|Year : 2015 | Volume
| Issue : 1 | Page : 46-48
Parapharyngeal space schwannoma of hypoglossal nerve
Surya Kanta Pradhan1, Sanjeev Gupta1, Manas R Baisakh2
1 Department of ENT - Head and Neck Surgery, Apollo Hospitals, Bhubaneswar, Odisha, India
2 Department of Pathology, Apollo Hospitals, Bhubaneswar, Odisha, India
|Date of Web Publication||20-May-2015|
Dr. Surya Kanta Pradhan
Department of ENT- Head and Neck Surgery, Apollo Hospitals, Plot No. 251, Sainik School Road, Unit - 15, Bhubaneswar - 751 005, Odisha
Source of Support: None, Conflict of Interest: None
Parapharyngeal schwannomas are rare benign neoplasms located in a difficult anatomical region. Most of them are asymptomatic and some presents late. Neurological deficit is a late finding, and it occurs only when the lesion is very large and compresses contiguous structures. Computed tomography (CT) guided fine needle aspiration cytology along with preoperative CT and magnetic resonance imaging can detect and diagnose it correctly and helps in proper planning and management. Total surgical excision is the treatment of choice. The approach is different as per the site, but trans-cervical approach is preferred. Recurrence is rare after complete excision. We are presenting a very rare parapharyngeal schwannoma arising from the hypoglossal nerve that was excised by trans-cervical approach without any complications and less morbidity as compared to other described approaches.
Keywords: Computed tomography scan, hypoglossal nerve, magnetic resonance imaging scan, parapharyngeal space, schwannoma, trans-cervical excision
|How to cite this article:|
Pradhan SK, Gupta S, Baisakh MR. Parapharyngeal space schwannoma of hypoglossal nerve. J Orofac Sci 2015;7:46-8
| Introduction|| |
The incidence of parapharyngeal space (PPS) tumor is very less. They are less than 0.5% of all head neck tumors. , It mainly comprises of tumors of salivary gland and lower cranial nerves. Almost two-third of the tumors are benign, and only one-third are found to be malignant.  Schwannoma is the most common neurogenic tumor of schwann cells in the PPS arising mainly from vagus followed by cervical sympathetic chain. We are presenting a very rare case of schwannoma that was arising from the hypoglossal nerve. It may be intracranial, both intra and extracranial or only extracranial. These tumors are slow growing and affect mainly the middle aged population.
| Case Report|| |
A 30-year-old female patient presented to the department of ear, nose and throat and head and neck surgery with hoarseness of voice for 6 months. She was having difficulty in swallowing for 4 months. On examination, there was a swelling over the left side of the posterior pharyngeal wall with normal mucosal cover. It was 5 cm × 4 cm in dimension, firm and nontender on palpation. There was hypotrophy over the left side of the tongue. The soft palate was less mobile in comparison to the right. Gag reflex was decreased, and the left vocal cord was paralyzed. The shrugging of left shoulder was decreased.
Magnetic resonance imaging (MRI) was done suspecting a parapharyngeal tumor. It showed a large well-defined elongated nodular mass lesion in left PPS appearing mildly hyperintense on T2-weighted images and isointense on T1-weighted images. Multiple small cystic areas noted within the lesion. Superiorly, it was extending up to left jugular foramen and inferiorly up to left PPS splaying the carotid and jugular vessels. It was causing mild oropharyngeal luminal narrowing. It was measuring 5 cm × 4 cm × 2.6 cm [Figure 1].
|Figure 1: Magnetic resonance imaging scan neck showing a large well defined elongated nodular mass lesion in left parapharyngeal space|
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Excision was done through trans-cervical approach. Submandiblar gland was excised. Hypoglossal nerve was identified, and tumor located. The nerve was travelling through the posterosuperior part of the capsule and was overstretched. The external and internal carotid artery, internal jugular vein and vagus nerve were dissected and saved. Intracapsular enucleation under microscope was done till most of the tumor tissue was cleared. It was sent for squash biopsy. Squash preparations and frozen section showed moderately cellular tumor composed of oval to spindle-shaped cells with oval nuclei. The cells were arranged in bundles and fascicular pattern. A few paucicellular areas were seen. The features were suggestive of schwannoma. After that the whole tumor was excised along the capsul [Figure 2] and [Figure 3].
|Figure 2: Intra-operative photograph showing tumor originating from the hypoglossal nerve|
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It was excised and sent for histopathology. Sections showed moderately cellular tumor with moderate vascularity, hemorrhagic areas and adjoining fibrous connective tissue. The tumor was composed of cellular and paucicellular areas. Then cellular areas showed spindle-shaped cells with oval nuclei, arranged in fascicular pattern and also whirling pattern. Nuclear palisading was seen (Antoni A type of cells). Paucicellular was composed of Antoni type 'B' cells and foamy cells. Nuclear anaplasia or mitotic figures are not observed [Figure 4].
|Figure 4: Section shows cellular and hypocellular areas composed of oval to spindle tumor cells in diffuse sheets with focal nuclear palisading|
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We could not save the hypoglossal nerve during dissection as it was passing through the tumor. Anastomosis of the nerve was done at the end. Postoperatively, she has improvement in swallowing and speech but the tongue has not recovered completely.
| Discussion|| |
Schwannoma is a benign tumor arising from Schwann cell or fibroblast supporting the nervous system. Only very few of the schwannomas are malignant.  Mostly they affect the intracranial cavity, face, neck and PPS. Most of the tumors in PPS arise from vagus and less commonly from other cranial nerves and sympathetic chain.  In our case, the schwannoma was arising from the hypoglossal nerve that was very rare. As per our review of literature total no of hypoglossal nerve schwannomas are 121 and extracranial part of the nerve was affected only in 12 cases. They are slow growing, and their symptoms are mostly due to pressure effect over the adjacent structures. In a study of 23 cases, Allison et al. found that even large PPS tumors may be asymptomatic.  Patients usually present with symptoms like hoarseness, dysphagia, neck swelling, swelling over the posterior pharyngeal wall and hypoglossal nerve palsy.  Sometimes they are mistaken as tonsillar abscess or tumor and cause delay in diagnosis. The affected age group can be from 30 to 70 years but mostly seen in young patients. Pediatric population is very rarely affected. Santarius et al. reported a case of isolated hypoglossal schwannoma in a 9-year-old child that was successfully excised without any recurrence.  Fine needle aspiration cytology (FNAC) is one of the important diagnostic modalities in head and neck tumors. But for PPS tumors it is less helpful. Computed tomography (CT) or ultrasound-guided FNAC has some role in determining the nature of the tumor. MRI and CT scan are done preoperatively to determine the extent and origin of the tumor and to help in surgical decision. MRI provides better preoperative information and relationship with surrounding structures. CT gives a better idea about bone involvement. Miller et al. in his study of 51 patients found that MRI is superior to CT to determine the anatomical locations of the tumors.  Carotid angiography should be done if the tumor is suspected to be arising from carotid artery.
Surgical excision is the treatment of choice with less chance of recurrence. Shahab et al. in his study found the 5 and 10 years survival for benign parapharyngeal tumors is 100% and for malignancy 5 years was 93% and 57% at 10 years.  The different approaches depending upon the site of tumors are trans-cervical, mandibular swing, transparotid and combination of transparotid and trans-cervical surgical. Most of the tumors of poststyloid division of PPS can be adequately excised through trans-cervical approach. , Radiotherapy is the treatment of choice for PPS extensions of nasopharyngeal carcinoma, but it's not well appreciated for the treatment of other tumors of neural origin. Chemoradiation are used for the treatment of rhabdomyosarcoma and other sarcomas of the PPS.  The risk of malignant transformation is very small in sporadic neurofibromas, but it is 5-15% in von Recklinghausen's disease. 
Hypoglossal nerve is a rare benign tumor of PPS. Most of the cases present with pressure symptoms over the surrounding structures. Surgical excision with different approaches is the treatment of choice. There is a very remote chance of malignant transformation and recurrence for which periodic follow-up is required. Our case is one of the rarest cases that presented with pressure symptoms over the surrounding structures that is, 9 th , 10 th , 11 th and 12 th nerves. We have excised the tumor using trans-cervical approach that is having fewer complications after diagnosing it with MRI scan of the neck and kept the patient under regular follow-up.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]