among Grades I, II and III. On the contrary, examinations directly connected with muscle functions, such as per cent vital capacity, Tensilon test, Curare test and electromyographic study, showed an apparent difference among the three groups. This classification is advantageous not only for decision of indication for surgery, but also for pre-and postoperative management.
4. Out of 19 cases, five males and one female were accompanied with thymoma. They belonged to Grade III and myasthenic symptoms were
extensive and grave. 5. Indication for surgery was concluded in: 1) the cases with thymoma, 2) the cases of Grade III, regardless of the presence or absence of thymoma, and 3) the cases of Grade II, where conservative treatment was not effective or caused severe side-effect.
6. Anterior mediastinum was entered through sternal splitting method. The whole thymus including the cervical portion should be excised, preserving the pleura and phrernic nerves as much as possible.
7. The most important measure for postoperative respiratory crisis is the maintenance of airway, and prophylactic tracheotomy is far superior to delayed forced tracheotomy. The indication for tracheotomy was decided in: 1) the cases of Grade III, and 2) the cases of Grade II whose per cent vital capacity were less than 59 per cent. Furthermore, 3) the cases of Grade II, where there was an increase in inspiratory capacity at preoperative Tensilon test even though per cent vital capacity was more than 50 per cent should be included. Tracheotomy is unnecessary for Grade I cases.
8. Follow-up results of 17 cases, excluding two recent cases, were: marked improvement in six cases, improvement in seven, and no change in four. The symptoms were improved in 76.5 per cent in total, and unchanged in two of Grade I and in two of Grade III with thymoma. No deaths related to surgery nor myasthenic deaths were observed. Results of female cases were better than those of male cases, and four of six cases with thymoma showed marked improvement.
9. Objection to thymeetomy for myasthenia gravis is mainly due to apprehension for risk of surgical intervention. So far as thymectom.y is performed as safely as the other mediastinal surgeries in co-operation with internists, anesthesiologists, surgeons and nursing members, thymectomy is the treatment of choice for this grave disease, in which otherwise only symptomatic therapy is possible.
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