Neurosurgical forum Letters to the editor
Bow hunter’s syndrome To The Editor: It was with interest that we read the case report by Anaizi et al.1 on the use of dynamic mag netic resonance angiography (MRA) for the diagnosis of bow hunter’s syndrome (BHS) (Anaizi AN, Sayah A, Berkowitz F, et al: Bow hunter’s syndrome: the use of dynamic magnetic resonance angiography and intra operative fluorescent angiography. Case report. J Neurosurg Spine 20:71–74, January 2014). The authors very nicely demonstrate the technical feasibility of MRA to detect positional occlusion of the vertebral artery (VA), and propose MRA as an alternative to conventional digi tal subtraction angiography (DSA) for evaluating patients suspected to have BHS. Compared to DSA, MRA allows for a noninvasive means of imaging the vasculature and, as such, circumvents the procedural risks associated with DSA. It is important to note, however, that the time re quired for MRA image acquisition is markedly longer that what is required for DSA, and the potential implica tions warrant discussion. As mentioned by the authors, vertebrobasilar insuf ficiency in BHS most commonly results from positional compression of a dominant VA.2 The presented case is atypical in the fact that the affected vessel was nondomi nant, and the patient was probably able to maintain ade quate perfusion in the vertebrobasilar territories given the patency of the dominant vessel, despite prolonged head turn. In most circumstances, however, this will not be the case. An MRA study of the entire neck (as illustrated in this case example) typically requires 10–20 minutes to complete. Ischemia resulting from compression of a dom inant VA for this length of time will not be tolerated in the majority of cases, and would put patients at significant and unnecessary risk. Acquisition time could be signifi cantly reduced if the field is limited to a shorter segment
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of the neck, but even if limited to C1–2 (the most com monly affected level), 2–3 minutes would still be required for completion and may not be tolerated. With DSA, on the other hand, images can be acquired with a patient’s head maintained in the provocative position for as few as 5 seconds. Before undergoing MRA for suspected BHS, it is critical that patients are thoroughly evaluated in the office to ensure that the provocative position can be safely maintained for the required duration of the study. Jay D. Turner, M.D., Ph.D. Robert F. Spetzler, M.D. Barrow Neurological Institute St. Joseph’s Hospital and Medical Center Phoenix, AZ Disclosure The authors report no conflict of interest. References 1. Anaizi AN, Sayah A, Berkowitz F, McGrail K: Bow hunter’s syndrome: the use of dynamic magnetic resonance angiogra phy and intraoperative fluorescent angiography. Case report. J Neurosurg Spine 20:71–74, 2014 2. Cornelius JF, George B, N’dri Oka D, Spiriev T, Steiger HJ, Hänggi D: Bow-hunter’s syndrome caused by dynamic verte bral artery stenosis at the cranio-cervical junction—a manage ment algorithm based on a systematic review and a clinical series. Neurosurg Rev 35:127–135, 2012
Response: No response was received from the authors of the original article. Please include this information when citing this paper: published online January 3, 2014; DOI: 10.3171/2013.10.SPINE13939. ©AANS, 2014
J Neurosurg: Spine / Volume 20 / March 2014
Bow hunter’s syndrome To The Editor: It was with interest that we read the case report by Anaizi et al.1 on the use of dynamic mag netic resonance angiography (MRA) for the diagnosis of bow hunter’s syndrome (BHS) (Anaizi AN, Sayah A, Berkowitz F, et al: Bow hunter’s syndrome: the use of dynamic magnetic resonance angiography and intra operative fluorescent angiography. Case report. J Neurosurg Spine 20:71–74, January 2014). The authors very nicely demonstrate the technical feasibility of MRA to detect positional occlusion of the vertebral artery (VA), and propose MRA as an alternative to conventional digi tal subtraction angiography (DSA) for evaluating patients suspected to have BHS. Compared to DSA, MRA allows for a noninvasive means of imaging the vasculature and, as such, circumvents the procedural risks associated with DSA. It is important to note, however, that the time re quired for MRA image acquisition is markedly longer that what is required for DSA, and the potential implica tions warrant discussion. As mentioned by the authors, vertebrobasilar insuf ficiency in BHS most commonly results from positional compression of a dominant VA.2 The presented case is atypical in the fact that the affected vessel was nondomi nant, and the patient was probably able to maintain ade quate perfusion in the vertebrobasilar territories given the patency of the dominant vessel, despite prolonged head turn. In most circumstances, however, this will not be the case. An MRA study of the entire neck (as illustrated in this case example) typically requires 10–20 minutes to complete. Ischemia resulting from compression of a dom inant VA for this length of time will not be tolerated in the majority of cases, and would put patients at significant and unnecessary risk. Acquisition time could be signifi cantly reduced if the field is limited to a shorter segment
350
of the neck, but even if limited to C1–2 (the most com monly affected level), 2–3 minutes would still be required for completion and may not be tolerated. With DSA, on the other hand, images can be acquired with a patient’s head maintained in the provocative position for as few as 5 seconds. Before undergoing MRA for suspected BHS, it is critical that patients are thoroughly evaluated in the office to ensure that the provocative position can be safely maintained for the required duration of the study. Jay D. Turner, M.D., Ph.D. Robert F. Spetzler, M.D. Barrow Neurological Institute St. Joseph’s Hospital and Medical Center Phoenix, AZ Disclosure The authors report no conflict of interest. References 1. Anaizi AN, Sayah A, Berkowitz F, McGrail K: Bow hunter’s syndrome: the use of dynamic magnetic resonance angiogra phy and intraoperative fluorescent angiography. Case report. J Neurosurg Spine 20:71–74, 2014 2. Cornelius JF, George B, N’dri Oka D, Spiriev T, Steiger HJ, Hänggi D: Bow-hunter’s syndrome caused by dynamic verte bral artery stenosis at the cranio-cervical junction—a manage ment algorithm based on a systematic review and a clinical series. Neurosurg Rev 35:127–135, 2012
Response: No response was received from the authors of the original article. Please include this information when citing this paper: published online January 3, 2014; DOI: 10.3171/2013.10.SPINE13939. ©AANS, 2014
J Neurosurg: Spine / Volume 20 / March 2014
