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July2010 Vol.47 Issue:      3 (Supp.) Table of Contents
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The Diagnostic Accuracy of 64-Row Multislice Computerized Tomography Angiography in Detection of Intracranial Aneurysms

Amr K. Elsamman1, Lamiaa I.A. Metwally2, Ahmed M. Abdelalim3

 

Departments of Neurosurgery1, Radiodiagnosis2, Neurology3, Cairo University; Egypt

 



ABSTRACT

Background: Accurate localization of intracranial aneurysms is crucial for determining the appropriate treatment. Objective: To emphasize on the accuracy of evaluation of intracranial aneurysms using CT angiography (CTA) technique. Methods: Twenty two patients with intracranial aneurysms were included in this study. They were evaluated clinically and radiologically using multislice CT angiography of the brain. Digital subtraction angiography was performed for 6 patients. Surgical clipping was performed for treatment. Results: Twenty four aneurysms were found in 22 patients with subarachnoid hemorrhage: 23 were clipped surgically. The site of aneurysms included: 11 anterior communicating artery, 8 middle cerebral artery, 2 posterior communicating artery, 1 posterior cerebral artery, and 1 carotid bifurcation aneurysms. The sensitivity and positive predictive value of detection of aneurysms >3mm was 100% compared to surgical findings. One aneurysm, 2.7mm in diameter, was suspicious on CTA and was confirmed by digital subtraction angiography. The surgical clipping was based on CTA alone in 16 patients (72.7%). Conclusion: CTA is a sensitive non-invasive tool for detection of intracranial aneurysms that would improve selection of management yet it cannot completely replace conventional angiography as its sensitivity is lower in aneurysms <3mm and it lacks dynamic information. Both modalities should be used complementary to each other. [Egypt J Neurol Psychiat Neurosurg.  2010; 47(3): 425-431]

 

Key Words: CT angiography, intracranial aneurysms, subarachnoid hemorrhage.

 

Correspondence to Amr K. Elsamman, Department of Neurosurgery, Cairo University, Egypt.

Tel.: +20127364056. Email: aa.samman@gmail.com





INTRODUCTION

 

Aneurysms of the intracranial vessels are relatively common, with a prevalence of 3%–6% in general population and more common in women1. Rupture of intracranial aneurysms results in subarachnoid hemorrhage (SAH) with a high mortality rate2. Accurate localization of intracranial aneurysms is crucial for determining the appropriate neurosurgical or endovascular intervention. Digital subtraction angiography (DSA) is currently considered the imaging modality of choice for the evaluation of suspected aneurysms; however, it is an invasive technique with a reported 0.07% risk of permanent neurologic complication and 0.8% overall risk of permanent and transient neurologic complications3. So, Taking in  consideration the high mortality associated with ruptured intracranial aneurysms, any new modality used to detect aneurysms must at least have a sensitivity equivalent to that of DSA4.

Computerized Tomography Angiography (CTA) is a non-invasive technique that compares favorably with DSA in the detection of intracranial aneurysms5,6. With the introduction of multi–detector row (multisection) CT scanners,  the increased spatial resolution and decreased scanning time; the sensitivity of the technique has markedly improved especially in depicting aneurysms of less than 5 mm in diameter4 which is the main deficiency of another well established imaging modality: the magnetic resonance angiography (MRA)7.

The aim of this study is to emphasize on the accuracy of evaluation of intracranial aneurysms using CTA technique in comparison to intraoperative findings which could help to improve the decision of management based on a less invasive technique.

 

SUBJECTS AND METHODS

 

This study included 22 patients (12 males & 10 females with age range of 32 to 65 years) with intracranial aneurysms who presented to neurology clinic or neurosurgical emergency, Cairo University hospitals during the period from August 2008 to December 2009. All patients with trauma at the onset (e.g. traumatic SAH) were excluded.

Methods:

1.        All patients were evaluated clinically on admission for assessment of level of consciousness or lateralization and Hunt and Hess score8 for patients with SAH (Table 1).

2.                Neuroradiologic technique:

A 64-multi-detector row CT scanner (Toshiba 64; Aquilion) was used for evaluation of all patients. The patient should be fasting for at least 4 hours prior to the examination. The patient lies on the CT table in the supine position followed by injection of 50 ml of non-ionic contrast medium (Ultravist) intravenously with a power injector using 320psi pressure, at 5mm/sec rate. The CT angiographic acquisition parameters were 0.5 mm slice thickness, 0.3 mm section interval, 135 KV, 400 mAs and 24 cm field of view. Routinely, scanning started from the level of the arch of aorta to include the common, external and internal carotids. Table speed was 41mm/sec with total scanning time 4 to 5 sec. The transverse source images were reformatted in the transverse, coronal, and sagittal planes. At the workstation, the angiographic studies were interpreted by using maximum intensity projection (MIP) images and multiplanar reformatted images from the source image data set in the coronal and sagittal planes.

DSA was performed prior to surgery in 6 cases: 5 cases to complete the data obtained from the CTA with the dynamic data like direction of flow and the filling; 1 case to exclude fetal circulation; and 1 Case to confirm the presence of a suspicious aneurysm.

3.                Surgical procedure:

Surgical clipping was performed for 23 out of the 24 aneurysm. One aneurysm with basilar tip in a patient with double aneurysms was sent for coiling upon patient’s preference to endovascular treatment over surgery. Surgical findings were compared to CT angiographic findings.

 

Table 1. Hunt & Hess score for evaluation of patients with subarachnoid hemorrhage 8.

 

Description

Grade

Asymptomatic, mild headache, slight nuchal rigidity

G1

Moderate to severe headache, nuchal rigidity, no neurologic deficit other than cranial nerve palsy

G2

Drowsiness / confusion, mild focal neurologic deficit

G3

Stupor, moderate-severe hemiparesis

G4

Coma, decerebrate posturing

G5

 

Statistical analysis:

Data were expressed as number (Frequency) and percentage. Descriptive data were computed and presented using Microsoft EXCEL 2007. Sensitivity and positive predictive value were evaluated in a 2x2 table in which both positive and negative events were found to occur.

 

RESULTS

 

All patients included in the study had spontaneous (non-traumatic) aneurysmal subarachnoid hemorrhage (n=22). Admission Hunt and Hess scores were G1 in 15 patients (68%), G2 in 4 patients (18%) and G3 in 3 patients (14%). These 3 patients improved to G2 after CSF diversion. All patients (n=22) presented with headache (100%) with a severity varying from moderate to severe thunderclap headache. Mild focal neurological signs were found in three patients (14%).

Twenty four intracranial aneurysms were detected in 22 patients. Twenty three were diagnosed using CTA and one aneurysm was suspicious in CTA and was confirmed using DSA with a diameter of 2.7mm which was confirmed surgically. One aneurysm was not operated upon and was sent for endovascular treatment upon patient’s request.

Aneurysms were located in the anterior communicating artery (A-comm) (n=11), the middle cerebral artery (MCA) (n=8), posterior communicating artery (P-comm) (n=2), the basilar tip (n=1), posterior cerebral artery (PCA) (n=1), and carotid bifurcation (n=1) (Table 2). There were twenty patients with single aneurysms and two patients with double aneurysms; the first had a carotid terminus aneurysm and an anterior communicating aneurysm; and the second had a basilar tip and an anterior communicating aneurysm. From those twenty four, we had twenty ruptured (83%) and two unruptured discovered accidentally in CTA in the two patients with double aneurysms (17).

The sizes of aneurysms ranged from 2.7 to 21mm: most of them were of medium size (10-20 mm) (n=13). The rest were either small (less than 10 mm) (n=6) or large (20-25 mm) (n=4) and we did not encounter any aneurysm more than 25 mm in diameter in the study (Table 3).

DSA was performed to 6 patients: 5 had A-comm aneurysms and one had P-comm aneurysm. DSA was used to study the dynamic characteristics of the aneurysms such as the direction of flow and filling of the aneurysm in the A-comm without apparent atretic or hypoplastic A1 segment of ACA on the CTA which was present in the other 6 cases of A-Comm’s. One case with the P-Comm to exclude fetal circulation.

The incidence of radiological vasospasm was 30.4% (7 cases) mainly in the A1 segment of ACA and M1 segment of MCA which appeared intraoperaively to be 17.4% (4 cases) and postoperatively to be 21.7% (5 cases) diagnosed by clinical deterioration of these patients in the form of increasing weakness or lowering of conscious level

The surgical clipping procedures was based on CTA alone in 16 patients (72.7%) where DSA was needed to acquire further information prior to surgery in 6 patients (26.3%). The direction and fundus orientation of aneurysms as appeared in the CTA was compared with intraoperative findings and the sensitivity in aneurysms size more than 3 mm was 100% accurate and with a positive predictive value of 100%.

CTA of some of the patients included in the study are shown in Figure (1) and compared to operative findings before and after clipping (Figure 2).


 

Table 2. Site of surgically clipped aneurysms (n=23) in 22 patients with subarachnoid hemorrhage (in order of frequency).

 

Description

Frequency

Percentage

Anterior communicating artery

11

47.8%

Middle cerebral artery

8

34.8%

Posterior communicating artery

2

8.7%

Posterior cerebral artery

1

4.35%

Carotid bifurcation

1

4.35%

 

Table 3. Size distribution among surgically clipped intracranial aneurysms (n=23) in 22 patients with subarachnoid hemorrhage.

 

Description

Frequency

Percentage

Large sized (20-25)

4

17.4%

Medium sized (10-20mm)

13

56.5%

Small (less than 10)

6

26.1%

N.B.: No aneurysms with size >25 mm were found

 

A

B

 

 

 

 

Figure 1. CT Angiography showing aneurysms (Arrows) of (A) Anterior communicating artery (B) Double aneurysm: Anterior communicating artery and internal carotid artery bifurcation.

 

 

 

Figure 2.  Left posterior communicating (P-comm) artery aneurysm pointing and showing size exactly as interpreted from: CT Angiography (A & B) and same aneurysm before (C) and after (D) clipping showing the P-comm artery free of clip and showing same relation as in CTA.

AC anterior clinoid, An aneurysm, C Carotid  artery, ON Optic nerve, P Posterior communicating artery

 

 

 


DISCUSSION

 

In this study we demonstrated a sensitivity and accuracy of 64-slice CTA for the detection of intracranial aneurysms site and morphology of 100% for aneurysms of size more than 3mm compared to operative field findings.

CTA has been shown to have a good sensitivity and specificity in detection of intracranial aneurysms >3mm together with an excellent inter-rater in comparison to DSA6,9-11 and even with 16-slice CTA12.

In the present study, CTA alone was sufficient to decide the line and procedure of treatment in 72.7% of cases. In a study by Agid et al.13 CTA alone was sufficient in 44 patients out of 46 patients (95.7%) to achieve a positive diagnosis of intracranial aneurysms and to decide the line of treatment whether surgical or endovascular intervention and suggested the use of DSA only in negative CTA. Also, Villablanca et al.14 concluded that CTA can be alone enough for the detection and decision of treatment even in small aneurysms.

Yet, in another study by Taschner et al.10 CTA alone was not sufficient to visualize the perianeurysmal branches and DSA was mandatory despite the overall good agreement between DSA and CTA (κ value of 0.072) as DSA can provide dynamic information about the aneurysm as direction of flow and filling which may be important for the decision of treatment whether surgery or endovascular intervention. In our study CTA had one suspicious unruptured aneurysm (4%) 2.7mm in diameter which was confirmed using DSA.

Westerlaan et al.15 have shown that DSA in CTA negative classic perimesencephalic SAH added no or marginal results and recommended it would only be done in non-perimesencephalic SAH due to higher possibility of false negative CTA.

Variations among different studies may be due to different techniques and patients’ selection and also due to the fast advance in the development of CTA adding higher resolutions and methods of interpretation.11

CTA was also helpful in defining important morphological and geometrical facts about the aneurysm like the neck to dome ratio, complexity of the fundus, important branches coming out of the dome, however, Yoon et al reported that dome to neck ratio measurements for 2D DSA were 11% greater than those on multidetector row CTA, but this difference was not statistically significant16

We found an incidence of vasospasm of 30.4% as detected by CTA but this percentage dropped down to 17.4% intraoperatively as the remainder proved to be congenital hypoplasia. This may reflect a deficiency in CTA ability to differentiate vasospasm from hypoplasia.

The limitations of our study were that the majority of aneurysms were larger than 3mm (n=23) and were found in areas not closely related to skull bone which may be the reason for the high sensitivity (100%) of CTA in the study which may have been less if we have encountered more aneurysms of smaller sizes in areas in proximity to the skull base (e.g: cavernous carotid or clinoidal aneurysms). Also all patients included in the study presented with subarachnoid hemorrhage (ruptured aneurysms) and with good prognosis on admission in 86.4% (Hunt and Hess scores G1 & G2) and only two aneurysms were detected as unruptured one of which was not operated upon, thus the CTA accuracy of detection of unruptured aneurysms and in worse clinical states of patients could not be commented upon. Yet, our results are more or less similar to most of literature.

 

Conclusion

CTA is an accurate and sensitive tool for detection of intracranial aneurysms (especially in aneurysms of size >3mm) and can replace DSA as a primary line of investigation in case of suspicion of intracranial aneurysms. DSA can be used for diagnosis in special cases where CTA is negative or dynamic information is important for decision of treatment. We believe that with further advance of technology and addition of higher resolutions and techniques, CTA may be candidate to completely replace DSA as the diagnostic tool of choice for detection of intracranial aneurysms and DSA would be rather reserved to therapeutic intervention in the future.

 

[Disclosure: Authors report no conflict of interest]

 

REFERENCES

 

1.      Wardlaw J, White P. The detection and management of unruptured intracranial aneurysms. Brain. 2000 Feb;123 ( Pt 2):205-21.

2.      Hop J, Rinkel G, Algra A, van Gijn J. Case-fatality rates and functional outcome after subarachnoid hemorrhage: a systematic review. Stroke. 1997 Mar;28(3):660-4.

3.      Cloft H, Joseph G, Dion J. Risk of cerebral angiography in patients with subarachnoid hemorrhage, cerebral aneurysm, and arteriovenous malformation: a meta-analysis. Stroke. 1999 Feb;30(2):317-20.

4.      Jayaraman M, Mayo-Smith W, Tung G, Haas R, Rogg J, Mehta N, et al. Detection of intracranial aneurysms: multi-detector row CT angiography compared with DSA. Radiology. 2004 Feb;230(2):510-8.

5.      Alberico R, Patel M, Casey S, Jacobs B, Maguire W, Decker R. Evaluation of the circle of Willis with three-dimensional CT angiography in patients with suspected intracranial aneurysms. AJNR Am J Neuroradiol. 1995 Sep;16(8):1571-8; discussion 9-80.

6.      Korogi Y, Takahashi M, Katada K, Ogura Y, Hasuo K, Ochi M, et al. Intracranial aneurysms: detection with three-dimensional CT angiography with volume rendering--comparison with conventional angiographic and surgical findings. Radiology. 1999 May;211(2):497-506.

7.      Jäger H, Mansmann U, Hausmann O, Partzsch U, Moseley I, Taylor W. MRA versus digital subtraction angiography in acute subarachnoid haemorrhage: a blinded multireader study of prospectively recruited patients. Neuroradiology. 2000 May;42(5):313-26.

8.      Hunt W, Hess R. Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg. 1968 Jan;28(1):14-20.

9.      Romijn M, Gratama van Andel H, van Walderveen M, Sprengers M, van Rijn J, van Rooij W, et al. Diagnostic accuracy of CT angiography with matched mask bone elimination for detection of intracranial aneurysms: comparison with digital subtraction angiography and 3D rotational angiography. AJNR Am J Neuroradiol. 2008 Jan;29(1):134-9.

10.    Taschner C, Thines L, Lernout M, Lejeune J, Leclerc X. Treatment decision in ruptured intracranial aneurysms: comparison between multi-detector row CT angiography and digital subtraction angiography. J Neuroradiol. 2007 Oct;34(4):243-9.

11.    Lubicz B, Levivier M, François O, Thoma P, Sadeghi N, Collignon L, et al. Sixty-four-row multisection CT angiography for detection and evaluation of ruptured intracranial aneurysms: interobserver and intertechnique reproducibility. AJNR Am J Neuroradiol. 2007 2007 Nov-Dec; 28(10): 1949-55.

12.    Chen W, Yang Y, Xing W, Qiu J, Peng Y. Sixteen-row multislice computed tomography angiography in the diagnosis and characterization of intracranial aneurysms: comparison with conventional angiography and intraoperative findings. J Neurosurg. 2008 Jun; 108(6): 1184-91.

13.    Agid R, Lee S, Willinsky R, Farb R, terBrugge K. Acute subarachnoid hemorrhage: using 64-slice multidetector CT angiography to "triage" patients' treatment. Neuroradiology. 2006 Nov; 48(11): 787-94.

14.    Villablanca J, Jahan R, Hooshi P, Lim S, Duckwiler G, Patel A, et al. Detection and characterization of very small cerebral aneurysms by using 2D and 3D helical CT angiography. AJNR Am J Neuroradiol. 2002 Aug; 23(7): 1187-98.

15.    Westerlaan H, Gravendeel J, Fiore D, Metzemaekers J, Groen R, Mooij J, et al. Multislice CT angiography in the selection of patients with ruptured intracranial aneurysms suitable for clipping or coiling. Neuroradiology. 2007 Dec; 49(12): 997-1007.

16.    Yoon DY, Lim KJ, Choi CS, Cho BM, Oh SM, Chang SK. Detection and characterization of intracranial aneurysms with 16 channel multidetector row CT angiography: a prospective comparison of volume-rendered images and digital subtraction angiography. AJNR Am J Neuroradiol. 2007; 28: 60-7.


 

 

الملخص العربى

 

الدقة التشخيصية للأشعة المقطعية على الأوعية الدموية متعددة المقاطع (64 صف) فى تحديد التمددات الدموية المخية

 

تهدف هذه الدراسة إلى تحديد الدقة التشخيصية للأشعة المقطعية على الأوعية الدموية متعددة المقاطع (64 صف) فى تحديد التمددات الدموية المخية. وشملت الدراسة 22 مريضا بالتمددات الدموية المخية ويعانون من النزيف تحت عنكبوتى تم تشخيصهم باستخدام الأشعة المقطعية على الأوعية الدموية متعددة المقاطع (64 صف). وتم عمل القسطرة المخية لست حالات لاستكمال المعلومات المطلوبة قبل العلاج الجراحى والذى تم بوضع الكلبسات الجراحية.

النتائج : وجد 24 تمددا دمويا لدى 22 مريضا. و كانت اماكن التمددات كما يلى: 11 بالشريان الأمامى المتصل, و 8 بالشريان المخى الأوسط و اثنان بالشريان الخلفى المتصل وواحد بالشريان المخى الخلفى وواحد بتفرع الشريان السباتى. وعند مقارنة نتائج الأشعة المقطعية على الأوعية الدموية بالنتائج الجراحية وجد أن الوصف الشكلى للتمددات الموجود بالأشعة المقطعية على الأوعية الدموية مطابق لما وجد أثناء التدخل الجراحى بنسبة 100% فى التمددات الدموية التى يزيد حجمها عن ثلاثة مليمترات (حساسية 100% و قيمة تكهن ايجابية 100 %) .وتم أخذ القرار العلاجى بعمل الأشعة المقطعية على الأوعية الدموية وحدها دون الحاجة لعمل القسطرة التشخيصية فى 72.7% من الحالات و تم عمل القسطرة التشخيصية لست حالات (17,3%) و ذلك لاستكمال المعلومات المطلوبة للتدخل الجراحى.  

الخلاصة : الأشعة المقطعية على الأوعية الدموية تعتبر اداة حساسة و دقيقة و يمكن الاعتماد عليها بشكل رئيسى فى تشخيص التمددات الدموية المخية وبخاصة التى يزيد قطرها عن ثلاثة مليمترات. أما القسطرة التشخيصية فيمكن ان تستخدم فى حالات محددة بشكل مكمل للأشعة المقطعية على الأوعية الدموية.

 



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