- Email: [email protected]
Inter-capsular resection of cervical vagus nerve schwannoma
Journal of Clinical Neuroscience xxx (2018) xxx–xxx
Contents lists available at ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Technical note
Inter-capsular resection of cervical vagus nerve schwannoma Masafumi Kuroiwa a,b,⇑, Takehiro Yako a, Tetsuya Goto b, Kayoko Higuchi c, Kazuo Kitazawa a, Tetsuyoshi Horiuchi b, Shigeaki Kobayashi a a
Department of Neurosurgery, Aizawa Hospital, 2-5-1 Honjo, Matsumoto, Nagano 390-8510, Japan Department of Neurosurgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan c Department of Diagnosis and Treatment, Aizawa Hospital, 2-5-1 Honjo, Matsumoto, Nagano 390-8510, Japan b
a r t i c l e
i n f o
Article history: Received 19 March 2018 Accepted 4 June 2018 Available online xxxx Keywords: Cervical vagus nerve schwannoma Inter-capsular resection Vagus nerve
a b s t r a c t Cervical vagus nerve schwannoma is rare and its surgical procedure is controversial. The tumor is in general benign and slowly growing without causing symptoms, and therefore it should be advised to remove the tumor while preserving neural function. We operated on two patients with cervical vagus nerve schwannoma with the inter-capsular resection technique proposed by Hashimoto et al. without causing neurological deficits. It is the first time that the plane between the tumor-complex capsule layer (epineurium and perineurium) and true tumor capsule layer was histopathologically proved in this paper. The true tumor capsule layer contained no normal neural fibers, tumor tissues and neural sheath. The inter-capsular resection technique is a safe and reliable method for removing cervical vagus nerve schwannoma. Ó 2018 Elsevier Ltd. All rights reserved.
1. Introduction Cervical vagus nerve schwannoma originates from schwann cells of the peripheral nerve sheath of the vagus nerve in the neck. The schwannoma is rare and its surgical procedure is uncertain [1– 4]. Although the tumor usually presents as a slow-growing, painless, palpable mass in the neck, it has often been removed by sacrificing the nerve of origin without preserving neural function [4,5]. The patients suffer from hoarseness, dysphagia, coughing attacks in the postoperative courses. On the other hand, enucleation technique, that is, removing the tumor inside the tumor capsule, leaves behind the tumor capsule and tumor tissues adherent to it [3,6]. Therefore, this technique could cause tumor recurrence. In order to resolve these problems, Hashimoto et al. proposed ‘‘Inter-capsular resection” method as a technique for preserving neural function while achieving total removal of the tumor [7,8]. We operated on two patients with cervical vagus nerve schwannoma with the inter-capsular resection technique without causing neurological deficits and there have been no signs of recurrence. In the literature dealing with this technique, no reports have clearly demonstrated histopathologically the plane between the tumor
Abbreviation: EMA, epithelial membrane antigen.
⇑ Corresponding author at: Department of Neurosurgery, Aizawa Hospital, 2-5-1 Honjo, Matsumoto, Nagano 390-8510, Japan. E-mail address: [email protected] (M. Kuroiwa).
complex capsule layer, composed of the epineurium and perineurium, and the true tumor capsule layer. In this paper, we made a histopathological study of the layer of the surgical specimen, and evaluated the safety and the efficacy of the inter-capsular resection technique. 2. Case reports 2.1 Case 1 A 52-year old woman presented to our hospital, complaining of painless left cervical mass which was growing in size gradually for the preceding 5 years. The MR image revealed a fusiform and boundary clear 50-mm mass in the left side of the neck, which showed low signal intensity on T1-weighted image and high signal intensity on T2-weighted image with heterogeneous gadolinium enhancement. The mass displaced the common carotid artery and internal jugular vein anteriorly. Digital subtraction angiogram demonstrated that there was no vascularity in the tumor. The radiographic studies were considered compatible with cervical schwannoma. The patient requested surgical resection for preventing the mass from causing symptoms. Under general anesthesia, an electromyographic endotracheal tube was used to monitor intraoperative action potential of the vocal cord. The action potential of the soft palate and sternocleidomastoid muscle were also monitored. The tumor-complex capsule
https://doi.org/10.1016/j.jocn.2018.06.003 0967-5868/Ó 2018 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Kuroiwa M et al. Inter-capsular resection of cervical vagus nerve schwannoma. J Clin Neurosci (2018), https://doi.org/ 10.1016/j.jocn.2018.06.003
2
M. Kuroiwa et al. / Journal of Clinical Neuroscience xxx (2018) xxx–xxx
Tumor-complex capsule layer ( Epineurium + Perineurium )
True tumor capsule layer
Fig. 1. The operative view showing the dissection between the tumor-complex capsule layer, composed of epineurium and perineurium, and the true tumor capsule layer.
was found in the carotid sheath. As the sheath was longitudinally cut, the tumor-complex capsule appeared. Electric stimulation of the exposed surface of the tumor-complex did not produce motor responses. As the tumor-complex capsule layer was sharply cut longitudinally in parallel with the suspected course of the vagus nerve, the true tumor capsule layer appeared (Fig. 1). The layer just overlying the true tumor capsule was dissected to remove the tumor according to the inter-capsular resection technique [7,8]. The dissection of the plane between the tumor-complex capsule layer and the true tumor capsule layer was easily carried out. The tumor was totally removed. The vagus nerve found in the bottom of the removed tumor cavity was identified by nerve stimulation (Fig. 2). The tumor was considered to have originated from a fascicle of the vagus nerve because we observed that the vagus nerve was coursing in close proximity and partly continuous to the tumor, although the tumor-bearing nerve fascicle entering and existing the tumor were not confirmed in the present cases. The histopathological examination of the removed tumor tissue revealed spindle cells positive for S-100 protein. No tumor tissues and neural sheath in the true tumor capsule layer stained with S100 protein and epithelial membrane antigen (EMA), respectively (Fig. 3). These findings histopathologically confirmed that the dissection between the tumor complex capsule layer and true tumor capsule layer was performed. Postoperative MR images demonstrated total removal of the tumor. The patients left the hospital without neurological deficits. No recurrence has been detected in the follow up studies for 2 years.
2.2 Case 2
CCA
Vagus nerve
Fig. 2. The operative view demonstrating the vagus nerve coursing in the bottom of the tumor removal cavity; it was identified by nerve stimulator.
A 69-year old woman referred to our hospital with a painless left cervical tumor, which was detected by a routine medical examination. The mass was gradually growing over the preceding 2 years. A MR image taken on admission demonstrated a fusiform and boundary clear 30-mm mass in the left side of the neck, which showed low signal intensity on both T1- and T2-weighted images with heterogeneous gadolinium enhancement. A CT angiogram demonstrated the tumor displacing the common carotid artery anteriorly without contrast enhancement. Although asymptomatic, she elected to receive preventive surgery. Under general anesthesia, action potential monitoring was set up in the same way as in Case 1. The tumor-complex capsule was detected in the carotid sheath. The carotid sheath containing the tumor-complex capsule was cut, exposing its capsule. A cord
*
*
S-100 x 20
EMA x 20
Fig. 3. Case 1. Histopathological findings of the removed tumor tissue; (Left) showing spindle cells positive for S-100 protein, and (Left and Right) staining no cells in the true tumor capsule layer (*) with S-100 protein and EMA.
Please cite this article in press as: Kuroiwa M et al. Inter-capsular resection of cervical vagus nerve schwannoma. J Clin Neurosci (2018), https://doi.org/ 10.1016/j.jocn.2018.06.003
3
M. Kuroiwa et al. / Journal of Clinical Neuroscience xxx (2018) xxx–xxx
like nerve ran on the surface of the mass. When it was stimulated by a nerve stimulator, an action potential of the vocal cord was elicited, identifying that it was the vagus nerve. The tumor-complex capsule layer, supposedly composed of the epineurium and perineurium, was sharply cut longitudinally in parallel to the vagus nerve, exposing the underlying true tumor capsule. The dissection between the tumor-complex capsule layer and true tumor capsule layer was performed using the inter-capsular resection technique [7,8]. Although the tumor thinly connected to the vagus nerve, the mass was totally removed in one piece without compromising the main vagus trunk. The origin of the tumor was considered to be the vagus nerve through the intraoperative findings. The histopathological findings revealed spindle cells strongly positive for S-100 protein. No tumor tissues and neural sheath in
the true tumor capsule layer stained with S-100 and EMA, respectively (Fig. 4). Thus, the pathological findings confirmed that dissection was performed between the tumor-complex capsule layer and true tumor capsule layer. The postoperative MR image confirmed that the tumor was totally removed. She left the hospital without neurological deficits. No recurrence has been detected in the follow up studies for half a year. 3. Discussion Various techniques described for removing cervical vagus nerve schwannoma include tumor excision with neural sacrifice followed by primary anastomosis or neural graft interposition, tumor
*
*
EMA x 20
S-100 x 20
Fig. 4. Case 2. Histopathological findings of the removed tumor tissue; (Left) showing spindle cells strongly positive for S-100 protein, and (Left and Right) staining no cells in the true tumor capsule layer (*) with S-100 protein and EMA.
(A)
Epineurium
}
Perineurium
(B)
Tumor-complex capsule layer
Epineurium Perineurium
}
Tumor-complex capsule layer
True tumor capsule layer
True tumor capsule layer Schwannoma
Schwannoma
Normal nerve fiber
Normal nerve fiber
Axial view
Sagittal view
(C)
Epineurium Perineurium
}
Tumor-complex capsule layer
(D) Cutline
Tumor-complex capsule layer ( Epineurium + Perineurium )
Dissection plane True tumor capsule layer
True tumor capsule layer
Schwannoma
Cutline
Normal nerve fiber
Fig. 5. (A) Schematic drawing demonstrates a sagittal view of a cervical vagus nerve schwannoma and tumor-complex capsule layer containing the epineurium and perineurium. (B) Axial view of a cervical vagus nerve schwannoma and tumor-complex capsule. (C) Tumor-complex capsule layer is cut longitudinally to expose the true tumor capsule layer. (D) Tumor-complex capsule layer just overlying the true tumor capsule layer is dissected to remove the tumor together with the true tumor capsule layer.
Please cite this article in press as: Kuroiwa M et al. Inter-capsular resection of cervical vagus nerve schwannoma. J Clin Neurosci (2018), https://doi.org/ 10.1016/j.jocn.2018.06.003
4
M. Kuroiwa et al. / Journal of Clinical Neuroscience xxx (2018) xxx–xxx
removal with neural preservation [5], tumor enucleation between adjacent healthy nerve fibers when possible [3], tumor emptying with the tumor capsule preserved, even the ‘‘shelling out” of the tumor leaving gross tumor inside the capsule, and the nervesparing subcapular resection technique [1]. Review of the literature demonstrated a 4% incidence of malignancy in cervical schwannomas [5]. Valentino et al. argued that enucleation and partial excision may be inadvisable for oncological reasons despite the appeal of functional preservation. They prefer to completely excise the tumor. In the case with a functionally important nerve, therefore, grafting or primary end-to-end neurorrhaphy is advised when possible, which does not guarantee complete functional preservation postoperatively [5]. However, because cervical vagus nerve schwannoma is in general benign, every effort should be made to preserve neural function so that the quality of life will be unaffected. Hashimoto et al. proposed ‘‘inter-capsular resection” method to achieve total removal of the cervical schwannoma while preserving neural functions [7,8]. The basic steps of the method are as follows: The tumor-complex capsule layer, which is composed of the epineurium and perineurium, is cut longitudinally by sharp scalpel to expose the true tumor capsule layer. Then, the tumor-complex capsule layer just overlying the true tumor capsule layer is dissected to remove the tumor tissues together with the true tumor capsule layer, whereby the cutline of the tumor-complex capsule layer should be set at the opposite side of the normal nerve fascicle when it is recognized, or in the area where no motor response is obtained by nerve stimulation (Fig. 5A–D). In the present cases, monitoring of the action potential of the vocal cord using electromyographic endotracheal tube served useful for confirming the absence of vagus nerve fascicles intraoperatively. The inter-capsular resection technique is based on the anatomical principle that normal neural fibers are located around the schwannoma, and the fascicle, which is constituted from the nerve fibers and schwannoma, is encircled by the perineurium, and the fascicle is further encircled with other fascicles by the epineurium, so that the tumor is encircled by normal neural fascicular layer. If only the true tumor capsule is removed, it would be possible to preserve the normal neural fascicles. Although the removed true tumor capsule may include a few normal fascicles, the main fascicles would be preserved by monitoring of the action potential of vocal cord leading to functional preservation of the vagus nerve. With this technique, intraoperative confirmation of the absence of tumor in the removed cavity is not considered necessary. In the past years, enucleation techniques similar to the intercapsular resection without histological confirmation were
employed for preserving neural function [3,6]. But, this technique would leave behind the tumor capsule and tumor tissues in various degrees adherent to the capsule, which could cause tumor recurrence in the future. It should be stressed that the inter-capsular resection technique can achieve total removal of the tumor, preserving neural function, and this is supported in this paper as we histopathologically proved in the first time that the true tumor capsule layer of the surgical specimen was the layer devoid of tumor tissues with S100 protein and neural sheath with EMA staining. 4. Conclusion The true tumor capsule layer of the obtained specimen was proved histopathologically to contain no neural fibers, schwannoma tissues and neural sheath. The inter-capsule resection technique with neurophysiological monitoring is useful for preserving neural function while achieving total tumor removal. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. 5. Declarations of interest None. References [1] Battoo A, Sheikh Z, Thankappan K, Hicks W, Iyer S, Kuriakose M. Nerve-sparing subcapsular resection of head and neck schwannomas: technique evaluation and literature review. J Laryngology Otology 2013;127:685–90. [2] Desai KI. The surgical management of symptomatic benign peripheral nerve sheath tumors of the neck and extremities: an experience of 442 cases. Neurosurgery 2017;81:568–80. [3] de Araujo CEN, Ramos DM, Moyses RA, Durazzo MD, Cernea CR, Ferraz AR. Neck nerve trunks schwannomas: clinical features and postoperative neurologic outcome. Laryngoscope 2008;118:1579–82. [4] Andrea G. Cervical Vagus nerve schwannoma. Rev Reported Cases Our Reports 2016. Int J Neurol Brain Disord 3 (2):1–6. Int J Neurol Brain Disord 2016;3. [5] Valentino J, Boggess MA, Ellis JL, Hester T, Jones RO. Expected neurologic outcomes for surgical treatment of cervical neurilemomas. Laryngoscope 1998;108:1009–13. [6] Fujino DK, Shinohara DK, Aoki DM, Hashimoto DK, Omori DK, Myers Eugene N. MD International Editor: intracapsular enucleation of vagus nerve-originated tumors for preservation of neural function. Otolaryngology–Head Neck Surgery 2000;123:334–6. [7] Hashimoto S. Concept of inter-capsular resection for cervical schwannoma. J Jpn Soc Head Neck Surgery 2007;17:91–2. [8] Kishimoto S. Technique for excision of cervical schwannoma. Master techniques in otolaryngology—head and neck surgery, head and neck surgery Eugene N Myers: Wolter Kluwer; 2013. p. 81–91.
Please cite this article in press as: Kuroiwa M et al. Inter-capsular resection of cervical vagus nerve schwannoma. J Clin Neurosci (2018), https://doi.org/ 10.1016/j.jocn.2018.06.003
Contents lists available at ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Technical note
Inter-capsular resection of cervical vagus nerve schwannoma Masafumi Kuroiwa a,b,⇑, Takehiro Yako a, Tetsuya Goto b, Kayoko Higuchi c, Kazuo Kitazawa a, Tetsuyoshi Horiuchi b, Shigeaki Kobayashi a a
Department of Neurosurgery, Aizawa Hospital, 2-5-1 Honjo, Matsumoto, Nagano 390-8510, Japan Department of Neurosurgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan c Department of Diagnosis and Treatment, Aizawa Hospital, 2-5-1 Honjo, Matsumoto, Nagano 390-8510, Japan b
a r t i c l e
i n f o
Article history: Received 19 March 2018 Accepted 4 June 2018 Available online xxxx Keywords: Cervical vagus nerve schwannoma Inter-capsular resection Vagus nerve
a b s t r a c t Cervical vagus nerve schwannoma is rare and its surgical procedure is controversial. The tumor is in general benign and slowly growing without causing symptoms, and therefore it should be advised to remove the tumor while preserving neural function. We operated on two patients with cervical vagus nerve schwannoma with the inter-capsular resection technique proposed by Hashimoto et al. without causing neurological deficits. It is the first time that the plane between the tumor-complex capsule layer (epineurium and perineurium) and true tumor capsule layer was histopathologically proved in this paper. The true tumor capsule layer contained no normal neural fibers, tumor tissues and neural sheath. The inter-capsular resection technique is a safe and reliable method for removing cervical vagus nerve schwannoma. Ó 2018 Elsevier Ltd. All rights reserved.
1. Introduction Cervical vagus nerve schwannoma originates from schwann cells of the peripheral nerve sheath of the vagus nerve in the neck. The schwannoma is rare and its surgical procedure is uncertain [1– 4]. Although the tumor usually presents as a slow-growing, painless, palpable mass in the neck, it has often been removed by sacrificing the nerve of origin without preserving neural function [4,5]. The patients suffer from hoarseness, dysphagia, coughing attacks in the postoperative courses. On the other hand, enucleation technique, that is, removing the tumor inside the tumor capsule, leaves behind the tumor capsule and tumor tissues adherent to it [3,6]. Therefore, this technique could cause tumor recurrence. In order to resolve these problems, Hashimoto et al. proposed ‘‘Inter-capsular resection” method as a technique for preserving neural function while achieving total removal of the tumor [7,8]. We operated on two patients with cervical vagus nerve schwannoma with the inter-capsular resection technique without causing neurological deficits and there have been no signs of recurrence. In the literature dealing with this technique, no reports have clearly demonstrated histopathologically the plane between the tumor
Abbreviation: EMA, epithelial membrane antigen.
⇑ Corresponding author at: Department of Neurosurgery, Aizawa Hospital, 2-5-1 Honjo, Matsumoto, Nagano 390-8510, Japan. E-mail address: [email protected] (M. Kuroiwa).
complex capsule layer, composed of the epineurium and perineurium, and the true tumor capsule layer. In this paper, we made a histopathological study of the layer of the surgical specimen, and evaluated the safety and the efficacy of the inter-capsular resection technique. 2. Case reports 2.1 Case 1 A 52-year old woman presented to our hospital, complaining of painless left cervical mass which was growing in size gradually for the preceding 5 years. The MR image revealed a fusiform and boundary clear 50-mm mass in the left side of the neck, which showed low signal intensity on T1-weighted image and high signal intensity on T2-weighted image with heterogeneous gadolinium enhancement. The mass displaced the common carotid artery and internal jugular vein anteriorly. Digital subtraction angiogram demonstrated that there was no vascularity in the tumor. The radiographic studies were considered compatible with cervical schwannoma. The patient requested surgical resection for preventing the mass from causing symptoms. Under general anesthesia, an electromyographic endotracheal tube was used to monitor intraoperative action potential of the vocal cord. The action potential of the soft palate and sternocleidomastoid muscle were also monitored. The tumor-complex capsule
https://doi.org/10.1016/j.jocn.2018.06.003 0967-5868/Ó 2018 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Kuroiwa M et al. Inter-capsular resection of cervical vagus nerve schwannoma. J Clin Neurosci (2018), https://doi.org/ 10.1016/j.jocn.2018.06.003
2
M. Kuroiwa et al. / Journal of Clinical Neuroscience xxx (2018) xxx–xxx
Tumor-complex capsule layer ( Epineurium + Perineurium )
True tumor capsule layer
Fig. 1. The operative view showing the dissection between the tumor-complex capsule layer, composed of epineurium and perineurium, and the true tumor capsule layer.
was found in the carotid sheath. As the sheath was longitudinally cut, the tumor-complex capsule appeared. Electric stimulation of the exposed surface of the tumor-complex did not produce motor responses. As the tumor-complex capsule layer was sharply cut longitudinally in parallel with the suspected course of the vagus nerve, the true tumor capsule layer appeared (Fig. 1). The layer just overlying the true tumor capsule was dissected to remove the tumor according to the inter-capsular resection technique [7,8]. The dissection of the plane between the tumor-complex capsule layer and the true tumor capsule layer was easily carried out. The tumor was totally removed. The vagus nerve found in the bottom of the removed tumor cavity was identified by nerve stimulation (Fig. 2). The tumor was considered to have originated from a fascicle of the vagus nerve because we observed that the vagus nerve was coursing in close proximity and partly continuous to the tumor, although the tumor-bearing nerve fascicle entering and existing the tumor were not confirmed in the present cases. The histopathological examination of the removed tumor tissue revealed spindle cells positive for S-100 protein. No tumor tissues and neural sheath in the true tumor capsule layer stained with S100 protein and epithelial membrane antigen (EMA), respectively (Fig. 3). These findings histopathologically confirmed that the dissection between the tumor complex capsule layer and true tumor capsule layer was performed. Postoperative MR images demonstrated total removal of the tumor. The patients left the hospital without neurological deficits. No recurrence has been detected in the follow up studies for 2 years.
2.2 Case 2
CCA
Vagus nerve
Fig. 2. The operative view demonstrating the vagus nerve coursing in the bottom of the tumor removal cavity; it was identified by nerve stimulator.
A 69-year old woman referred to our hospital with a painless left cervical tumor, which was detected by a routine medical examination. The mass was gradually growing over the preceding 2 years. A MR image taken on admission demonstrated a fusiform and boundary clear 30-mm mass in the left side of the neck, which showed low signal intensity on both T1- and T2-weighted images with heterogeneous gadolinium enhancement. A CT angiogram demonstrated the tumor displacing the common carotid artery anteriorly without contrast enhancement. Although asymptomatic, she elected to receive preventive surgery. Under general anesthesia, action potential monitoring was set up in the same way as in Case 1. The tumor-complex capsule was detected in the carotid sheath. The carotid sheath containing the tumor-complex capsule was cut, exposing its capsule. A cord
*
*
S-100 x 20
EMA x 20
Fig. 3. Case 1. Histopathological findings of the removed tumor tissue; (Left) showing spindle cells positive for S-100 protein, and (Left and Right) staining no cells in the true tumor capsule layer (*) with S-100 protein and EMA.
Please cite this article in press as: Kuroiwa M et al. Inter-capsular resection of cervical vagus nerve schwannoma. J Clin Neurosci (2018), https://doi.org/ 10.1016/j.jocn.2018.06.003
3
M. Kuroiwa et al. / Journal of Clinical Neuroscience xxx (2018) xxx–xxx
like nerve ran on the surface of the mass. When it was stimulated by a nerve stimulator, an action potential of the vocal cord was elicited, identifying that it was the vagus nerve. The tumor-complex capsule layer, supposedly composed of the epineurium and perineurium, was sharply cut longitudinally in parallel to the vagus nerve, exposing the underlying true tumor capsule. The dissection between the tumor-complex capsule layer and true tumor capsule layer was performed using the inter-capsular resection technique [7,8]. Although the tumor thinly connected to the vagus nerve, the mass was totally removed in one piece without compromising the main vagus trunk. The origin of the tumor was considered to be the vagus nerve through the intraoperative findings. The histopathological findings revealed spindle cells strongly positive for S-100 protein. No tumor tissues and neural sheath in
the true tumor capsule layer stained with S-100 and EMA, respectively (Fig. 4). Thus, the pathological findings confirmed that dissection was performed between the tumor-complex capsule layer and true tumor capsule layer. The postoperative MR image confirmed that the tumor was totally removed. She left the hospital without neurological deficits. No recurrence has been detected in the follow up studies for half a year. 3. Discussion Various techniques described for removing cervical vagus nerve schwannoma include tumor excision with neural sacrifice followed by primary anastomosis or neural graft interposition, tumor
*
*
EMA x 20
S-100 x 20
Fig. 4. Case 2. Histopathological findings of the removed tumor tissue; (Left) showing spindle cells strongly positive for S-100 protein, and (Left and Right) staining no cells in the true tumor capsule layer (*) with S-100 protein and EMA.
(A)
Epineurium
}
Perineurium
(B)
Tumor-complex capsule layer
Epineurium Perineurium
}
Tumor-complex capsule layer
True tumor capsule layer
True tumor capsule layer Schwannoma
Schwannoma
Normal nerve fiber
Normal nerve fiber
Axial view
Sagittal view
(C)
Epineurium Perineurium
}
Tumor-complex capsule layer
(D) Cutline
Tumor-complex capsule layer ( Epineurium + Perineurium )
Dissection plane True tumor capsule layer
True tumor capsule layer
Schwannoma
Cutline
Normal nerve fiber
Fig. 5. (A) Schematic drawing demonstrates a sagittal view of a cervical vagus nerve schwannoma and tumor-complex capsule layer containing the epineurium and perineurium. (B) Axial view of a cervical vagus nerve schwannoma and tumor-complex capsule. (C) Tumor-complex capsule layer is cut longitudinally to expose the true tumor capsule layer. (D) Tumor-complex capsule layer just overlying the true tumor capsule layer is dissected to remove the tumor together with the true tumor capsule layer.
Please cite this article in press as: Kuroiwa M et al. Inter-capsular resection of cervical vagus nerve schwannoma. J Clin Neurosci (2018), https://doi.org/ 10.1016/j.jocn.2018.06.003
4
M. Kuroiwa et al. / Journal of Clinical Neuroscience xxx (2018) xxx–xxx
removal with neural preservation [5], tumor enucleation between adjacent healthy nerve fibers when possible [3], tumor emptying with the tumor capsule preserved, even the ‘‘shelling out” of the tumor leaving gross tumor inside the capsule, and the nervesparing subcapular resection technique [1]. Review of the literature demonstrated a 4% incidence of malignancy in cervical schwannomas [5]. Valentino et al. argued that enucleation and partial excision may be inadvisable for oncological reasons despite the appeal of functional preservation. They prefer to completely excise the tumor. In the case with a functionally important nerve, therefore, grafting or primary end-to-end neurorrhaphy is advised when possible, which does not guarantee complete functional preservation postoperatively [5]. However, because cervical vagus nerve schwannoma is in general benign, every effort should be made to preserve neural function so that the quality of life will be unaffected. Hashimoto et al. proposed ‘‘inter-capsular resection” method to achieve total removal of the cervical schwannoma while preserving neural functions [7,8]. The basic steps of the method are as follows: The tumor-complex capsule layer, which is composed of the epineurium and perineurium, is cut longitudinally by sharp scalpel to expose the true tumor capsule layer. Then, the tumor-complex capsule layer just overlying the true tumor capsule layer is dissected to remove the tumor tissues together with the true tumor capsule layer, whereby the cutline of the tumor-complex capsule layer should be set at the opposite side of the normal nerve fascicle when it is recognized, or in the area where no motor response is obtained by nerve stimulation (Fig. 5A–D). In the present cases, monitoring of the action potential of the vocal cord using electromyographic endotracheal tube served useful for confirming the absence of vagus nerve fascicles intraoperatively. The inter-capsular resection technique is based on the anatomical principle that normal neural fibers are located around the schwannoma, and the fascicle, which is constituted from the nerve fibers and schwannoma, is encircled by the perineurium, and the fascicle is further encircled with other fascicles by the epineurium, so that the tumor is encircled by normal neural fascicular layer. If only the true tumor capsule is removed, it would be possible to preserve the normal neural fascicles. Although the removed true tumor capsule may include a few normal fascicles, the main fascicles would be preserved by monitoring of the action potential of vocal cord leading to functional preservation of the vagus nerve. With this technique, intraoperative confirmation of the absence of tumor in the removed cavity is not considered necessary. In the past years, enucleation techniques similar to the intercapsular resection without histological confirmation were
employed for preserving neural function [3,6]. But, this technique would leave behind the tumor capsule and tumor tissues in various degrees adherent to the capsule, which could cause tumor recurrence in the future. It should be stressed that the inter-capsular resection technique can achieve total removal of the tumor, preserving neural function, and this is supported in this paper as we histopathologically proved in the first time that the true tumor capsule layer of the surgical specimen was the layer devoid of tumor tissues with S100 protein and neural sheath with EMA staining. 4. Conclusion The true tumor capsule layer of the obtained specimen was proved histopathologically to contain no neural fibers, schwannoma tissues and neural sheath. The inter-capsule resection technique with neurophysiological monitoring is useful for preserving neural function while achieving total tumor removal. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. 5. Declarations of interest None. References [1] Battoo A, Sheikh Z, Thankappan K, Hicks W, Iyer S, Kuriakose M. Nerve-sparing subcapsular resection of head and neck schwannomas: technique evaluation and literature review. J Laryngology Otology 2013;127:685–90. [2] Desai KI. The surgical management of symptomatic benign peripheral nerve sheath tumors of the neck and extremities: an experience of 442 cases. Neurosurgery 2017;81:568–80. [3] de Araujo CEN, Ramos DM, Moyses RA, Durazzo MD, Cernea CR, Ferraz AR. Neck nerve trunks schwannomas: clinical features and postoperative neurologic outcome. Laryngoscope 2008;118:1579–82. [4] Andrea G. Cervical Vagus nerve schwannoma. Rev Reported Cases Our Reports 2016. Int J Neurol Brain Disord 3 (2):1–6. Int J Neurol Brain Disord 2016;3. [5] Valentino J, Boggess MA, Ellis JL, Hester T, Jones RO. Expected neurologic outcomes for surgical treatment of cervical neurilemomas. Laryngoscope 1998;108:1009–13. [6] Fujino DK, Shinohara DK, Aoki DM, Hashimoto DK, Omori DK, Myers Eugene N. MD International Editor: intracapsular enucleation of vagus nerve-originated tumors for preservation of neural function. Otolaryngology–Head Neck Surgery 2000;123:334–6. [7] Hashimoto S. Concept of inter-capsular resection for cervical schwannoma. J Jpn Soc Head Neck Surgery 2007;17:91–2. [8] Kishimoto S. Technique for excision of cervical schwannoma. Master techniques in otolaryngology—head and neck surgery, head and neck surgery Eugene N Myers: Wolter Kluwer; 2013. p. 81–91.
Please cite this article in press as: Kuroiwa M et al. Inter-capsular resection of cervical vagus nerve schwannoma. J Clin Neurosci (2018), https://doi.org/ 10.1016/j.jocn.2018.06.003