Original articleComputed tomography angiography in detection and characterization of ruptured anterior cerebral artery aneurysms at uncommon location for emergent surgical clipping
Introduction
The subarachnoid hemorrhage (SAH) due to ruptured aneurysm accounted for 2.1% of stroke patients and the reported surgical mortality rates ranged from 7.7% to 12.5% of patients in Taiwan [1]. Selective intraarterial digital subtraction angiography (DSA) has been used as a diagnostic standard for the detection and characterization of intracranial aneurysms, with false-negative rate of detection 5% to 10% [2]. Obtaining less than optimal projection with angiographic equipment may limit detection of some intracranial aneurysms [3], [4] or measurement of the aneurysmal neck relating to the parent artery, impairing selection of the treatment method [3], [4]. Other disadvantages of DSA include the invasiveness of arterial puncture and intraarterial catheter manipulation, and that it is a time-consuming procedure and that the devices are expensive.
Helical computed tomography angiography (CTA) is a new noninvasive volumetric imaging technique. By using optimized acquisition and postprocessing protocols, the sensitivity of CTA in the detection of very small (<5 mm) cerebral aneurysms is higher than that of DSA, with equal specificity and higher interoperator reliability [4]. Imaging acquisition of CTA requires only 1 min or less, thereby benefiting high-risk patients.
Cerebral SAH may result from rupture of saccular aneurysm of anterior cerebral artery (ACA), which is commonly originated from anterior communicating artery (ACOM). Only 0.88% of all intracranial aneurysms have been reported to have originated from the A1 segment and 5.3% from the distal ACA [5], [6]. Anterior cerebral artery aneurysm in such uncommon locations is usually associated with multiple aneurysms and vascular anomalies and may exhibit a similar appearance to ACOM aneurysm rupture on plain computed tomography (CT) [5], [6]. The surgical approach of these aneurysms is different from those of the other anterior circulation aneurysms [6]. Previous CTA studies have reported only 14 aneurysms at such uncommon locations in a total of 545 intracranial aneurysms [4], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. The purpose of this study was to evaluate the usefulness of plain CT and helical CTA in detection and characterization of intracranial aneurysms at such uncommon location before emergent surgical clipping.
Section snippets
Patients
Between 1998 and 2003, the records of 50 consecutive patients who underwent emergency aneurysm clipping for intracranial aneurysms were reviewed. Eighteen of them had aneurysms that occurred in the ACA. After exclusion of those patients with typical ACOM aneurysms, eight aneurysms at uncommon location of the ACA were recruited in this study. Plain CT and CTA were performed in all eight patients, and DSA was done in three patients. Plain CT and CTA images were reviewed without knowledge of DSA
Results
There were eight patients (five women and three men) who presented with intracranial aneurysms in uncommon location of the ACA. Their age ranged from 41 to 73 years old (mean, 60 years old). All patients were sent to the emergency room with chief complaints of severe headache or loss of consciousness.
Table 1 summarizes the patients' data and plain CT findings. The emergent plain CT scan revealed an SAH in all patients, with the most increased density area in interhemispheric fissure in six
Discussion
Cerebral SAH due to ruptured aneurysms often results in poor prognosis. Most of the patients die of rebleeding in additional to the initial intracranial hemorrhage [17]. Rebleeding can be prevented by early neurosurgical intervention. In our hospital, CTA has been employed as a first-line imaging modality in screening patients with SAH possibly caused by ruptured aneurysm. When ruptured aneurysm was detected in CTA, surgical clipping was performed to minimize rebleeding. Digital subtraction
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