The diagnostic yield of CT angiography in assessment of acute non-traumatic subarachnoid haemorrhage in emergency department of tertiary care hospital

 

 

Abstract               Background: CT angiography (CTA) is non-invasive method yielding three-dimensional information required for planning of therapeutic intervention. Sensitivity of CTA is in the range of 80 to 97% depending on the location and size of an aneurysm. Aim: To assess diagnostic yield of CTA in detection of aetiology and site of occurrence of non-traumatic SAH with compare to diagnostic modality like digital subtraction angiography (DSA). Material and methods: A hospital based descriptive cross-sectional study was conducted in emergency department and radiology department of tertiary care hospital. The study period was of two years and study conducted on acute non-traumatic SAH cases. Results: Out of total 40 cases, half were males and half were females with age of cases ranging from 7 years to 70 years. Sensitivity and Specificity of CT angiography was 97.22% and 100%, respectively. Two aneurysm were detected on DSA while CT angiography picked only one of them. Twenty four patients had aneurysm, 12 patients were found to have arteriovenous malformations (AVM) and in remaining 4 cases, no causative factor found on CTA. Conclusion: CTA can be the first investigation in settings of acute non-traumatic subarachnoid haemorrhage and for institutions with ample experience using state-of-the-art equipment. It may be safe to rely on the findings provided by CTA alone for both therapeutic decisions and therapy planning.

Key Word: DSA, MRI, ICH, Aneurysm, Sensitivity.

 

 

INTRODUCTION

Non-traumatic sub-arachnoid haemorrhage (SAH), commonly attributed to a ruptured aneurysm, often leads to disability or death. Mortality rates are as high as 42 to 45% as recorded in some community based studies.¹ Although early diagnosis and prompt management are very essential for better outcome, delay in treatment especially due to misdiagnosis are still common. Patients with throbbing headache accounts for 1% to 2% of visits to the emergency department (ED).² A sudden severe headache which is the cardinal symptom of SAH. Non-contrast CT of head is the modality of choice to detect SAH in patients presenting with throbbing headache to emergency department. To detect source of bleeding in order to initiate treatment is the most important thing after detection of SAH. Vascular aneurysms are the most common causative factors for SAH. Digital Subtraction Angiography (DSA) is still the most sensitive tool for detection of intracranial aneurysms. But DSA has disadvantage of being an invasive study having low risk of permanent neurological deficit (<0.1%).³ CT angiography (CTA) is non-invasive method yielding three-dimensional (3D) information required for planning of therapeutic intervention. Sensitivity of CTA is in the range of 80 to 97% depending on the location and size of an aneurysm.^4,5 So this study was planned to assess diagnostic yield of CTA with compare to gold standard diagnostic modality i.e. DSA in detection of aetiology and site of occurrence of non-traumatic SAH.

 

MATERIAL AND METHODS

The hospital based descriptive cross-sectional study was conducted in emergency department and radiology department of tertiary care hospital. The study period was of two years from August 2005 to August 2007. Patients presenting to Emergency Department (ED) with any of complaints like sudden onset of throbbing headache of different in quality and intensity from usual headaches over 1 minute or less, associated with loss of consciousness with or without neurological deficits and altered mental status; and detected SAH on plain non-contrast enhanced CT scans were included. Cases with known SAH presenting with sudden deterioration of neurological status were also included. Pregnant females and patients with evidence of renal insufficiency as determined by a measured serum creatinine level >2.0 mg/dl or having history of an allergic reaction to contrast dye or iodine allergy were excluded. Institutional Ethical Committee (IEC) permission was taken before data collection. Before collecting information from cases, a valid informed consent and ascent were taken. Cases were interviewed for sociodemographic parameters and thorough general and neurological examination was conducted. Standard operating definitions and protocol were set up before commencement of study and followed till end. Non-contrast CT scan was used to detect SAH. After that CT angiography was performed to detect aetiology and site of occurrence. Results were confirmed with digital subtraction angiography (DSA). DSA was used as gold standard diagnostic technique to check diagnostic yield of CTA. Scanning protocol and specifications: Siemens Somatom Vol. Zoom Multislice Spiral CT scanner (Siemens Ltd.) was used to scan all patients. Initially a plain scan was done to confirm SAH. The details of CT angiography (CTA) was a fast thin-section volumetric spiral (helical) CT examination performed with a time-optimized bolus of contrast medium in order to enhance the cerebral arteries. In order to visualize the intracranial arteries, the examination included the region from the first vertebral body up to the vertex. Atlas was used in the study to ensure incorporation of the posterior inferior cerebellar artery (PICA). For enhancement of intracranial arteries, 70 mL of contrast medium (lohexol 300 mg %w/v) was injected intravenously at a flow rate of 3-4 mL/sec by using power injector (pressure injector; Medrad). A bolus tracking method was used routinely to achieve optimal synchronization of contrast medium flow and scanning. Once the injection is started, the bolus tracking software measures attenuation values within one internal carotid artery (ICA), and the spiral scan automatically started as soon as a threshold of 80 HU is exceeded. In present study, four-row multisection scanner (Somatom 4 Volume Zoom, Siemens Medical Solutions) was used with the following parameters: collimation of 4 × 1 mm, 200 mAs, 120 kVp, table feed of 2. 7 mm per rotation and rotation time of 0. 5 seconds. Image reconstruction parameters were section overlapping steps of 0. 8 mm, thickness of 1. 00 mm, and field of view (FOV) of 120 mm². It is possible to perform reconstructions in steps of 0.23 mm to produce isotropic data thus yielding voxels of equal extent in all three dimensions. This does not noticeably increase image quality while doubling the number of source images, thus leading to an extension of time spent on post processing of source data. The images of the patient were studied with the regular software of the workstation supplied with a Somatom Volume Zoom CT scanner (Syngo Wizard, Siemens Medical Solutions). The dVR images were created on a separate workstation (3D Virtuoso; Siemens Medical Solutions). Raw information was recorded in Microsoft Excel 2007 and summarized with the help of tables, graphs and figures. Data was analysed with SPSS v.21. Frequency, proportion mean and standard deviation were calculated to draw the inference.

 

RESULTS

A hospital based study was conducted on 40 cases of non-traumatic sub arachnoid haemorrhage (SAH) confirmed on non-enhanced CT scans. Patients presenting with history of throbbing headache or unconscious at the time of diagnosis were included. All the patients underwent CT angiography and were assessed with Clinical examination, digital subtraction angiography (DSA) and various methods of post processing such as multiplanar reconstruction (MPR), surface shaded display (SSD) and volume rendering (dVR) so as to arrive at a diagnosis in all patients. As shown in figure no. 1, out of total 40 cases, half (20; 50%) were males and (20;50%) were females. Age of cases ranged from 7 years to 70 years of age and female to male ratio was 1:1. Among both gender, highest number of patients were from age group of 41 to 50 years (30%) followed by 31 to 40years (17.5%) and 11 to 20 years of age (17.5%). In females, highest number of patients were of age group 41 to 50 years (30%) followed by 61 to 70 years (20%) and 11 to 20 years (20%) while in males, highest number of patients were of age group 41 to 50 years (30%) followed by 31 to 40 years (25%) and 11 to 20 years (15%). Diagnostic yield of CT angiography is shown in table no. 1 with compare to gold standard method DSA. Out of 36 patients in which aetiology was detected on CT angiography, 20 underwent DSA and remaining 16 were confirmed on neurosurgical examination. Out of 24 aneurysm detected on CT angiography, 1 was falsely diagnosed as aneurysm and was found to be infundibular dilatation of posterior communicating artery. Also in one patients, 2 aneurysm were detected on DSA while CT angiography picked only one of them. Also out of twenty patients who underwent DSA, 2 underwent therapeutic coiling. Sensitivity and Specificity of CT angiography was 97.22% and 100%, respectively. Causative factors for sub arachnoid haemorrhage present in study subjects were listed in table no. 2. Among 40 cases, 24 patients had aneurysm, 12 patients were found to have arteriovenous malformations (AVM) and in remaining 4 cases, no causative factor found on CT angiography.      Sites of aneurism among male and female cases are shown in figure no. 2. Out of 24 aneurysm cases detected on CT angiography, 54.16% were females and 45.83% were males. Among both sexes, lowest proportion of aneurysm found at basilar (8.3%) and posterior circulation arteries (4.2%) while bifurcation of posterior carotid artery (PCA) and internal carotid artery (ICA) was commonest site (33.3%) followed by anterior communicating artery (29.2%), middle carotid artery (25%). In female cases, middle carotid artery and bifurcation of internal carotid artery and posterior carotid artery were common sites while in male cases, anterior communicating artery and bifurcation of internal carotid artery and posterior carotid artery were common sites.

 

Figure 1: Sociodemographic profile of study subjects (n=40).

 

Table 1: Diagnostic yield of CT angiography with compare to digital subtraction angiography (DSA).

 

Table 2: Causative factors among cases (n=40)

 

Figure 2: Sites of aneurysm among cases (n=24).

 

DISCUSSION

The CT angiography has both high specificity and sensitivity for the detection of aneurysms. The diagnostic yield is mainly related to arterial attenuation in the internal carotid artery (ICA).⁶ The sensitivity of CT angiography largely depends upon duration of scan and it falls to 73% on day three.^[7] DSA is accepted as the gold standard imaging modality in diagnosis and evaluation of aneurysms but it is a time consuming, expensive invasive procedure that may lead to complications in 1% and permanent neurologic deficit in 0.5%.^[8]It was reported that the sensitivity of CTA in diagnosing intracranial aneurysms ranges from 67% to 100% and specificity between 50% and 100% (22-24), Maximum intensity projection (MIP), shaded surface display (SSD) and volume rendering (VR) are among methods for processing the source images chained at CTA examination. CT angiography identified an aneurysm as the cause of SAH in 97% of patients in current study. Domitille et al⁹ reported in their study that mean age of cases was of 54 years; age range from 27 years to 84 years and female to male ratio of 0.78:1. In the study done by Aaron et al¹⁰ noted throbbing headache was commonest symptoms which was noted in present study also. Heit et al¹¹ recorded female to male ratio was 1:1.05; average age of 54 years with age range from 19 to 92. In present study, female to male ratio was 1:1; age range was from 7 years to 70 years with average age was 49.56 years. Many previous studies have recorded varying degree of sensitivity and specificity for computed tomography angiography when it is performed over a longer duration window. Few of the recent studies had retrospectively estimated sensitivities of 91-99%.^12,13 Perry et al¹⁴ reported 92.9% sensitivity, 100% specificity which is quite similar to findings noted in present study. Boesiger et al¹⁵ in their retrospective study with 177 patients reported 100% sensitivity with undifferentiated headache. The diagnostic yield of computed tomography for subarachnoid haemorrhage assessed through systematic review based on two studies reported was 93% (sensitivity) with 95% C.I (66% to 98%).¹⁶ Cortnum et al¹⁷ conducted a study on patients with confirmed subarachnoid haemorrhage could identified only one patient on DSA who did not have positive results on computed tomography. The single patient in their study had imaging after five days of the onset of headache and required LP (lumbar puncture). In present study, sensitivity of CT angiography was 97% and specificity was 100% probably because of a timely imaging and newer multislice scanners, which provided better resolution and thinner slice protocols. In present study, DSA picked up aneurysms in approximately 3% of patients with negative CT angiography for sub-arachnoid haemorrhage. In current study, out of total 40 cases 30% cases had arteriovenous malformations (AVM) while 60% patients had aneurysm. Jung et al¹⁸ reported about 60% aneurysm, 4% arteriovenous malformation (AVM) and 1% Moya moya disease. Kitkhuandee et al¹⁹ in their study, reported posterior communicating artery (17.1%), anterior communicating artery (35.5%), internal carotid artery (11.8%) , middle cerebral artery (15.7%), vertebra-basilar junction (1.3%) and basilar artery (2.6%) as a sites of aneurysm. Domitille et al⁹ reported, MCA, anterior complex artery and ICA were common sites. Similar trend of findings were also reported by previous studies.^18,20 In the study conducted by Heit et al¹¹, the distribution of SAH which was perimesencephalic (31%), diffuse (40%), and sulcal (16%). These findings are similar to the distribution found in present study. Sectional images picked up calcification of aneurysm wall or intra-aneurysmal thrombosis very easily.

 

CONCLUSION

In present study CT angiography detected aetiology with sensitivity of 97% which correlates with many studies. So, CT angiography can be the first investigation in settings of acute non-traumatic subarachnoid haemorrhage and for institutions with ample experience using state-of-the-art equipment. It may be safe to rely on the findings provided by CT angiography alone for both therapeutic decisions and therapy planning.

 

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