Cervical Sympathetic Chain Schwannoma—Our Experience

Abstract

Tumours arising from the parapharyngeal space are uncommon. The most common tumour arising primarily from this region is a neurogenic tumour, especially Schwannoma. The most common site of origin of a Schwannoma in parapharyngeal space is Vagus nerve. Cervical sympathetic chain (CSC) schwannomas are extremely rare. Here, we discuss a case of a 30-year old female with cervical sympathetic chain schwannoma, the clinical presentation, diagnosis and management.

Introduction

Schwannomas are benign, slow growing tumours arising from the Schwann cells of the nerves. These tumours are relatively uncommon in the head and neck regions. Parapharyngeal space Schwannomas can arise from the Vagus nerve, Glossopharyngeal nerve, Accessory nerve, Hypoglossal nerve or the Sympathetic chain. Out of which Vagal Schwannomas are the most common ones. Cervical sympathetic chain Schwannomas are very rare tumours [1–4]. Most of these tumours can be asymptomatic, or present with a progressively enlarging mass or with acute onset Horner syndrome. Radiological evaluation is a must for diagnosis of these tumours and their treatment planning. Here we discuss a case of cervical sympathetic chain Schwannoma, its presentation, diagnosis and management.

Case report

A 30-year old female presented with progressive difficulty in swallowing for past 1 year. Later she noted a swelling in the left upper neck 4 months back, which was slowly increasing in size. She also had a hot-potato voice. There were no other symptoms. Physical examination revealed a firm, non-tender ovoid mass measuring almost 3 × 2 cm on the left side situated just below and behind the angle of mandible, extending up to the mastoid tip. Oropharynx showed a large mass on the left side crossing the mid-line, but not touching the opposite side. Rest of the examination was normal. Fibre optic laryngoscopy examination was normal apart from the mass in the oropharynx.

A computed tomography was done, which revealed a well-circumscribed, heterogenous mass 5.3 × 4.9 × 6.8 cm in the left parapharyngeal space extending superiorly till the skull base, inferiorly to the level of vallecula, just posterior to the left submandibular gland. The tumour had displaced the internal jugular vein posteriorly & laterally and the carotid artery anteriorly & laterally (Fig. 1). CT angiogram showed mild splaying of external and internal carotid arteries with vascularity from the ascending pharyngeal branch of left external carotid artery. MRI was done, which showed a central necrotic area probably due to haemorrhage, with low signal intensity on T1 and high signal intensity on T2-weighted images. The mass also showed good post contrast enhancement. From the radiological investigations we concluded that the parapharyngeal tumour is a cervical sympathetic chain Schwannoma considering the characteristic features and displacement of surrounding structures (Fig. 2). Fine needle aspiration cytology showed spindle shaped cells with irregular nuclei.

Fig. 1.

Tumour is shown in the left parapharyngeal space displacing the carotid arteries and internal jugular veins laterally

Fig. 2.

MRI showing a heterogenous tumour with post contrast enhancement

The tumour excision was planned through a trans-cervical approach. A skin incision was placed on the left side of the neck. Superior and inferior flaps were elevated. Sternocleidomastoid muscle was retracted. The carotid artery and internal jugular vein were identified (Fig. 3). The tumour was seen medial to these great vessels. The tumour was found arising from the cervical sympathetic chain without any involvement of the Vagus or Hypoglossal nerves. Digastric muscle was divided and styloidectomy was done with division of all 3 muscles attached to styloid and division of stylohyoid ligament for proper superior exposure (Fig. 4). The external carotid artery was ligated and divided for good exposure (Fig. 5). Extra-capsular excision of the tumour was done preserving the Vagus nerve and the Hypoglossal nerve (Fig. 6). The specimen was sent for histopathological evaluation. The final report was consistent with a Schwannoma. Post-operatively the patient had First bite syndrome which was managed conservatively.

Fig. 3.

The tumour is shown along with the surrounded structures

Fig. 4.

The digastric muscle was divided and styloidectomy was done for exposing the tumour superiorly

Fig. 5.

The external carotid artery was divided and ligated for additional exposure

Fig. 6.

The tumour specimen after extra-capsular excision

Discussion

Schwannomas are benign, slow growing tumours arising from the myelin producing Schwann cells of the nerve sheaths [5]. The other names given to Schwannoma are neurilemmoma, solitary nerve sheath tumour and perineural fibroblast tumour [3, 6]. Head and neck are the site for 25–40% of extra-cranial Schwannomas [7]. Schwannomas are the second most common tumours of parapharyngeal space next to parotid tumours. In parapharyngeal space Schwannomas can arise from lower cranial nerves and sympathetic trunk. The most common site is the Vagus nerve. Cervical sympathetic chain Schwannomas are very rare [3–5, 8, 9]. CSC Schwannomas are reported to present from 20 to 50 years, with a male to female ratio of 1:1 [4, 10].

Schwannomas usually are asymptomatic at the time of presentation or can present as an asymptomatic slow growing, solitary neck mass with or without vague symptoms like sore throat or dysphagia. Pre-operative Horner syndrome can be a rare symptom [3–5, 9, 11]. Other symptoms include change in voice, hearing loss or cranial nerve deficit [2, 7]. The differential diagnosis includes carotid body tumours, paragangliomas, neurofibroma, lymphadenopathy and salivary gland tumours.

Preoperative diagnosis is incomplete without imaging studies. Computed tomography imaging without contrast generally shows hypodense mass lesion (compared to muscle) and with contrast the lesion shows some degree of enhancement. CT angiogram shows mild splaying of internal and external carotid arteries in CSC Schwannomas and in carotid body tumour [5, 6, 9, 12]. In case of a vagal Schwannoma there can be splaying between internal jugular vein and internal carotid artery [13, 14]. The CSC Schwannoma displaces both carotid artery and internal jugular vein anterolaterally as the cervical trunk is situated posteromedial to the carotid sheath. The vagal Schwannoma on the other hand displaces the carotid artery anteromedially and the internal jugular vein anterolaterally [4, 12]. Paragangliomas are classical isodense lesions compared to muscle in a non-contrast CT and shows more reliable homogenous enhancement in post-contrast studies (light-bulb sign) [4, 15]. MRI of Schwannomas reveals relatively low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Post-Gadolinium MRI images show homogenous enhancement and sometimes a salt and pepper pattern, which can also be seen in other hyper vascular lesions like paragangliomas and carotid body tumour [11, 16]. Ultrasonography with 7.5 MHz transducer can show the tumour origin in case of vagal Schwannoma and Schwannomas arising from cervical sympathetic trunk [14].

A fine needle aspiration (FNA)cytology is usually inconclusive [3, 16]. The sensitivity of FNA cytology for schwannomas is relatively low at 0–40% [17]. The FNA cytology features of Schwannoma include fascicles of cohesive cells and loose component, wavy/fibrillary, indistinct cytoplasm, and bipolar cells with cigar-shaped/fishhook nuclei with blunt ends [18]. The malignant Schwannoma usually shows a variable histologic pattern. Only obviously malignant, undifferentiated, spindle-shaped cells not capable of further characterization are seen on cytology [19]. These lesions show presence of marked cellular pleomorphism and emphasize a discohesive and dispersed cell population. There can be aggregates of spindled cells and occasional detached single cells. Other features include nuclear palisading, a tumour diathesis, intranuclear pseudo inclusions, and occasional nuclear bends or folds [18, 20].

Histopathology examination shows a well-defined encapsulated lesion showing large number of vessels at the level of the capsule [9]. On microscopic examination tumour show areas of high cellularity with specific areas of palisading nuclei arranged in rows called Antoni A regions and areas of low cellularity with loose and disorderly arrangement called Antoni B tissue. The Antoni A areas may contain foci of palisaded nuclei called Verocay bodies [2, 10, 16]. Malignant lesions on the other hand shows anaplasia, high mitotic rate, cellularity, necrosis, and invasiveness [21]. It is proposed thar malignant changes begin in Antoni A areas and invades adjacent Antoni B areas.[22].

Schwannomas are to be treated surgically whenever possible because of its growing potential, leading to local and neural compression symptoms. In neck this tumour usually involve V, VII, IX, X, XI, or XII cranial nerves, sympathetic chain, brachial or cervical plexus, and the presentation of the patient depends on the nerve involvement and also on the compression of surrounding nerves (usually in intracranial/skull base tumours) by the tumour [23]. A pre-operative neurological examination will give us an idea regarding the nerve involvement even before a radiological evaluation. This will help us to counsel the patient regarding the probable post-operative neurological outcomes.

Surgery is the treatment of choice, usually by an external approach. Varma RR et al. [8] prefers transcervical excision of tumour. Nabuco de Araujo et al. [23] have described mandibulotomy for tumour removal in one case, and in nine cases a cervical parapharyngeal approach was done. In their study Wax et al. [3] explains how they removed the CSC Schwannoma by a trans-cervical approach. Apart from the commonly performed transcervical approach, other options include trans-parotid, infratemporal and trans-oral approaches (separately or in combination). In their experience, Lin et al. [4] describe that the transcervical approach provides adequate exposure for excision of the parapharyngeal space CSC Schwannoma. Bass et al. [24] in 1982 describes other approaches for tumour excision which include submandibular approach and trans-parotid approach with (in case of large tumours) or without mandibulotomy. All vascular and neural structures, including cranial nerves IX to XII and the superior laryngeal nerve can be easily identified, approached and carefully preserved with minimal injury to surrounding structures by a trans cervical route [2, 25, 26].

Trans-cervical approach provides adequate exposure for excision of Schwannomas of parapharyngeal space [4]. Extracapsular excision is usually done preserving all the surrounding neurovascular structures. Here, the nerve function can be compromised as these tumours run in the length of the nerve fibres and the nerve fibres are usually thinned out and well separated, in spite of complete tumour removal and minimal chance of recurrence [27, 28]. Intracapsular enucleation is preferred by Ku H et al. [29] where the capsule is left behind after tumour removal. This helps in preserving the nerve of tumour origin and minimize the risk of post-op neurological deficits. Hence pre-operative counselling is a must. Schwannomas are radio-resistant tumours; hence radiotherapy has no role in treatment. Horner’s syndrome [27, 28] (miosis, ptosis, anhidrosis and enophthalmos) and first bite syndrome (acute pain in parotid region/mouth on first bite of each meal) are the common complications of surgical treatment of CSC Schwannoma. Other complications of surgery within the parapharyngeal space include injuries of cranial nerves IX-XII manifested by vocal cord paralysis, aspiration, dysphagia, shoulder weakness and transient tachycardia [30]. There are different function conservation techniques, viz. nerve resection with primary anastomosis or neural graft interposition, tumour enucleation between adjacent healthy nerve fibres when possible, tumour emptying (preserving tumour capsule) and even tumour shelling out (leaving gross tumour inside the capsule). that these techniques offered different function preservation rates, ranging from 9% (excision plus nerve reconstruction), 31% (enucleation with nerve sparing), up to 71% (emptied or shelled-out tumours) [23, 31]. Ptosis can be managed by levator aponeurosis lengthening. Other symptoms due to Horner syndrome usually resolves over time. Tumour recurrence following enucleation is very rare [8]. Malignant transformation is also very rare in Schwannomas [31]. The prognosis after surgical excision of Schwannomas is generally excellent.

Summary

CSC Schwannoma is a rare neurogenic tumour that arise in the parapharyngeal space. Clinical presentation can mimic other tumours like a carotid body tumour or a paraganglioma. Proper pre-operative radiological evaluation should be done for diagnosis. Surgical resection is the treatment of choice. Local recurrence risk is very low. Post-operative complications like Horner syndrome and first bite syndrome are very common with CSC Schwannomas.

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