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Compared with transfemoral access (TFA), transradial access (TRA) for neurointerventional procedures is known to have superior safety, earlier ambulation, greater patient comfort, and possibly reduced cost with shorter hospital stay. The most compelling advantage is the lower rate of serious hemorrhagic access site complications, which is particularly relevant given the high rates of concurrent antithrombotic and/or thrombolytic medications used. TRA also has clear value over TFA where there is obesity, pregnancy, prior aortofemoral bypass or stents, and a type III aortic arch. Given the entrenched historical convention of using TFA, early advocates of TRA suggested a ‘radial first’ approach whereby a concentrated experience in TRA could more effectively yield sufficient proficiency. This messaging may have had unintended consequences of promoting the notion that TRA should be the default first option in all neurointerventional cases. The large volume of recent JNIS publications on this topic suggests otherwise: TRA should not be the default first choice. Instead, as these publications suggest, access decisions deserve a more thoughtful consideration of a variety of variables including the type of procedure being performed, the disease process being managed, and patient anatomy. Elective versus emergent, value of large catheters, and number of vessels that need catheterization are among several specific considerations when choosing access approach. Elective, single vessel neurointerventional cases seem wellsuited for a TRA approach. A review of seven studies reported radial access procedural success for carotid artery stent placement with low rates of asymptomatic radial artery occlusion, forearm hematoma, stroke/ transient ischemic attack, major stroke, and mortality. A twocenter retrospective study of 39 flow diversion cases showed similarly favorable results. Patient satisfaction surveys among patients who have undergone both TRA and TFA have shown a preference for TRA. Although patient comfort, access site complications, early ambulation, etc, may have value in elective cases, the importance of these concerns diminishes in the context of an acute large vessel occlusion, particularly if the relatively smaller access site jeopardizes consistent procedural success. Many physicians feel the smaller radial artery access limits their use of balloon guide catheters and/ or large bore aspiration catheters because of the concern for radial artery spasm and/or other access complications. When comparing 222 consecutive patients at a single center undergoing mostly anterior circulation stroke thrombectomy, TFA was associated with significantly higher rates of successful reperfusion, fewer passes, rate of first pass effect, lower 3 month mortality, and improved 90 day functional outcome. However, TFA should not necessarily always be considered superior to TRA for acute ischemic stroke. Maud et al found, in a very small sample size, a trend towards better results with TRA when compared with TFA for posterior circulation occlusions. Also, very recent reports show the feasibility of using 8F guide catheters with or without balloons, often without a short sheath via TRA, with only 3/20 cases showing significant vasospasm or technical failure. Kinking of the balloon guide catheter was noted during right carotid catheterization in several cases. Lastly, bovine arches with a left anterior circulation occlusion may fare better with TRA. In addition to disease state, the number of vessels to be catheterized may be another consideration. When compared with TFA, TRA has been found to be associated with higher diffusion weighted imaging (DWI) lesions and longer procedural times (for diagnostics especially) when compared with TFA. In a single center study of 120 consecutive diagnostic cerebral angiograms split evenly between TRA and TFA, with similar numbers of vessels catheterized and procedure time, eight TRA cases showed DWI changes compared with only one TFA case. Fortunately, no patient experienced neurological symptoms. Another single center community hospital showed in 198 diagnostic cerebral angiograms, split 3:1 TFA to TRA, significantly higher rates of fluoroscopic time, higher total dose and dose area product, with the highest difference seen in patients undergoing six vessel studies among TRA patients. Unlike with TFA, with TRA, reformatting the Simmons catheter sometimes involves blind guidewire interaction with the aortic valve, which may be one explanation for the observed increased rates of DWI lesions. The angled TRA trajectory rather than the straighter TFA trajectory may explain the additional manipulation needed to catheterize multiple vessels during a diagnostic cerebral angiogram. Selective catheterization of the internal and external carotid arteries with a Simmons catheter as opposed to an angle tip catheter often requires additional manipulation, which may increase the chance for additional endothelial irritation which may lead to thromboembolic complications when compared with a TFA. Hence, early reports suggest that TFA may be safer than TRA for diagnostic procedures where multiple vessels need catheterization. Lastly, reviewing the arterial anatomy of the upper arm and the aortic arch, including the configuration of the great vessels, may help determine whether additional measures may be needed or whether TFA would be preferable. In a review of 21 studies evaluating 1342 patients with radial access for neurointerventional procedures, crossover to TFA occurred in 4.8% of patients, most often due to radial artery spasm or inability to catheterize the target vessel. Several anatomic configurations are well known to complicate radial artery access and include radial artery spasm, radial artery loop, subclavian stenosis, extreme angulation between the origin of the right subclavian artery and common carotid artery, and a nonbovine aortic arch. The threshold to switch to TFA should not be too low. Several techniques have been recently described to increase the opportunities to use TRA, even with radial loops or occlusion. Routine confirmation of radial artery diameter to be >2.5 mm on ultrasound before sheath placement has been advocated by some authors. The anatomic variant of the radial artery termed a radial artery loop results from a tethered recurrent radial artery, leading to the formation of a 360° loop. A multicenter study evaluated 32 transradial neurointerventions with radial loops and described techniques to straighten the loop. 13 They describe the use of microcatheters and microguidewires in an incremental method to less traumatically allow access to the brachial artery with straightening of the loop, followed by placement of a long radial artery sheath to maintain access. Radial artery occlusion or severe spasm often occurs after prior arterial line Neurological Sciences, Rush University Medical Center, Chicago, Illinois, USA