Diagnosis and neurosurgical treatment of intracranial vascular occlusive syndromes.

Intracranial atherosclerosis represents the most prevalent form of intracranial vascular occlusive disease in the adult population and is a major contributor to ischemic stroke. The most reliable method for diagnosing intracranial stenosis relies on conventional catheter angiography; MRI and CT imaging and transcranial Doppler currently are valuable screening tools, and ongoing advances in these modalities may render angiography nonessential for accurate diagnosis in the future. Given the potential for hemodynamic compromise from intracranial occlusive disease, a variety of imaging modalities may be used to assess the adequacy of cerebral perfusion, relying on direct measurements of oxygen extraction fraction or the response to vasodilatory stimuli to determine hemodynamic status. The modalities are well established for assessing the anterior circulation but have proven less useful for the posterior circulation, in which direct measurements of large vessel flow using quantitative magnetic resonance angiography may be more valuable. Surgical and endovascular interventions for treating intracranial stenosis are not, as of yet, proven therapies for routine management. Extracranial-intracranial bypass surgery and endovascular angioplasty and stenting are being investigated in randomized trials to evaluate their efficacy in treating intracranial vascular occlusive disease.