Treatment of Internal Carotid Artery Dissections with Endovascular Stent Placement: Report of Two Cases

Extracranial carotid artery dissection may manifest as arterial stenosis or occlusion, or as dissecting aneurysm formation. Anticoagulation and/or antiplatelet therapy is the first-line treatment, but because it is effective and less invasive than other procedures, endovascular treatment of carotid artery dissection has recently attracted interest. We encountered two consecutive cases of traumarelated extracranial internal carotid artery dissection, one in the suprabulbar portion and one in the subpetrosal portion. We managed the patient with suprabulbar dissection using a self-expandable metallic stent and managed the patient with subpet-rosal dissection using a balloon-expandable metallic stent. In both patients the dissecting aneurysm disappeared, and at follow-up improved luminal patency was observed.

Congenital Absence or Hypoplasia of the Internal Carotid Artery: Angiography and HRCT Evaluation at the Skull Base

PURPOSE: To evaluate the findings of angiography and high-resolution CT of the skull base in the patients with congenital absence or hypoplasia of the unilateral internal carotid artery. MATERIALS AND METHODS: Eight patients with congenital unilateral absence (n=6) or hypoplasia (n=2) of the internal carotid artery were included in this study. None showed symptoms related to the absence of the artery. All underwent selective arteriography and six underwent high-resolution CT of the skull base. The angio-graphic findings of the carotid artery and collateral pathways to the absent side, as well as the high-resolution CT findings of the bony carotid canal at the skull base, were evaluated. RESULTS: In all cases, intracranial collaterals were of the adult type. The anterior cerebral arteries were supplied via the anterior communicating artery in all patients, and the middle cerebral arteries via the posterior communicating artery in five. In two, collateral flows were supplied by both the anterior and posterior communicating arteries, and in four, high-resolution CT of the skull base showed remnants or sclerosis of the carotid canal. One patient showed a hypoplastic bony carotid canal, and in one, this canal was absent. Intracranial aneurysms were found in four patients; in three, thses were located at the anterior communicating artery, and in the other, at the posterior cerebral artery. In four of six patients with no internal carotid artery, the ophthalmic arteries were opacified via the middle meningeal artery. CONCLUSION: In cases involving congenital absence or hypoplasia of the internal carotid artery, differentiation between agenesis and aplasia may be based on the pattern of collateral circulation. High-resolution CT find-ings may suggest that this change has a congenital origin.

Usefulness of CT Angiogra p hy after Metallic Stent Implantation of the Internal Carotid Artery

PURPOSE: To evaluate the usefulness of CT angiography in Patients with implantation of metallic stent for stenosed internal carotid artery. MATERIALS AND METHODS: Seven patients with atherosclerotic stenosis of the internal carotid artery underwent metallic stent implantation. All were male and their ages ranged from 36 to 69 years. A total of seven stents were placed in the internal carotid artery in five patients and in the carotid bifurcation in two. Spiral CT scans were obtained and CT angiographic images were reconstructed using MPR or curved MPR techniques at a workstation. The interval between CT and conventional angiography did not exceed six days except in one patient, in whom it was 61days. CT and conventional angiography were compared for stent position with respect to the carotid bifurcation, stent deformation, intraluminal filling defect, and luminal caliber and outflow. Luminal patency of the implanted stent was measured according to NASCET(North American Symptomatic Carotid Endarterectomy Trial) criteria, and statistically processed (p<.05). The presence or absence of intrastent thrombus and vascular wall calcification was determined using axial source images. RESULTS: In all patients, CT angiographic findings matched those obtained by conventional angiography. Complications such as migration or deformation of an implanted stent, intraluminal filling defect, change of luminal caliber or outflow of implanted stent were not observed in any patient. In two studies in which Wilcoxon signed rank test was used, degree of stent expansion correlated closely(p=0.237). Axial source images showed that in no patient was an intrastent thrombus present, though in five, vascular wall calcification of internal carotid arteries outside the stent was noted. CONCLUSION: CT angiography is useful for the assessment of positional change, occlusion, and luminal patency of a stent-implanted internal carotid artery.

What is the Cause of Signal Inhomogeneity at the Carotid Bifurcation During Contrast Enhanced Carotid MRA?: In Vivo and in Vitro Studies

PURPOSE: To evaluate the hemodynamic causes of signal inhomogeneity at the carotid bulb that might be misinterpreted as pathologic signal defect in carotid contrast enhanced MRA(CEMRA). MATERIALS AND METHODS: Both carotid CEMRA and fast digital subtraction angiography(DSA) were conducted on 15 patients (28 carotid arteries) and arterial phase CEMRA images were compared with fast DSA images of the same patients. A 1.5T MR imager was used. The Turbo-FLASH sequence emplayed was TR/TE/FA= 3 .2m s / 1.3m s / 35 degree. For experimental study, we utilized handmade silicon phantoms of the tortuous carotid bifurcation; these might be expected to clearly demonstrate turbulent flow at the carotid bulb. In a closed circulatory system, both CEMRA and fast DSA involved the use of these phantoms. RESULTS: During CEMRA, inhomogeneous signals of varying degrees were found at the carotid bulb in 12/28 carotid arteries. When compared with sequential DSA images, incomplete mixing of contrast agent due to turbulent flow at the carotid bulb might be responsible for this inhomogeneity. This hypothesis was reinforced by successfully reproducing signal defects at the carotid bulb from the experimental CEMRA study using carotid phantoms that showed marked turbulent flow in the same area during DSA. CONCLUSION: Incomplete mixing of contrast agent caused by turbulent flow at the carotid bulb might be responsible for the signal inhomogeneity seen on carotid CEMRA.

Aberrant Internal Carotid Artery in the Middle Ear: A Case Report

Aberrant internal carotid artery in the middle ear is a rare disease which, if unrecognized on radiological studies, can lead to serious complications during tissue biopsy. We report the imaging features of a case with aberrant internal carotid artery in the middle ear. A 60-year-old woman visited our hospital because of hearing difficulty on the right side. Temporal bone CT showed a well-defined mass of the right middle ear and lateral bony defect in the carotid canal adjacent to the mass. After arterial phase temporal bone CT with spiral CT andangiography, the mass could be diagnosed as aberrant internal carotid artery in the middle ear.

Usefulness of CT Angiography in Patients with Intracranial Occlusive Vascular Disease of the Circle of Willis: Comparison with Conventional Angiography

PURPOSE: To assess the usefulness of CT angiography(CTA) compared with compared with conventional angiography(CA) in the evaluation of intracranial occlusive vascular disease. MATERIALS AND METHODS: We evaluated 26 patients with clinically suspected intracranial occlusive vascular disease studied with both CTA and CA. Incases where there was no vascular lesion on CA, we used CTA to retrospectively review the detection rate and size of individual vessels, and compared the findings with those obtained by CA. In cases of occlusive vascular lesion, we evaluated the degree of stenosis on CTA and compared this with the CA findings. We also measured the time taken to use both modalities. RESULTS: Sixteen patients had no vascular lesion and ten patients had occlusive vascularlesions. Compared with CA, CTA detected 97%(124/128) of normal intracranial arteies ; their diameter measured on CTA was slightly smaller than that on CA. On CTA, the degree of stenosis was correctly estimated in eight lesions, underestimated in one and overestimated in one. Examination time ranged between 15 and 20 minutes with CTA and between 40 and 60 minutes with CA. CONCLUSION: Compared with CA, CTA shows good correlation in the delineation of intracranial normal and occlusive vessels around the Circle of Willis. CTA may be an additional tool for the evaluation of the Circle of Willis in patients with suspected intracranial occlusive vascular disease. CTA may, additionally, be used as a follow-up method in patients with acute cerebral infarctions after thrombolytic therapy.

Angiographic Demonstration of External Carotid-Vertebral Arteries Anastomosis

PURPOSE: The aim of the study is to evaluate collateral circulations between external carotid and vertebral arteries in the individuals with no occlusive cerebro vascular diseases. METHODS AND MATERIALS: Vertebral angiography was performed in 20 patients with subarachnoid hemorrhage, with temporal occlusion of the ipsilateral common carotid artery by finger pressure compression. In each case, the following were analyzed in each case :presence or absence of collateral channels ; pattern of collateral channels ; level of anastomosis. RESULTS: The anastomotic channels were as follows : occipital artery by posterior radicular artery : 15 cases ; ascending pharyngeal artery by musculospinal artery : 16 cases ; odontoid arterial arch : ten cases ; proximal external carotid artery by anterior radicular artery three cases. CONCLUSION: Awareness of external carotid - vertebral arteries anastomosis as described above can be helpful for effective and safe embolization.