Rheumatology 2001; 40: 235-237
© 2001 British Society for Rheumatology
Letters to the Editor |
Three-dimensional computed tomography for visualization of carotid bypasses in Takayasu arteritis
Department of Radiology,
1 Department of Surgery and
2 Department of Internal Medicine I, University of Regensburg, Germany
SIR, In Takayasu arteritis, predominantly the aorta and its major branches are affected by the inflammatory process, and frequently non-specific cerebral symptoms such as headache and dizziness precede overt and accompany long-term disease [1]. When surgery of major arteries is required, visualization of vascular alterations and restenosis in the affected vessels during the follow-up period is difficult. Here we report the case of a young woman who underwent carotid bypass surgery due to an obstruction of the proximal part of the left carotid artery after an extended course of disease, and we demonstrate the potential of three-dimensional computed tomography (3D CT) for the visualization of both artificial and venous bypasses.
A 30-yr-old white female was admitted to our rheumatology out-patient clinic 6 yr ago due to increasing recurrent left arm claudication followed by dizziness and headache. Interestingly, cerebral symptoms had started more than 10 yr ago with intermittent migraine-like headache, which had been attributed consecutively to the development of a papillary thyroid carcinoma detected 8 yr ago. Therapy included thyroid resection and right-side neck dissection followed by adjuvant transcutaneous telecobalt irradiation (65 Gy) followed by adequate thyroid hormone substitution. Metastasis did not occur and the patient has remained in remission. The preliminary diagnosis at the time of first admission to our clinic was subclavian steal syndrome of unknown origin, and radiological examinations, including angiography of the aortic arch, magnetic resonance imaging (MRI) angiography and duplex ultrasonography, revealed an occlusion of the left subclavian artery. As the patient fulfilled the American College of Rheumatology classification criteria for Takayasu arteritis [2] as well as all obligatory criteria and the majority of the minor criteria of two recent modified criteria systems [3, 4], immunosuppressive therapy was started immediately. During this period, subclavian steal symptoms improved considerably and the patient had only a few periods of slight dysaesthesia of the left arm and rare episodes of migraine-like headaches for the following 3 yr.
Two years ago, the patient was admitted to our out-patient clinic due to increasing symptoms of a subclavian steal syndrome of the right side, which was confirmed by duplex ultrasonography. Four months later, using MRI, the right subclavian artery was found to be completely occluded, and an increasing stenosis of the left carotid artery was also detected. To clarify the pathophysiology of the increasing stenoses of the arterial branches of the aortic arch, surgical intervention was initiated, including resection of the proximal left carotid artery for histological analysis and application of a retropharyngeal artificial (Dacron®) bypass from the right to the left carotid artery. Radiological examination 4 weeks after surgery was performed using 3D CT, and showed adequate vascular anastomosis without any sign of leakage (Fig. 1A
). Histological and immunohistological analysis of the stenosis of the proximal carotid artery revealed typical signs of active Takayasu arteritis, showing abundant inflammatory infiltrates without giant cells. The postoperative clinical status of the patient was excellent, and any symptoms of the subclavian steal syndrome had vanished. However, on the basis of the course of the disease and the histological findings, cyclophosphamide pulse therapy was initiated 3 months after surgery to protect the right carotid artery from stenosis. In addition, the Dacron bypass was protected by coumarin anticoagulation at an international normalized ratio of 3.5–4.5 and ticlopidine at a dose of 250 mg/day.
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Three weeks after cyclophosphamide application, the patient was admitted to the emergency room because of rapidly increasing throat pain, dysphagia and fever of 39°C. Immediate radiological examination by oesophagogram revealed two fistulas from the hypopharynx to the bypass, indicating infection of the bypass itself. Revision of the infected bypass was performed immediately and the Dacron bypass was replaced by a subcutaneous venous bypass derived from the left femoral vein. During the period of wound-healing, there was no sign of persistence of the infection and the fistulas were completely occluded when examined by oesophagogram 4 weeks after surgery. To examine the bypass itself and to compare the result of the anastomoses of venous bypass with those of the initial Dacron bypass, 3D CT was performed again 8 weeks after surgery. As shown in Fig. 1B
, revascularization and adequate cerebral perfusion was achieved, and up to the time of writing the subclavian steal symptoms have not recurred. Radiological evaluation of the major branches of the aorta is usually performed by direct intraaortic angiography as digital subtraction angiography [4]. As invasive angiography bears some risks, such as high radiation exposure and embolization, and does not differentiate between stenosis due to fibrosis and active inflammation, other techniques, including CT and MRI, are used more frequently [5]. Although earlier studies have shown rather disappointing results [6, 7], modern techniques could enhance sensitivity and specificity significantly [8]. Interestingly, in some cases ultrasonography and CT appeared to be more sensitive than direct angiography [9].
In previous work, the sensitivity of 3D reconstructions in the diagnosis of internal carotid artery stenosis has ranged from 80 to 92.8% [10, 11], and maximal intensity projection (another possible way of postprocessing the primary axial data) has shown a sensitivity between 50 and 92%, whereas MRI has shown a sensitivity between 54 and 96% [12, 13]. It is generally accepted that the differences in these values are caused by different scanning parameters. Therefore, we used small slices and table-feed for reconstruction in combination with additional evaluation of axial slices to achieve high accuracy in the postprocessing, facilitating clinical and surgical evaluation of the bypasses.
In summary, 3D CT appears to be a valuable tool for the visualization of bypass surgery in Takayasu arteritis, especially if the direction of the bypass is parallel to the axial CT slices.
Notes
Correspondence to: U. Müller-Ladner, Department of Internal Medicine I, University of Regensburg, D-93042 Regensburg, Germany. 
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