- Email: [email protected]
Tongue base schwannoma: report, review, and unique surgical approach
Available online at www.sciencedirect.com
American Journal of Otolaryngology–Head and Neck Medicine and Surgery 29 (2008) 119 – 122 www.elsevier.com/locate/amjoto
Case reports
Tongue base schwannoma: report, review, and unique surgical approach Raja Sawhney, MD, MFAa, Michael A. Carron, MDb, Robert H. Mathog, MDb,4 a
b
Abstract
Wayne State University School of Medicine, Detroit, MI, USA Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine, Detroit, MI, USA
Base of tongue schwannomas are exceedingly rare and therefore often are not immediately included in the differential diagnosis and treatment of oropharyngeal tumors. After a thorough review of the English literature, we found only 6 previously reported cases of tongue base schwannomas. We are contributing a report of a 37-year-old woman with progressive dysphagia, dysarthria, and large tongue base schwannoma. Diagnosis was confirmed by imaging studies and biopsy followed by surgical excision designed to preserve nerve function. A number of surgical approaches have been described for tongue base schwannomas. Each has its own degree of postoperative morbidity. The use of a unilateral transcervical incision with blunt dissection was simple and quickly accomplished with protection of nearby nerves. Histologic identification of Antoni A and B areas along with strong and diffuse staining with S-100 stain pathologically completed the diagnosis of schwannoma. D 2008 Elsevier Inc. All rights reserved.
Schwannomas and neurofibromas comprise most peripheral nerve sheath tumors. Also known as neurilemomas, schwannomas are benign, slow-growing, epineurium-encapsulated neoplasms arising from Schwann cells that comprise the myelin sheaths surrounding peripheral nerves [1]. They may take origin from many different nerve types including cranial nerves, spinal nerves, and the sympathetic chain and may be found intra-, extra-, or transcranially. Portions of these tumors may undergo cystic degeneration when out growing their vascular supply [2]. Typically, they are solitary lesions with no genetic predisposition, although they may on occasion occur in multiples or be associated with diseases such neurofibromatosis 2 [3-5]. Schwannomas normally arise between the second and fifth decade of life and have no predilection to race or sex. Arising most often from sensory nerves, head and neck schwannomas can occur in all cranial nerves except the olfactory or optic nerves, which are simply extensions of white matter from the brain. These tumors are found with the highest frequency in the superior vestibular division of 4 Corresponding author. Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. Tel.: +1 313 577 0804; fax: +1 313 577 8555. 0196-0709/$ – see front matter D 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.amjoto.2006.08.003
the vestibulocochlear nerve, and more than 90% of intracranial schwannomas involve the eighth cranial nerve. In decreasing incidence, trigeminal, glossopharyngeal, and vagus nerves also form schwannomas both intra- and extracranially, although their exact incidence has not been determined. Schwannomas rarely form on the hypoglossal nerve [6] and because of the close proximity of the hypoglossal and glossopharyngeal nerves, it is difficult to determine the exact origin and incidence [7]. The tongue as a whole is the most common location for intraoral schwannomas to occur; however, it is quite rare to form schwannomas at the tongue base [1]. After an extensive review of the English literature, we could only find 6 reported cases of schwannoma occurring in the tongue base [7-12]. A similar review of articles in foreign languages had titles describing schwannomas in the base of the tongue, but neither their abstract nor the article itself was translated to English; hence, they were not included. In our patient population of the reported cases, 4 of 6 were female. The ages of the patients were 9, 9, 20, 24, 31, and 37. Surgical removal was the treatment of choice. Three patients were treated with transoral resection [8-10], 1 with a visor incision [7], and 2 approaches were not specifically described [11,12].
120
R. Sawhney et al. / American Journal of Otolaryngology–Head and Neck Medicine and Surgery 29 (2008) 119 – 122
1. Case report After extensive workup for a syncopal episode 3 months prior, a 37-year-old woman was referred to our otolaryngology office for evaluation of radiographic findings on magnetic resonance imaging (MRI) consistent with a floor of mouth mass. She was experiencing dysphagia, impaired tongue mobility, difficulty with articulation, and significant obstructive sleep apnea. A large, easily palpable submucosal mass was present at the right tongue base and was creating significant airway obstruction on flexible nasopharyngolaryngoscopy. A repeat MRI of the orbit, face, and neck with and without contrast revealed a hyperdense mass that involved the right tongue base and right vallecula. The wellcircumscribed mass measured 4.6 cm anterior to posterior, 3.3 cm in width, and 2.9 cm in depth. Although its location was predominantly situated at the right tongue base, it did cross the midline posteriorly. The patient was taken to the operating room the following day for biopsy of the mass as well as tracheotomy tube placement to control her airway. Frozen sections of the tongue mass were consistent with benign nerve sheath tumor, and immunostain S-100 was diffusely positive.
Fig. 2. Axial (A) and sagittal (B) T1-weighted images after gadolinium enhancement show a well-defined and homogeneously enhancing mass.
Two weeks later, the patient returned to the operating room for excision of the mass. An incision was made 3 fingerbreadths below the mandible and a subplatysmal skin flap elevated. The marginal mandibular nerve was identified and preserved. The right submandibular gland was then excised to allow exposure of the hypoglossal nerve. Next, the dissection was carried down to carotid bifurcation where the hypoglossal nerve was also observed crossing between the internal and external carotid arteries. With the nerve fully identified, a finger was placed within the patient’s mouth, and downward pressure to the tongue allowed the mass to be pushed below the mandible. Blunt dissection was used to remove the mass from the right tongue base without injury to the nerve. Postoperatively, the patient quickly recovered and within 3 weeks was tolerating a full diet with recovery of complete tongue function. Her airway was found to be open and was decannulated. Final pathologic examination was consistent with benign schwannoma with histopathologic findings of Antoni A and B areas, Verocay bodies, and positive staining for S-100. Fig. 1. Axial T1-weighted nonenhanced image shows a homogeneous welldefined soft tissue mass in the right posterior aspect of the floor of mouth between the genioglossus and hyoglossus muscles. The external carotid artery is displaced posteriorly.
2. Discussion Because schwannomas are quite rare in the oral cavity, they are often not immediately included in the differential
R. Sawhney et al. / American Journal of Otolaryngology–Head and Neck Medicine and Surgery 29 (2008) 119 – 122
Fig. 3. Disorganized Antoni B area with myxoid morphology (B) surrounded by Antoni A areas (A) (hematoxylin-eosin, 4).
diagnosis of oropharyngeal masses, causing delay in identification and treatment. Symptoms, however, can be significant as seen in our patient who experienced dysphagia and apnea severe enough to warrant tracheotomy. Patients with tongue base schwannomas may also complain of pain, swelling, fasciculations, loss of tongue control, and weight loss, although most are asymptomatic until the tumor reaches a significant size [6,7,9,11,15]. Radiologic imaging by computed tomography (CT) shows schwannomas to be well-circumscribed, homogeneous masses that enhance with contrast. The use of CT is less than ideal because it can be limited by bone artifact, especially when imaging smaller lesions. Its true value lies is in its ability to determine the amount adjacent bony damage that has occurred secondarily to schwannoma growth [16]. Magnetic resonance imaging is the imaging modality of choice for radiologic evaluation of schwannomas because of its increased tissue contrast and spatial resolution when compared to CT [9,14]. An MRI detects tumors that are too small or hindered by artifact to be viewed with CT. Most schwannomas appear hypointense or isointense relative to muscle on T1-weighted images. This can be seen in the homogenous-appearing right tongue mass as compared with the surrounding genioglossus and hyoglossus musculature (Fig. 1). With T2-weighted MRI, the tumor is usually homogenous in signal intensity, although cysts or degenerative changes within the schwannoma may be seen. With gadolinium enhancement T1-weighted images, schwannomas are hyperintense compared with surrounding tissue (Fig. 2A and B). Histologically, schwannomas are defined by a mixture of 2 growth patterns, namely Antoni A and B types. The former is highly cellular and composed of elongated Schwann cells, which in areas, exhibit a palisading orderliness to the nuclei. The Antoni B areas are composed of elongated Schwann cells but are arranged in a less dense myxoid morphology and is more disorganized than Antoni
121
A. Between these palisades are regions that are devoid of nuclei termed Verocay bodies [3,13], after the man who first described schwannomas (Figs. 3 and 4). The Antoni A and B areas are used strictly for pathologic determination of the tumor and have no clinical significance [17,18]. The protein S-100 is found on the supporting cells of both central and peripheral nervous systems, therefore allowing the use of immunohistochemical S-100 in identifying the Schwann cells of peripheral nerve sheath tumors [5]. Compared with schwannomas, which are composed entirely of Schwann cells, plexiform neurofibromas, the other major group of nerve sheath tumors, are not only composed of Schwann cells but other elements like large multipolar fibroblasts, reticulin, and a mucoid matrix. This diverse lineage of cells allows the use of a myriad of markers beyond S-100 stain for identification. Histologically, neurofibromas often contain a few inflammatory cells including mast cells that can be distinguished on microscopy. Neurofibromas are less cellular and more disorganized, lacking the organization of the Antoni A palisades found in their schwannoma counterparts. This disorganized composition has been described as having a bshredded carrotQ appearance [3]. Both types of nerve sheath tumors are typically benign in nature, although only plexiform neurofibromas can degenerate into malignant peripheral nerve sheath tumors [3]. In contrast to schwannomas, plexiform neurofibromas frequently occur in multiples and are not encapsulated. This along with the fact that they are less likely than schwannomas to undergo cystic degeneration may help in radiologically differentiating the 2 tumors. The edges of neurofibromas are often ill defined as the tumor infiltrates in between the individual fascicles of the nerve. This makes it extraordinarily difficult to salvage the involved nerve when removing the tumor. This intimate relationship between nerve and tumor also means that on microscopy, the individual axons of the involved nerve may be seen and help further delineate the tumor as a neurofibroma. Because recurrence of schwannomas usually occur only with incomplete excision, treatment is aimed at total surgical
Fig. 4. Verocay bodies (arrows) between palisading nuclei of Antoni A areas (hematoxylin-eosin, 10).
122
R. Sawhney et al. / American Journal of Otolaryngology–Head and Neck Medicine and Surgery 29 (2008) 119 – 122
removal of the tumor [5,7]. Different approaches for removal of tongue base schwannomas have been described in the literature, and each is associated with different degrees of exposure, infection rates, residual tongue function, and postoperative appearance. These involve either a transoral approach or inferior mandibular approach combined with a transhyoid or visor-type incision [7,19]. Employing a single unilateral, transcervical incision with exposure of the hypoglossal nerve for excision of a tongue base schwannoma is unique in the literature. Our approach avoided an anterior mandibulotomy, with mandibular swing, which threatens damaging the temporomandibular joint (TMJ) and neurovascular structures while rotating the mandible. This risk is outside of the inherent complications that dividing the mandible has, including malunion, nonunion, and osteomyelitis. Using a Visor approach would have required a very wide incision. Such a wide exposure was unnecessary for observation and excision of the tumor. In summary, using a transcervical approach allowed for minimal morbidity, provided adequate exposure, involved no bony cuts, and required minimal postoperative care. 3. Conclusion The low incidence of base of tongue schwannomas often leads to omission of the tumor on the differential diagnosis of oropharyngeal tumors. Although these tumors are often asymptomatic, given enough time, they can cause significant health issues as witnessed in our patient who suffered from significant dysphagia, dysarthria, and obstructive sleep apnea. In treatment, a number of approaches have been described to surgically approach tongue base schwannomas, each with its own operative time and degree of postoperative morbidity. The use of a unilateral transcervical incision with blunt dissection and excision of the base of tongue hypoglossal schwannoma was simple and quickly accomplished with protection of nearby nerves. This approach provides excellent exposure without the need of mandibulotomy, which has been associated with up to 13% chance of infection or fistula formation [7]. We feel that the implementation of a unilateral transcervical incision is an excellent choice when faced with a schwannoma or other masses located unilaterally at the base of the tongue.
References [1] Enzinger FM, Weiss SW. Soft tissue tumors. 3rd ed. St. Louis, MO7 Mosby-Year Book, Inc; 1995. p. 821 - 88. [2] Kim S, Han MH, Park SW, et al. Radiologic-pathologic correlation of unusual lingual masses: Part II: benign and malignant tumors. Korean J Radiol 2001;2(1):42 - 51. [3] Frosch M, Anthony D, De Girolami U. Central nervous system. In: Kumar V, editor. Robbins and Cotran: pathologic basis of disease. 7th ed. Elsevier. p. 1411 - 3 [Copyright]. [4] Chin L, Aldrich E, Di Parti E, et al. Central nervous system tumors. Townsend: sabiston textbook of surgery, 17th ed. Philadelphia, PA7 Elsevier; 2004. p. 2147. [5] Kao G. Neurilemoma. Retrieved December 2004 from eMedicine. com website http://www.emedicine.com/derm/topic285.htm#targetA, 2004. [6] Gomez Beldarrain M, Fernandez Canton G, Garcia-Monco JC. Hypoglossal schwannoma: an uncommon cause of twelfth-nerve palsy. Neurologia 2000;15(4):182 - 3. [7] de Bree R, Westervedl GJ, Smeele LE. Submandibular approach for excision of a large schwannoma in the base of the tongue. Eur Arch Otorhinolaryngol 2000;257:283 - 6. [8] Chadwick D. Neurilemoma of the tongue. J Laryngol Otol 1964; 78:959 - 62. [9] Spandow O, Fagerlund M, Bergmark L, et al. Clinical and histopathological features of a large parapharyngeal neurilemoma located at the base of tongue. ORL 1999;61:25 - 30. [10] Nakasato T, Kamada Y, Ehara S, et al. Multilobular neurilemoma of the tongue in a child. AJNR Am J Neuroradiol 2005;26(2):421 - 3. [11] Bassichis BA, McClay JE. Pedunculated neurilemoma of the tongue base. Otolaryngol Head Neck Surg 2004;130(5):639 - 41. [12] Dreher A, Gutmann R, Grever G. Extracranial schwannoma of the ENT region. Review of the literature with a case report of benign schwannoma of the base of the tongue. HNO 1997;45(6):468 - 71. [13] Pfeifle R, Baur DA, Paulino A, et al. Schwannoma of the tongue: report of 2 cases. J Oral Maxillofac Surg 2001;59:802 - 4. [14] Jager R., Rich P.. Extra-axial tumours: Grainger and Allison’s diagnostic radiology: a textbook of medical imaging. 4th ed. Orlando, FL7 Churchill Livingstone, Inc.; 2001. p. 2339. [15] Okura A, Shigemori M, Abe T, et al. Hemiatrophy of the tongue due to hypoglossal schwannoma shown by MRI. Neuroradiology 1994;36(3):239 - 40. [16] Jayaraman M, Schwannoma. Cranial nerve. Retrieved December 2004 from eMedicine.com website http://www.emedicine.com/radio/ topic7.htm. [17] Golfarb A. Pathologist. Department of Anatomical and Clinical Pathology, Southwest Memorial Hospital, Cortez, CO. Telephone Interview; May 2006. [18] Coons, Pathologist. Barrow Neurological Institute, Phoenix, AZ. Telephone Interview; May 2006. [19] Mevio E, Gorini E, Sbrocca M, et al. Schwannoma of the tongue: one case report. Rev Laryngol Otol Rhinol 2002;123(4):259 - 61.
American Journal of Otolaryngology–Head and Neck Medicine and Surgery 29 (2008) 119 – 122 www.elsevier.com/locate/amjoto
Case reports
Tongue base schwannoma: report, review, and unique surgical approach Raja Sawhney, MD, MFAa, Michael A. Carron, MDb, Robert H. Mathog, MDb,4 a
b
Abstract
Wayne State University School of Medicine, Detroit, MI, USA Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine, Detroit, MI, USA
Base of tongue schwannomas are exceedingly rare and therefore often are not immediately included in the differential diagnosis and treatment of oropharyngeal tumors. After a thorough review of the English literature, we found only 6 previously reported cases of tongue base schwannomas. We are contributing a report of a 37-year-old woman with progressive dysphagia, dysarthria, and large tongue base schwannoma. Diagnosis was confirmed by imaging studies and biopsy followed by surgical excision designed to preserve nerve function. A number of surgical approaches have been described for tongue base schwannomas. Each has its own degree of postoperative morbidity. The use of a unilateral transcervical incision with blunt dissection was simple and quickly accomplished with protection of nearby nerves. Histologic identification of Antoni A and B areas along with strong and diffuse staining with S-100 stain pathologically completed the diagnosis of schwannoma. D 2008 Elsevier Inc. All rights reserved.
Schwannomas and neurofibromas comprise most peripheral nerve sheath tumors. Also known as neurilemomas, schwannomas are benign, slow-growing, epineurium-encapsulated neoplasms arising from Schwann cells that comprise the myelin sheaths surrounding peripheral nerves [1]. They may take origin from many different nerve types including cranial nerves, spinal nerves, and the sympathetic chain and may be found intra-, extra-, or transcranially. Portions of these tumors may undergo cystic degeneration when out growing their vascular supply [2]. Typically, they are solitary lesions with no genetic predisposition, although they may on occasion occur in multiples or be associated with diseases such neurofibromatosis 2 [3-5]. Schwannomas normally arise between the second and fifth decade of life and have no predilection to race or sex. Arising most often from sensory nerves, head and neck schwannomas can occur in all cranial nerves except the olfactory or optic nerves, which are simply extensions of white matter from the brain. These tumors are found with the highest frequency in the superior vestibular division of 4 Corresponding author. Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. Tel.: +1 313 577 0804; fax: +1 313 577 8555. 0196-0709/$ – see front matter D 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.amjoto.2006.08.003
the vestibulocochlear nerve, and more than 90% of intracranial schwannomas involve the eighth cranial nerve. In decreasing incidence, trigeminal, glossopharyngeal, and vagus nerves also form schwannomas both intra- and extracranially, although their exact incidence has not been determined. Schwannomas rarely form on the hypoglossal nerve [6] and because of the close proximity of the hypoglossal and glossopharyngeal nerves, it is difficult to determine the exact origin and incidence [7]. The tongue as a whole is the most common location for intraoral schwannomas to occur; however, it is quite rare to form schwannomas at the tongue base [1]. After an extensive review of the English literature, we could only find 6 reported cases of schwannoma occurring in the tongue base [7-12]. A similar review of articles in foreign languages had titles describing schwannomas in the base of the tongue, but neither their abstract nor the article itself was translated to English; hence, they were not included. In our patient population of the reported cases, 4 of 6 were female. The ages of the patients were 9, 9, 20, 24, 31, and 37. Surgical removal was the treatment of choice. Three patients were treated with transoral resection [8-10], 1 with a visor incision [7], and 2 approaches were not specifically described [11,12].
120
R. Sawhney et al. / American Journal of Otolaryngology–Head and Neck Medicine and Surgery 29 (2008) 119 – 122
1. Case report After extensive workup for a syncopal episode 3 months prior, a 37-year-old woman was referred to our otolaryngology office for evaluation of radiographic findings on magnetic resonance imaging (MRI) consistent with a floor of mouth mass. She was experiencing dysphagia, impaired tongue mobility, difficulty with articulation, and significant obstructive sleep apnea. A large, easily palpable submucosal mass was present at the right tongue base and was creating significant airway obstruction on flexible nasopharyngolaryngoscopy. A repeat MRI of the orbit, face, and neck with and without contrast revealed a hyperdense mass that involved the right tongue base and right vallecula. The wellcircumscribed mass measured 4.6 cm anterior to posterior, 3.3 cm in width, and 2.9 cm in depth. Although its location was predominantly situated at the right tongue base, it did cross the midline posteriorly. The patient was taken to the operating room the following day for biopsy of the mass as well as tracheotomy tube placement to control her airway. Frozen sections of the tongue mass were consistent with benign nerve sheath tumor, and immunostain S-100 was diffusely positive.
Fig. 2. Axial (A) and sagittal (B) T1-weighted images after gadolinium enhancement show a well-defined and homogeneously enhancing mass.
Two weeks later, the patient returned to the operating room for excision of the mass. An incision was made 3 fingerbreadths below the mandible and a subplatysmal skin flap elevated. The marginal mandibular nerve was identified and preserved. The right submandibular gland was then excised to allow exposure of the hypoglossal nerve. Next, the dissection was carried down to carotid bifurcation where the hypoglossal nerve was also observed crossing between the internal and external carotid arteries. With the nerve fully identified, a finger was placed within the patient’s mouth, and downward pressure to the tongue allowed the mass to be pushed below the mandible. Blunt dissection was used to remove the mass from the right tongue base without injury to the nerve. Postoperatively, the patient quickly recovered and within 3 weeks was tolerating a full diet with recovery of complete tongue function. Her airway was found to be open and was decannulated. Final pathologic examination was consistent with benign schwannoma with histopathologic findings of Antoni A and B areas, Verocay bodies, and positive staining for S-100. Fig. 1. Axial T1-weighted nonenhanced image shows a homogeneous welldefined soft tissue mass in the right posterior aspect of the floor of mouth between the genioglossus and hyoglossus muscles. The external carotid artery is displaced posteriorly.
2. Discussion Because schwannomas are quite rare in the oral cavity, they are often not immediately included in the differential
R. Sawhney et al. / American Journal of Otolaryngology–Head and Neck Medicine and Surgery 29 (2008) 119 – 122
Fig. 3. Disorganized Antoni B area with myxoid morphology (B) surrounded by Antoni A areas (A) (hematoxylin-eosin, 4).
diagnosis of oropharyngeal masses, causing delay in identification and treatment. Symptoms, however, can be significant as seen in our patient who experienced dysphagia and apnea severe enough to warrant tracheotomy. Patients with tongue base schwannomas may also complain of pain, swelling, fasciculations, loss of tongue control, and weight loss, although most are asymptomatic until the tumor reaches a significant size [6,7,9,11,15]. Radiologic imaging by computed tomography (CT) shows schwannomas to be well-circumscribed, homogeneous masses that enhance with contrast. The use of CT is less than ideal because it can be limited by bone artifact, especially when imaging smaller lesions. Its true value lies is in its ability to determine the amount adjacent bony damage that has occurred secondarily to schwannoma growth [16]. Magnetic resonance imaging is the imaging modality of choice for radiologic evaluation of schwannomas because of its increased tissue contrast and spatial resolution when compared to CT [9,14]. An MRI detects tumors that are too small or hindered by artifact to be viewed with CT. Most schwannomas appear hypointense or isointense relative to muscle on T1-weighted images. This can be seen in the homogenous-appearing right tongue mass as compared with the surrounding genioglossus and hyoglossus musculature (Fig. 1). With T2-weighted MRI, the tumor is usually homogenous in signal intensity, although cysts or degenerative changes within the schwannoma may be seen. With gadolinium enhancement T1-weighted images, schwannomas are hyperintense compared with surrounding tissue (Fig. 2A and B). Histologically, schwannomas are defined by a mixture of 2 growth patterns, namely Antoni A and B types. The former is highly cellular and composed of elongated Schwann cells, which in areas, exhibit a palisading orderliness to the nuclei. The Antoni B areas are composed of elongated Schwann cells but are arranged in a less dense myxoid morphology and is more disorganized than Antoni
121
A. Between these palisades are regions that are devoid of nuclei termed Verocay bodies [3,13], after the man who first described schwannomas (Figs. 3 and 4). The Antoni A and B areas are used strictly for pathologic determination of the tumor and have no clinical significance [17,18]. The protein S-100 is found on the supporting cells of both central and peripheral nervous systems, therefore allowing the use of immunohistochemical S-100 in identifying the Schwann cells of peripheral nerve sheath tumors [5]. Compared with schwannomas, which are composed entirely of Schwann cells, plexiform neurofibromas, the other major group of nerve sheath tumors, are not only composed of Schwann cells but other elements like large multipolar fibroblasts, reticulin, and a mucoid matrix. This diverse lineage of cells allows the use of a myriad of markers beyond S-100 stain for identification. Histologically, neurofibromas often contain a few inflammatory cells including mast cells that can be distinguished on microscopy. Neurofibromas are less cellular and more disorganized, lacking the organization of the Antoni A palisades found in their schwannoma counterparts. This disorganized composition has been described as having a bshredded carrotQ appearance [3]. Both types of nerve sheath tumors are typically benign in nature, although only plexiform neurofibromas can degenerate into malignant peripheral nerve sheath tumors [3]. In contrast to schwannomas, plexiform neurofibromas frequently occur in multiples and are not encapsulated. This along with the fact that they are less likely than schwannomas to undergo cystic degeneration may help in radiologically differentiating the 2 tumors. The edges of neurofibromas are often ill defined as the tumor infiltrates in between the individual fascicles of the nerve. This makes it extraordinarily difficult to salvage the involved nerve when removing the tumor. This intimate relationship between nerve and tumor also means that on microscopy, the individual axons of the involved nerve may be seen and help further delineate the tumor as a neurofibroma. Because recurrence of schwannomas usually occur only with incomplete excision, treatment is aimed at total surgical
Fig. 4. Verocay bodies (arrows) between palisading nuclei of Antoni A areas (hematoxylin-eosin, 10).
122
R. Sawhney et al. / American Journal of Otolaryngology–Head and Neck Medicine and Surgery 29 (2008) 119 – 122
removal of the tumor [5,7]. Different approaches for removal of tongue base schwannomas have been described in the literature, and each is associated with different degrees of exposure, infection rates, residual tongue function, and postoperative appearance. These involve either a transoral approach or inferior mandibular approach combined with a transhyoid or visor-type incision [7,19]. Employing a single unilateral, transcervical incision with exposure of the hypoglossal nerve for excision of a tongue base schwannoma is unique in the literature. Our approach avoided an anterior mandibulotomy, with mandibular swing, which threatens damaging the temporomandibular joint (TMJ) and neurovascular structures while rotating the mandible. This risk is outside of the inherent complications that dividing the mandible has, including malunion, nonunion, and osteomyelitis. Using a Visor approach would have required a very wide incision. Such a wide exposure was unnecessary for observation and excision of the tumor. In summary, using a transcervical approach allowed for minimal morbidity, provided adequate exposure, involved no bony cuts, and required minimal postoperative care. 3. Conclusion The low incidence of base of tongue schwannomas often leads to omission of the tumor on the differential diagnosis of oropharyngeal tumors. Although these tumors are often asymptomatic, given enough time, they can cause significant health issues as witnessed in our patient who suffered from significant dysphagia, dysarthria, and obstructive sleep apnea. In treatment, a number of approaches have been described to surgically approach tongue base schwannomas, each with its own operative time and degree of postoperative morbidity. The use of a unilateral transcervical incision with blunt dissection and excision of the base of tongue hypoglossal schwannoma was simple and quickly accomplished with protection of nearby nerves. This approach provides excellent exposure without the need of mandibulotomy, which has been associated with up to 13% chance of infection or fistula formation [7]. We feel that the implementation of a unilateral transcervical incision is an excellent choice when faced with a schwannoma or other masses located unilaterally at the base of the tongue.
References [1] Enzinger FM, Weiss SW. Soft tissue tumors. 3rd ed. St. Louis, MO7 Mosby-Year Book, Inc; 1995. p. 821 - 88. [2] Kim S, Han MH, Park SW, et al. Radiologic-pathologic correlation of unusual lingual masses: Part II: benign and malignant tumors. Korean J Radiol 2001;2(1):42 - 51. [3] Frosch M, Anthony D, De Girolami U. Central nervous system. In: Kumar V, editor. Robbins and Cotran: pathologic basis of disease. 7th ed. Elsevier. p. 1411 - 3 [Copyright]. [4] Chin L, Aldrich E, Di Parti E, et al. Central nervous system tumors. Townsend: sabiston textbook of surgery, 17th ed. Philadelphia, PA7 Elsevier; 2004. p. 2147. [5] Kao G. Neurilemoma. Retrieved December 2004 from eMedicine. com website http://www.emedicine.com/derm/topic285.htm#targetA, 2004. [6] Gomez Beldarrain M, Fernandez Canton G, Garcia-Monco JC. Hypoglossal schwannoma: an uncommon cause of twelfth-nerve palsy. Neurologia 2000;15(4):182 - 3. [7] de Bree R, Westervedl GJ, Smeele LE. Submandibular approach for excision of a large schwannoma in the base of the tongue. Eur Arch Otorhinolaryngol 2000;257:283 - 6. [8] Chadwick D. Neurilemoma of the tongue. J Laryngol Otol 1964; 78:959 - 62. [9] Spandow O, Fagerlund M, Bergmark L, et al. Clinical and histopathological features of a large parapharyngeal neurilemoma located at the base of tongue. ORL 1999;61:25 - 30. [10] Nakasato T, Kamada Y, Ehara S, et al. Multilobular neurilemoma of the tongue in a child. AJNR Am J Neuroradiol 2005;26(2):421 - 3. [11] Bassichis BA, McClay JE. Pedunculated neurilemoma of the tongue base. Otolaryngol Head Neck Surg 2004;130(5):639 - 41. [12] Dreher A, Gutmann R, Grever G. Extracranial schwannoma of the ENT region. Review of the literature with a case report of benign schwannoma of the base of the tongue. HNO 1997;45(6):468 - 71. [13] Pfeifle R, Baur DA, Paulino A, et al. Schwannoma of the tongue: report of 2 cases. J Oral Maxillofac Surg 2001;59:802 - 4. [14] Jager R., Rich P.. Extra-axial tumours: Grainger and Allison’s diagnostic radiology: a textbook of medical imaging. 4th ed. Orlando, FL7 Churchill Livingstone, Inc.; 2001. p. 2339. [15] Okura A, Shigemori M, Abe T, et al. Hemiatrophy of the tongue due to hypoglossal schwannoma shown by MRI. Neuroradiology 1994;36(3):239 - 40. [16] Jayaraman M, Schwannoma. Cranial nerve. Retrieved December 2004 from eMedicine.com website http://www.emedicine.com/radio/ topic7.htm. [17] Golfarb A. Pathologist. Department of Anatomical and Clinical Pathology, Southwest Memorial Hospital, Cortez, CO. Telephone Interview; May 2006. [18] Coons, Pathologist. Barrow Neurological Institute, Phoenix, AZ. Telephone Interview; May 2006. [19] Mevio E, Gorini E, Sbrocca M, et al. Schwannoma of the tongue: one case report. Rev Laryngol Otol Rhinol 2002;123(4):259 - 61.