Conventional Cerebral Arteriography

Introduction

Cerebral angiography was introduced and expanded by the Portuguese neurologist Egas Moniz close to a century ago . Significant morbidity and mortality in the first procedures lead to a transition to iodinated solution as contrast media, leading to satisfactory technical results. Despite the original “distrust” and controversy regarding this method and its future , cerebral angiography not only remains the gold standard for the diagnosis of vascular conditions affecting the craniocervical and cerebral vessels, but has developed itself into a very sophisticated interventional field. Even though neuroangiography is suited for the evaluation and treatment of craniocervical arteries, capillaries, and veins, this chapter specifically focuses on cerebral arterial angiography.

Indications

Conventional catheter-based arterial cerebral angiography constituted the only available cerebrovascular diagnostic test for decades, and has more recently shared indications with noninvasive imaging studies. CT angiogram, MR angiogram, cervical duplex, transcranial Doppler (TCD), and even SPECT/PET scan technology have evolved significantly and are now, often times, first-line modalities in the evaluation of the cerebral vasculature. Angiography is typically reserved for situations in which noninvasive imaging investigation is inconclusive or when interventional plans exist. The advantages of catheter angiography rely on its better spatial resolution (submilimetric), dynamic evaluation flow patterns of each individual artery, and high-temporal resolution (up to 30 frames per second).

A discussion regarding the indications and diagnostic accuracy of noninvasive imaging studies is beyond the scope of this chapter. The indications for diagnostic catheter angiography include accurate characterization of aneurysm angioarchitecture, allowing for optimal definition of shape, size, and location. Although microsurgical treatment may be performed based on CTA or MRA, conventional angiography prior to treatment of aneurysms revealed by noninvasive imaging studies is performed in most institutions ( Fig. 134.1 ). In cases of arteriovenous malformations, conventional angiography is typically indicated for all patients. In individuals with suspicion for dural arteriovenous fistulas (including carotid-cavernous fistulas), an angiogram is indicated for all patients for the analysis of potential dangerous features, such as cortical venous drainage and venous ectasia. Subjects with intracerebral hemorrhages in atypical settings (such as lack of risk factors for hypertensive hemorrhage, atypical locations, hemorrhage in young age, and questionable findings on MR or CT) may benefit from more careful investigation with conventional angiography. We reserve conventional angiography in patients with dissections for when there is potential hypoperfusion or repeated embolic phenomena despite aggressive medical management, or when there is controversy regarding its diagnosis. The use of conventional angiography for the evaluation of carotid atherosclerotic disease has declined substantially, given the relatively high risk of navigation/catheterization of the aortic arch and craniocervical vessels in this specific patient population, and the relatively good accuracy and safety of noninvasive imaging for this condition. Typically, catheter angiography is reserved for cases determined to be suitable candidates for stent revascularization or when doubt exists regarding etiology, lesion site (cervical and/or intracranial carotid disease), degree of stenosis, or when perfusion/flow patterns are unclear despite noninvasive imaging ( Fig. 134.2 ). Intracranial atherosclerotic disease is a controversial topic, however, we may consider conventional angiography for patients with high-grade stenosis from atherosclerotic disease that have failed maximal medical therapy for risk-stratification. Although vasculopathies encompass a multitude of different etiologies and phenotypes (e.g., systemic or CNS vasculitis, reversible cerebral vasoconstrictive syndrome, intravascular lymphoma, infectious endarteritis, moyamoya changes, and cerebral vasospasm), we favor a cerebral angiogram in cases of unclear diagnosis. Although venous conditions, such as cortical vein or sinus thrombosis, can be identified on venous phases of arterial angiograms, the diagnosis and follow-up rely strongly on noninvasive imaging; angiogram can be performed in cases of equivocal diagnosis, or when flow patterns must be better depicted, or when manometric measures are required (such as suspicion for congestion secondary to venous outflow limitation). Finally, diagnostic conventional angiography is often required for neurosurgical or endovascular planning (such as balloon-test occlusions, Wada testing, petrosal sinus sampling, aneurysm treatment, and preoperative embolization of vascular lesions or tumors).

From the interventional perspective, modern sheaths, guide and distal access catheters, as well as microcatheters and microwires allow for unprecedented navigability and safety. The field of endovascular treatment of acute ischemic stroke has directly benefited from these advances and has dramatically evolved, with a multitude of different available devices and techniques. The technological development has led to a wide arsenal of coil variations, leading to the ability of providing remarkable coil/aneurysm conformation. Stents for coil-assisted embolization have also evolved considerably and now allow great deliverability, conformability, and support. The flow-diversion technology (with lower-porosity stents) revolutionized the aneurysm treatment arena, allowing the treatment of previously inoperable large and wide-necked aneurysms. Intra-arterial chemotherapy for retinoblastomas, lacrimal gland tumors, and gliomas are emerging as a potential oncological adjuvant treatment. The management of craniocervical blowout from tumor invasion or lacerations with covered stents is effective and safe. Embolization of tumors of the head and neck are critical for bleeding control or as a preoperative risk reduction maneuver. Arteriovenous malformations, dural fistulas, and intracranial tumors can also be treated via embolization. Angioplasty/stenting can be performed in carotids and vertebrals (atherosclerosis, fibromuscular dysplasia, Takayasu’s arteritis, dissections), selected intracranial steno-occlusive lesions, as well as in certain venous steno-occlusive conditions. The diagnosis and treatment of vasospasm from subarachnoid hemorrhage and even of reversible vasoconstriction syndrome can also be pursued.

Basic Concepts