Progression or Regression of Intracranial or Extracranial Arterial Stenosis: Role of Ultrasound

Abstract

Atherosclerosis of intracranial or extracranial artery is a major cause of ischemic stroke, which may be a dynamic lesion with progression or regression. Ultrasound examinations are useful and important tools for the diagnosis of progression or regression of intracranial or extracranial arterial stenosis. Progression of intracranial stenosis may increase the risk of stroke, therefore adequate diagnosis is important. Transcranial Doppler sonography (TCD) may be useful for this purpose, however, optimal diagnostic criteria have not been defined well. According to our subgroup analysis from the prospective clinical trial, which had evaluated the efficacy of cilostazol combined with aspirin in symptomatic intracranial stenosis, sensitivity of TCD criteria ranged 23-42% for progression and 13-67% for regression, while specificity ranged 83-92% for progression and 91-97% for regression. Among the criteria validated, Δ20cm/s increment or decrement criteria had the highest sensitivity (42% for progression and 67% for regression) and specificity (90% for progression and 96% for regression). With these criteria, we compared long-term TCD changes with MRA in patients with intracranial stenosis. Among 164 patients included (84 males, mean age 64 years, mean follow-up period 35 months), progression was observed in 5.7% among MCA and 5.0% among BA. With diagnosis of progression, more aggressive medical management (BP control, blood glucose and lipid lowering, antiplatelet agents, etc.) is indicated and higher-dose statin may be recommended. Carotid duplex ultrasound (CDU) has an important role for the screening of asymptomatic carotid stenosis (ACS), detection of vulnerable plaques, or monitoring of progression or regression of arterial stenosis. With qualified examination and optimal diagnostic criteria, the sensitivity and specificity has been reported up to 90% and 94% for the detection of stenosis of 70% or greater. In addition to the degree of stenosis, CDU also reveal the morphology and distribution of the plaques. Natural course of ACS also has been studied with CDU and several factors related to the progression/regression of ACS have been reported. Recent advance of medical treatment diminished the risk of stroke (< 1%/year) compared with carotid revascularization in ACS. Therefore, current issue is to identify “high-risk” patients who will get more benefit from the carotid revascularization. With optimal criteria, CDU may diagnose progression of arterial stenosis, which is an important predictor for future stroke. TCD is also useful for the detection of microembolic signals (MES), which is potently associated with the risk of stroke in ACS. In summary, adequate ultrasound examination is useful for the diagnosis of intracranial or extracranial arterial stenosis, progression/regression of stenosis, and possibly for the identification of the “high risk” patients, therefore is useful for the adequate clinical decision making.