Emergency Department Visits for Chronic Subdural Hematomas within 30 Days after Surgical Evacuation with and without Middle Meningeal Artery Embolization
=========================================================================================================================================================

* J.S. Catapano
* L. Scherschinski
* K. Rumalla
* V.M. Srinivasan
* T.S. Cole
* J.F. Baranoski
* M.T. Lawton
* A.P. Jadhav
* A.F. Ducruet
* F.C. Albuquerque

## Abstract

**BACKGROUND AND PURPOSE:** Middle meningeal artery embolization after surgical evacuation of a chronic subdural hematomas is associated with fewer treatment failures than surgical evacuation. We compared emergency department visits within 30 days for patients with chronic subdural hematomas with and without adjunctive middle meningeal artery embolization.

**MATERIALS AND METHODS:** All cases of chronic subdural hematoma treated from January 1, 2018, through December 31, 2020, were retrospectively reviewed. Treatment was classified as surgery only or surgery combined with middle meningeal artery embolization. The primary outcome was 30-day emergency department presentation and readmission.

**RESULTS:** Of 137 patients who met the study criteria, 28 (20%) underwent surgery combined with middle meningeal artery embolization. Of these 28 patients, 15 (54%) underwent planned middle meningeal artery embolization and 13 (46%) underwent embolization after surgical failure. The mean chronic subdural hematoma size at presentation in the group with surgery only (*n* = 109, 20.5 [SD, 6.9] mm) was comparable with that in the combined group (*n* = 28, 18.7 [SD, 4.5] mm; *P* = .16). A significantly higher percentage of the surgery-only group presented to the emergency department within 30 days compared with the combined group (32 of 109 [29%] versus 2 of 28 [7%] patients; *P* = .02). No significant difference was found with respect to readmission (16 [15%] versus 1 [4%] patient; *P* = .11). Nine patients (8%) in the surgery-only group were readmitted for significant reaccumulation or residual subdural hematoma compared with only 1 patient (4%) in the combined group (*P* = .40).

**CONCLUSIONS:** Surgical evacuation combined with middle meningeal artery embolization in patients with chronic subdural hematoma is associated with fewer 30-day emergency department visits compared with surgery alone.

## ABBREVIATIONS:

cSDH
:   chronic subdural hematoma
ED
:   emergency department
GCS
:   Glasgow Coma Scale
MMA
:   middle meningeal artery
SDH
:   subdural hematoma

Chronic subdural hematoma (cSDH) is a common neurosurgical condition that is most prevalent among elderly patients and can be challenging to treat.1⇓⇓⇓⇓-6 Surgical evacuation using burr- hole irrigation or craniotomy is the preferred treatment option for patients with primary or recurrent subdural hematoma (SDH) who present with symptomatic brain compression.1⇓-3,7 However, these procedures are associated with recurrence rates as high as 28%, with nearly one-tenth of patients requiring re-operation within 30–60 days.3,7,8 Conservative management may be indicated in patients with small or asymptomatic SDHs, but many cSDHs may eventually require surgical evacuation.9⇓-11 Middle meningeal artery (MMA) embolization has recently been proposed as an alternative or adjunct to surgery for primary or recurrent cSDHs, and it has been associated with a decreased risk of treatment failure.3,9,12

Although several case series have outlined the potential benefits of MMA embolization during the past few years, no studies have used standard outcome measures to examine these findings. In this single-center study conducted during a 3-year study period, we compared the rates of emergency department (ED) use and readmission within 30 days for patients with cSDHs who underwent surgical evacuation with and without adjunctive MMA embolization.

## MATERIALS AND METHODS

The medical records of all patients who presented with a cSDH to a single quaternary center from January 1, 2018, through December 31, 2020, were retrospectively reviewed. The study was approved by the institutional review board at St. Joseph’s Hospital and Medical Center in Phoenix, Arizona, and informed consent was waived because of the low risk to patients. The endovascular treatment database was reviewed to abstract data on age, sex, Glasgow Coma Scale (GCS) scores at admission and discharge, comorbid conditions, and previous trauma. Patients in this cohort were assigned to 2 groups: surgical evacuation only or surgery combined with MMA embolization. The group with surgery only included patients who presented during the first 2 years of the study, whereas the surgery and MMA embolization group (the combined group) included patients who received the combined treatment during the entire 3-year study period. The medical records of patients in the surgery-only and combined groups were analyzed for ED visits and readmission within 30 days as primary outcomes.

Statistical analysis was performed using SPSS Statistics for Windows, Version 26.0 (IBM). Comparisons of ED visits and re-admissions within 30 days were performed using an independent samples *t* test. The level of significance was set at *P* < .05. Patient data and outcomes are expressed as mean (SD) or as frequency (percentage) or both.

## RESULTS

The total study cohort consisted of 137 patients, of whom 109 (80%) underwent surgery only and 28 (20%) underwent combined surgery and MMA embolization. Of the 28 patients in the combined group, 15 (54%) underwent planned elective MMA embolization and 13 (46%) underwent unplanned MMA embolization after surgical failure. No significant differences were found in age or sex between the 2 groups (Table 1). The mean age was 70 (SD, 12.8) years in the surgery-only group and 71 (SD, 10.2) years in the combined group. Most patients in both groups were men (81 of 109 [74%] in the surgery-only group and 21 of 28 [75%] in the combined group). Both groups of patients had a mean GCS score of 14 at both admission and discharge. No significant differences were found in comorbid conditions between the 2 groups. Comorbid conditions for the 2 groups are presented in Table 1.

View this table:
[Table 1:](http://www.ajnr.org/content/early/2022/07/21/ajnr.A7572/T1)

Table 1: 
Characteristics of 137 patients with cSDH who underwent surgery only versus surgery combined with MMA embolizationa

The mean size of the cSDHs at presentation was not significantly different in the surgery-only group (20.5 [SD, 6.9] mm) compared with the combined group (18.7 [SD, 4.5] mm; *P* = .16). The overall rate of ED visits within 30 days for the entire cohort was 24% (33 of 137 patients). This rate was significantly higher in patients who underwent surgery only (29%, 32 of 109) compared with those who underwent MMA embolization with surgery (7%, 2 of 28; *P* = .02) (Table 2).

View this table:
[Table 2:](http://www.ajnr.org/content/early/2022/07/21/ajnr.A7572/T2)

Table 2: 
ED visits and readmissions within 30 days for patients with cSDH who underwent surgery only versus surgery combined with MMA embolization

The overall rate of readmission within 30 days was 12% (17/137 patients). The readmission rate was higher in the surgery only group (15%, 16/109) compared with the combined group (4%, 1/28), but this difference could not be compared statistically because of the small number of ED presentations in each group and because of the small sample size of the combined group. Most readmissions (59%, 10/17) were due to reaccumulation or residual cSDH. Only 1 patient who underwent both surgery and MMA embolization was readmitted for reaccumulation or residual cSDH compared with 9 in the surgery-only group. In the 10 patients with reaccumulated/residual SDH, the mean cSDH diameter was 12.3 (SD, 2.2) mm.

## DISCUSSION

MMA embolization has emerged as a promising minimally invasive procedure to treat primary and refractory cSDH.3,8,9,12⇓⇓-15 Compared with surgery alone, it has been associated with fewer treatment failures and a reduced rate of hematoma reaccumulation in patients with cSDH.9,12 To examine this association, we compared the 30-day ED use and readmission rates among patients with surgery only with those among patients with surgery combined with MMA embolization during a 3-year study period at a single institution. We found significantly less ED use in the combined treatment group than in the surgery-only group (*P* = .02).

In this era of continually increasing health care costs, institutions are under pressure to identify ways to reduce expenditures while maintaining and improving the quality of care. Returns to the hospital within 30 days can be devastating for both patients and the health care system. Federal policies and insurance payors even penalize hospitals for unplanned readmissions. To our knowledge, this study is the first to demonstrate that MMA embolization for SDHs decreases the likelihood of ED visits and hospital readmissions. Our results indicate that the recurrence of cSDH is the most common reason for readmission. However, only 1 patient who underwent MMA embolization was readmitted for recurrence. These findings suggest that MMA embolization may reduce hospital readmissions and their associated cost to both the patient and the health care system. A previous analysis of the National Surgical Quality Improvement Program database similarly found that recurrent SDH was the most common reason for hospital readmission within 30 days for patients who had undergone cSDH evacuation.16

Previous estimates of readmission rates after treatment of cSDH are limited. The lack of a specific billing code for cSDH has hindered analyses of nationwide administrative databases. Lakomkin et al16 reported a 30-day readmission rate of 7.7% (45 of 585) in patients who underwent surgery for SDH. However, several limitations minimize the generalizability of this and other reported readmission rates. Their study was conducted using an administrative billing database, and cSDH was defined by International Classification of Disease, Ninth Revision ([https://www.cdc.gov/nchs/icd/icd9cm.htm](https://www.cdc.gov/nchs/icd/icd9cm.htm)) billing code 432.1 for “nontraumatic” SDH. This code has not been validated against institutional records to accurately detect cSDH. Furthermore, the National Surgical Quality Improvement Program does not have a specific code for burr- hole evacuation, which is the criterion standard surgical approach for evacuating cSDHs. In addition, their readmission rates were calculated without consideration of how many patients died before discharge, possibly leading to further underestimates.

Previous studies have demonstrated the safety and efficacy of MMA embolization for cSDH. A recent meta-analysis and systematic review by Srivatsan et al2 identified 3 two-arm studies (embolization versus conventional surgery) and 6 single-arm case series. The authors’ pooled analysis showed that hematoma recurrence was significantly less common among patients who underwent embolization (2.1%) than among those who underwent conventional surgical treatment (27.7%; *P *< .001). In our study, only 1 of 28 patients who underwent MMA embolization was readmitted for cSDH recurrence, a finding consistent with that of Srivatsan et al. In addition to the outstanding efficacy of MMA embolization for cSDHs, the procedure has been found to be relatively safe, largely because of the recent advent of newer endovascular techniques (eg, transradial access).17⇓⇓⇓⇓⇓⇓⇓-25

Limitations to the study include those inherent in all retrospective analyses. Additionally, the study included only 28 patients in the combined group, limiting its power, and the patients were treated at a single institution by multiple neurosurgeons who ultimately decided which patients underwent surgery with no standardized guidelines.

## CONCLUSIONS

Our results show that surgical evacuation combined with MMA embolization in patients with cSDH is associated with decreased ED visits within 30 days compared with surgery alone. Most readmissions after cSDH treatment were due to hematoma recurrences, which were markedly decreased in patients who underwent MMA embolization. These findings warrant the design of future prospective, large-cohort studies to substantiate our data and expand on this preliminary research.

## Acknowledgments

The authors thank the Neuroscience Publications staff at Barrow Neurological Institute for assistance with manuscript preparation. The authors acknowledge Candice L. Nguyen, BS, and Caleb Rutledge, MD, for their assistance.

## Footnotes

*   [Disclosure forms](http://www.ajnr.org/sites/default/files/additional-assets/Disclosures/August%202022/0143.pdf) provided by the authors are available with the full text and PDF of this article at [www.ajnr.org](http://www.ajnr.org).

## References

1.  1.Catapano JS, Nguyen CL, Wakim AA, et al. Middle meningeal artery embolization for chronic subdural hematoma. Front Neurol 2020;11:557233 doi:10.3389/fneur.2020.557233 pmid:33192990
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.3389/fneur.2020.557233&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=http://www.n&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

2.  2.Srivatsan A, Mohanty A, Nascimento FA, et al. Middle meningeal artery embolization for chronic subdural hematoma: meta-analysis and systematic review. World Neurosurg 2019;122:613–19 doi:10.1016/j.wneu.2018.11.167 pmid:30481628
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1016/j.wneu.2018.11.167&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=http://www.n&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

3.  3.Link TW, Boddu S, Paine SM, et al. Middle meningeal artery embolization for chronic subdural hematoma: a series of 60 cases. Neurosurgery 2019;85:801–07 doi:10.1093/neuros/nyy521 pmid:30418606
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1093/neuros/nyy521&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=30418606&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

4.  4.Balser D, Farooq S, Mehmood T, et al. Actual and projected incidence rates for chronic subdural hematomas in United States Veterans Administration and civilian populations. J Neurosurg 2015;123:1209–15 doi:10.3171/2014.9.JNS141550 pmid:25794342
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.3171/2014.9.JNS141550&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=http://www.n&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

5.  5.Foreman P, Goren O, Griessenauer CJ, et al. Middle meningeal artery embolization for chronic subdural hematomas: cautious optimism for a challenging pathology. World Neurosurg 2019;126:528–29 doi:10.1016/j.wneu.2019.03.160 pmid:30922909
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1016/j.wneu.2019.03.160&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=http://www.n&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

6.  6.Miranda LB, Braxton E, Hobbs J, et al. Chronic subdural hematoma in the elderly: not a benign disease. J Neurosurg 2011;114:72–76 doi:10.3171/2010.8.JNS10298 pmid:20868215
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.3171/2010.8.JNS10298&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=20868215&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 
    
    [Web of Science](http://www.ajnr.org/lookup/external-ref?access_num=000285669500018&link_type=ISI) 

7.  7.Mehta V, Harward SC, Sankey EW, et al. Evidence based diagnosis and management of chronic subdural hematoma: a review of the literature. J Clin Neurosci 2018;50:7–15 doi:10.1016/j.jocn.2018.01.050 pmid:29428263
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1016/j.jocn.2018.01.050&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=http://www.n&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

8.  8.Catapano JS, Ducruet AF, Nguyen CL, et al. Middle meningeal artery embolization for chronic subdural hematoma: an institutional technical analysis. J Neurointerv Surg 2021;13:657–60 doi:10.1136/neurintsurg-2020-016552 pmid:33077579
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEzLzcvNjU3IjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

9.  9.Catapano JS, Ducruet AF, Nguyen CL, et al. A propensity-adjusted comparison of middle meningeal artery embolization versus conventional therapy for chronic subdural hematomas. J Neurosurg 2021 Feb 26. [Epub ahead of print] doi:10.3171/2021.8.JNS211060 pmid:3636706
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.3171/2021.8.JNS211060&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=3636706&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

10. 10.Chan DY, Chan DT, Sun TF, et al. The use of atorvastatin for chronic subdural haematoma: a retrospective cohort comparison study. Br J Neurosurg 2017;31:72–77 doi:10.1080/02688697.2016.1208806 pmid:27881024
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1080/02688697.2016.1208806&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=27881024&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

11. 11.Jiang R, Zhao S, Wang R, et al. Safety and efficacy of atorvastatin for chronic subdural hematoma in Chinese patients: a randomized clinical trial. JAMA Neurol 2018;75:1338–46 doi:10.1001/jamaneurol.2018.2030 pmid:30073290
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1001/jamaneurol.2018.2030&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=30073290&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

12. 12.Ban SP, Hwang G, Byoun HS, et al. Middle meningeal artery embolization for chronic subdural hematoma. Radiology 2018;286:992–99 doi:10.1148/radiol.2017170053 pmid:29019449
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1148/radiol.2017170053&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=http://www.n&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

13. 13.Shapiro M, Walker M, Carroll KT, et al. Neuroanatomy of cranial dural vessels: implications for subdural hematoma embolization. J Neurointerv Surg 2021;13:471–77 doi:10.1136/neurintsurg-2020-016798 pmid:33632880
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEzLzUvNDcxIjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

14. 14.Rajah GB, Tso MK, Dossani R, et al. Transradial embolization of the left middle meningeal artery and accessory middle meningeal artery for treatment of subacute-chronic subdural hematoma. J Neurointerv Surg 2020;12:436 doi:10.1136/neurintsurg-2019-015493 pmid:31937602
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEyLzQvNDM2IjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

15. 15.Fiorella D, Hirsch JA, Arthur AS. Embolization of the middle meningeal artery for the treatment of chronic subdural hematoma: considerations for pragmatic trial design. J Neurointerv Surg 2021;13:295–97 doi:10.1136/neurintsurg-2021-017458 pmid:33674392
    
    [FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiRlVMTCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEzLzQvMjk1IjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

16. 16.Lakomkin N, Graffeo CS, Hadjipanayis CG. Specific causes and predictors of readmissions following acute and chronic subdural hematoma evacuation. J Clin Neurosci 2020;75:35–39 doi:10.1016/j.jocn.2020.03.042 pmid:32245599
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1016/j.jocn.2020.03.042&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=32245599&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

17. 17.Majmundar N, Wilkinson DA, Catapano JS, et al. Reaccessing an occluded radial artery for neuroendovascular procedures: techniques and complication avoidance. J Neurointerv Surg 2021;13:942–45 doi:10.1136/neurintsurg-2020-016758 pmid:33303697
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjk6IjEzLzEwLzk0MiI7czo0OiJhdG9tIjtzOjM4OiIvYWpuci9lYXJseS8yMDIyLzA3LzIxL2FqbnIuQTc1NzIuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) 

18. 18.Luther E, Chen SH, McCarthy DJ, et al. Implementation of a radial long sheath protocol for radial artery spasm reduces access site conversions in neurointerventions. J Neurointerv Surg 2021;13:547–51 doi:10.1136/neurintsurg-2020-016564 pmid:32843358
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEzLzYvNTQ3IjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

19. 19.Luther E, Burks J, Abecassis IJ, et al. Navigating radial artery loops in neurointerventions. J Neurointerv Surg 2020;13:1027–31 doi:10.1136/neurintsurg-2020-016856] pmid:33443135
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjEwOiIxMy8xMS8xMDI3IjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

20. 20.Kuhn AL, de Macedo Rodrigues K, Singh J, et al. Distal radial access in the anatomical snuffbox for neurointerventions: a feasibility, safety, and proof-of-concept study. J Neurointerv Surg 2020;12:798–801 doi:10.1136/neurintsurg-2019-015604 pmid:31915209
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEyLzgvNzk4IjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

21. 21.Khan NR, Peterson J, Dornbos Iii D, et al. Predicting the degree of difficulty of the trans-radial approach in cerebral angiography. J Neuronterv Surg 2021;13:552–58 doi:10.1136/neurintsurg-2020-016448 pmid:32792364
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1136/neurintsurg-2020-016448&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=32792364&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

22. 22.Dossani R, Waqas M, Tso MK, et al. Navigating a proximal loop in the radial artery and avoiding the recurrent radial artery. J Neurointerv Surg 2020;12:724 doi:10.1136/neurintsurg-2019-015712 pmid:32317370
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEyLzcvNzI0IjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

23. 23.Catapano JS, Fredrickson VL, Fujii T, et al. Complications of femoral versus radial access in neuroendovascular procedures with propensity adjustment. J Neurointerv Surg 2020;12:611–15 doi:10.1136/neurintsurg-2019-015569 pmid:31843764
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEyLzYvNjExIjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

24. 24.Catapano JS, Ducruet AF, Nguyen CL, et al. Propensity-adjusted comparative analysis of radial versus femoral access for neurointerventional treatments. Neurosurgery 2021;88:E505–09 doi:10.1093/neuros/nyab036 pmid:33582816
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1093/neuros/nyab036&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=http://www.n&link_type=MED&atom=%2Fajnr%2Fearly%2F2022%2F07%2F21%2Fajnr.A7572.atom) 

25. 25.Catapano JS, Ducruet AF, Koester SW, et al. Propensity-adjusted cost analysis of radial versus femoral access for neuroendovascular procedures. J Neurointerv Surg 2021;13:752–54 doi:10.1136/neurintsurg-2020-016728 pmid:33106321
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTE6Im5ldXJpbnRzdXJnIjtzOjU6InJlc2lkIjtzOjg6IjEzLzgvNzUyIjtzOjQ6ImF0b20iO3M6Mzg6Ii9ham5yL2Vhcmx5LzIwMjIvMDcvMjEvYWpuci5BNzU3Mi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

*   Received February 10, 2022.
*   Accepted after revision May 16, 2022.


*   © 2022 by American Journal of Neuroradiology