The value of computed tomography in myasthenia gravis.
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Biomedical subjects
Publications and source records attributed to J R Muhm.
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Approximately 8% of all mediastinal tumors are benign teratomas. We reviewed 86 cases of benign teratoma seen at the Mayo Clinic from 1930 through 1981. The mean age of the patients was 28 years and the sex distribution was approximately equal. The most common symptoms were chest, back, or shoulder pain, dyspnea, and cough, but 36% were asymptomatic at the time of presentation. Chest roentgenograms showed a well-circumscribed anterior mediastinal mass which often protruded into one lung field. Detectable calcification was observed in 22 patients: a calcified tumor wall in seven, bone or teeth in the mediastinum of seven, and nonspecific calcifications in eight. Surgical excision remains the best means of diagnosing and treating this benign tumor. Though the tumors are histologically benign, they may present difficult surgical problems because of the vital structures involved. Since 1952 there has been a change in the clinical presentation of patients with this entity: More patients are asymptomatic and have smaller tumors and fewer complications than prior to 1952.
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Among 69 cases of thymoma, 16 of the lesions were not detected immediately in the first Mayo Clinic posteroanterior radiographs. Often they resembled right heart enlargement, their margins overlay the shadow of the right heart or hilus, or they were too small to be seen. A helpful sign was lobulation of the mass. Used selectively within the series, lateral views, computed tomography (CT), oblique views guided by fluoroscopy, and plain-film tomography contributed variously to accuracy of diagnosis and description. Until a determination is made, application in the order listed is recommended. Lateral tomograms often showed details of small, isolated abnormalities in the anterior mediastinum. Although CT did not reveal any lesions that were not suspected from other radiographic studies, it did show important anatomic relations. Early detection is important: 29% of the lesions were malignant, including 22% of those smaller than 5 cm. However, diagnosis was delayed after initial radiologic investigation (either elsewhere or at Mayo Clinic) in 17 cases (25% of the series), for intervals averaging 41 months. None of the imaging techniques was accurate in predicting malignancy, although CT best demonstrated adherence and invasion.
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Review of 91 confirmed cases of thoracic aortic dissection revealed that the findings on the plain films of the chest often were suggestive of the diagnosis, with abnormalities in the aortic countour, especially when comparison was made with previous roentgenograms. The diagnosis was definitively made in 52 cases by retrograde transfemoral or transaxillary catheterization accomplished without complication. The most common angiographic findings were opacification of the false lumen, visualization of an intimal flap, and deformity of the true lumen. Early diagnosis and institution of appropriate therapy can improve survival in this disease.
In an effort to determine if routine prenatal chest roentgenograms were of practical value, the records of 12,109 consecutive deliveries at the Mayo Clinic were reviewed retrospectively. The roentgenograms were obtained during the first or second prenatal visit and additionally when warranted by notable symptoms or physical findings in subsequent prenatal visits. Forty-eight patients had appreciable roentgenographic abnormalities. The findings of the general medical examination (which was routinely done at the first prenatal visit) were reviewed to determine if the chest abnormalities would have been suspected from the results of physical examination alone. In every case, a positive history or abnormal physical finding would have suggested the presence of the major abnormality or of the need for roentgenography to be performed.
Findings from the first 430 CT examinations of the thorax performed at the Mayo Clinic were compared with results of film studies and the most certain later diagnoses in the same cases. Results were analyzed by disease and by mediastinal compartment. CT was superior in staging bronchogenic carcinoma, detecting abnormal masses, and in demonstrating mediastinal normally when plain films were equivocal. It generally gave clear delineations of lesions and distinguished them better from normal structures, and, in correlation with clinical data, it was more accurate in suggesting whether they were benign or malignant.
Detecting pulmonary metastasis is important when planning surgical therapy, radiotherapy, or chemotherapy in patients with known malignancy. A series of 91 patients was studied by both whole lung tomography and computed tomography (CT) of the lungs. More pulmonary nodules were detected with CT than with whole lung tomography in 32 (35%) of the patients. Of the 91 patients in the study, 31 had resection of some or all of the pulmonary nodules. In 27 patients, the nodules were primary or metastatic malignant lesions. Bilateral pulmonary nodules were detected with CT in 13 patients when whole lung tomography had demonstrated nodules in only one lung. CT has replaced whole lung tomography as the method preferred by the authors for detecting pulmonary nodules in selected patients at risk to develop pulmonary metastasis.
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Among 706 collected cases of mediastinal neurogenic tumors were 69 patients (9.8%) with extension through an intervertebral foramen, so that the composite neoplastic mass was dumbbell-shaped. Although only 10% of these dumbbell tumors were malignant, the majority of the patients presented with neurologic symptoms of spinal cord compression. In about 40% of reported cases, the intraspinal component, although present, was not clinically apparent. Such cases of asymptomatic intraspinal extension should be suspected when special roentgenologic views of the spine demonstrate erosion of the vertebral pedicle or enlargement of the intervertebral foramen adjacent to the posterior mediastinal mass. Workup of these patients should include myelographic studies to determine whether a dumbbell tumor is indeed present; if it is, surgery should be carried out by a team of thoracic surgeons and neurosurgeons in a one-stage combined resection of both the intraspinal and the mediastinal component of the tumor. With early diagnosis and surgical intervention, long-term survival is the rule. When the patient is in the pediatric age bracket, an orthopedic surgeon should be included on the team to help minimize subsequent skeletal growth deformity.
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In 11 of 23 patients, computed tomography of the chest detected pulmonary nodules that were not detected by conventional chest radiography or whole lung tomography. CT is recommended for patients suspected of having pulmonary metastasis and those with a solitary pulmonary nodule.
The ability of computed tomography of the lungs to detect pulmonary nodules was compared with that of conventional chest roentgenography and whole-lung tomography. Computed tomography detected more pulmonary nodules in 10 of 29 patients studied with both computed tomography and whole-lung tomography. Computed tomography of the lungs is the most accurate noninvasive method available for detecting pulmonary nodules.
In published reports, the incidence of pleuropulmonary involvement in ankylosing spondylitis varies from 0 to 30%. A review of the records of 2,080 patients with ankylosing spondylitis disclosed 28 who had pleuropulmonary manifestations that we believe are typical of those associated with ankylosing spondylitis (an incidence of 1.3%). Among these 28 patients, the most common abnormality was upper lobe fibrobullous lesions. Five had aspergillomas and two had infections-one caused by Mycobacterium kansasii and one by Mycobacterium avium. Three patients had transient pleural effusion of an exudate with normal sugar content. Two had nonspecific pleuritis, found on pleural biopsy. Thoracotomy for aspergilloma was followed by bronchopleural fistula in one of two cases--approximately the ratio found in the literature.
Of 269 patients with histoplasmosis, 259 had radiographic manifestations of the disease. Of these, 217 showed multiple or solitary nodules, 28 infiltrates, 25 adenopathy, 5 fibrosing mediastinitis, 5 cavitation (3 infiltrates, 2 nodules), and 1 pleural effusion.