Keywords
Benign tumor - encapsulated tumor - hoarseness of voice - schwannoma
Introduction
Cervical vagal schwannomas are rare, slow-growing tumors usually reported to occur
in patients between 30 and 50 years of age. Males and females are equally affected.
They are usually asymptomatic benign lesions, and complete surgical resection is the
treatment of choice. Imaging plays a central role in diagnosing and in optimal surgical
treatment in vagal nerve neoplasm.
Case Report
A 28-year-old female was admitted to our department for swelling on the left side
of the neck. On palpation, a soft, smooth-surfaced mass on the left cervical region
(at Level II), measuring 5 cm × 3 cm, was present. Neither paroxysmal cough nor bradycardia
on palpation was observed. Cranial nerve examination was normal.
Ultrasound (US) of the neck showed a well-defined heterogeneous lesion of size 4.5
cm × 2.6 cm with necrotic areas within left postauricular and infra-auricular region,
showing minimal vascularity on Doppler imaging. Fat plane with adjacent muscles and
vessels is maintained. Computed tomography (CT) scan of the neck demonstrated a well-defined
heterogeneously enhancing hypodense lesion of approximate size 5.3 cm × 4.2 cm × 3.2
cm with nonenhancing necrotic areas within deep to the left sternocleidomastoid muscle
extending from C2 to C6 vertebral level. The lesion is compressing and displacing
internal jugular vein anterolaterally abutting left internal carotid artery, posterior
belly of digastric muscle anteriorly, and splenius and semispinalis muscles posteromedially.
The fat plane between lesion and adjacent soft tissue is maintained [Figure 1] and [Figure 2].
Figure 1: Contrast-enhanced computed tomography neck (sagittal section) showing mass
occupying posterior triangle
Figure 2: Contrast-enhanced computed tomography neck (coronal section) showing mass
occupying posterior triangle
The results of fine needle aspiration cytology of the mass, performed before the admission,
were inconclusive. The patient, therefore, underwent surgery. Under general anesthesia,
a cervical incision along the anterior border of the sternocleidomastoid muscle was
made and the dissection proceeded beneath the muscle. A grayish-white, round-shaped
mass was observed, measuring ~3 cm × 3 cm lying between the left carotid artery and
the internal jugular vein. Both the superior and inferior ends of the mass appeared
in continuity with the vagus nerve. Multiple tiny nerve branches were seen around
the tumor [Figure 3].
Figure 3: Intraoperative photograph showing vagal schwannoma
The tumor was removed leaving the capsule of the tumor, preserving the tiny branches
of the vagus [Figure 4].
Figure 4: Specimen of the left cervical vagal schwannoma
Surgical technique
The nerve-sparing subcapsular resection technique for schwannomas is based on the
principle that nerve fibers get expanded and stretched out on the tumor rather than
getting embedded within it. The technique described herein potentially preserves these
nerve fibers without significantly compromising nerve function as nerve continuity
is maintained.
After identifying the location of the important blood vessels and nerves in relation
to the tumor, the mass is delineated on all sides. The proximal and distal ends of
the nerve abutting the tumor are identified, and meticulous sharp dissection is carried
out, parallel to the axis of the nerve (minimizing damage to collateral nerve fibers),
until the cleavage plane between the tumor tissue and tumor capsule is reached. Once
in the subcapsular plane, the tumor mass is carefully freed proximally, distally,
and from the sides, and then excised. Care is taken to minimize traction to the surrounding
nerve fibers. The tumor is thus resected with preservation of the majority of nerve
fibers.
The histopathological examination confirmed the diagnosis of benign schwannoma of
the vagus nerve. Postoperatively, the patient does not develop any hoarseness of voice,
and examination of the larynx was normal. At follow-up, 15 days after surgery, the
patient was well, without evidence of disease and with no vocal cord palsy.
Discussion
Schwannomas are rare peripheral nerve tumours; about one third occur in the head and
neck region.[1] Clinically, they present as asymptomatic slow-growing lateral neck masses that can
be palpated along the medial border of the sternocleidomastoid muscle.
Pre-operative diagnosis of schwannoma is difficult because many vagal schwannomas
do not present with neurological deficits and several differential diagnoses for tumour
of the neck may be considered, including paraganglioma, branchial cleft cyst, malignant
lymphoma, metastatic cervical lymphadenopathy.[2] As schwannomas are mostly asymptomatic we should have an index of suspicion for
this tumour.
Magnetic Resonance Imaging (MRI) is the investigation of choice. In this case patient
has undergone Computed Tomography (CT) of neck. We reached the definitive diagnosis
by histopathological examination showing presence of Verocay bodies which are definitive
for schwannoma [Figure 5].
Figure 5: Verocay body with palisaded rows around it
Treatment of vagal nerve tumours is complete surgical excision. At surgery, these
tumours appear as yellowish-white, well-circumscribed masses. Dissection of the tumour
from the vagus with preservation of the neural pathway should be the primary aim of
surgical treatment for these tumours. Incomplete treatment, such as open biopsy, should
be avoided, since it makes definitive excision of the tumour much more difficult.
As schwannomas are benign, all efforts should be made to preserve nerve function so
that quality of life is unaffected. Valentino et al.[3] considered neural deficits to be the result of tumour neuritis, and Russel and Rubinstein
[4] reported neural fibres within schwannomas to be the cause of such deficits, independent
of the employed surgical technique. Various techniques have been described for removal
of these tumours, including: tumour excision with neural sacrifice followed by primary
anastomosis or neural graft interposition; tumour excision with neural preservation;
tumour enucleation between adjacent healthy nerve fibres when possible; tumour emptying
(preserving the tumour capsule); and even the 'shelling out' of the tumour (leaving
gross tumour inside the capsule). The nerve-sparing subcapsular resection technique
for schwannomas described in the current study potentially preserves the nerve fibres,
without significantly compromising the nerve function as nerve continuity is maintained.
A literature review by Valentino et al. showed that the various surgical techniques offered different function preservation
rates [3] In those who underwent tumour excision without neural sacrifice, 64 per cent had
permanent neural deficits, while 29 per cent had temporary deficits. Patients who
had their tumours either enucleated or shelled out had a permanent neural deficit
rate of 29 per cent and a transient deficit rate of 42 per cent. In those who underwent
a shelling out procedure, 29 per cent had no neural deficits at all.
The reported incidence of pre-operative vocal cord paralysis is about 12%, but hoarseness
is almost always present following surgery. Therefore, pre-operative assessment of
vocal cord mobility should be strongly recommended. Although it is very rare, clinicians
should bear in mind the possibility of a nerve sheath tumour in the presence of a
neck mass. Pre-operative suspicion is very important, because the patient, and the
patient's family, should be informed about the possible post-operative neurological
complications;[5] as far as postoperative vocal cord palsy is concerned, an incidence of 85% has been
reported.[6],[7] Furthermore, since vagal schwannomas are almost invariably benign in nature, a conservative
approach should always be considered in first instance.[2],[8] In the presence of post-operative vocal cord palsy, aggressive voice therapy, for
vocal cord compensation, should be started soon after surgery.
Conclusion
Cervical schwannomas, which most often present as asymptomatic unilateral neck masses,
are rare tumors. The preoperative diagnosis may be difficult, and it is often not
made until the time of surgery. The definitive diagnosis relies on clinical suspicion
and histopathological confirmation. In the treatment of head and neck schwannomas,
complete surgical excision with appropriate approaches is efficient. It is important
bearing in mind possible vagal or sympathetic chain injury. Local recurrence is extremely
rare.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
