CT angiography for the detection and characterization of carotid artery bifurcation disease.

BACKGROUND AND PURPOSE: Computed tomographic angiography (CTA) is a relatively new and minimally invasive method of imaging intracranial and extracranial blood vessels. The main purpose of this study was to compare CTA to the current gold standard of arterial imaging, digital subtraction angiography (DSA), for the detection and quantification of carotid artery bifurcation stenosis. We also compared Doppler ultrasound (US) with these 2 techniques. METHODS: In a prospective study, 40 patients (80 carotid arteries) underwent CTA, US, and DSA. Patients chosen for inclusion were symptomatic with TIAs or stroke and had initial US screening that indicated >50% carotid stenosis on the side appropriate for the symptoms. Source axial, maximum intensity projection (MIP), and shaded-surface display (SSD) images were produced for each CTA study. The US, CTA, and DSA images were reviewed, with the degree of stenosis quantified and presence of ulcers determined; each type of imaging was reviewed by a separate investigator blinded to the results of the other 2 modalities. The results of CTA and US imaging were compared with the DSA images for degrees of carotid stenosis. RESULTS: CTA source axial images correlated with DSA more closely than MIP or SSD images for all degrees of stenosis. The correlation between US and DSA (0.808) was poorer than that between CTA and DSA (0.892 to 0.922). CTA performed well in the detection of mild (0% to 29%) carotid stenosis, as well as carotid occlusion, with values for sensitivity, specificity, and accuracy near 100%. In determining that a stenosis was >50% by DSA measurement, CTA was again useful, with a sensitivity, specificity, and accuracy of 89%, 91%, and 90%, respectively. While CTA was quite specific and accurate in identifying degrees of stenoses in either the 50% to 69% or the 70% to 99% ranges, in this task it was much less sensitive: 65% for 50%-69% stenosis and 73% for 70%-99% stenosis. These results did not change significantly when only the data from the most clinically relevant symptomatic arteries were analyzed. CTA was found to correlate quite well with DSA in the detection of ulcers associated with the carotid stenosis. CONCLUSIONS: CTA was found to be an excellent examination for the detection of carotid occlusion and categorization of stenosis in either the 0%-29% or >50% ranges. However, CTA was unable to reliably distinguish between moderate (50%-69%) and severe (70%-99%) stenosis, which is an important limitation in the investigation and treatment of carotid stenosis.

Heparin-induced thrombocytopenia and thrombosis following subarachnoid hemorrhage. Case report.

The authors present a case of heparin-induced thrombocytopenia and thrombosis (HITT) that occurred after aneurysmal subarachnoid hemorrhage (SAH), and they review the relevant literature. An immune-mediated syndrome, HITT is characterized by moderate thrombocytopenia and paradoxical vascular thromboses. Although it has been estimated in prospective studies that HITT occurs in between 1 and 3% of patients receiving heparin, it is underrecognized in the neurosurgical literature. In the present case, a 49-year-old woman underwent clipping of a right posterior communicating artery aneurysm after suffering a Hunt and Hess Grade III SAH. She had an uncomplicated postoperative course with good clip positioning and no vasospasm observed on a cerebral angiogram obtained on Day 7. On Day 23, the patient developed a right hemiparesis and experienced a grand mal seizure. A head computerized tomography scan revealed a hemorrhagic infarct in the left middle cerebral artery distribution. Repeated cerebral angiograms did not show vasospasm. She was thrombocytopenic (platelet count as low as 46 x 10(9)/L on Day 28 compared with 213 x 10(9)/L on Day 1) and had been receiving heparin flushes to maintain intravenous catheter patency. An assay for HITT-associated antibodies was positive. The heparin flushes were discontinued and the platelet count recovered (121 x 10(9)/L). She improved neurologically, but was left with a significant right hemiparesis at discharge. This patient had assay-proven heparin-induced thrombocytopenia despite minimal exposure to heparin. Because there was no evidence of vasospasm or other factors to account for her delayed hemorrhagic infarction, an HITT-related disorder seemed most likely. Despite a large body of literature describing HITT in nonneurosurgical patients, only three previous neurosurgical cases have been published. This case report may serve to heighten awareness of this disorder.

CT angiography for the detection of cerebral vasospasm in patients with acute subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Digital subtraction angiography (DSA) is the standard of reference for detecting cerebral vasospasm after subarachnoid hemorrhage (SAH). CT angiography (CTA) is a relatively recent method for depicting the intracranial arterial vasculature. The purpose of this study was to compare CTA and DSA in the detection and quantification of cerebral vasospasm. METHODS: Seventeen patients with SAH underwent initial CTA with or without DSA and follow-up CTA and DSA. The follow-up CTA and DSA studies were performed within 24 hours of each other and 5 to 10 days after SAH. Maximum intensity projection images were produced for each CTA. Six arterial locations were examined for spasm: the suprasellar internal carotid artery (ICA), the M1 and M2 segments of the middle cerebral artery, the A1 and A2 segments of the anterior cerebral artery, and the basilar artery. Vasospasm was categorized as none, mild (<30% luminal reduction), moderate (30% to 50% reduction), or severe (>50% reduction). RESULTS: The overall correlation between CTA and DSA was 0.757, but was better for proximal than distal locations (0.88-1.00 versus 0.152-0.446). Agreement between CTA and DSA was greater for no spasm (92%) and severe spasm (100%) than for mild (57%) or moderate (64%) spasm. CTA was highly accurate for no spasm or severe spasm in proximal locations (96%, and 100%, respectively); it was less accurate (90% and 95%, respectively) for mild or moderate spasm in these locations. For distal locations, the accuracy for absent, mild, moderate, or severe spasm was 78%, 81%, 94%, and 100%, respectively. CONCLUSION: CTA is highly sensitive, specific, and accurate in detecting no spasm or severe cerebral vasospasm in proximal arterial locations; it is less accurate for detecting mild and moderate spasm in distal locations.

Computed tomographic angiography versus digital subtraction angiography for the diagnosis and early treatment of ruptured intracranial aneurysms.

OBJECTIVE: Computed tomographic angiography (CTA) is a rapid and minimally invasive method of detecting intracranial aneurysms. We wished to determine whether CTA could replace digital subtraction angiography (DSA) in the diagnosis and operative planning of ruptured cerebral aneurysms. METHODS: In a prospective study, patients with subarachnoid hemorrhage diagnosed by plain computed tomography underwent CTA, DSA, or both. Computed tomographic scans and CTA studies were first reviewed by the treating surgeon, along with a neuroradiologist, and a decision to proceed to DSA or directly to surgery was made on the basis of the type and quality of information provided by CTA. All patients underwent postoperative DSA. RESULTS: A total of 173 patients were studied. In 24 patients, both CTA and DSA were negative for a source of subarachnoid hemorrhage. Twelve patients underwent DSA without prior CTA because a technologist capable of performing CTA was not available when the patient was evaluated. Nine patients in poor neurological condition underwent CTA, and all tested positive for aneurysms but died without surgical intervention. Of the 126 patients who underwent CTA and surgery, 65 (52%) also required preoperative DSA. The decision to proceed to DSA after CTA was influenced by aneurysm location; posterior communicating artery (62%) and posterior circulation locations (67-75%) more commonly proceeded to DSA than middle cerebral artery aneurysms (34%; 0.025 > P > 0.01). The sensitivity and specificity of CTA for the detection of all aneurysms, ruptured and unruptured, in the group of patients who underwent both types of angiograms preoperatively were 84 and 100%, respectively. In the group of 61 patients in whom aneurysm surgery was performed on the basis of CTA results alone, the sensitivity and specificity for the detection of all aneurysms, as compared with postoperative DSA, were 90 and 100%, respectively. Missed aneurysms (n = 24) were always small (<4 mm) and were usually found in patients with multiple aneurysms in whom the larger, ruptured aneurysm was identified by CTA. In one patient, the aneurysm missed by preoperative CTA would have resulted in a different operation if detected preoperatively. CONCLUSION: It is possible to proceed to ruptured aneurysm repair entirely on the basis of good-quality CTA studies that demonstrate an aneurysm consistent with the pattern of bleeding observed on plain computed tomography (48% of the patients in this series and most common middle cerebral artery aneurysms). However, detection of small unruptured aneurysms in patients with multiple lesions remains a problem.

Experience with computed tomographic angiography for the detection of intracranial aneurysms in the setting of acute subarachnoid hemorrhage.

OBJECTIVE: To objectively compare computed tomographic angiography (CTA) with selective digital subtraction angiography (DSA) in the detection and anatomic definition of intracranial aneurysms, particularly in the setting of acute subarachnoid hemorrhage (SAH). METHODS: In a blinded prospective study, 40 patients with known or suspected intracranial saccular aneurysms underwent both CTA and DSA, including 32 consecutive patients with SAH in whom CTA was performed after CT images were obtained diagnostic for SAH. The CT angiograms were interpreted for presence, location, and size of the aneurysms, and anatomic features, such as the number of aneurysms lobes, aneurysm neck size (< or = 4 mm), and the number of adjacent arterial branches were suggested. The images obtained with CTA were then compared with the images obtained with DSA, with the later images serving as controls. RESULTS: DSA revealed 43 aneurysms in 30 patients and ruled out intracranial aneurysms in the remaining 10 patients. For aneurysm presence alone, the sensitivity and specificity for CTA was 86 and 90%, respectively. For the presence of an aneurysms, six CT angiogram showed false negative results and one CT angiogram showed a false positive result. False negative results were usually caused by technical problems with the image, tiny aneurysm domes (< 3 mm), and unusual aneurysm locations (i.e., intracavernous carotid or posterior inferior cerebellar artery aneurysms). The results obtained with CTA were, compared with the results obtained with DSA, more than 95% accurate in determining dome and neck size of aneurysm, aneurysm lobularity, and the presence and number of adjacent arterial branches. In addition, CTA provided a three-dimensional representation of the aneurysmal lesion, which was considered useful for surgical planning. CONCLUSION: CTA is useful for rapid and relatively noninvasive detection of aneurysms in common locations, and the anatomic information provided in images showing positive results is at least equivalent to that provided by DSA. In cases of SAH in which the nonaugmented CT and CTA results indicate a clear source of bleeding and provide adequate anatomic detail, we think it is possible to forego DSA before urgent early aneurysm surgery. In all other cases, DSA is indicated.

A trial of the 21-aminosteroid U74006F in a primate model of chronic cerebral vasospasm.

The efficacy of U74006F in the prophylaxis of chronic cerebral vasospasm (VSP) was evaluated in a randomized, double-blind, placebo-controlled trial. Forty cynomolgus monkeys were divided by restricted randomization into 2 treatment groups of 20. Five animals from each treatment group were randomized into subgroups 1 and 2. The animals of subgroup 1 were studied pathologically. Brain biopsies of the animals in subgroup 2 were performed and studied with high-performance liquid chromatography (HPLC). The remaining 20 animals supplemented the number studied angiographically. Significant VSP (P less than 0.05) was detected in the majority of vessels from the clot site (right) of both treatment groups. Electron microscopy results showed positive correlation with the angiographic data. When comparing the effects of U74006F to those of the placebo at day 7, there was a significant difference (P less than 0.05) in the degree of VSP in the right extradural internal carotid and right middle cerebral arteries. This resulted from a greater degree of VSP in placebo animals. Two animals developed delayed ischemic deficits, one from each group. The infarct of the U74006F animal was smaller than the infarct in the placebo animal. Although overall changes in phosphagen levels did not reach statistical significance, HPLC analysis of the cortical biopsies did show a decrease in the ATP/ADP +/- AMP ratio of 54% in placebo animals and only 7% in animals receiving U74006F. The middle cerebral arteries of 2 animals were also studied with HPLC.(ABSTRACT TRUNCATED AT 250 WORDS)