Transradial Access for Cerebral Angiography: An Old Idea Made New Again
Introduced nearly 100 years ago, cerebral angiography has undergone numerous advances in technique and technology. It remains a bedrock of cerebral diagnostic imaging, and advances in device and catheter technology have only served to cement its role in non-surgical management of vascular pathology of the nervous system. Focusing on the latest in flow diverters and stent-retrieval devices, we often take for granted the significant advances that have taken place around the ‘lowly’ issue of vascular access.
The Birth of Cerebral Angiography
Contrast injection for neuro-diagnostic imaging was initially reported by the French physicians Sicard and Forestier, who used intravenous lipiodol injection for the diagnosis of medullary compression induced by a brain-tumor (1921). Inspired by their work, the famous Portugese neurologist, Egas Moniz, was the first to introduce direct carotid puncture as a means of diagnosing and studying the cerebral vasculature. In 1927, Moniz published his cadaveric work in Revue Neurologique and named it “encephalographie arterielle.”
Like any revolutionary medical breakthrough, several experiments were required to test the preferred contrast agent (lithium bromide, strontium bromide, sodium iodide), dosing and toxicity levels in both cadaveric and animal subjects. Initial testing was intravenous, until sodium iodide was determined to be the contrast agent of choice, with the least patient discomfort upon injection.
Direct Carotid Puncture – The Path of Least Resistance
Once the contrast agent was determined, Moniz worked on cadavers to identify the location and mode of delivering sufficient contrast to produce an adequate image. Moniz first performed transcutaneous carotid puncture. Unfortunately, the results were not promising. This was likely due to the small puncture needle size that resulted in non-diagnostic contrast spread into the tissues. Moniz subsequently exposed the carotid artery via a surgical cut-down and injected the carotid artery under direct visualization. This led to the first successful cerebral arteriogram, which was performed with intravascular injection of sodium iodide (25% solution) in a formaldehyde-fixed cadaveric specimen (Figure 1).
The First Clinical Cerebral Angiogram
Similar to the current FDA-approval process for novel technology, successful cadaveric and animal studies were required prior to testing human subjects. Unfortunately, the initial eight human attempts were unsuccessful. On his ninth attempt, Moniz was able to perform a successful cerebral angiogram in a 20-year-old patient and diagnose a pituitary tumor based on cerebral arterial displacement (Figure 2). Despite Moniz’s reputation as the pioneer of cerebral arteriography and its continued importance today, he earned the Nobel Prize in Medicine and Physiology in 1949 for a more sensational procedure, which has since been condemned and abandoned – pre-frontal leukotomy.
The Seldinger Technique and the rise of Femoral Access
Advancements in medicine arise out of necessity – improving on existing technology in order to minimize the shortcomings of existing techniques. Direct carotid puncture led to significant morbidity including stroke due to ligation of the artery during cut-down, anterior cervical bleeding and airway compromise, and arterial injury from direct catheterization of large injecting catheters/cannulas. A revolutionary intra-vascular concept was introduced by the radiologist Sven-Ivar Seldinger of the University of Lund, Sweden, in 1953. As depicted in Figure 3, Seldinger proposed:
- Initial access via a puncture needle,
- Then introduction of a supple leading wire, and
- Finally, exchanging the needle for the catheter.
This solved the need for direct access via cut-down and permitted exchange and dilation for sequentially larger catheters. In 1951, Bierman proposed accessing the vertebral system via the femoral artery, and by 1956, combining Seldinger’s technique with Bierman’s proposal, Sten Cronqvist (also of University of Lund) reported one of the earliest clinical series of successful cerebral angiograms via transcutaneous femoral access. The femoral artery has remained the mainstay access site for most cerebral arteriograms based on its large caliber, superficial location, and (theoretical) compressibility.
Limitations of Femoral Access and the Rise of Radial Access
Femoral arterial puncture can have devastating complications, such as retroperitoneal hematoma and limb compromise due to existing atherosclerosis or vascular injury (such as pseudo-aneurysm). Trans-radial arteriography is well described in the cardiac literature. However, the first trans-radial cerebral angiogram was reported in 1947 by Radner, who described a direct radial ligation for vertebral angiography. However, it would be another 50 years until the engineering of catheters, wires and other endovascular devices paved the way for a resurgence of interest in transradial access in the early 2000s.
This technique has gained popularity over the last few years and provides an alternate route for endovascular access. The lack of life-threatening bleeding complications and decreased risk of limb compromise due to collateral vascular supply by the ulnar artery make this technique favorable, especially in patients on anticoagulation or with severe peripheral vascular disease. Certainly, this technique has its own inherent limitations, including increase in operating and fluoroscopy time, higher radiation exposure for patient and operator and potential thromboembolic events during catheter shaping in the aortic arch.
It remains to be seen whether or not radial access will become the dominant methodology over femoral access for cerebral angiography. Radial access was, for many years, reserved as a salvage technique to navigate/bypass difficult arch anatomy which was not amenable to transfemoral access. Furthermore, despite the advent of femoral access, the most primitive methods of cerebral angiography have withstood the test of time. Direct carotid puncture, either transcutaneous or via carotid cut-down remains a critical element in the endovascular management of cerebral pathology. Endovascular neurosurgery is one of the most rapidly evolving fields, and yet it is just catching up in practice to what our ground-breaking predecessors initially imagined.
1. Artico, M., Spoletini, M., Fumagalli, L., Biagioni, F., Ryskalin, L., Fornai, F., . . . Taurone, S. (2017). Egas Moniz: 90 Years (1927–2017) from Cerebral Angiography. Frontiers in Neuroanatomy, 11.
2. Seldinger, S. I. (1953). Catheter Replacement of the Needle in Percutaneous Arteriography: A new technique. Acta Radiologica, 39(5), 368-376.
3. Pierot, L., & Wakhloo, A. K. (2013). Endovascular Treatment of Intracranial Aneurysms. Stroke, 44(7), 2046-2054.
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