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Usefulness of transcervical approach for surgical treatment of hypoglossal schwannoma with paraspinal extension: case report
Surgical Neurology 65 (2006) 397 – 401 www.surgicalneurology-online.com
Technique
Usefulness of transcervical approach for surgical treatment of hypoglossal schwannoma with paraspinal extension: case report Kimitoshi Sato, MD, Satoru Shimizu, MDT, Hidehiro Oka, MD, Kuniaki Nakahara, MD, Satoshi Utsuki, MD, Kiyotaka Fujii, MD Department of Neurosurgery, Kitasato University School of Medicine, Kanagawa 228-8555, Japan Received 2 May 2005; accepted 3 August 2005
Abstract
Background: Usefulness of transcervical approach to hypoglossal schwannoma with paraspinal extension is described herein. Case Description: A 54-year-old woman presented with gradually worsening left hypoglossal nerve palsy. The findings were of a tumor lying in the left hypoglossal canal and paraspinal region and were consistent with hypoglossal schwannoma. Subtotal intracapsular removal of the tumor was performed via transcervical approach. The symptoms improved, and no additional symptoms were noted. Conclusion: The transcervical approach and intracapsular removal of the tumor under electrophysiological monitoring provided for successful minimally invasive surgery in this case of hypoglossal schwannoma. D 2006 Elsevier Inc. All rights reserved.
Keywords:
Schwannoma; Hypoglossal tumor; Transcervical approach
1. Introduction The surgical approach to a tumor in the craniovertebral junction depends on the location and accessibility of the tumor. We present herein a case of hypoglossal schwannoma lying in the hypoglossal canal and paraspinal region, which was treated surgically via transcervical approach [6]. The usefulness and limitations of this approach are discussed. 2. Case report A 54-year-old woman with no remarkable medical history began to experience difficulty in speech and stiffness of the tongue on the left side in July 2002, and these symptoms gradually worsened. She was referred to our institution 3 months after onset. On admission, she was alert, and neurological examination showed fasciculation and atrophy of the tongue on the left side, consistent with hypoglossal
T Corresponding author. Tel: +81 42 778 9337; fax: +81 42 778 7788. E-mail address: [email protected] (S. Shimizu). 0090-3019/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2005.08.020
nerve palsy. Computed tomography showed enlargement of the left hypoglossal canal. Magnetic resonance imaging showed a well-demarcated tumor (2 2 2.5 cm) lying in the hypoglossal canal and paraspinal region. The tumor was hypointense on T1-weighted images, hyperintense on T2-weighted images, and homogeneously enhanced with gadolinium (Fig. 1A-C). The radiological findings were consistent with hypoglossal schwannoma with extracranial extension. Surgery was planned, and feeding arteries of the tumor, that is, branches of the ascending pharyngeal artery and occipital artery, were embolized endovascularly with the use of detachable coils. A transcervical approach was chosen because the tumor was located mainly in the retropharyngeal space below the hypoglossal canal. Under general anesthesia with nasotracheal intubation, the patient was placed in supine position with the neck extended and fixed by applying tape to the forehead (Fig. 2). For intraoperative electrophysiological monitoring of the lower cranial nerves, electromyography needles were placed ipsilaterally in the tongue and sternocleidomastoid muscle (SCM). A curvilinear skin incision was made from the
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K. Sato et al. / Surgical Neurology 65 (2006) 397 – 401
Fig. 1. Gadolinium-enhanced magnetic resonance images, axial (A), coronal (B), and sagittal (C) views, showing a tumor lying in the hypoglossal canal (arrowhead) and paraspinal region (arrows).
Fig. 2. Photograph showing the neck-extended surgical position and skin incision. Nasotracheal intubation has been established.
Fig. 3. Operative view showing the anatomical relations (A). Caudal view showing that the tumor capsule has been opened (arrows), and the tumor is being removed intracapsularly toward the skull base (B). Posterior belly of the digastric muscle is retracted. ECA indicates external carotid artery; ICA, internal carotid artery; IJV, internal jugular vein.
K. Sato et al. / Surgical Neurology 65 (2006) 397 – 401
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stiffness and fasciculation of the tongue, disappeared 3 and 7 days after surgery, respectively. No additional signs related to the lower cranial nerves were observed. Pathologically, the tumor was diagnosed as a schwannoma. With the aid of postoperative magnetic resonance imaging, all but a part of the tumor in the hypoglossal canal was removed (Fig. 4). The patient was discharged and followed up for 1 year, with no symptoms. Magnetic resonance imaging 2 years after surgery showed no regrowth of the tumor. 3. Discussion
Fig. 4. Postoperative gadolinium-enhanced magnetic resonance image, sagittal view, showing the residual tumor lying in the hypoglossal canal region (arrow).
retroauricular region to the anterior margin of the SCM. The carotid sheath was exposed by blunt dissection between the SCM and omohyoid muscle, and a well-demarcated encapsulated tumor mass was found between the internal carotid artery and internal jugular vein (Fig. 3A). After we confirmed that contraction of the tongue and SCM could not be induced by electric stimulation of the anterior surface of the tumor capsule, the capsule was incised in the caudal to cephalad direction (Fig. 3B). The posterior belly of the digastric muscle was retracted superiorly to extend the surgical field. The tumor was fragile and was removed piece by piece along its axis as proximally as possible. No pathological vagal nerve reflex was induced during manipulation. The preoperative symptoms, that is, feeling of
Schwannoma arising from the hypoglossal nerve, a pure motor nerve, is rare. A tumor lying within the paraspinal space without intracranial extension, as in our case, is extremely rare. To our knowledge, only 11 other cases have been reported [2,5,11,15-17,20,21,27,28,34]. In general, a far lateral or transcondylar approach [19,24] may be applied to hypoglossal schwannoma lying mainly in the posterior fossa to reach the hypoglossal canal and foramen magnum. However, these approaches are not appropriate for tumors that lie strictly within the extracranial space. The transcervical approach that was applied in the present case makes it possible to reach both the lower part of the clivus and the inferior aspect of the petrous bone [6]. The surgical route, dissection between the SCM and omohyoid muscle, is similar to that in endarterectomy. With these approaches, obstacles to exposing the region just below the skull base and the high cervical region are the parotid gland, marginal mandibular branch of the facial nerve, posterior belly of the digastric muscle in the cephalad region, and the angle and ramus of the mandible in the anterior surgical field. Thus,
Fig. 5. Cadaver specimen showing anatomical relations between the lower cranial nerves and adjacent structures in the left neck. The parotid gland and mandible have been partially removed.
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K. Sato et al. / Surgical Neurology 65 (2006) 397 – 401
several modifications have been proposed to expose the high cervical carotid artery: a posterolateral approach by division of the SCM or mastoidectomy [9,23,26], an anterolateral approach by removal or osteotomy of the mandibular angle [1,7,14,18,19,22,31,32], temporary mandibular subluxation through the use of various wiring techniques [8,10,12,13], and a lateral approach by division of the posterior belly of the digastric muscle [6] or the styloid process and the muscles attached to it [25]. Although anterior subluxation of the mandible and mandibular osteotomy provide a wide surgical field, some complications may occur. Excessive subluxation may cause injury of the ipsilateral temporomandibular joint and lateral ligament, postoperative pain in the temporomandibular joint, and cerebral ischemic symptoms caused by compression of the contralateral carotid sheath between the mandibular angle or transverse vertebral process when the head is turned in the opposite direction [8]. Osteotomy carries a risk of injury to the mandibular marginal branch of the facial nerve and inferior alveolar nerve, and postoperative restriction of mastication and maxillomandibular fixation are needed [1,7,19,22,31]. Some simpler and less invasive techniques for reaching the high cervical region have been proposed: a combination of nasotracheal intubation and fixation of the mandible with tape to keep the mouth closed [30], extended skin incision [33], fixed neck extension [29], and superior retraction of the posterior belly of the digastric muscle [3]. In the present case, we established a surgical field using these techniques. Proximal to the surgical field, the hypoglossal nerve runs parallel to the vagus and accessory nerves between the internal carotid artery and internal jugular vein and turns medially toward the hypoglossal canal at a level proximal to the transverse process of the atlas. Therefore, the tumor was removed along its axis in the layer below superficial structures, such as the parotid gland, muscles attached to the mastoid and styloid processes (such as the posterior belly of the digastric muscle, styloglossus, and stylohyoid muscle), and the occipital artery below the atlas (Fig. 5). Most of the tumor inferior to the region where the tumor turned medially to reach the hypoglossal canal could be removed, but the part in the canal could not be reached because it was in a dead angle. However, the benign histology and completion of surgery with minimum invasiveness justified the surgical approach. Because tumor volume was reduced, stereotactic radiosurgery may now be suitable for the residual part. In surgery for hypoglossal schwannoma in the neck, injury to the hypoglossal nerve itself and adjacent lower cranial nerves has been reported, when total removal of the tumor including the capsule is performed [4,20]. Therefore, tumor removal within the capsule is important for protecting nerves from mechanical injury during surgical manipulation. Neurosurgeons who can perform carotid endarterectomy or a cervical procedure are familiar with the anatomy involved in the transcervical approach. Although the surgery in this case was accomplished by our neurosurgical team, it
may be a choice to perform the approach by multidisciplinary surgical team that includes otolaryngologists in more complicated cases. 4. Conclusion The transcervical approach was particularly useful in our case of hypoglossal schwannoma in terms of accessibility and minimal invasiveness. The combination of transcervical approach and intracapsular tumor removal under electrophysiological monitoring provided adequate results: subtotal removal, except for the part in the hypoglossal canal, and preservation of the function of the hypoglossal nerve, where the tumor originated, and adjacent lower cranial nerves.
References [1] Batzdorf U, Gregorius FK. Surgical exposure of the high cervical carotid artery: experimental study and review. Neurosurgery 1983; 13:657 - 61. [2] Brandenburg JH. Neurogenic tumors of the parapharyngeal space. Laryngoscope 1972;82:1292 - 305. [3] Cardoso ER, West M. Modified Mayo-Adams self-retaining retractor for carotid endarterectomy. Surg Neurol 1987;27:437 - 8. [4] Carrau RL, Myers EN, Johnson JT. Management of tumors arising in the parapharyngeal space. Laryngoscope 1990;100:583 - 9. [5] Chang KC, Leu YS. Hypoglossal schwannoma in the submandibular space. J Laryngol Otol 2002;116:63 - 4. [6] Crowell RM, Ogilvy CS, Ojemann RG. Extracranial carotid artery atherosclerosis; carotid endarterectomy. In: Wilkins RH, Rengachary SS, editors. Neurosurgery. 2nd ed. New York7 McGraw-Hill; 1996. p. 2103 - 15. [7] Dichtel WJ, Miller RH, Feliciano DV, Woodson GE, Hurt J. Lateral mandibulotomy: a technique of exposure for penetrating injuries of the internal carotid artery at the base of the skull. Laryngoscope 1984;94:1140 - 4. [8] Dossa C, Shepard AD, Wolford DG, Reddy DJ, Ernst CB. Distal internal carotid exposure: a simplified technique for temporary mandibular subluxation. J Vasc Surg 1990;12:319 - 25. [9] Fisch UP, Oldring DJ, Senning A. Surgical therapy of internal carotid artery lesions at the skull base and temporal bone. Otolaryngol Head 1980;88:548 - 54. [10] Fisher Jr DF, Clagett GP, Parker JI, Fry RE, Poor MR, Finn RA, Brink BE, Fry WJ. Mandibular subluxation for high carotid exposure. J Vasc Surg 1984;1:727 - 33. [11] Foer BD, Hermans R, Sciot R, Fossion E, Baert AL. Imaging study of the month hypoglossal schwannoma. Ann Otol Rhinol Laryngol 1995;104:490 - 2. [12] Frim DM, Padwa B, Buckley D, Crowell RM, Ogilvy CS. Mandibular subluxation as an adjunct to exposure of the distal internal carotid artery in endarterectomy surgery. Technical note. J Neurosurg 1995;83:926 - 8. [13] Fry RE, Fry WJ. Extracranial carotid artery injuries. Surgery 1980; 88:581 - 7. [14] Goldsmith MM, Postma DS, Jones FD. The surgical exposure of penetrating injuries to the carotid artery of the skull base. Otolaryngol Head Neck Surg 1986;95:278 - 84. [15] Hida O, Nakanoboh M, Isoda Y, Itoh Y, Kohno N, Kitahara S. Hypoglossal neurilemmoma in the submandibular region; case report. Jibirinsho 2000;93:307 - 10. [16] Hirano S, Shinohara S, Shoji K, Kojima H. Intracapsular enucleation of cervical neurilemmomas for preservation of neural function. Jibirinsho 1996;89:75 - 80.
K. Sato et al. / Surgical Neurology 65 (2006) 397 – 401 [17] Karpati RL, Loevner LA, Cunning DM, Yousem DM, Li S, Weber RS. Synchronous schwannomas of the hypoglossal nerve and cervical sympathetic chain. AJR Am J Roentgenol 1998;171:1505 - 7. [18] Krespi YP, Sisson GA. Transmandibular exposure of the skull base. Am J Surg 1984;148:534 - 8. [19] Kumins NH, Tober JC, Larsen PE, Smead WL. Vertical ramus osteotomy allows exposure of the distal internal carotid artery to the base of the skull. Ann Vasc Surg 2001;15:25 - 31. [20] Leonetti JP, Wachter B, Marzo SJ, Petruzzelli G. Extracranial lower cranial nerve sheath tumors. Otolaryngol Head Neck Surg 2001; 125:640 - 4. [21] McCurdy Jr JA, Hays LL, Johnson GK. Parapharyngeal neurilemmoma of the hypoglossal nerve. Laryngoscope 1976;86:724 - 7. [22] Nelson SR, Schow SR, Stein SM, Read LA, Talkington CM. Enhanced surgical exposure for the high extracranial internal carotid artery. Ann Vasc Surg 1992;6:467 - 72. [23] Pellegrini RV, Manzetti GW, DiMarco RF, Bekoe S, Arena SA, Marrangoni AG. The direct surgical management of lesions of the high internal carotid artery. J Cardiovasc Surg (Torino) 1984;25:29 - 35. [24] Rhoton Jr AL. The far-lateral approach and its transcondylar, supracondylar, and paracondylar extensions. Neurosurgery (Suppl) 2000; 47:195 - 209. [25] Sandmann W, Hennerici M, Aulich A, Kniemeyer H, Kremer KW. Progress in carotid artery surgery at the base of the skull. J Vasc Surg 1984;1:734 - 43. [26] Shaha A, Phillips T, Scalea T, Goluene P, McGinn J, Sealfamo S, Hoover E, Jaffe BM. Exposure of the internal carotid artery near the skull base: the posterolateral anatomic approach. J Vasc Surg 1988;8: 618 - 22. [27] Singh B, Shaha AR. Solitary malignant schwannoma invading the hypoglossal nerve. Ear Nose Throat J 1994;73:842 - 9. [28] Sutay S, Tekinsoy B, Ceryan K, Aksu Y. Submaxillary hypoglossal neurilemmoma. J Laryngol Otol 1998;107:953 - 4. [29] Takigawa T, Yanaka K, Yasuda M, Asakawa H, Matsumaru Y, Nose T. Head and neck extension-fixation with a head frame for exposure of the distal internal carotid artery in carotid endarterectomy: technical note. Neurol Med Chir (Tokyo) 2003;43:271 - 3. [30] Weiss MR, Smith HP, Patterson AK, Weiss RM. Patient positioning and nasal intubation for carotid endarterectomy. Neurosurgery 1986; 19:256 - 7. [31] Welsh P, Pradier R, Repetto R. Fibromuscular dysplasia of the distal cervical internal carotid artery. J Cardiovasc Surg (Torino) 1981;22: 321 - 6. [32] Wylie EJ, Ehrenfeld WK. Extracranial occlusive cerebrovascular disease. Diagnosis and management. Philadelphia7 WB Saunders; 1970. p. 192. [33] Yamamoto I, Ikeda A, Shimoda M, Oda S, Miyazaki Y, Ito K, Shinozuka S, Sato O. Surgical treatment of extracranial distal internal carotid artery dissecting aneurysm. Case report. Neurol Med Chir (Tokyo) 1992;32:21 - 7. [34] Yoshida K, Shigemi H, Kurono Y, Mogi G. Neurinoma involving hypoglossal nerve; a case report. Jibirinsho 1994;87:391 - 5.
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but this is of limited interest. It seems that incomplete resection was done to preserve the nerve, but nothing is clearly said about the mobility and the atrophy of the tongue after surgery. The 1-year follow-up is not sufficient to assess that partial resection is beneficial for the patient. If there is a recurrence needing reoperation after 2 or 3 years, I think it would have been better to entirely remove the tumor at the first surgery. Bernard George, MD Service de Neurochirurgie Hopital Lariboisiere 75745 Paris, France Using a case report that deals with a hypoglossal schwannoma, Sato et al have outlined their surgical strategy to approach this type of lesion. To illustrate this, the authors have provided illustrations that show both the intraoperative anatomy and a nice anatomical diagram correlating it all. Although these are rare lesions and not commonly seen by neurosurgeons, nevertheless, I think that the operating planning and discussion are excellent for those rare cases that might arise. I think that our readership will find this a useful anatomical approach for high transcervical lesions. James T. Goodrich, MD, PhD Department of Neurosurgery Montefiore Medical Center Bronx, NY 10467, USA
The authors have described the benefit of subtotal excision of a hypoglossal schwannoma to preserve nerve function. The tumor was predominantly in the upper cervical area with a small extension into the hypoglossal canal. They resected this through a purely transcervical approach, leaving behind the intracanalicular portion. This practice is not unique, and the surgeon’s goals and judgment are the primary determinants of the approach. They have illustrated their technique and rationale well. More often, the tumors are dumbbell-shaped, straddling the posterior fossa and the upper cervical region, when a more extensive approach is necessary, combining the posterior fossa along with the upper cervical exposure.
Commentary This is a case report on a 12th nerve neurinoma incompletely removed through a cervical approach. Obviously, hypoglossal schwannomas are extremely rare lesions,
Chandranath Sen, MD Department of Neurosurgery St. Luke’s–Roosevelt Hospital Center New York, NY 10019, USA
Technique
Usefulness of transcervical approach for surgical treatment of hypoglossal schwannoma with paraspinal extension: case report Kimitoshi Sato, MD, Satoru Shimizu, MDT, Hidehiro Oka, MD, Kuniaki Nakahara, MD, Satoshi Utsuki, MD, Kiyotaka Fujii, MD Department of Neurosurgery, Kitasato University School of Medicine, Kanagawa 228-8555, Japan Received 2 May 2005; accepted 3 August 2005
Abstract
Background: Usefulness of transcervical approach to hypoglossal schwannoma with paraspinal extension is described herein. Case Description: A 54-year-old woman presented with gradually worsening left hypoglossal nerve palsy. The findings were of a tumor lying in the left hypoglossal canal and paraspinal region and were consistent with hypoglossal schwannoma. Subtotal intracapsular removal of the tumor was performed via transcervical approach. The symptoms improved, and no additional symptoms were noted. Conclusion: The transcervical approach and intracapsular removal of the tumor under electrophysiological monitoring provided for successful minimally invasive surgery in this case of hypoglossal schwannoma. D 2006 Elsevier Inc. All rights reserved.
Keywords:
Schwannoma; Hypoglossal tumor; Transcervical approach
1. Introduction The surgical approach to a tumor in the craniovertebral junction depends on the location and accessibility of the tumor. We present herein a case of hypoglossal schwannoma lying in the hypoglossal canal and paraspinal region, which was treated surgically via transcervical approach [6]. The usefulness and limitations of this approach are discussed. 2. Case report A 54-year-old woman with no remarkable medical history began to experience difficulty in speech and stiffness of the tongue on the left side in July 2002, and these symptoms gradually worsened. She was referred to our institution 3 months after onset. On admission, she was alert, and neurological examination showed fasciculation and atrophy of the tongue on the left side, consistent with hypoglossal
T Corresponding author. Tel: +81 42 778 9337; fax: +81 42 778 7788. E-mail address: [email protected] (S. Shimizu). 0090-3019/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2005.08.020
nerve palsy. Computed tomography showed enlargement of the left hypoglossal canal. Magnetic resonance imaging showed a well-demarcated tumor (2 2 2.5 cm) lying in the hypoglossal canal and paraspinal region. The tumor was hypointense on T1-weighted images, hyperintense on T2-weighted images, and homogeneously enhanced with gadolinium (Fig. 1A-C). The radiological findings were consistent with hypoglossal schwannoma with extracranial extension. Surgery was planned, and feeding arteries of the tumor, that is, branches of the ascending pharyngeal artery and occipital artery, were embolized endovascularly with the use of detachable coils. A transcervical approach was chosen because the tumor was located mainly in the retropharyngeal space below the hypoglossal canal. Under general anesthesia with nasotracheal intubation, the patient was placed in supine position with the neck extended and fixed by applying tape to the forehead (Fig. 2). For intraoperative electrophysiological monitoring of the lower cranial nerves, electromyography needles were placed ipsilaterally in the tongue and sternocleidomastoid muscle (SCM). A curvilinear skin incision was made from the
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K. Sato et al. / Surgical Neurology 65 (2006) 397 – 401
Fig. 1. Gadolinium-enhanced magnetic resonance images, axial (A), coronal (B), and sagittal (C) views, showing a tumor lying in the hypoglossal canal (arrowhead) and paraspinal region (arrows).
Fig. 2. Photograph showing the neck-extended surgical position and skin incision. Nasotracheal intubation has been established.
Fig. 3. Operative view showing the anatomical relations (A). Caudal view showing that the tumor capsule has been opened (arrows), and the tumor is being removed intracapsularly toward the skull base (B). Posterior belly of the digastric muscle is retracted. ECA indicates external carotid artery; ICA, internal carotid artery; IJV, internal jugular vein.
K. Sato et al. / Surgical Neurology 65 (2006) 397 – 401
399
stiffness and fasciculation of the tongue, disappeared 3 and 7 days after surgery, respectively. No additional signs related to the lower cranial nerves were observed. Pathologically, the tumor was diagnosed as a schwannoma. With the aid of postoperative magnetic resonance imaging, all but a part of the tumor in the hypoglossal canal was removed (Fig. 4). The patient was discharged and followed up for 1 year, with no symptoms. Magnetic resonance imaging 2 years after surgery showed no regrowth of the tumor. 3. Discussion
Fig. 4. Postoperative gadolinium-enhanced magnetic resonance image, sagittal view, showing the residual tumor lying in the hypoglossal canal region (arrow).
retroauricular region to the anterior margin of the SCM. The carotid sheath was exposed by blunt dissection between the SCM and omohyoid muscle, and a well-demarcated encapsulated tumor mass was found between the internal carotid artery and internal jugular vein (Fig. 3A). After we confirmed that contraction of the tongue and SCM could not be induced by electric stimulation of the anterior surface of the tumor capsule, the capsule was incised in the caudal to cephalad direction (Fig. 3B). The posterior belly of the digastric muscle was retracted superiorly to extend the surgical field. The tumor was fragile and was removed piece by piece along its axis as proximally as possible. No pathological vagal nerve reflex was induced during manipulation. The preoperative symptoms, that is, feeling of
Schwannoma arising from the hypoglossal nerve, a pure motor nerve, is rare. A tumor lying within the paraspinal space without intracranial extension, as in our case, is extremely rare. To our knowledge, only 11 other cases have been reported [2,5,11,15-17,20,21,27,28,34]. In general, a far lateral or transcondylar approach [19,24] may be applied to hypoglossal schwannoma lying mainly in the posterior fossa to reach the hypoglossal canal and foramen magnum. However, these approaches are not appropriate for tumors that lie strictly within the extracranial space. The transcervical approach that was applied in the present case makes it possible to reach both the lower part of the clivus and the inferior aspect of the petrous bone [6]. The surgical route, dissection between the SCM and omohyoid muscle, is similar to that in endarterectomy. With these approaches, obstacles to exposing the region just below the skull base and the high cervical region are the parotid gland, marginal mandibular branch of the facial nerve, posterior belly of the digastric muscle in the cephalad region, and the angle and ramus of the mandible in the anterior surgical field. Thus,
Fig. 5. Cadaver specimen showing anatomical relations between the lower cranial nerves and adjacent structures in the left neck. The parotid gland and mandible have been partially removed.
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K. Sato et al. / Surgical Neurology 65 (2006) 397 – 401
several modifications have been proposed to expose the high cervical carotid artery: a posterolateral approach by division of the SCM or mastoidectomy [9,23,26], an anterolateral approach by removal or osteotomy of the mandibular angle [1,7,14,18,19,22,31,32], temporary mandibular subluxation through the use of various wiring techniques [8,10,12,13], and a lateral approach by division of the posterior belly of the digastric muscle [6] or the styloid process and the muscles attached to it [25]. Although anterior subluxation of the mandible and mandibular osteotomy provide a wide surgical field, some complications may occur. Excessive subluxation may cause injury of the ipsilateral temporomandibular joint and lateral ligament, postoperative pain in the temporomandibular joint, and cerebral ischemic symptoms caused by compression of the contralateral carotid sheath between the mandibular angle or transverse vertebral process when the head is turned in the opposite direction [8]. Osteotomy carries a risk of injury to the mandibular marginal branch of the facial nerve and inferior alveolar nerve, and postoperative restriction of mastication and maxillomandibular fixation are needed [1,7,19,22,31]. Some simpler and less invasive techniques for reaching the high cervical region have been proposed: a combination of nasotracheal intubation and fixation of the mandible with tape to keep the mouth closed [30], extended skin incision [33], fixed neck extension [29], and superior retraction of the posterior belly of the digastric muscle [3]. In the present case, we established a surgical field using these techniques. Proximal to the surgical field, the hypoglossal nerve runs parallel to the vagus and accessory nerves between the internal carotid artery and internal jugular vein and turns medially toward the hypoglossal canal at a level proximal to the transverse process of the atlas. Therefore, the tumor was removed along its axis in the layer below superficial structures, such as the parotid gland, muscles attached to the mastoid and styloid processes (such as the posterior belly of the digastric muscle, styloglossus, and stylohyoid muscle), and the occipital artery below the atlas (Fig. 5). Most of the tumor inferior to the region where the tumor turned medially to reach the hypoglossal canal could be removed, but the part in the canal could not be reached because it was in a dead angle. However, the benign histology and completion of surgery with minimum invasiveness justified the surgical approach. Because tumor volume was reduced, stereotactic radiosurgery may now be suitable for the residual part. In surgery for hypoglossal schwannoma in the neck, injury to the hypoglossal nerve itself and adjacent lower cranial nerves has been reported, when total removal of the tumor including the capsule is performed [4,20]. Therefore, tumor removal within the capsule is important for protecting nerves from mechanical injury during surgical manipulation. Neurosurgeons who can perform carotid endarterectomy or a cervical procedure are familiar with the anatomy involved in the transcervical approach. Although the surgery in this case was accomplished by our neurosurgical team, it
may be a choice to perform the approach by multidisciplinary surgical team that includes otolaryngologists in more complicated cases. 4. Conclusion The transcervical approach was particularly useful in our case of hypoglossal schwannoma in terms of accessibility and minimal invasiveness. The combination of transcervical approach and intracapsular tumor removal under electrophysiological monitoring provided adequate results: subtotal removal, except for the part in the hypoglossal canal, and preservation of the function of the hypoglossal nerve, where the tumor originated, and adjacent lower cranial nerves.
References [1] Batzdorf U, Gregorius FK. Surgical exposure of the high cervical carotid artery: experimental study and review. Neurosurgery 1983; 13:657 - 61. [2] Brandenburg JH. Neurogenic tumors of the parapharyngeal space. Laryngoscope 1972;82:1292 - 305. [3] Cardoso ER, West M. Modified Mayo-Adams self-retaining retractor for carotid endarterectomy. Surg Neurol 1987;27:437 - 8. [4] Carrau RL, Myers EN, Johnson JT. Management of tumors arising in the parapharyngeal space. Laryngoscope 1990;100:583 - 9. [5] Chang KC, Leu YS. Hypoglossal schwannoma in the submandibular space. J Laryngol Otol 2002;116:63 - 4. [6] Crowell RM, Ogilvy CS, Ojemann RG. Extracranial carotid artery atherosclerosis; carotid endarterectomy. In: Wilkins RH, Rengachary SS, editors. Neurosurgery. 2nd ed. New York7 McGraw-Hill; 1996. p. 2103 - 15. [7] Dichtel WJ, Miller RH, Feliciano DV, Woodson GE, Hurt J. Lateral mandibulotomy: a technique of exposure for penetrating injuries of the internal carotid artery at the base of the skull. Laryngoscope 1984;94:1140 - 4. [8] Dossa C, Shepard AD, Wolford DG, Reddy DJ, Ernst CB. Distal internal carotid exposure: a simplified technique for temporary mandibular subluxation. J Vasc Surg 1990;12:319 - 25. [9] Fisch UP, Oldring DJ, Senning A. Surgical therapy of internal carotid artery lesions at the skull base and temporal bone. Otolaryngol Head 1980;88:548 - 54. [10] Fisher Jr DF, Clagett GP, Parker JI, Fry RE, Poor MR, Finn RA, Brink BE, Fry WJ. Mandibular subluxation for high carotid exposure. J Vasc Surg 1984;1:727 - 33. [11] Foer BD, Hermans R, Sciot R, Fossion E, Baert AL. Imaging study of the month hypoglossal schwannoma. Ann Otol Rhinol Laryngol 1995;104:490 - 2. [12] Frim DM, Padwa B, Buckley D, Crowell RM, Ogilvy CS. Mandibular subluxation as an adjunct to exposure of the distal internal carotid artery in endarterectomy surgery. Technical note. J Neurosurg 1995;83:926 - 8. [13] Fry RE, Fry WJ. Extracranial carotid artery injuries. Surgery 1980; 88:581 - 7. [14] Goldsmith MM, Postma DS, Jones FD. The surgical exposure of penetrating injuries to the carotid artery of the skull base. Otolaryngol Head Neck Surg 1986;95:278 - 84. [15] Hida O, Nakanoboh M, Isoda Y, Itoh Y, Kohno N, Kitahara S. Hypoglossal neurilemmoma in the submandibular region; case report. Jibirinsho 2000;93:307 - 10. [16] Hirano S, Shinohara S, Shoji K, Kojima H. Intracapsular enucleation of cervical neurilemmomas for preservation of neural function. Jibirinsho 1996;89:75 - 80.
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but this is of limited interest. It seems that incomplete resection was done to preserve the nerve, but nothing is clearly said about the mobility and the atrophy of the tongue after surgery. The 1-year follow-up is not sufficient to assess that partial resection is beneficial for the patient. If there is a recurrence needing reoperation after 2 or 3 years, I think it would have been better to entirely remove the tumor at the first surgery. Bernard George, MD Service de Neurochirurgie Hopital Lariboisiere 75745 Paris, France Using a case report that deals with a hypoglossal schwannoma, Sato et al have outlined their surgical strategy to approach this type of lesion. To illustrate this, the authors have provided illustrations that show both the intraoperative anatomy and a nice anatomical diagram correlating it all. Although these are rare lesions and not commonly seen by neurosurgeons, nevertheless, I think that the operating planning and discussion are excellent for those rare cases that might arise. I think that our readership will find this a useful anatomical approach for high transcervical lesions. James T. Goodrich, MD, PhD Department of Neurosurgery Montefiore Medical Center Bronx, NY 10467, USA
The authors have described the benefit of subtotal excision of a hypoglossal schwannoma to preserve nerve function. The tumor was predominantly in the upper cervical area with a small extension into the hypoglossal canal. They resected this through a purely transcervical approach, leaving behind the intracanalicular portion. This practice is not unique, and the surgeon’s goals and judgment are the primary determinants of the approach. They have illustrated their technique and rationale well. More often, the tumors are dumbbell-shaped, straddling the posterior fossa and the upper cervical region, when a more extensive approach is necessary, combining the posterior fossa along with the upper cervical exposure.
Commentary This is a case report on a 12th nerve neurinoma incompletely removed through a cervical approach. Obviously, hypoglossal schwannomas are extremely rare lesions,
Chandranath Sen, MD Department of Neurosurgery St. Luke’s–Roosevelt Hospital Center New York, NY 10019, USA