CORRESPONDENCE
Fiducials on the spine would have to be placed on paramedian landmarks (eg, facet joints, transverse processes); given the confined space, the location of fiducials in the coronal rather than the sagittal plane, and potential issues of projection errors depending on how the iPhone is tilted, it is unlikely that the proposed augmented reality environment may add accuracy to our method. We estimate that it is possible to position a patient within a rotational tolerance of about 5°. Nevertheless, before the iPod touch can be used, the surgeon must ensure that the axial orientation of a given vertebra corresponds to the orientation that was used to measure the lateromedial angle, which in our report was referenced to the vertical axis and not, as stated by Chen et al, to the midplane of the vertebra. We agree with the authors that accounting for position-dependent changes of vertebral orientation may enhance the accuracy of our technique. Indeed, in our ongoing research, we have developed a solution wherein an inertia measurement unit (an accelerometer and gyroscope-equipped chip similar to those used in handheld devices) is referenced to each vertebra, and the inertia measurement unit is used for trajectory guidance in both the axial and sagittal planes.2,3 With our pilot study, we have shown that an iPod touch can be used as guidance to implant pedicle screws and that this may improve the surgeon's ability to correctly address the lateromedial angulation of a pedicle screw. We have described this method for open surgeries in which the surgeon can find the entry points according to easily recognizable anatomic landmarks (eg, facet joints, transverse processes, isthmus). This method is a simple adjunct to C-arm-guided instrumentation, but, as such, it cannot be expected to provide the visual feedback and features of 3-dimensional navigation. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Gregory F. Jost, MD* Meic H. Schmidt, MD, MBA‡ *Department of Neurosurgery University Hospital Basel Basel, Switzerland ‡Department of Neurosurgery Clinical Neurosciences Center University of Utah Salt Lake City, Utah 1. Jost GF, Bisson EF, Schmidt MH. iPod touch-assisted instrumentation of the spine: a technical report. Neurosurgery. 2013;73(2 suppl operative):233-237. 2. Jost GF, Walti J, Mariani L, et al. A Simple and Low-Cost Navigation Technique for Placement of S2-Ilium Screws without Intraoperative Imaging. J Neurol Surg A Cent Eur Neurosurg. 2014;75(suppl 2):58. 3. Walti J, Jost G, Catt P. A New Cost-Effective Approach to Pedicular Screw Placement. In: Linte C, Yaniv Z, Fallavollita P, Abolmaesumi P, Holmes D, III, eds. Augmented Environments for Computer-Assisted Interventions. Vol 8678: Springer International Publishing; 2014:90-97. 10.1227/NEU.0000000000000537
NEUROSURGERY
Fascicular Constrictions in Spontaneous Anterior Interosseous Nerve Palsy and Spontaneous Posterior Interosseous Nerve Palsy To the Editor: Pan et al1 reported a well-documented and interesting study on spontaneous peripheral nerve palsy with accompanying hourglass-like fascicular constrictions. We have several comments on this study based on our published English papers. Although our work was not cited in their paper, we previously reported 45 cases with fascicular deformities, including 35 cases with fascicular constrictions in spontaneous anterior interosseous nerve (AIN) palsy and spontaneous posterior interosseous nerve (PIN) palsy.2-4 In those papers, we first classified fascicular deformities without external compression into 3 categories, including fascicular constriction. Fascicular constriction, which was defined as “every instance of thinning in the fascicle regardless of its extent,” was further divided into 4 subgroups.2,3 With our classification, we found that (1) the age at onset of palsy was significantly younger in those with severe types of fascicular constriction compared with those with less severe types of fascicular constriction and (2) no significant difference was seen between the preoperative periods of the severe and less severe types of fascicular constriction.3 The first point suggests that the pathophysiology of fascicular constriction may be related to some aging-associated factor. This may support the results of the Pan et al study because younger patients could have more severe immune responses than older patients, resulting in a severe type of fascicular constriction. The second point suggests that less severe types of fascicular constriction may not change into severe types of fascicular constriction in a time-dependent manner, indicating that fascicular constriction might have a different pathophysiology compared with entrapment neuropathy. This may also support their conclusion that fascicular constriction may be immunological in origin. Several reports actually have shown that diagnostic imaging is a useful noninvasive tool for visualizing fascicular constriction. Nakamichi and Tachibana5 and Kodama et al6 visualized fascicular constrictions on ultrasonography in patients with spontaneous AIN and spontaneous PIN palsies and described the usefulness of ultrasound examination. A fascicular constriction in spontaneous PIN palsy has also been visualized with a magnetic resonance diffusion weighted imaging protocol.7 These 2 diagnostic imaging techniques will be useful in visualizing fascicular constrictions in the near future. In our series of patients with spontaneous AIN palsy, the results of interfascicular neurolysis were better in patients younger than 40 years of age than in those older than 40 years of age.4 In our series of patients with spontaneous PIN palsy, the results of interfascicular neurolysis were significantly better in patients younger than 50 years of age. Moreover, a preoperative period of less than 7 months was significantly associated with good results in patients younger than 50 years of age.2 We, therefore, believe that, for surgical intervention, not only the duration between the onset and surgery, but also the patient's age should be considered to achieve a better recovery.
VOLUME 75 | NUMBER 6 | DECEMBER 2014 | E737
Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited
CORRESPONDENCE
We agree that it is still unclear whether resection should be recommended for a patient with a severe fascicular constriction. However, similar to Nagano et al and Haussmann et al, we perform interfascicular neurolysis and do not resect severe fascicular constrictions. A representative case of spontaneous AIN palsy is presented in our paper with a photograph of a severe fascicular constriction (Figures 1Eand1G).3 This patient had a complete recovery after interfascicular neurolysis alone (patient 23).4 We hope that our experience along with their study will provide more insights into the pathophysiology and treatment of this type of palsy. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Kensuke Ochi, MD*‡ Yukio Horiuchi, MD‡ *Department of Orthopaedic Surgery School of Medicine, Keio University Tokyo, Japan ‡Department of Orthopaedic Surgery Kawasaki Municipal Kawasaki Hospital Kanagawa, Japan
1. Pan Y, Wang S, Zheng D, et al. Hourglass-like constrictions of peripheral nerve in the upper extremity: a clinical review and pathological study. Neurosurgery. 2014;75 (1):10-22. 2. Ochi K, Horiuchi Y, Tazaki K, et al. Surgical treatment of spontaneous posterior interosseous nerve palsy: a retrospective study of 50 cases. J Bone Joint Surg Br. 2011; 93(2):217-222. 3. Ochi K, Horiuchi Y, Tazaki K, Takayama S, Matsumura T. Fascicular constrictions in patients with spontaneous palsy of the anterior interosseous nerve and the posterior interosseous nerve. J Plast Surg Hand Surg. 2012;46(1):19-24. 4. Ochi K, Horiuchi Y, Tazaki K, Takayama S, Matsumura T. Surgical treatment of spontaneous anterior interosseous nerve palsy: a comparison between minimal incision surgery and wide incision surgery. J Plast Surg Hand Surg. 2013;47(3): 213-218. 5. Nakamichi K, Tachibana S. Ultrasonographic findings in isolated neuritis of the posterior interosseous nerve: comparison with normal findings. J Ultrasound Med. 2007;26(5):683-687. 6. Kodama A, Sunagawa T, Ochi M. Early treatment of anterior interosseous nerve palsy with hourglass-like fascicular constrictions by interfascicular neurolysis due to early diagnosis using ultrasonography: a case report. J Hand Surg Eur. 2014 [Epub ahead of print]. 7. Okinaga S. A case of spontaneous posterior interosseous nerve palsy whose lesion was visualized by diffusion weighted magnetic resonance imaging. Jpn J Elbow Soc. 2011;18(1):S71. 8. Nagano A. Spontaneous anterior interosseous nerve palsy. J Bone Joint Surg Br. 2003;85(3):313–318. 9. Haussmann P, Patel MR. Intraepineurial constriction of nerve fascicles in pronator syndrome and anterior interosseous nerve syndrome. Orthop Clin North Am. 1996; 27(2):339–344.
10.1227/NEU.0000000000000546
E738 | VOLUME 75 | NUMBER 6 | DECEMBER 2014
In Reply: Fascicular Constrictions in Spontaneous Anterior Interosseous Nerve Palsy and Spontaneous Posterior Interosseous Nerve Palsy We are honored that Dr Ochi and Dr Horiuchi were willing to share their experience and would like to thank them for adding their view on spontaneous peripheral nerve palsy with accompanying hourglass-like fascicular constrictions to our observations. As we mentioned in our report, an hourglass-like constriction of the nerve is a newly discovered neuropathy, the clinical manifestations have not been well defined, the origin remains unclear, and the treatment strategy has not yet been determined. Ochi et al made astute observations, and we agree with their point of view that there is no correlation between preoperative periods and the severity of fascicular constriction, that means that less severe types of fascicular constriction may not change into severe types of fascicular constriction in a time-dependent manner. However, relapse may occur in a few patients. Because the number of cases was small, we did not compare the relationship between age and immune response. We do not know whether younger patients could have more severe immune responses than older patients, resulting in a severe type of fascicular constriction. Based on our experience, we did not find the age of onset of palsy correlated with the severity of fascicular constriction, or the results of neurolysis. Some of our poor recovery cases had a long preoperative period, so we agree that early surgical intervention may be favorable for nerve recovery. The question is how to avoid unnecessary surgery. Case selection and timing of surgery are particularly important for such patients. As we had pointed out in our report, magnetic resonance neurography and high-resolution ultrasound studies may be useful tools to visualize the neuropathy status of affected nerves. If neurotmetic lesions are detected, an early surgical intervention should be encouraged to ensure full recovery. Otherwise, a conservative treatment should be implemented. As Ochi et al pointed out, the option of treatment for nerve constrictions at surgery is controversial. Since large series studies and controlled trials are still absent, it is difficult to draw any sound conclusions on the basis of retrospective study. Further study is required. Disclosure The author has no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Yongwei Pan, MD, PhD Department of Hand Surgery Beijing Jishuitan Hospital Beijing, China 10.1227/NEU.0000000000000548
www.neurosurgery-online.com
Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited
Fiducials on the spine would have to be placed on paramedian landmarks (eg, facet joints, transverse processes); given the confined space, the location of fiducials in the coronal rather than the sagittal plane, and potential issues of projection errors depending on how the iPhone is tilted, it is unlikely that the proposed augmented reality environment may add accuracy to our method. We estimate that it is possible to position a patient within a rotational tolerance of about 5°. Nevertheless, before the iPod touch can be used, the surgeon must ensure that the axial orientation of a given vertebra corresponds to the orientation that was used to measure the lateromedial angle, which in our report was referenced to the vertical axis and not, as stated by Chen et al, to the midplane of the vertebra. We agree with the authors that accounting for position-dependent changes of vertebral orientation may enhance the accuracy of our technique. Indeed, in our ongoing research, we have developed a solution wherein an inertia measurement unit (an accelerometer and gyroscope-equipped chip similar to those used in handheld devices) is referenced to each vertebra, and the inertia measurement unit is used for trajectory guidance in both the axial and sagittal planes.2,3 With our pilot study, we have shown that an iPod touch can be used as guidance to implant pedicle screws and that this may improve the surgeon's ability to correctly address the lateromedial angulation of a pedicle screw. We have described this method for open surgeries in which the surgeon can find the entry points according to easily recognizable anatomic landmarks (eg, facet joints, transverse processes, isthmus). This method is a simple adjunct to C-arm-guided instrumentation, but, as such, it cannot be expected to provide the visual feedback and features of 3-dimensional navigation. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Gregory F. Jost, MD* Meic H. Schmidt, MD, MBA‡ *Department of Neurosurgery University Hospital Basel Basel, Switzerland ‡Department of Neurosurgery Clinical Neurosciences Center University of Utah Salt Lake City, Utah 1. Jost GF, Bisson EF, Schmidt MH. iPod touch-assisted instrumentation of the spine: a technical report. Neurosurgery. 2013;73(2 suppl operative):233-237. 2. Jost GF, Walti J, Mariani L, et al. A Simple and Low-Cost Navigation Technique for Placement of S2-Ilium Screws without Intraoperative Imaging. J Neurol Surg A Cent Eur Neurosurg. 2014;75(suppl 2):58. 3. Walti J, Jost G, Catt P. A New Cost-Effective Approach to Pedicular Screw Placement. In: Linte C, Yaniv Z, Fallavollita P, Abolmaesumi P, Holmes D, III, eds. Augmented Environments for Computer-Assisted Interventions. Vol 8678: Springer International Publishing; 2014:90-97. 10.1227/NEU.0000000000000537
NEUROSURGERY
Fascicular Constrictions in Spontaneous Anterior Interosseous Nerve Palsy and Spontaneous Posterior Interosseous Nerve Palsy To the Editor: Pan et al1 reported a well-documented and interesting study on spontaneous peripheral nerve palsy with accompanying hourglass-like fascicular constrictions. We have several comments on this study based on our published English papers. Although our work was not cited in their paper, we previously reported 45 cases with fascicular deformities, including 35 cases with fascicular constrictions in spontaneous anterior interosseous nerve (AIN) palsy and spontaneous posterior interosseous nerve (PIN) palsy.2-4 In those papers, we first classified fascicular deformities without external compression into 3 categories, including fascicular constriction. Fascicular constriction, which was defined as “every instance of thinning in the fascicle regardless of its extent,” was further divided into 4 subgroups.2,3 With our classification, we found that (1) the age at onset of palsy was significantly younger in those with severe types of fascicular constriction compared with those with less severe types of fascicular constriction and (2) no significant difference was seen between the preoperative periods of the severe and less severe types of fascicular constriction.3 The first point suggests that the pathophysiology of fascicular constriction may be related to some aging-associated factor. This may support the results of the Pan et al study because younger patients could have more severe immune responses than older patients, resulting in a severe type of fascicular constriction. The second point suggests that less severe types of fascicular constriction may not change into severe types of fascicular constriction in a time-dependent manner, indicating that fascicular constriction might have a different pathophysiology compared with entrapment neuropathy. This may also support their conclusion that fascicular constriction may be immunological in origin. Several reports actually have shown that diagnostic imaging is a useful noninvasive tool for visualizing fascicular constriction. Nakamichi and Tachibana5 and Kodama et al6 visualized fascicular constrictions on ultrasonography in patients with spontaneous AIN and spontaneous PIN palsies and described the usefulness of ultrasound examination. A fascicular constriction in spontaneous PIN palsy has also been visualized with a magnetic resonance diffusion weighted imaging protocol.7 These 2 diagnostic imaging techniques will be useful in visualizing fascicular constrictions in the near future. In our series of patients with spontaneous AIN palsy, the results of interfascicular neurolysis were better in patients younger than 40 years of age than in those older than 40 years of age.4 In our series of patients with spontaneous PIN palsy, the results of interfascicular neurolysis were significantly better in patients younger than 50 years of age. Moreover, a preoperative period of less than 7 months was significantly associated with good results in patients younger than 50 years of age.2 We, therefore, believe that, for surgical intervention, not only the duration between the onset and surgery, but also the patient's age should be considered to achieve a better recovery.
VOLUME 75 | NUMBER 6 | DECEMBER 2014 | E737
Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited
CORRESPONDENCE
We agree that it is still unclear whether resection should be recommended for a patient with a severe fascicular constriction. However, similar to Nagano et al and Haussmann et al, we perform interfascicular neurolysis and do not resect severe fascicular constrictions. A representative case of spontaneous AIN palsy is presented in our paper with a photograph of a severe fascicular constriction (Figures 1Eand1G).3 This patient had a complete recovery after interfascicular neurolysis alone (patient 23).4 We hope that our experience along with their study will provide more insights into the pathophysiology and treatment of this type of palsy. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Kensuke Ochi, MD*‡ Yukio Horiuchi, MD‡ *Department of Orthopaedic Surgery School of Medicine, Keio University Tokyo, Japan ‡Department of Orthopaedic Surgery Kawasaki Municipal Kawasaki Hospital Kanagawa, Japan
1. Pan Y, Wang S, Zheng D, et al. Hourglass-like constrictions of peripheral nerve in the upper extremity: a clinical review and pathological study. Neurosurgery. 2014;75 (1):10-22. 2. Ochi K, Horiuchi Y, Tazaki K, et al. Surgical treatment of spontaneous posterior interosseous nerve palsy: a retrospective study of 50 cases. J Bone Joint Surg Br. 2011; 93(2):217-222. 3. Ochi K, Horiuchi Y, Tazaki K, Takayama S, Matsumura T. Fascicular constrictions in patients with spontaneous palsy of the anterior interosseous nerve and the posterior interosseous nerve. J Plast Surg Hand Surg. 2012;46(1):19-24. 4. Ochi K, Horiuchi Y, Tazaki K, Takayama S, Matsumura T. Surgical treatment of spontaneous anterior interosseous nerve palsy: a comparison between minimal incision surgery and wide incision surgery. J Plast Surg Hand Surg. 2013;47(3): 213-218. 5. Nakamichi K, Tachibana S. Ultrasonographic findings in isolated neuritis of the posterior interosseous nerve: comparison with normal findings. J Ultrasound Med. 2007;26(5):683-687. 6. Kodama A, Sunagawa T, Ochi M. Early treatment of anterior interosseous nerve palsy with hourglass-like fascicular constrictions by interfascicular neurolysis due to early diagnosis using ultrasonography: a case report. J Hand Surg Eur. 2014 [Epub ahead of print]. 7. Okinaga S. A case of spontaneous posterior interosseous nerve palsy whose lesion was visualized by diffusion weighted magnetic resonance imaging. Jpn J Elbow Soc. 2011;18(1):S71. 8. Nagano A. Spontaneous anterior interosseous nerve palsy. J Bone Joint Surg Br. 2003;85(3):313–318. 9. Haussmann P, Patel MR. Intraepineurial constriction of nerve fascicles in pronator syndrome and anterior interosseous nerve syndrome. Orthop Clin North Am. 1996; 27(2):339–344.
10.1227/NEU.0000000000000546
E738 | VOLUME 75 | NUMBER 6 | DECEMBER 2014
In Reply: Fascicular Constrictions in Spontaneous Anterior Interosseous Nerve Palsy and Spontaneous Posterior Interosseous Nerve Palsy We are honored that Dr Ochi and Dr Horiuchi were willing to share their experience and would like to thank them for adding their view on spontaneous peripheral nerve palsy with accompanying hourglass-like fascicular constrictions to our observations. As we mentioned in our report, an hourglass-like constriction of the nerve is a newly discovered neuropathy, the clinical manifestations have not been well defined, the origin remains unclear, and the treatment strategy has not yet been determined. Ochi et al made astute observations, and we agree with their point of view that there is no correlation between preoperative periods and the severity of fascicular constriction, that means that less severe types of fascicular constriction may not change into severe types of fascicular constriction in a time-dependent manner. However, relapse may occur in a few patients. Because the number of cases was small, we did not compare the relationship between age and immune response. We do not know whether younger patients could have more severe immune responses than older patients, resulting in a severe type of fascicular constriction. Based on our experience, we did not find the age of onset of palsy correlated with the severity of fascicular constriction, or the results of neurolysis. Some of our poor recovery cases had a long preoperative period, so we agree that early surgical intervention may be favorable for nerve recovery. The question is how to avoid unnecessary surgery. Case selection and timing of surgery are particularly important for such patients. As we had pointed out in our report, magnetic resonance neurography and high-resolution ultrasound studies may be useful tools to visualize the neuropathy status of affected nerves. If neurotmetic lesions are detected, an early surgical intervention should be encouraged to ensure full recovery. Otherwise, a conservative treatment should be implemented. As Ochi et al pointed out, the option of treatment for nerve constrictions at surgery is controversial. Since large series studies and controlled trials are still absent, it is difficult to draw any sound conclusions on the basis of retrospective study. Further study is required. Disclosure The author has no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Yongwei Pan, MD, PhD Department of Hand Surgery Beijing Jishuitan Hospital Beijing, China 10.1227/NEU.0000000000000548
www.neurosurgery-online.com
Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited
