Download A Case of Large Foramen Magnum Schwannoma

J Korean Neurosurg Soc 35 : 317-320, 2004
KISEP
Case Report
A Case of Large Foramen Magnum Schwannoma
Jin Ho Jeon, M.D., Seung Heon Cha, M.D.,
Geun Seong Song, M.D., Chang Hwa Choi, M.D.
Department of Neurosurgery, School of Medicine, Pusan National University, Busan, Korea
Most intracranial schwannomas originate from the cranial nerve especially CN V, VIII. However, schwannomas from
low-cranial nerve are rarely reported. We report a case of large foramen magnum schwannoma in a 26 year-old-man
presenting swallowing difficulty, nausea and vomiting. Magnetic resonance image revealed a cystic multilobulated huge
mass from midclivus to atlas which compressed brain stem. The mass was removed by far-lateral transcondylar approach
and confirmed with schwannoma which originated from hypoglossal nerve.
KEY WORDS : Far-lateral transcondylar approach Schwannoma Hypoglossal.
Introduction
M
ost intracranial schwannomas arise from the sensory
cranial nerve, primarily from the vestibular, and much
less frequently from the trigeminal nerve and Gasserian
ganglion1). Schwannomas have also been reported in lowcranial nerve including cranial nerve IX, X, XI, XII
rarely9,11,15,16,18,21,22). Hypoglossal schwannoma are very rare
and may, in rare cases, extend into the extracranial
compartment18). The most common sign is a hypoglossal
palsy, although in very rare cases the hypoglossal nerve not
injured3,11,18). But in this region, there are a lot of cases that
could not confirm its origins due to its anatomical character.
We report a case of large hypoglossal schwannoma extending
extracranially from midclivus to atlas which removed by farlateral transcondylar approach in presenting cervicalgia and
mild swallowing difficulty without preoperative hypoglossal
palsy.
Case Report
A
26-year-old man experienced dull pain in the nuchal and
occipital regions, and mild discomfort in swallowing for
6 months. But in neurologic examinations, there were no
definite cranial nerve deficit including hoarseness, dysphagia,
sternocleidomastoid muscle weakness and cerebellar
ysfuntion. Enhanced brain computed tomography(CT)
Received：September 15, 2003 Accepted：October 31, 2003
Address for reprints：Seung Heon Cha, M.D., Department of
Neurosurgery, School of Medicine, Pusan National University, 1-10
Ami-dong, Seo-gu, Busan 602-739, Korea
Tel : 051) 240-7257, Fax : 051) 244-0282
E-mail : [email protected]
showed a huge low-density cystic mass with heterogenous
solid component in ventral side of brain stem. Magnetic
resonance(MR) image showed 6.5 6 7cm sized huge mass
based on the ventral side of stem extended from midclivus to
atlas. The mass was thick-rim enhanced, well demarcated and
multilobulated, cystic in character and showed low intensity
on T1-weighted images and high intensity on T2-weighted
images. The pons and medulla were displaced posteiorly
terribly. Vertebral angiogram showed displacement of right
vertebral artery, but there was no definite tumor stains from
posterior circulations(Fig. 1).
The tumor was removed via far-lateral transcondylar
approach4,10,13,20). After dissection of the muscle along the
right posterolateral aspect of the craniocervical junction to
permit an adequate exposure of suboccipital triangle, the
posterior arch of atlas was removed maximally with
identification of vertebral artery above the posterior arch of
the atlas and in its ascending course between the transverse
process of the atlas and axis. A suboccipital craniotomy was
done near the point where the transverse sinus empties into
the sigmoid sinus. To maximize lateral approach, drilling of
the posterior portion of the occipital condyle and mastoid
process was done after detection of atlanto-occipital joint.
The dural incision began from the sigmoid sinus and
extended behind the vertebral artery into upper cervical area.
A brown-colored cystic component covered by arachnoidal
membranes encounterd after reflecting dura medially. The
lesion was expansive and stretched the 6th nerve superiomedially, the 7th and 8th nerve laterally, and the 9th, 10th, 11th
nerve inferiolaterally. Its capsule was incised and the lesion
was debulked. The intradural portion of the right vertebral
artery and the origin of the posterior inferior cerebellar artery
was dissected away from the caudal portion of the tumor. The
VOLUME 35
March, 2004
317
Foramen Magnum Schwannoma
Discussion
A
A
B
C
D
Fig. 1. Enhanced computed tomography(A) shows a huge lowdensity cystic mass with heterogenous solid component in ventral
side of brain stem. Vertebral angiogram(B) showing displacement of
right vertebral artery. Magnetic resonance image(C,D) show huge
mass based on the ventral side of stem extended from midclivus to
atlas. The mass is thick-rim enhanced, well demarcated and
multilobulated, cystic in character. Pons and medulla are displaced
posteiorly terribly.
tumor was removed with ultrasonic aspirator and tumor forceps
piece by piece taking precaution about cranial nerve injury. The
character of tumor is soft and brittle. A small rootlet which
thought to be origin of tumor extend toward hypoglossal canal.
After gently drawing a rootlet, we identified a portion of hypoglossal nerve abutting this small rootlet. The tentorial and caudal
edge of tumor completely seperated from the brain stem due to
well demarctrated arachnoid plane, but there is solid portion
attached with ventral brain stem terribly. So small solid portion
in ventral pontome-dullary junction could not be removed.
Follw-up MR image confirmed that the tumor was almost
totally removed and small portion was left at ventral side of
the pontomedullary junction(Fig. 2). Postoperative three
dimensional CT showed that a part of occipital condyle and mastoid
process were drilled to maximize the lateral approach(Fig. 3).
Pathologic finding showed spindle cells with no mitoses and
nearby hyaline changes compatible with schwannoma(Fig. 4).
Postoperatively, the patient did well but transient 10th, 11th,
12th nerve palsy including vocal cord palsy and swallowing
difficulty were presented. But they were completely resolved
except only hypoglossal nerve palsy.
318 J Korean Neurosurg Soc 35
ll cranial nerves, with the exception of the cranial nerve
I, II possessing myelinated sheaths, have the potential
for developing associated intracranial schwannomas21). The
vestibular division of the cranial nerve VIII is the most commonly affected. Trigeminal nerve schwannomas are the most
common in non-vestibular groups1), but schwannomas from
other cranial nerve were rarely reported9,11,16,18,21,22). Sarma et al.
reported 46 cases of non-vestibular schwannoma for 7-year
period, jugular foramen schwannoma and hypoglossal schwannoma were reported only 5 cases among them15).
Intracranial schwannomas present a variable symptoms according to its cranial nerve impairment. In our cases, the presenting
sympotoms consisted of headache, nausea owing to increased
intracranial pressure and swallowing discomfort and cervicalgia. But there was no definite evidence of low cranial nerve
palsy in neurologic examination objectively despite of its huge
size. Sarma et al. reported one case with the facial nerve schwannoma, extended to the jugular foramen area but did not
produce any symptoms of jugular foramen involvement15). Lee
et al. reported 2 cases of hypoglossal schwannoma without
preoperative hypoglossal nerve palsy11). Berger et al. and
Spinnato et al. reported 1 case individually3,18).
The far-lateral transcondylar approach requires some consideratioins. Special care should be taken at the stage of muscular
dissection about the damage of vertebral artery and vertebral
venous plexus. To avoid this hazard, identification of the indivisual muscles including trapezius, stenocleidomastoid, splenius
capitis, and longissimus capitis muscle is an essential portion
of completing the far-lateral transcondylar approach, especially
in suboccipital triangle20). Surgical resection of condyle allows a more lateral approach and provides access to the lower
A
B
Fig. 2. Follw-up magnetic resonance images(A, B) reveal that hte
tumor is almost totally removed and small solid portion is left at ventral
side of the pontomedullary junction.
JH Jeon, et al.
clivus and premedullary area. It is also important to confine the
extent of condylar drilling considering occipitoatlantal instability
and required exposure. But it is still arguable whether drilling of
the occipital condyle was necess-ary for the approach21).
Rhoton insisted that the occipital con-dyle should be drilled to
the depth of cortical bone surrounding the hypoglossal canal
because the change from cancellous bone indicates the hypoglossal canal has been reached13).
But some author described that the jugular tubercle reduction
on the ipsilateral side between the undersurface of the jugular
bulb and the hypoglossal canal is the most important factor
for maximal exposure across the anterior brain stem surface6).
So very little of the occipital condyle is removed (“transtubercular approach” rather than “transcondylar approach”), and
atlantooccipital stability is preserved. Babu et al. reported that
more than one third of condylar resection resulted in increased
mobility of joint2) and George et al. reported a half range brought atlatooccipital instability7). Vishteh et al. reported that
fusion procedure should be considered in case of condylar
drilling has been performed over than 50%19). In our case, we
ensured surgical field via hemilaminectomy of C1 with drilling of posterior third of the occipital condyle and posterior tip
of mastoid process(Fig. 3). Thus atlantooccipital fusion was
unnecessary.
In literature review, schwannoma appears as regions of decreased signal intensity on T1-weighted images and increased
signal intensity on T2-weighted images11). Ginsberg et al.
reported a case of sixth nerve schwannoma showing markedly increased signal intensity on T2-weighted images with a
“cystic” appearance8). An enlargement or an erosion of the
hypoglossal canal have significant impact on the differential
diagnosis with jugular foramen tumor3,16). In our case, cystic
structure compatible with MR image of other schwannoma
was also observed, but the hypoglossal canal was intact.
Since schwannomas are benign tumors, the goal of the treatment is complete surgical removal. Their locations in a complex region of the skull base can make confirming its origins
difficult due to the intimate anatomical relationship to neurovascular and brain stem structure5,12). Yun et al. reported one
case of spinal accessory schwannoma confirming its origin by
stimulating the nerve root attached with tumor led to sternocleidomastoid constriction22). In our case, we could identify
posterior inferior cerebellar artery, its territories, contralateral
clivus and cranial nerves from the abducens nerve to spinal
portion of the accessory nerve. However we could not certify
the root entry zone of cranial portion of the accessory nerve
and the hypoglossal nerve arising along the front of the inferior
olive anterior to the origin of the cranial accessory fiber because
huge size of the
tumor and severe adhesion.
But we identified a small rootlet which considered to origin
of tumor extending toward hypoglossal canal after
debulking of tumor and certified
a portion of hypoglossal nerve Fig. 3. Postoperative spiral three dimensio nal
abutting this ro- computed tomography(CT) image shows that
otlet. So we co- a part of occipital condyle and mastoid
process are drilled to maximize the lateral
nfirmed that the surgical field.
origins of the
tumor must be
the hypoglossal
nerve because
of intraoperative
finding and postoperative his
hypoglossal palsy.
Surgical app- Fig. 4. Pathologic finding shows spindle cells
roach to the po- with no mitoses and nearby hyaline
sterior skull ba- changes.The tumor mass confirmed to
schwannoma(H &E, ×400).
se and craniovertebral junction
Fig. 4. Pathologic finding shows spindle cells
are often complex with no mitoses and nearby hyailne changes.
and lengthy pr- The tumor mass confirmed to schwannoma(H
ocedure associ- & E, ×400).
ated with significant morbidity. Respiratory complications
account for the high postperative mortality(40%) reported in
the early literature and were seen most frequently in patients
who had exhibited preoperative 12th and 10th cranial nerve
dysfunction17).
Because of this complication, it has been suggested that a
tracheostomy should be performed at the completion of the
operation. However, Robinson et al. reported that careful use
of microsurgical technique and intensive postoperative management could obviate the need for tracheostomy14). In our case, it
was not necessary to perform tracheostomy considering no definite
preoperative low cranial nerve palsy, intensive postoperative care
taking precaution about as-piration pneumonia and relatively his
young age.
VOLUME 35
March, 2004
319
Foramen Magnum Schwannoma
Conclusion
W
e report unusual case of large foramen magnum
schwannoma originated from hypoglossal nerve,
which removed via far-lateral transcondylar approach. This
approach provides satisfactory exposure to ventral brain stem
and foramen magnum lesions.
References
1. Arseni C, Dumitrescu L, Consaninescu A : Neurinomas of the
trigeminal nerve. Surg Neurol 4 : 497-503, 1975
2. Babu RP, Sekhar LN, Wright DC : Extreme lateral transcondylar
app-roach : Technical improvements and lessons learned : J
Neurosurg 81 : 49-59, 1994
3. Berger MS, Edwards MSB, Bingham WG : Hypoglossal
neurilemmoma. Case report and review of the literature :
Neurosurgery 10 : 617-620, 1982
4. Cho JY, Kim HK, Lee HD : The modular concept in the lateral and
posterior skull base approach : J Korean Neurosurg Soc 28 : 903914, 1999
5. De Olivera E, Rhoton AL Jr, Peace DA : Microsurgical anatomy of
the region of the foramen magnum : Sug Neurol 24 : 293-352, 1985
6. Dowd GC, Zeiller S, Awasthi D : Far lateral transcondylar approach
: Dimensional anatomy : Neurosurgery 45 : 95-100, 1999
7. George B, DeMatons C, Cophignon J : Lateral approach to the
anterior protion of the foramen magnum : Surg Neurol 29 : 484-490,
1988
8. Ginsberg F, Peyster RG, Rose WS, Drapkin AJ : Sixth nerve
schwan-noma : MR and CT demonstration : J Comput Assit
Tomogr 12 : 482-484, 1988
9. Kang MH, Chung H, Lee SP : Modified transcondylar approach for
a case of hypoglossal neurinoma-Technique : J Korean Neurosurg
Soc 27 : 648-654, 1998
10. Katsuta T, Rhoton AL Jr, Matsushima T : The jugular foramen : Mi-
320 J Korean Neurosurg Soc 35
crosurgical anatomy and operative approach : Neurosurgery 41 :
149-202, 1997
11. Lee DY, Lee SH, Yoo H, Jung HW, Han DH, Cho BK : Hypoglossal
neurinoma without preoperative hypoglossal nerve palsy-Report of
2cases. J Korean Neurosurg Soc 28 : 1800-1804, 1999
12. Lister JR, Rhoton AL Jr, Matsushima T, Peace DA : Microsurgical
anatomy of the posterior inferior cerebellar artery : Neurosurgery 10 :
170-199, 1982
13. Rhoton AL Jr : The far-lateral approach and its transcondylar, supracondylar, and paracondylar extensions : Neurosurgery 47(Suppl) : 195208, 2000
14. Robinson JS, Lopes J, Moody R : Intracranial hypoglossal neurilemmoma : Surg Neurol 12 : 496-498, 1979
15. Sarma S, Sekhar LN, Schessel DA : Nonvestibular schwannoma of the
brain : Neurosurgery 50 : 437-448, 2002
16. Sato M, Kanai N, Fukushima Y, Matsumoto S, Tatsumi C : Hypo-glossal
neurinoma extending intra- and extracranially : Case report : Surg
Neurol 45 : 172-175, 1996
17. Scott M, Wycis HT : Intracranial neurinoma of the hypoglossal nerve :
Successful removal, case report : J Neurosurg 6 : 333-336, 1949
18. Spinnato S, Talacchi A, Musumeci A, Turazzi S, Bricolo A : Dumbell- shaped hypoglossal neurinoma : Surgical removal via a dorsolateral trans condylar approach, A case report and review of the
literature. Acta Neurochir(Wien) 140 : 827-832, 1998
19. Vishteh AG, Crawford NR, Melton MS, Spetzler RF, Sonntag VKH,
Dickman CA : Stability of the craniovertebral junction after unilateral
occipital condyle resection : A biomechanical study : J Neurosurg
(Spine) 90 : 91-98, 1999
20. Wen HT, Rhoton AL Jr, Katsuta T, de Oliveira E : Microsurgical
anatomy of the transcondylar, supracondylar, and paracondylar extensions of the far-lateral approach : J Neurosurg 87 : 555-585,
1997
21. Yoshikazu O, Takeshi S, Masahiro N, Shinji O : Large Sixth Nerve
Neuroma involving the prepontine region. Neurosurgery 40 : 608610, 1997
22. Yun JS, Hwang SN, Park SW, Kim YB, Choi DY : Intracranial schwannoma of the spinal accessory nerve : J Korean Neurosurg Soc
27 : 678-682, 1998