CORRESPONDENCE
Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Alessandro Della Puppa, MD* Renato Scienza, MD* Oriela Rustemi, MD‡ Giorgio Gioffré, MD‡ *Department of Neurosurgery Padua University Hospital Padua, Italy ‡Department of Neuroscience University Hospital of Padova Padua, Italy 1. Zaidi HA, Abla AA, Nakaji P, Chowdhry SA, Albuquerque FC, Spetzler RF. Indocyanine green angiography in the surgical management of cerebral arteriovenous malformations: lessons learned in 130 consecutive cases. Neurosurgery. 2014;10(suppl 2):246-251.
by difficulties related to operator inexperience with this modality, difficulty in interpreting data, particularly with higher flow lesions, and disruption of work flow during the resection, especially when using the intraoperative microscope. In addition, the Doppler probe can only be used when the draining vein is superficial and accessible to the probe and is not valuable for deep-seated lesions. One additional tool not mentioned by Della Puppa et al is the FLOW 800 imaging software (Carl Zeiss Surgical, Oberkochen, Germany), which provides color-coded overview maps of time to half maximal peak. This may provide a more efficient method for identifying flow via the primary draining vein using indocyanine green angiography, but this tool is again limited to superficially located draining veins.1 We believe that outside of the numerous adjunctive tools available to assist the surgeon during resection of these complex lesions, the most important element to achieving acceptable clinical outcomes is the surgeon's thorough understanding of the relevant surgical anatomy and experience with this complex surgical entity. Disclosure
10.1227/NEU.0000000000000531
In Reply: Can the Efficacy of Indocyanine Green Videoangiography in Cerebral Arteriovenous Malformations Surgery Be Further Improved? We thank Della Puppa et al for their generous and well-written comments, and we agree that a multimodal approach is necessary to achieve acceptable clinical outcomes when resecting a cerebral arteriovenous malformation (AVM). Nevertheless, it is important to be aware of the limits of each intraoperative diagnostic tool. For example, Della Puppa et al provide an excellent method for identifying an en passage vessel during resection of an AVM using temporary clip occlusion followed by close electrophysiological monitoring. Although this is one viable alternative, we would like to emphasize that it is only applicable in a very small subset of cases when the en passage vessel in question is feeding the primary motorsensory strip. Often, a redundant vascular supply to these functional regions can buffer any electrophysiological changes. Furthermore, this method is not particularly useful when en passage vessels are supplying the visual or language areas because these structures are not directly assessed during standard intraoperative electrophysiological monitoring. Surgeons should be highly cognizant of these limitations when interpreting the results of a temporary vessel occlusion test. The editorial also advocates the use of the Ultrasonic Flow Probe (Charbel Micro Flowprobe; Transonic Systems, Inc, Ithaca, New York) to assess the amount of residual flow through the draining vein and gain a sense of how much the nidus has been disconnected during the course of the resection. We agree with the authors that this is an important intraoperative tool that should be used in select cases, but, as alluded to in our original article, Doppler probes are often fraught
E734 | VOLUME 75 | NUMBER 6 | DECEMBER 2014
The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Hasan A. Zaidi, MD Robert F. Spetzler, MD Division of Neurological Surgery Barrow Neurological Institute St. Joseph's Hospital and Medical Center Phoenix, Arizona 1. Scerrati A, Della Pepa GM, Conforti G, et al. Indocyanine green video-angiography in neurosurgery: a glance beyond vascular applications. Clin Neurol Neurosurg. 2014;124C:106-113. 10.1227/NEU.0000000000000532
iPod Touch-Assisted Instrumentation of the Spine: Is It Accurate and Reliable? To the Editor: With great interest, we have read the article by Jost et al “iPod Touch-Assisted Instrumentation of the Spine: A Technical Report” in Operative Neurosurgery.1 The authors explored a new method to use an iPod touch application to measure and intraoperatively determine the angles that were used to assist with screw implantation. We agree that the accelerometer- or gyroscope-based applications with handheld devices or smartphones are simple and helpful to measure angles.2-4 However, we cannot replicate the author's method, and we doubt if this method is accurate and reliable. The authors measured the lateromedial angulation on preoperative images and reproduced in the operative field with the iPod touch. However, with the application they used (Angle, Smudge Apps,
www.neurosurgery-online.com
Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited
Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Alessandro Della Puppa, MD* Renato Scienza, MD* Oriela Rustemi, MD‡ Giorgio Gioffré, MD‡ *Department of Neurosurgery Padua University Hospital Padua, Italy ‡Department of Neuroscience University Hospital of Padova Padua, Italy 1. Zaidi HA, Abla AA, Nakaji P, Chowdhry SA, Albuquerque FC, Spetzler RF. Indocyanine green angiography in the surgical management of cerebral arteriovenous malformations: lessons learned in 130 consecutive cases. Neurosurgery. 2014;10(suppl 2):246-251.
by difficulties related to operator inexperience with this modality, difficulty in interpreting data, particularly with higher flow lesions, and disruption of work flow during the resection, especially when using the intraoperative microscope. In addition, the Doppler probe can only be used when the draining vein is superficial and accessible to the probe and is not valuable for deep-seated lesions. One additional tool not mentioned by Della Puppa et al is the FLOW 800 imaging software (Carl Zeiss Surgical, Oberkochen, Germany), which provides color-coded overview maps of time to half maximal peak. This may provide a more efficient method for identifying flow via the primary draining vein using indocyanine green angiography, but this tool is again limited to superficially located draining veins.1 We believe that outside of the numerous adjunctive tools available to assist the surgeon during resection of these complex lesions, the most important element to achieving acceptable clinical outcomes is the surgeon's thorough understanding of the relevant surgical anatomy and experience with this complex surgical entity. Disclosure
10.1227/NEU.0000000000000531
In Reply: Can the Efficacy of Indocyanine Green Videoangiography in Cerebral Arteriovenous Malformations Surgery Be Further Improved? We thank Della Puppa et al for their generous and well-written comments, and we agree that a multimodal approach is necessary to achieve acceptable clinical outcomes when resecting a cerebral arteriovenous malformation (AVM). Nevertheless, it is important to be aware of the limits of each intraoperative diagnostic tool. For example, Della Puppa et al provide an excellent method for identifying an en passage vessel during resection of an AVM using temporary clip occlusion followed by close electrophysiological monitoring. Although this is one viable alternative, we would like to emphasize that it is only applicable in a very small subset of cases when the en passage vessel in question is feeding the primary motorsensory strip. Often, a redundant vascular supply to these functional regions can buffer any electrophysiological changes. Furthermore, this method is not particularly useful when en passage vessels are supplying the visual or language areas because these structures are not directly assessed during standard intraoperative electrophysiological monitoring. Surgeons should be highly cognizant of these limitations when interpreting the results of a temporary vessel occlusion test. The editorial also advocates the use of the Ultrasonic Flow Probe (Charbel Micro Flowprobe; Transonic Systems, Inc, Ithaca, New York) to assess the amount of residual flow through the draining vein and gain a sense of how much the nidus has been disconnected during the course of the resection. We agree with the authors that this is an important intraoperative tool that should be used in select cases, but, as alluded to in our original article, Doppler probes are often fraught
E734 | VOLUME 75 | NUMBER 6 | DECEMBER 2014
The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Hasan A. Zaidi, MD Robert F. Spetzler, MD Division of Neurological Surgery Barrow Neurological Institute St. Joseph's Hospital and Medical Center Phoenix, Arizona 1. Scerrati A, Della Pepa GM, Conforti G, et al. Indocyanine green video-angiography in neurosurgery: a glance beyond vascular applications. Clin Neurol Neurosurg. 2014;124C:106-113. 10.1227/NEU.0000000000000532
iPod Touch-Assisted Instrumentation of the Spine: Is It Accurate and Reliable? To the Editor: With great interest, we have read the article by Jost et al “iPod Touch-Assisted Instrumentation of the Spine: A Technical Report” in Operative Neurosurgery.1 The authors explored a new method to use an iPod touch application to measure and intraoperatively determine the angles that were used to assist with screw implantation. We agree that the accelerometer- or gyroscope-based applications with handheld devices or smartphones are simple and helpful to measure angles.2-4 However, we cannot replicate the author's method, and we doubt if this method is accurate and reliable. The authors measured the lateromedial angulation on preoperative images and reproduced in the operative field with the iPod touch. However, with the application they used (Angle, Smudge Apps,
www.neurosurgery-online.com
Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited
