Re: Ogata A et al. Carotid artery stenting without post-stenting balloon dilatation. J NeuroIntervent Surg 2013; Dec 6: (Epub ahead of print)

We read with interest this article regarding carotid stenting (CAS) without post-stent balloon angioplasty. The authors believe that this method reduces the risk of embolic complications. They point out that every passage of a device across a carotid stenosis can generate emboli, and that the post-stent angioplasty is the most embologenic part of standard CAS techniques.

Our group and others (1,2) have shown that primary carotid stenting (PCS), in which a self-expanding stent alone, without the use of an embolic protection device or balloon angioplasty, can safely and effectively treat the majority of carotid stenoses. PCS is particularly effective in patients with moderate amounts of "soft" plaque and minimal plaque calcification. PCS minimizes the potential for embolus generation, results in less hemodynamic depression, is faster and cheaper and may be safer than standard techniques. Although re-stenosis rates are higher, these patients are rarely symptomatic and re-angioplasty of recurrent lesions with neointimal formation is usually straightforward.

Ogata et al are on the right path towards making CAS safer, but in appropriate patients, PCS may be an even better option.

1. Bussiere M, Pelz DM, Kalapos P et al. Results using a self- expanding stent alone in the treatment of severe, symptomatic carotid bifurcation stenosis. J Neurosurg 2008; 109: 454-460 2. Baldi S, Zander T, Rabellino M, Gonzalez G, Maynar M. Carotid artery stenting without angioplasty and carotid protection: a single center experience with up to 7 years follow-up. AJNR Am J Neuroradiol 2011; 32 (4): 759-763

David M. Pelz, MD, FRCPC Department of Medical Imaging

Stephen P. Lownie, MD, FRCSC Department of Clinical Neurological Sciences Division of Neurosurgery

Schulich School of Medicine and Dentistry Western University, London, Ontario Canada

Conflict of Interest:

None declared

Dear Dr. Tarr,

We read with interest the recent editorial by Fiorella et al., entitled "Should Neurointerventional fellowship training be suspended indefinitely?", detailing the potential hazards of neurointerventional (NI) overtraining in the United States (US).1 We face similar issues in Australia pertaining to our own current NI workforce demand and NI trainee employment outlook.

The landmass of Australia is twice the size of the European Union and almost as large as continental US (excluding Alaska and Hawaii).2 However the vast majority (>85%) of the 23 million population live within 30 miles of the coastline, and 98% live in major cities or regional areas where access to NI services are considered to be available.3

Currently, 30 practising neurointerventionalists service this population. Similar to the USA, most perform additional non-NI work such as diagnostic radiology, medical neurology, or open surgery. Given the core NI skillset of intracranial aneurysm and intra-arterial stroke treatment, we focused our analysis on these specific services.

Local vendor survey estimates reveal that approximately 1300 aneurysms are treated by endovascular techniques per annum in Australia. This has remained relatively stable over the last 3 years. This yields just over 40 aneurysms per practitioner per year, or almost 1 case every week.

Approximately 50, 000 people suffered a new or recurrent stroke in 2012 in Australia.4 Approximately 80% were ischemic strokes, and if all patients had presented to comprehensive stroke centers, optimistically 3% could have received intra-arterial therapy. 5 Extrapolating from this data, this could yield a theoretical 1200 cases per year, or under 1 case per practitioner per week. However, the recent simultaneous publication of three randomized clinical trials that failed to demonstrate benefit for intra-arterial therapy in acute ischemic stroke patients will undoubtedly slow this potential growth.6-9 Even if this potential growth came to part fruition, the fact that the current practicing neurointerventionalists in some centers spend up to 50% of their work hours performing non-NI work, means this demand could be easily met by the current pool of practitioners increasing their NI work load.

Despite this relatively low average case volume per operator, we continue to train additional NI fellows. Currently, 15 Australians are in various stages of NI training either in Australia or overseas. Thus our NI workforce is predicted to expand by up to 50% within four years.

The oversupply of US NI trainees may be potentially leading to the expansion of NI services at community hospitals, and to the shift of cerebral aneurysm treatment from high-volume to low-volume centers.10 This is a concerning trend for patient safety, as higher volume centers are known to have better outcomes. In Australia, NI services are largely provided by public health services that have significant budgetary constraints. Given the costs associated with an active NI program, there are pressures to contain rather than expand NI services, which are already fully or nearly fully staffed. This situation will persist until there are solid data provided to justify service expansion. For the primary author who is a current NI trainee, this translates into a bleak NI job market. Many NI trainees will likely find that there is no NI position available to them after a protracted and intense course of NI training.

The low case volume and concerns for quality of patient care also highlight the need to have credentialing for both fellowship programs and existing practitioners to ensure future NI trainees receive an adequate breadth of experience, and existing practitioners maintain safe and quality practice. The Royal Australian and New Zealand Society for Neuroradiology is already in the process of introducing a system of registration and credentialing of NI training programs and defining guidelines for ongoing credentialing of current and future practitioners. This may assist in regulating the imbalance that appears to currently exist.

We commend Dr. Fiorella and his colleagues for highlighting this important issue. As a global NI community, we have a responsibility to provide prospective NI trainees with a pragmatic view of the current and future NI workforce while protecting the quality of care for our patients. The current Australian reality is that there are too many NI trainees, and too few NI jobs.

1. Fiorella D, Hirsch JA, Woo HH, Rasmussen PA, Shazam Hussain M, Hui FK, et al. Should neurointerventional fellowship training be suspended indefinitely? Journal of neurointerventional surgery. 2012;4:315-318 2. Australian bureau of statistics: 1301.0 - year book australia, 2009-10. http://www.abs.gov.au/AUSSTATS/abs@.nsf/0/047D4BA4016F7A0BCA25773700169C25?opendocument. Accessed 25 Dec 2013. Last updated 4 Jun 2010. 3. Australian bureau of statistics: 3218.0 - regional population growth, australia, 2012. http://www.abs.gov.au/ausstats/abs@.nsf/Products/3218.0~2012~Main+Features~Main+Features?OpenDocument#PARALINK3. Accessed 25 Dec 2013. Last updated 30 Aug 2013. 4. Stroke foundation.2013 5. Cloft HJ, Rabinstein A, Lanzino G, Kallmes DF. Intra-arterial stroke therapy: An assessment of demand and available work force. AJNR. American journal of neuroradiology. 2009;30:453-458 6. Mocco J, O'Kelly C, Arthur A, Meyers PM, Hirsch JA, Woo HH, et al. Randomized clinical trials: The double edged sword. Journal of neurointerventional surgery. 2013;5:387-390 7. Broderick JP, Palesch YY, Demchuk AM, Yeatts SD, Khatri P, Hill MD, et al. Endovascular therapy after intravenous t-pa versus t-pa alone for stroke. The New England journal of medicine. 2013;368:893-903 8. Kidwell CS, Jahan R, Gornbein J, Alger JR, Nenov V, Ajani Z, et al. A trial of imaging selection and endovascular treatment for ischemic stroke. The New England journal of medicine. 2013;368:914-923 9. Ciccone A, Valvassori L, Nichelatti M, Sgoifo A, Ponzio M, Sterzi R, et al. Endovascular treatment for acute ischemic stroke. The New England journal of medicine. 2013;368:904-913 10. Brinjikji W, Lanzino G, Kallmes DF, Cloft HJ. Cerebral aneurysm treatment is beginning to shift to low volume centers. Journal of neurointerventional surgery. 2013

Conflict of Interest:

None declared

I have read, with great interest, the paper by Ellis et al. titled 'Angioarchitectural features associated with hemorrhagic presentation in pediatric cerebral arteriovenous malformations [1]. The authors retrospectively reviewed the angiographic features of 135 pediatric patients, mean age 10.1 years (range 0-19 years), who were referred to Hospital for Sick Children in Toronto, Canada and Boston Children's Hospital over a period of 11 years from 2000 to 2011. The most common presenting symptoms were hemorrhage (64%), seizure (13%), and focal neurological deficits or headache (13%). The authors sought to identify angiographic features associated with AVM rupture at presentation. Multivariate logistic regression analysis identified smaller size (P<0.01), exclusive deep venous drainage (P=0.02), and infratentorial location (P=0.01) to be independent predictors of hemorrhagic presentation.

Given the relatively little information available regarding the natural history of pediatric compared to adult AVMs, this study represents an important contribution to the pediatric AVM literature. As the authors note, there is an increased tendency to aggressively treat AVMs, especially ruptured ones, presenting in children compared to those in adults due to the higher exposure to hemorrhage risk and hemorrhage- related morbidity and mortality by children. Given what is currently known regarding the natural history of AVMs, which is largely derived from adult patients, this rationale is seems valid [2]. A Randomized Trial of Unruptured Brain AVMs (ARUBA) is a study of adult patients only [3]. It is unknown whether the results of ARUBA, which are pending imminent publication, will alter the management of unruptured pediatric AVMs.

It would be very interesting to know how the patients described in this study were treated and whether hemorrhagic presentation and AVM angioarchitectural features influenced the treatment strategies. Although the method by which AVM obliteration is achieved is biased, at times significantly, by the treating physician and institution, no single modality, including endovascular embolization, microsurgical resection, and radiosurgery, has emerged superior to its counterparts. For example, AVMs with smaller size and exclusive deep venous drainage, which typically implies deep location, are ideal radiosurgery targets [4-5]. However, in the setting of AVM rupture, some may advocate for microsurgical resection in order to rapidly eliminate future hemorrhage risk. Additionally, the authors did not distinguish infratentorial location by brainstem versus cerebellum. Recently, the UCSF cerebrovascular group described cerebellar AVMs as anatomically distinct lesions from cerebral AVMs with a higher propensity for hemorrhagic presentation [6]. Not surprisingly, cerebellar AVMs are significantly more conducive than brainstem AVMs to surgical resection therefore underscoring the importance of distinguishing the two locations.

In summary, the authors should be congratulated for identifying independent predictors of hemorrhagic presentation in a relatively large cohort of pediatric AVMs combined from two tertiary pediatric referral centers of international repute. Given the difficulty of obtaining prospective data regarding the natural history of pediatric AVMs, the cerebrovascular community will continue to rely on this study and others like it to guide decision-making for the management of these rare and complex vascular lesions.

References

1. Ellis, M.J., D. Armstrong, S. Vachhrajani, A.V. Kulkarni, P.B. Dirks, J.M. Drake, E.R. Smith, R.M. Scott, and D.B. Orbach, Angioarchitectural features associated with hemorrhagic presentation in pediatric cerebral arteriovenous malformations. J Neurointerv Surg, 2013. 5(3): p. 191-5. 2. Gross, B.A. and R. Du, Natural history of cerebral arteriovenous malformations: a meta-analysis. J Neurosurg, 2013. 118(2): p. 437-43. 3. Mohr, J.P., A.J. Moskowitz, C. Stapf, A. Hartmann, K. Lord, S.M. Marshall, H. Mast, E. Moquete, C.S. Moy, M. Parides, J. Pile-Spellman, R. Al-Shahi Salman, A. Weinberg, W.L. Young, A. Estevez, I. Kureshi, and J.L. Brisman, The ARUBA trial: current status, future hopes. Stroke, 2010. 41(8): p. e537-40. 4. Kano, H., D. Kondziolka, J.C. Flickinger, H.C. Yang, T.J. Flannery, N.R. Awan, A. Niranjan, J. Novotny, and L.D. Lunsford, Stereotactic radiosurgery for arteriovenous malformations, part 2: management of pediatric patients. J Neurosurg Pediatr, 2012. 9(1): p. 1-10. 5. Yen, C.P., S.J. Monteith, J.H. Nguyen, J. Rainey, D.J. Schlesinger, and J.P. Sheehan, Gamma Knife surgery for arteriovenous malformations in children. J Neurosurg Pediatr, 2010. 6(5): p. 426-34. 6. Rodriguez-Hernandez, A., H. Kim, T. Pourmohamad, W.L. Young, and M.T. Lawton, Cerebellar arteriovenous malformations: anatomic subtypes, surgical results, and increased predictive accuracy of the supplementary grading system. Neurosurgery, 2012. 71(6): p. 1111-24.

Conflict of Interest:

None declared

I am glad to see that my letter has piqued the interest of interventional neuroradiologists like Dr. Jagadeesan. I agree with him that no one should be running a fellowship that does not have the volume to expose trainees to enough cases so that they may obtain the necessary experience to practice safely. However, I think he has misunderstood my point. As I stated about the original piece, "I have no objection to the logic and opinions expressed, and actually have no opinion on the issue for or against these fellowships." My only request was for the authors of the original article to disclose the fact (as Dr. Jagadeesan has nicely done in his own letter) that they may have potential conflicts of interest by way of already completed and reaping the potential rewards of the very same fellowship training that they now advocate curtailing, so that the reader may use this information when making up his or her own mind. I have no interest in standing between interventional neuroradiologists and their patients (unless one is trying to run over the other, in which case I hope I could intervene). As far as taxi drivers, I would applaud their specialty if one disclosed that he gotten his driver's license from the black market instead of completing the required training and tests - indeed, that information might affect my decision to ride in his or another cab.

Conflict of Interest:

None declared