Infarction Patterns in Posterior Cerebral Circulation: Etiology and Prognosis

Study Objectives: About a quarter of strokes and transient ischemic attacks occur in the vertebrobasilar distribution. Vertebrobasilar stroke is particularly prone to devastating consequences especially brain stem infarctions due to damage of the regional brain tissues that contain vital centers, and is associated with high rates of death and disability. Study Design: This was across sectional observational prospective hospital-based study conducted on 60 patients with first-ever acute posterior circulation ischemic stroke. The aim of the current study was to determine the relationship between different risk factors and different infarction patterns in posterior circulation; single small lacunar lesion, single large lesion, or multiple scattered lesions. Diagnosis of ischemic stroke and stroke subtypes were defined using the Trial of ORG 10,172 in Acute Stroke Treatment (TOAST) criteria as well as clinical and brain imaging features. Stroke severity using National Institutes of Health Stroke Scale (NIHSS) score was done on admission, after 24 hours from admission, and at 7 days from onset of symptoms. The patients functional status was assessed by modified Rankin scale (mRS) done on admission and on discharge from hospital and at 7-day follow up from onset of symptoms. Patients were classified according to infarction patterns into a single small lacunar lesion (group I), a single large lesion (group II), and multiple scattered lesions (group III) 20 patients in each group. Results: There was no significant difference between the three groups as regard the presence of vascular risk factors and the only significant difference as regard vascular risk factors was atrial fibrillation (AF). There was significant difference between the three groups as regard the occurrence of previous transient ischemic attacks (TIA). There was significant difference between the three groups as regard NIHSS score on admission, after 24 hours, and at 7 days from admission. There were significant differences between the three groups as regard mRS score at discharge and at 7-day follow up from the onset of symptoms and the degree of improvement from admission to discharge. There was significant difference between the three groups as regard volume of infarction in Brain magnetic resonance imaging (MRI). Group II and group III patients had larger volumes of infarction when compared to group I patients. There was no significant difference between the three groups as regard presence of significant intracranial stenosis in magnetic resonance angiography (MRA). There was significant difference between the three groups as regard stroke etiology. It was found that largeartery atherosclerosis (LAA) was the most common stroke etiology in posterior circulation being present in (53.3%) of the patient group and was common in group II and III in contrast to group I patients. Conclusions: Different vascular risk factors such as hypertension, diabetes, dyslipidemia, and smoking are present in all infarction patterns of posterior circulation ischemic stroke either single or multiple infarctions. However, AF and significant vertebrobasilar stenosis were mostly associated with large and multiple infarct lesion patterns. Small vessel disease was the most common stroke etiology for single small lacunar lesion while large artery atherosclerosis was associated with single large lesion and multiple lesions in the posterior circulation. Early MRI and MRA help in define type and prognosis of posterior circulation infarcts. Early diagnosis and control of potentially modifiable risk factors and comorbid conditions are an important aspect in the early management of patients with infarction in the posterior circulation.