NOVEMBER,
SCHWANNOMAS NERVOUS Downloaded from www.ajronline.org by 45.32.65.22 on 06/21/16 from IP address 45.32.65.22. Copyright ARRS. For personal use only; all rights reserved
By
J. DANZIGER, S. BLOCH,
D.M.R.D.
D.M.R.D.
R.C.P.
UNIV.
EDIN.,
OF
LOND.,
and
H.
THE SYSTEM*
CENTRAL
R.C.S. ENG., M.MED. PODLAS, D.M.R.D.
JOHANNESBURG,
SOUTH
5975
(RAD.D.)
R.C.P.
UNIV. CAPE TOWN, LOND, R.C.S. ENG.
AFRICA
ABSTRACT:
Isolated schwannomas may occur in many different situations within the central nervous system. Most neurilemmomas are benign, and enucleation after longitudinal dissection of the nerve will usually affect a cure. It is for this reason that the roentgenological appearances should be appreciated and this diagnosis considered so as to attempt total surgical removal. pharyngeal and other motor nerves are usually involved in the multiple manifestation of von Recklinghausen’s disease, but as sites for solitary schwannomas are cxtremely rare.
I SOLATED eight percent
schwannomas form of all primary intracranialabout tumors, usually occur during the middle years of life, and are twice as common in females as in males.9”3 They are extremely rare in childhood8 and, as in an adult, the acoustic nerve is the site of predilection.3 Neurinomas of the spinal cord are relatively common, accounting for about 30 percent of all spinal tumors.7 The purpose of this communication is to report the roentgenographic appearances of schwannomas occurring in the central nervous system. CRANIAL
NERVE
This tumor has a affect sensory nerves segment of the root the pia mater. The frequently involved, the tumor has been the trigeminal nerve.
B
projection,
From the Department
of Radiology,
non-filling Princess
Nursing
NEURINOMAS
Acoustic
neurinomas account for apeight percent of all intracranial tumors and for 8o percent of tumors of the cerebello-pontine angle.’3 Most, but not all, acoustic neurinomas originate within the internal auditory canals, presumably at the junction between the neunilemma! sheath arising from the peripheral ganglia and the neuroglial fibers extending peripherally from the brain stem. The patient usually presents with unilateral sensonineural hearing loss, followed by slight dizziness or imbalance and less frequently by true vertigo.’7 Roentgenographic evaluation of the internal auditory canal is best performed by
tendency to selectively and arises on a distal after it has penetrated acoustic nerve is most although on occasions observed arising from The vagus, glosso-
demonstrating
ACOUSTIC
proximately
INVOLVEMENT
FIG. I . (A) Tomography of the internal auditory canal ( I ) with shortening of its posterior
oblique
(A)
meatus wall. (B)
demonstrating
widening
of the
Posterior of the left internal
fossa cisternogram, auditory canal
Home,
South
Johannesburg,
692
Africa.
left
shoot (
).
internal
through
auditory
prone!
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VOL.
No.
525,
Schwannomas
3
of the
Central
Nervous
System
693
p.-
FIG.
tion
2.
(A)
Vertebral
angiogram,
of the left anterior
demonstrating
a mass
anteroposterior
inferior superolaterally
projection
with
cerebellar
artery ( I ) around in the cerebello-pontine
tomography where : (a) erosion of the cortical line surrounding the lumen of the canal; (b) widening by i to 2 mm of any portion of the internal auditory canal in comparison to the corresponding segment of the opposite side; (c) shortening of the posterior wall by at least 2 to 3 mm; and (d) shorten-
ing more
of
subtraction,
the mass. angle. the
when
demonstrating
(B) Posterior
crista
compared
falciformis
with
marked elevacisternogram,
fossa
by
the
i
normal
mm
or side
(Fig. i1) may be observed. Study of the cerebello-pontine cistern and of the subarachnoid space within the internal auditory canal is performed by vertebral angiography (Fig. 2d), air studies,
J’
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694
Danziger,
S. Bloch
and
FIG. 5. strating bone
H.
Podlas
NOVEMBER,
Skull, anteroposterior projection, destruction of the apex of the left
5975
demonpetrous
( 1).
ment
in the internal auditory meatus (Fig. In the study of the internal auditory canal with positive contrast medium, incomplete filling may occur due to anatomic variants or conditions other than a tumor. These include the size of the canal, which varies from 2 to 10 mm with an average of 4.5 tO 5 mm, shortening of the meningeal sleeve cul-de-sac, and viscosity of the myodil, when the canal is relatively small, since the size of the neurovascular bundle remains constant.’6 I f pneumoencephalography or ventniculography is performed, this will demonstrate the size of the tumor within the cerebello-. IB).
FIG. 4. Myodil ventriculogram, posterior projection, showing aqueduct and partially filled the right.
brow up anterodisplacement of the fourth ventricle to
and posterior fossa cisternography (Fig. iB). When a mass is present, its vertical diameter and extension along the posteromedial aspect of the petrous bone can be evaluated as well as the extent of involve-
L
6. Left
forward physeal
I angiogram, and medial artery ( I).
displacement
(
Anteroposterior
and
of the
portion
ganglion
I
..) lateral of the
projections, carotid
siphon.
demonstrating Note
the
downward, meningohypo-
VOL.
No.
125,
Schwannomas
3
of the
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pontine angle, by the extent that stem is displaced with related (Fig. 3, ii and B; and 4). (B) TRIGEMINAL
These
are rare
Central
Nervous
System
695
the brain rotation
TUMORS
and
comprise only 0.2 pertumors and occur most commonly in the fourth decade.’4 They originate in the gassenian ganglion or tngeminal nerve root and therefore will be located in Meckels’ cave or in the cenebellopontine angle. When the tumor increases in size, it may become dumbell in shape and will then be located in both the middle and posterior cranial fossae. These tumors are well circumscribed, grow very slowly and consequently reach a large size before of intracranial
cent
causing
sufficient
symptoms
to
require
FIG. 7. Carotid angiogram, lateral arterial showing elevation and posterior displacement the proximal portion of the middle cerebral by a mass. Note the meningohypophyseal tery ( I ) supplying the tumor.
in-
vestigation. Their although depending
symptomatology is fairly typical the manifestations may be varied upon the site ofonigin and direction of spread of the tumor.’2 Plain roentgenograms of the skull may show destruction of the anteromedial portion of the petrous apex which is smooth and well delineated (Fig. 5). With extension of the tumor into the middle cranial fossa, carotid angiography will demonstrate that the ganglial part of the siphon (which is normally located cxtradurally) is displaced forward, downward
and
medially
also
be
group
(Fig.
6, 1
elevation
of
of arteries,
phase, of artery ar-
and B). There may the middle cerebral
stretching
of the
anterior
basal ofRosenthal. A tumor circulation may be evident, usually deep within the middle fossa supplied by the tentonial branch of the meningo-hypophyseal artery (Fig. 7). Spread of tumor into the posterior cranial fossa will be shown by elevation of the posterior cerebral artery, and destruction choroidal
artery,
and
of the
elevation
vein
of
the
anteromedial
portion
of the
petrous
apex.
w .
I
. -
.
.
..
S
.
.
.
.
-.
.
.
.5
*
..
S
S
.
..
, .
.
.. S
.
. .
.
.
.
S
.
. S
4
.
S
. .
S
.
S S S
A -
FIG.
--
=
8. Brain
__.
scan,
-
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-
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-‘
..
.
.
kt,
fl
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.
S
the
and (B) lateral projections, anterior part of the middle
. S
S
‘
demonstrating cranial
fossa
.
.
-
I
---s-
(A) anteroposterior uptake within
.
#{149}
. S
.
#{149}
..
an area
( I).
#{149}
S
#{149}
S of increased
J.
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696
Danziger,
S. Bloch
and
H.
Podlas
NOVEMBER,
1975
rounding the area ofcalcification suggesting that the latter lay in the pes hippocampi (Fig. io). Right carotid angiography demonstrated slight asymmetry of the middle cerebral arteries, the knee of the right middle cerebral artery being displaced medially. No tumor circulation was demonstrated. The mass was removed surgically from the temporal lobe and histologically proved to be a schwannoma. SCHWANNOMA
Fio.
9. Tomography of middle cranial fossa, lateral projection, demonstrating an area of irregular calcification in the right temporal region ( ).
Radioactive brain scanning may demonstrate the situation of the tumor by an area of increased uptake lying deep within the middle cranial fossa (Fig. 8, 4 and B). INTRACEREBRAL
SCHWANNOMA
Parenchymatous schwannomas of the brain are rare.’8 As far as we are aware, only two other documented reports of intracerebral schwannomas have been published.6” Our patient complained of episodes of uncontrollable behaviour of which he had no recollection. Roentgenograms of the skull showed an area of calcification in the right temporal region and slight enlargement of the right middle cranial fossa. Tomography confirmed the presence of a well defined area or irregular calcification in the right middle fossa (Fig. 9). Pneumoencephalography showed a cap of air sur-
FIG. 30. Pneumoencephalogram, right temporal horn
( I ) located
showing
above
an area
in the pes hippocampi.
air
in
of calcification
the
ARISING PITUITARY
WITHIN
THE
FOSSA
To the best of our knowledge, a schwannoma arising within the pituitary fossa has not been previously reported. This patient presented with a history of headaches and progressive blindness. This tumor produced destruction of the pituitary fossa, extending upward to dcvate and encroach onto the optic nerves and downwards into the sphenoid sinus and nasopharynx. Lateral extension of the tumor produced occlusion of both carotid arteries by direct involvement as well as destruction of the right petrous temporal bone (Fig. i I ; and i 2, ii). The tumor was surgically visualized and histologically proved. ORBITAL
A schwannoma
bit
is considered
SCHWANNOMAS
occurring within the orto be a rare tumor.5 This
FIG. I I . Pneumoencephalogram, intrasellar mass extending Note the destruction of literation of the sphenoid
the nasopharynx
( I).
demonstrating an superiorly (open arrow). the pituitary fossa, obsinus and extension into
VOL.
525,
No.
3
Schwannomas
of the
Central
Nervous
System
697
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S
FIG. I 2. Bilateral carotid angiogram, lateral arterial phases, demonstrating occlusion of both internal carotid arteries as far as the carotid siphon. The intracranial circulation on the left is filling via the vertebrobasilar system by means of collateral circulation in the neck.
is a localized, nerve sheath distinctive exophthalmos
encapsulated, tumor growing clinical features. and blurring
usually benign slowly without It can cause of vision by
pressure may
be
larged strated
on the optic nerve.’0 very vascular, supplied ophthalmic artery, and on carotid angiography
This tumor by an enwell demon(Fig. 13, 4
A FIG. 13. Selective left internal carotid onstrating an enlarged ophthalmic
bit(1).
angiogram
artery
with
supplying
subtraction,
a vascular
(A)
tumor
arterial
within
(B) venous phases, demthe superior part of the or-
and
J.
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698
Danziger,
S. Bloch
and
H.
14. Lu ,.r spine, (A) lateral and (B) anteropostenior prc posterior margin of a lumbar vertebra produced by a schwannoma Note that the adjacent pedicle is thinned inferiorly and medially.
and B). Venography may aid in defining the situation of the mass lesion within the orbit, but gives no indication as to its pathology. If the intra-orbital pressure is significantly elevated, there may be nonvisualization of the superior ophthalmic
FIG.
15. Myelography
in three
patients,
showing
Podlas
NOVEMBER,
ections, demonstrating originating within
the
scal spinal
)ing of canal (
5975
I).
vein on the involved side. Recurrence of the tumor after total cxcision is uncommon but does occur. This is considered to be due to residual elements of tumor remaining after surgery rather than due to malignant change.
the
typical
cap
deformity
of intradural
neurinomas.
VOL.
525,
No.
Schwannomas
3
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SPINAL
of the
Central
Nervous
System
699
NEURINOMAS
These tumors may be situated at any point along the long axis of the spinal cord or cauda equina. Since these tumors originate from the nerve sheath, they may be situated extradurally, intradurally, or have an element which is situated both extra and intradurally. ( A)
INTRADURAL
NEURINOMAS
These are in direct contact with the contrast medium. Hence, they are sharply outlined by the dye as clear cut cap defects (Fig. ii). This is their most common characteristic feature.’ As they arise from the
FIG. 17. Cervical demonstrating
dumbbell larged
1”
-.
demonstrating contrast column
an extradural at T2 ( I).
displacement
schwannoma intervertebral
at foramen
oblique projection, component of
C3/C4.
(
Note
the
a
en-
).
roots, they tend to lie to one side of the midline and displace the cord to the contralateral side. Those that occupy a more central position during their growth, either in front of or behind the spinal cord, displace the cord in a sagittal direction. This results in an anteroposterior compression of the cord, causing an increase in its coronal diameter. The block produced by such a tumor will be indistinguishable from that produced by an intramedullary tumor in the anteroposterior projection. A lateral projection will, however, reveal the relationship of the tumor to the spinal cord. The symptomatology varies according to nerve
jection, of the
myelogram, the intradural
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700
J.
Danziger,
S. Bloch
and
H.
Podlas
NOVEMBER,
1975
the cauda equina if eccentrically situated. If the tumor is centrally located a central cap-shaped defect is produced. Neurinomas in this region attain a large size and produce featureless total blocks.4 (B)
EXTRADURAL
NEURINOMAS
Like other extradural tumors, these displace the arachnoid from the pedicles, producing a lateral indentation on the contrast column with or without complete obstruction, depending on the size of the tumor (Fig. i6). ( C) INTRA AND EXTRADURAL
FIG. I 8. Vertebral angiogram, lateral demonstrating anterior displacement bral artery by a schwannoma.
projection, of the verte-
the situation of the tumor in the spinal canal.’ Plain roentgenograms are helpful only in approximately 30 percent of cases.2 The most frequent primary roentgenographic finding is enlargement of the adjacent intervertebral foramen due to pressure erosion produced by growth of the tumor along the axis of the root through the foramen. This area of constriction at the foramen causes the tumor to be dumbbell in shape, and thus produces pressure erosion of the adjacent bone. Widening of the spinal canal with indentation into the dorsal aspect of the related vertebral body may also be observed (Fig. 14, 4 and B). Diagnostic accuracy is in the region of 98 percent with myelography.2 The myelographic appearances will vary depending upon whether the tumor is situated extraor intradurally : intradural tumors situated below the level of the spinal cord may cause displacement of the nerve roots of
NEURINOMAS
The myelographic pattern is influenced by the size of each component of the dumbbell tumor (Fig. 17). The intradural portion generally produces the typical cap deformity with displacement of the spinal cord. The extradural part can be discerned only if there is a lateral indentation on the side of the tumor in addition to the cap defect. This will be evident ifthe extradural part is of sufficient size and is intraspinally located. When the schwannoma is situated in the cervical region, vertebra! angiography is valuable in defining the extent of the antenor and medial displacement of the yentebral artery by the tumor, since this may not be evident from the size of the enlarged intervertebral foramen (Fig. i 8). J. Danziger, Princess Esselen
M.D. of Radiology Nursing Home
Department
Street
Hillbrow
2001
J ohannesburg,
South
Africa
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