Ultrasound Study of Intracranial Stenoses: Pre- and Post- Endovascular Treatment

Intracranial atherosclerotic stenosis (ICAS) represents a major cause of ischemic stroke in the world. Its incidence varies by ethnicity being highest among Asians and still underestimated in Caucasians. ICAS is held as a malignant cause of stroke with a very high stroke recurrence rate, highest for 70-99% stenosis and during the first 2-3 weeks after the initial event.
A systematic assessment of intracranial vessels by ultrasound is useful in diagnosing stroke patients with intracranial stenosis, understanding the nature of the stenosis, identifying ICAS patients at a higher risk of stroke recurrence. In fact ultrasound can provide real-time flow information (grade of stenosis, collaterals), study hemodynamic changes with time (regression/progression/stability of stenosis) or in response to various stimuli including breath-holding index to induce or augment a steal, and it can also detect transient emboli. All the information gathered by ultrasound has immediate therapeutic implications: anticoagulants for a partially recanalized embolus, calcium channel blockers for vasospasm, antiplatelet agents for dissection, immunosuppressants for vasculitis, intensive risk factor management and dual antiplatelet treatment for ICAS. In patients with recurrent symptoms despite best medical therapy, ultrasound can detect a progression of the stenosis, check for a possible increase of the embolic count downstream, assess intracranial arterial hemodynamics changes post-operatively (angioplasty alone or combined with new stents). In the latter cases, when verifying treatment efficacy, it is important to know the effects of a stent on cerebral blood flow in order to avoid misdiagnosis.