Nagoya J. Med. Sci. 74. 199 ~ 206, 2012
SCHWANNOMA ORIGINATING FROM
LOWER CRANIAL NERVES:
REPORT OF 4 CASES
HIROFUMI OYAMA, AKIRA KITO, HIDEKI MAKI, KENICHI HATTORI,
TOMOYUKI NODA and KENTARO WADA
Department of Neurosurgery, Ogaki Municipal Hospital, Ogaki, Japan
Four cases of schwannoma originating from the lower cranial nerves are presented. Case 1 is a schwan-
noma of the vagus nerve in the parapharyngeal space. The operation was performed by the transcervical
approach. Although the tumor capsule was not dissected from the vagus nerve, hoarseness and dysphagia
happened transiently after the operation. Case 2 is a schwannoma in the jugular foramen. The operation
was performed by the infralabyrinthine approach. Although only the intracapsular tumor was enucle-
ated, facial palsy, hoarseness, dysphagia and paresis of the deltoid muscle occurred transiently after the
operation. The patient’s hearing had also slightly deteriorated. Case 3 is a dumbbell-typed schwannoma
originating from the hypoglossal nerve. The hypoglossal canal was markedly enlarged by the tumor. As
the hypoglossal nerves were embedded in the tumor, the tumor around the hypoglossal nerves was not
resected. The tumor was significantly enlarged for a while after stereotactic irradiation. Case 4 is an
intracranial cystic schwannoma originating from the IXth or Xth cranial nerves. The tumor was resected
through the cerebello-medullary fissure. The tumor capsule attached to the brain stem was not removed.
Hoarseness and dysphagia happened transiently after the operation. Cranial nerve palsy readily occurs after
the removal of the schwannoma originating from the lower cranial nerves. Mechanical injury caused by
retraction, extension and compression of the nerve and heat injury during the drilling of the petrous bone
should be cautiously avoided.
Key Words: Schwannoma, Hypoglossal nerve, Vagus nerve, Parapharyngeal tumor, Infralabyrinthine
The development of lower cranial (IXth–XIIth) nerves-derived schwannoma in the cervical
region, jugular foramen, and hypoglossal canal is comparatively rare. As for the cervical region,
the nerves of origin were identified in 62% and they were the brachial plexus, facial nerve,
trigeminal nerve, vagus nerve and sympathetic chain.1) Sixty-nine percent of the patients presented
with symptoms secondary to mass effect or nerve deficit and the main symptoms were neck mass
(27%), dyspnea/dysphonia (15%), nasal obstruction/epistaxis (12%), odynophagia/dysphagia (12%)
and shoulder/upper extremity pain (8%).1) The parapharyngeal space is the most common site
of tumor origin (31%), followed by the neck (23%), skull base (19%), sinonasal cavity (15%),
middle ear (8%) and posterior pharynx (4%).1)
Corresponding Author: Hirofumi Oyama, M.D.
Department of Neurosurgery, Ogaki Municipal Hospital, Minamikawamachi 4-86, Ogaki, Gifu 503-8502, Japan
Phone: 0584-81-3341, Fax: 0584-75-5715, E-mail: firstname.lastname@example.org
Hirofumi Oyama et al.
It was reported that the origin of the jugular foramen schwannoma was the glossopharyngeal
(IXth) nerve in 40%, vagus (Xth) nerve in 25% and spinal accessory (XIth) nerve in 35% of
cases.2) As for symptoms, the presentation of the patients reportedly varied according to the
tumor growth pattern.3) Deafness, vertigo, and ataxia were present in all patients with a major
intracranial component.3) By contrast, lower cranial nerve involvement, including hoarseness and
weakness of the trapezius and sternocleidomastoid muscles, occurred in patients in whom the
tumor was primarily within the bone or extracranial.3) Patients with the major component of the
schwannoma within the bone also experienced deafness.3)
Hypoglossal schwannoma is considered to be comparatively rare. The locations of these tumors
were reported to be intracranial (31.5%), both intra- and extracranial (50%) and extracranial
(18.5%).4) They mainly presented with cerebellar dysfunction (45.3%) and pareses of the facial
(VIIth) (17.6%), IXth (57.4%), Xth (40.3%), XIth (20.9%), and hypoglossal (XIIth) (85.7%)
We describe 4 cases of schwannomas in those areas and discuss the operative complications
and methods to avoid them.
Case 1 (Vagal nerve-derived schwannoma in the parapharyngeal space)
A 31-year-old female presented with difficulty in swallowing. She showed no other neu-
rological abnormalities. A palpable tumor was observed under the right mandible. Computed
tomography (CT) and magnetic resonance imaging (MRI) showed a schwannoma in the right
parapharyngeal space (Fig. 1A). A 10-cm-long transverse incision was placed 2 cm below the
Fig. 1A Preoperative gadolinium-enhanced magnetic resonance imaging, T1-weighted image, axial view. Tumor
(arrow) is found in right parapharyngeal space.
SCHWANNOMA OF LOWER CRANIAL NERVES
right lower mandible to exfoliate and elevate the caudal portion of the submaxillary gland. The
digastric muscle and facial artery/vein were cut to allow the external carotid artery to be moved
out of place. Although the internal carotid artery was thin and adhered to the dorsal side of the
tumor capsule, the artery could be exfoliated (Fig. 1B). It was impossible to exfoliate the vagal
nerve because it was completely integrated with the tumor capsule on the dorsal side of the
tumor. Although the cranial portion of the tumor was not exfoliated, and an extremely thin tumor
capsule remained, the entire tumor was removed completely. Pathological examination showed a
palisade arrangement of spindle cells, and thus the tumor was diagnosed to be schwannoma. The
patient showed a mild swallowing disorder and moderate dysphonia following surgery, but both
were resolved within 3 months, and there was no recurrence as of 11 months after surgery.
Case 2 (Jugular foramen schwannoma)
A 56-year-old female patient presented with dizziness, hearing loss of 58.8 dB in her left
ear, hoarseness, and a swallowing disorder. CT and MRI showed that an extradural tumor had
damaged the left petrous bone (Fig. 2A). Cerebral angiography showed that the left sigmoid sinus
was obstructed, and the tumor was fed by the left ascending pharyngeal artery. The intracapsular
tumor was completely removed using a left infralabyrinthine approach (Fig. 2B). The tumor
had mainly located in the pars nervosa containing the IXth, Xth and XIth cranial nerves, but
the nerve of the tumor origin was not identified. Pathological examination showed that there
were cells with spindle- and elliptically-shaped nuclei with infiltration of inflammatory cells.
There were also some cells with large heterotypic nuclei. In addition, there were many blood
vessels with hemorrhage. Immunostaining showed that the tumor was positive for S-100 protein
Fig. 1B Preoperative enhanced 3-dimensional computed tomography scan. Tumor (purple-colored, enclosed
with black lines, arrowhead) is located behind external carotid artery (white-colored, arrow). Internal
carotid artery (white-colored, double arrow) and internal jugular vein (blue-colored, asterisk) are pushed
backward by tumor.
Hirofumi Oyama et al.
and negative for epithelial membrane antigen, and it was diagnosed to be schwannoma. There
was some loss of hearing, in addition to transient hoarseness, swallowing disorder, accessory
nerve paralysis (difficulty in elevating left shoulder), and left facial nerve paralysis following
the resection. These symptoms resolved almost completely and there was no recurrence as of
18 months after surgery.
Fig. 2A Preoperative gadolinium-enhanced magnetic resonance imaging, T1-weighted image, axial view. Tumor
(arrow) is found in left anterior petrous bone.
Fig. 2B Operative view, infralabyrinthine approach. Left sigmoid sinus (arrow) is dissected from petrous
bone. Red-colored tumor (arrow head) is found beyond compressed blue-colored jugular bulb (double
SCHWANNOMA OF LOWER CRANIAL NERVES
Case 3 (Dumbbell-shaped hypoglossal schwannoma)
A 25-year-old male patient presented with headache and nausea. The right side of the tongue
showed paralysis and atrophy. CT and MRI demonstrated a dumbbell-shaped tumor in the right
hypoglossal canal, extending in and out of the skull (Fig. 3A). There was a large multilocular
cyst in the right cerebellopontine angle, strongly compressing the brain. In addition, the right
Fig. 3A Preoperative magnetic resonance imaging, T2-weighted image, axial view. Tumor is found in right
hypoglossal canal (arrow) and posterior fossa (arrowhead).
Fig. 3B Operative view, right retromastoid suboccipital approach. Tumor remnant (arrowhead) is found around
hypoglossal nerves (arrow). Accessory nerves (double arrow) and right posterior inferior cerebellar
artery (asterisk) are also shown.