Distribution, Severity and Radiologic Features of Intracranial Stenosis in Asymptomatic Pakistanis

Abstract

Background: Intracranial atherosclerotic disease (ICAD) is the most common ischemic stroke subtype globally. It accounts for 30-50% of all ischemic strokes in Asians.

Aims: The aim of the study is to report the frequency of asymptomatic ICAD and its associated Magnetic Resonance Imaging (MRI) findings.

Methods: 200 adult participants were recruited from the Radiology Departments of two major diagnostic centers in Karachi. Eligible participants were confirmed for the absence of stroke symptoms via the Questionnaire for Verifying Stroke Free Status (QVSFS). QVSFS negative subjects underwent MRI on a 1.5 Tesla scanner. Images were centrally reviewed on Di com Viewer 3.0 with electronic calipers to calculate the degree of ICAD.

Results: Mean age of subjects was 37.1 years (S.D 15.1) with 50.5% men (n=101) and 49.5% women (n=99). Asymptomatic ICAD was found in 34.5% (n=69) subjects. Of the 3800 intracranial arteries studied, 2.2% (n=88) had biological disease. 20.5% (n=18) of these vessels had atherosclerotic irregularities, 43.2% (n=38) had mild stenos is, 11.4% (n=10) had moderate stenos is, 5.7% (n=5) had severe stenos is while 19.3% (n=17) were completely occluded. The posterior cerebral artery (42% of stenosed arteries, n=37) was most affected. 23.5% (n=47) of subjects had peri-ventricular lucencies, 10.5% (n=21) had brain atrophy while 3.5% (n=7) had silent brain infarcts. There was a significant association between asymptomatic ICAD and peri ventricular lucencies (PR 1.59; 95% CI 1.35-1.99).

Conclusion: Asymptomatic ICAD is common in young Pakistanis, with no gender predilection; it preferentially affects the posterior circulation. Silent infarcts are rare compared to peri ventricular lucencies and atrophy.

Keywords: Asymptomatic; Developing Countries; Epidemiology; Intracranial Stenosis; Prevention; Radiology; Stroke.

Figure 1. MRI images showing Asymptomatic ICAD in the posterior circulation

The arrows point at the point of stenosis in each vessel (A) Left Posterior Cerebral Artery (B) Right Posterior Communicating Artery (C) Left Vertebral Artery.

Figure 2. Silent brain infarct

The Arrow points at the region of infarction.

Figure 3. Periventricular Hyperintensities

Increased signals as pointed by the arrows is evident on T2 images in the periventricular areas.

Figure 4. Brain volume reduction

Diffuse reduction in brain volume is evident by the narrowing of gyri and widening of sulci.