Role of Multi Detector Computed Tomography Cervicocerebral Angiography in Evaluation of Patients with Stroke

Background: Stroke is the second single most common cause of death in the world causing approximately 6.7 million deaths each year. It has a greater disability impact on an individual than any other chronic disease. The aim of the study is to review the value of CTA in detection and evaluation of non-traumatic cervicocerebral vascular disease (stroke). Subjects & Methods: A prospective observational study conducted in the Department of Radiodiagnosis, Kamineni Hospitals, L.B. Nagar, Hyderabad over 60 patients during April 2016 to May 2017. Results: Out of 60 patients, 35(58.3%) patients had ischemic stroke, 25(41.6%) had hemorrhagic stroke. Overall stroke was seen mostly in the age group of 61-70 (28.3%) years, with a Male to female ratio of 3:2. Conclusion: Hypertension was the most common risk factor associated with this disease, followed by diabetes. CTA helps in accurate diagnosis, risk stratification and planning management protocols.


Introduction
Stroke is an acute neurological injury caused either by the occlusion or rupture of cerebral blood vessels. Broadly classified into two types, ischemic and hemorrhagic. Ischemia due to thrombosis or embolism constitutes about 85% and hemorrhage due to intra cerebral or subarachnoid bleed constitutes the rest. [1,2] Stroke is one of the leading causes of death and disability in developing countries like India , with an estimated prevalence ranging from 44 to 843 per 100,000 population. [3] The estimated age-adjusted prevalence rate in India for stroke ranges between 84/100,000 and 262/100,000 in rural and between 334/100,000 and 424/100,000 in urban areas. [4] A number of clinical tests have been developed over the years for initial triage of patients presenting with symptoms of stroke. But they lacked the sensitivity and specificity of an imaging examination, nor could accurately differentiate ischemic and hemorrhagic stroke. Therefore, the initial step in the management of a suspected stroke patient is an imaging examination starting with a non-enhanced computed tomography (NECT), often used to quickly exclude the presence of haemorrhage, look for ischemia, helps exclude stroke mimics, mapping of arterial calcification and localization of the anatomy of interest.
Imaging the cervicocerebral vasculature, the origin of all stroke pathology, is an essential part of Stroke protocol and follows the native NECT. A single bolus of contrast agent is sufficient to achieve both angiography and perfusion images, thus improves diagnostic precision, providing insight in to the source of dysfunction and may lead to accurate management towards intervention. [5] Thus Multi detector computed tomography (MDCT) Cervicocerebral angiography forms an important tool for diagnosis and prognostication of patients presenting with stroke. Computed tomography angiography (CTA) using latest generation of multislice scanners permits rapid and comprehensive assessment of the cervicocerebral vasculature, thus becoming a valuable tool in stroke patients. [6] The main role of CTA is to reveal the status of large cervical and intra cranial arteries and thereby help define etiopathogenesis of the disease, thus very useful in providing guidance for further intervention. [7] CTA is the most common first-line diagnostic modality for vascular imaging in the setting of acute stroke. [8] The diagnostic accuracy of CTA in Stroke patients reported at present is far superior to the previously published studies.Purpose of this study is to review the diagnostic performance of CTA in evaluation of cervicocerebral vascular pathologies as a non-invasive imaging modality in patients presenting with stroke.

Aim
To review the value of CTA in detection and evaluation of non-traumatic cervicocerebral vascular disease (stroke).

Objectives
To analyse the findings of cervicocerebral vascular diseases on 128 slice multi detector computed tomography angiography (MDCTA).
To determine the morphology and imaging patterns of various vascular lesions.
To provide information that could accurately determine the choice of management.

Subjects and Methods
In this cross sectional study, 90 subjects were included. Among them, 45 were type 2 diabetes mellitus patients with duration of 5 years or more, with diabetic complications are included as cases and 45 age and sex matched healthy controls, who attended the Department of Medicine and Radio-diagnosis, Akash Institute of Medical Sciences & Research Centre, Devanahalli. This prospective observational study done in the Department of Radiodiagnosis, Kamineni Hospitals, L.B. Nagar, Hyderabad during the period of April 2016 to May 2017 over 60 patients.

Inclusion criteria
All Clinically suspected and prior diagnosed cases of stroke on initial screening imaging modalities, which were further referred to the department of radio-diagnosis for CT angiography. All age groups are included.Both sexes are included.

Exclusion criteria
Patients with h/o trauma. Any person with abnormal renal function tests.Known severe allergy to intravenous contrast agents.

Results
In our study, a total of 60 patients with diagnosis of cerebrovascular accident (CVA) were studied.

Figure 1: Showing distribution of various sites of occlusion
Most common sub segment involved among ICA was both proximal cervical ICA and Cavernous portion, involved in 11 each. In 6 patients entire ICA is occluded.
Total number of patients with imaging findings of aneurysm were 18.Total no of aneurysms encountered in 18 patients were 23.Total no of patients with single aneurysm were 14(77.8%) and with multiple (>1) were 4(22.2%).
Among 25 cases of hemorrhagic stroke, only 1 patient was diagnosed to have Arteriovenous malformation (AVM).

Discussion
Cerebrovascular accident (CVA) is a significant cause of morbidity and a poor prognostic factor amongst the elderly. MDCT cervicocerebral angiography as a new diagnostic modality is likely to add to the diagnostic accuracy of CT in vascular disease with enhanced spatial and temporal resolution.
Aim of CTA in stroke patients is to delineate the cause of underlying vascular pathology, morphological evaluation for risk stratification and for planning appropriate treatment regime.
Out of 60 patients included in our study:-35(58.3%) patients had ischemic stroke, 25(41.6%) had hemorrhagic stroke.Ischemic stroke is more common, representing approximately 85 % of all stroke cases, and has a much lower 30-day mortality rate at approximately 12 %. [9] Although the incidence of Hemorrhagic stroke is low, it is associated with significant morbidity and mortality. Up to 38 % of patients that experience hemorrhagic stroke will die within 30 days. [10] stroke was seen most commonly in the age group of 61-70 years (28.3%).The second most common age group was 51-60 years (25%), followed by 41-50 years (23%) age group. Most common age group with diagnosis of ischemic stroke in our study were in the age group of 61-70 and among hemorrhagic stroke were 41-50 years. This shows that the incidence of overall stroke increases with increasing age. Age is the single most important risk factor for stroke. Brown RD et al and Wolf PA et al in their respective studies concluded that the risk of having a stroke doubles every decade after the age of 55. [11,12] Dalal PM et al and sridharan SE et al in their study on stroke patients in Mumbai and Trivandrum in 2008 and 2009 respectively concluded that the mean age of patients with stroke was 66 and 67 years respectively. [13,14] 36 (60%) patients were males and 24 (40%) were females. This shows that male sex itself is an independent (non modifiable) risk factor for stroke. Townsend, N. et alconcluded that men are at a 25% higher risk of having a stroke and at a younger age compared to women. [15] Dalal PM et al in Mumbai, stated that men had a higher stroke incidence rate than did women. [13] Out of 35 patients with ischemic stroke, Male to female ratio is 5:2.Out of 25 patients with hemorrhagic stroke, Male to female ratio is 2:3.Out of 18 patients with aneurysms, Male to female ratio is 1:2. J.L. Chasonand W.M. Hindman study concluded that the Unruptured intracranial aneurysms are more common in women with a 1:3 ratio of men to women. [16] Similar predominance is seen in our study.  [17] followed by hypercholesterolemia (15%) and tobacco smoking (12%). Jeyaraj Durai Pandian study on stroke epidemiology and stroke care services in India stated that, hypertension was the most important risk factor associated with stroke. [4] Out of 18 patients with aneurysms, 4(22%) patients were diabetic and 4(22%) were hypertensive.1 (5%) patient had both risk factors. Greving JP et al in their pooled analysis of six prospective cohort studies on predictors of aneurysm rupture concluded that patients with hypertension are at higher risk of rupture. [18] Thus, considering Hypertension alone, 5 patients with aneurysm in our study are at higher risk of rupture.
Out of 60 patients in our study, 24 (40%) patients had atherosclerotic disease, 18 (30%) patients had aneurysms, 8 (13.3%) patient had thrombosis, 1(1.66%) patient had AVM, no obvious demonstrable etiological cause was found in 9 patients. Thus, Atherosclerosis is most common cause of stroke overall. Wong KS, Li H study stated that intra cranial atherosclerotic disease (ICAD) is a much more important cause of stroke in Asia, where it can account for 33% to 67% of stroke cases. [19] Out of total 48 occluded arterial segments, ICA (77%) is the most commonly involved, followed by CCA (6.2%) and VA (6.2%). Thus ICA is the most common segment involved over all. Most common sub segment involved among ICA in our study was both proximal cervical ICA and Cavernous portion, involved in 11 each. According to Dragajichici, proximal 2 cm of ICA origin and intracranially, the carotid siphon (cavernous portion) are the most common sites of occlusion among ICA.
Similar observations were seen in our study.
Among 48 segments involved in ischemic stroke, 39 segments had atheromatous disease, of which fibro fatty plaque were seen in 32 (82%) segments and fibro calcific plaque in 7(18%) segments. Thus, soft plaques are more commonly encountered.
CTA is a reliable tool to diagnose extracranial large artery disease. [20] In a large retrospective study, the presence of intraluminal thrombus detected on CTA was found to be highly predictive of the symptomatic side in carotid disease when compared to a smooth plaque surface or extensive calcification, thus suggesting certain plaque characteristics that could predict an unstable plaque with a tendency for recurrent thromboemboli. [21] Thus, determining plaque type is important for patient triage.
Out of 48 stenotic arterial segments, 14(29%) showed mild stenosis, 8(16.6%) showed moderate stenosis and 26 (54%) showed severe stenosis. Most common segment involved in severe stenosis is ICA. In both NASCET and ECST, it has been established that carotid endarterectomy is more effective than medical therapy in reducing stroke risk in symptomatic patients with severe (70%-99%) carotid artery stenosis. Carotid endarterectomy may also be beneficial for asymptomatic patients with carotid artery stenosis of less than 60%. [22] Thus, classification of grades of stenosis helps in risk stratification and planning appropriate treatment regime.
Among 23 aneurysms encountered in 18 patients in our study, total no of patients with single aneurysm were 14(77.8%) and with multiple (>1) were 4(22.2%). According to Takahashi S, [23] Multiple aneurysms constitutes 15-30% overall. Similar prevalence is seen in our study. D.O. Wiebers, [24] stated that patients with multiple aneurysms are at higher risk of rupture. 91.3% of aneurysms were located in anterior circulation and 8.69% in posterior circulation. Overall, Acom (34.7%) is the most commonly involved site. According to Takahshi S, [23] Approximately 90% of aneurysms arise from the anterior circulation. Similar observations were seen in our study.
In Prospective Cohort Study by Morita et al, [25] concluded that, Aneurysm located in anterior and posterior communicating arteries are at greater risk of rupture. In our study 11(47.8%) aneurysms were seen in these sites.
Aneurysm shape was categorized by de Rooji NK et al, [26] into spherical, non-spherical, and irregularly shaped. Daan Backes, MD et al, [27] study concluded that irregular shaped aneurysms and aspect ratio >1.3are associated with aneurysm rupture independent of aneurysm size and location, and independent of patient characteristics. Thus, 5(21.7%) aneurysms in our study are at higher risk of rupture considering shape of aneurysm alone.
Aneurysms with size <7mm is seen in 13 (56.5%) aneurysms and >7mm in size in10 (43.5%) aneurysms. According to D.O. Wiebers, [24] size and location are the two important factors predicting risk of rupture. A.Morita et al, [25] in a Japanese cohort study stated that, the risk of rupture increased with size for aneurysms measuring 7mm or larger. Thus considering size alone, 13 (56.5%) aneurysms in our study are at higher risk of rupture.
Among 23 aneurysms detected in 18 patients on CTA, bifurcation type of parent artery configuration is seen in 12(52%) aneurysms and side wall type of configuration in 11(48%). Bifurcation type, are at higher risk of rupture compared to sidewall type.
Among 21 aneurysms, aneurysms with narrow neck are seen in 18 (78.2%) and with wide neck are seen in 5 (21.8%).According to J. Thornton et al, [2] study on detachable coiling for intracranial aneurysms in 2001, Neck width, along with dome to neck ratio is an important predictor for identifying ideal candidates for use of coiling alone for aneurysms with Narrow neck (width<4mm) and adjunct techniques (balloon inflation or stent placement) for aneurysms with wide neck (width>4mm). These adjunct techniques prevent coil migration in wide neck aneurysm in to parent artery, therefore reduce the risk of thromboembolism. Thus, neck width is an important factor determining the choice of technique to be employed in the management of aneurysms.
Among 21 aneurysms aspect ratio >1.3 were seen in 17 (80.9%) and with <1.3 in 4 (19.04%). Daan Backes, MD et al, [27] study concluded that irregular shaped aneurysms and aspect ratio >1.3are associated with aneurysm rupture independent of aneurysm size and location, and independent of patient characteristics. Considering aspect ratio alone, 17(80.9%) aneurysms among 21 are at higher risk of rupture in our study.
Norman Ajiboye et al, [28] Based on patient age, aneurysm characteristics, associated risks and benefits of intervention formulated an approach for the management of un ruptured aneurysm. Following his protocol, 6 aneurysms require conservative management and 17 requires either coiling or clipping in our study. Sorek PA, Mehta BA study observed an association between fenestration and aneurysm formation. [29] Simon J. Dimmick, B Pthy, Kenneth C. Faulder review stated that the knowledge of the presence and clinical relevance of normal variants such as fenestrations, duplications, and persistent foetal arteries plays a crucial role in the diagnosis and management of acute stroke and subarachnoid hemorrhage and may aid in surgical planning. [15] Fenestration has a risk of aneurysm formation. Thus careful evaluation and reporting is required. Azygous ACA is an important normal variant because, thromboembolism in this variant leads to infarct in bilateral ACA territories. As seen in one of our study population. Out of 33 hypoplastic segments, Most commonly encountered hypoplastic segments were A1 segment of right ACA and Left PCA.
Among 25 cases with hemorrhagic stroke, only 1 patient is diagnosed to have Arteriovenous malformation (AVM). Spetzler-Martin Scale is used to estimate the risk of surgical resection of an AVM with higher grades being associated with greater surgical morbidity and mortality.
A meta-analysis comprising 2425 patients treated between 1990 and 2000 showed a surgical mortality of 3.3% and a permanent postoperative morbidity of 8.6%, with an increasing morbidity-mortality rate associated with an increasing Spetzler-Martin grade. [30] Following Spetzler-Martin grading scale for AVM's, our patient scores 2 points for size (medium), 1 point for eloquent site (language) and 1 point for pattern of venous drainage. According to this scale, our patient is at greater risk of surgical morbidity and mortality.
Thus, CTA as an imaging modality in a patient with cerebral AVM's is immensely helpful in preoperative work up, patient management and assessing surgical morbidity and mortality.

Conclusion
Hypertension was the most common risk factor associated with this disease, followed by diabetes. CTA helps in accurate diagnosis, risk stratification and planning management protocols.