Yutaka Nemoto, MD #{149}Yuichi Inoue, MD #{149}Takahiko Tashiro, Junro Oda, MD #{149}Saeko Kogame, MD #{149} Junsuke Katsuyama, Akira Hakuba, MD #{149}Yasuto Onoyama, MD

Intramedullary Spinal Significance of Associated at MR Imaging’ Magnetic resonance obtained in 35 patients tramedulbary spinal viewed. Hypointense Ti- and T2-weighted seen within or around all of which were in Hypointensity at the

Cord

MD MD

Kunizo

Mochizuki,

#{149}

MD

Tumors: Hemorrhage

(MR) images with intumors were reareas on both images were eight tumors, the cervical cord. tumor margin

was seen in seven cases. Hypointensity within the tumor was seen in two cases. (One case had both types of

hypointensity.) In seven surgically confirmed cases, hypointensity at the tumor margin was found to be a relatively firm pseudocapsule, and hypointensity

within

the

tumor

corre-

sponded to intratumoral hematoma. All of the tumors with hypointensity were ependymomas at histologic examination. When MR imaging shows an intramedullary tumor with hypointensity at the tumor margin, it is suggestive,

but

not

pathognomonic,

of an ependymoma. Index

terms:

Spinal

341.3674 #{149} Spinal cord, neoplasms,

Radiology

1992;

cord, hemorrhage,

cord, MR. 341.3636

341.1214

#{149} Spinal

182:793-796

b.

a. Figure

1. Case

weighted mass mass,

Y.N. (

RSNA,

1992

level

Ependymoma.

which

800/22,

of C2-3

with

to C-5, bloody

resonance

TI-weighted

20#{176} flip angle, hypointense

firm pseudocapsule

contained

AGNETIC

(a) Sagittal

(gradient-echo

a relatively

M

I From the Departments of Radiology (Y.N., Y.I., T.T., KM., JO., S.K., Y.O.) and Neurosurgery (J.K., A.H.), Osaka City University Medical School, 1-5-7 Asahi-machi, Abeno-ku, Osaka 545, Japan. Received June 11, 1991; revision requested July 2; revision received August 29; accepted September 6. Address reprint requests to

image

at the

showed

4.

diagnosis

of tumors,

to be difficult,

(MR)

however,

even

of the

MR

each

tumor

(1). A hypointense although on at the

(SE 600/40)

excitations)

at the

bottom

top

and

reveal

and

(b) 12-

a hyperintense

bottom.

Surgery

of the well-demarcated

cystic

fluid.

basis

sometimes, seen within

signal

areas

at the top and

imag-

ing can be used in the detection of spinal tumors, especially intramedullary tumors. MR imaging will demonstrate not only morphologic changes but also changes in signab intensity that are expected to give some clue in the differential diagnosis of intramedullary tumors. Histologic believed

image

four

intensity infrequently, periphery

is now

on the

intramedullary and T2-weighted our

tumor on both Tiimages. We focused

attention

on

this

hypomntense

area and found it to be particularly helpful in predicting the histologic findings

of the

tumor.

In this

article,

we describe (a) the surgical findings this hypointense area, (b) the correlation of this area with the histologic characteristics tumors, and

of the intramedublary (c) a possible pathophysi-

Abbreviation:

SE

of

of

area of an

is =

spin

echo.

793

of MR Imaging,

Summary

Surgical,

and Histologic

MR Im aging

Findings

Findings

Surgical

Findings Histologic

Case No.

Age/Sex

Tumor

I

59/F

C3-4

Site*

Hypointensity

to C-5

Tumor

margin

Well-demarcated

with multiple 2

49/F

C-i

Tumor

to C-S

Hypointense

Tumor

margin

solid

mass

cysts

Well-demarcated

cystic

Portion

Pseudocapsule

at top

Findings and

Ependymoma

at top and

Ependymoma

at top and

Ependymoma

bottom mass

Pseudocapsule

bottom 3

40/M

M, C5-6

Tumor margin; within the tumor

Well-demarcated with a cyst; hematoma

4

60/F

C2-3

Tumor

Well-demarcated

solid mass intratumoral

Pseudocapsule bottom Intratumoral

to C-S

margin

mass; 5

44/M

C-i

to C-4

Tumor

intratumoral

toma Well-demarcated

margin

cystic

hemacystic

hematoma

Pseudocapsule

mass

at top and

Ependymoma

at top

Ependymoma

bottom Pseudocapsule

and

bottom 6

18/M

C-3 to T6-7

Within

the

tumor

Well-demarcated

solid

with multiple cysts; tumorab hematoma 7

43/M

C-3 to C-S

Tumor

8

43/F

C2-3

Tumor

C

=

cervical,

M

obogic mechanism this hypointense

Between female)

AND

April

1985

(4-74

years

with

referred

T

to our

and old;

Well-demarcated No surgery

solid

mass

hematoma

Pseudocapsule No surgery

Ependymoma

Ependymoma Unknown

thoracic.

of

December

1990,

20 male

and

tumors

institution

None

margin margin

Intratumoral

METHODS

intramedullary

examination.

=

of production area.

MATERIALS 35 patients

medulla,

=

to C-6

mass intra-

for

of the

15

were

MR

imaging

patients

had

a

history of trauma and surgery of the spine. In 26 of the 35 patients, the histologic diagnosis was obtained, and in the remaining nine patients, clinical observation

was

ment.

performed

The

included mas, three

multiforme,

two

surgical

treat-

verified

11 ependymomas, hemangioblastomas,

blastomas

phomas,

without

26 histologically

five two

metastatic

tumors

astrocytotwo glio-

malignant

tumors,

lym-

and

one

neurinoma.

MR examinations

were

performed

with

a 0.5-T unit (Vista-MR; Picker International, Highland Heights, Ohio) and face coil. Sagittal spin-echo (SE) Tiweighted images (600/40 [repetition msec/echo and two

time

msecl,

axial SE TI-weighted excitations) with

two

a surtime

excitations)

images a contiguous

Figure

(800/40, section

thickness of 5 mm were obtained in all cases. Sagittal SE T2-weighted images (2,000/120, two excitations) were also obtamed with a section thickness of 5-10 mm without an intersection gap. Cradient-

echo flip

images angle)

(800/22, were

four

employed

excitations, in two

1.

Ependymoma.

(a) Sagittal

Ti-weighted

image

c. (SE 600/40)

shows

an inho-

mogeneous hypointense mass at the level of C3-4 to C-5 with hypointense areas. (b) Sagittal T2-weighted image (SE 2,000/i20) demonstrates an inhomogeneous hyperintense mass with edema. The hypointense areas at the tumor margin are more clearly depicted. (c) Sagittal Tiweighted image (SE 600/40) obtained after intravenous administration of gadopentetate dimeglumine shows inhomogeneous contrast enhancement. Surgery showed a relatively firm pseudocapsule at the top and bottom of the tumor.

20#{176}

Among the 35 cases, a hypointense area associated with a tumor was seen on both Ti- and T2-weighted images in eight cases. All tumors with the hypointense areas were located in the cervical cord. Total removal or subtotab removal of the tumor was performed in seven of the eight cases, #{149} Radiology

b. 2. Case

cases.

RESULTS

794

a.

while in the remaining case, histologic diagnosis was not obtained. The hypointense areas on MR images that were associated with tumors were divided into two different types (Table). One type was somewhat tnangular and seen at the top and bottom margins of the tumor (Figs 1, 2). The other was seen within the tumor along the long axis of the cord (Fig 3). Hypointense areas at the tumor mar-

gins were seen in seven cases and hypointense areas within the tumors, in two cases. (One tumor had both types of hypointense area.) Surgery showed that all the tumors with hypointense areas at the tumor margins were relatively well demarcated and that the hypointense areas corresponded to a relatively firm pseudocapsule that seemed to result from an old hematoma in the inter-

sharply marginated focal enhancement and to occupy the whole width of the spinal cord in the affected segment, while astrocytomas tended to enhance in a more patchy, irregular way, consistent with a more diffusely infiltrating

tumor,

eccentrically All of the with

and

to be located

in the affected cord. surgically verified tumors

hypointense

areas

were

ependy-

momas and accounted for approximately 64% (7 of ii) of the tumors in our ependymoma group. This high frequency seemed to be more or less based on the hesitation of the neurosurgeon in our institute to use surgical intervention for even a biopsy unless the tumor appeared so well circumscribed that total resection was possible, or unless the symptoms of the patient had progressively worsened. The hypointensity at the tumor margin demonstrated on MR images is attributed to hemosidenin deposits (7). While this hypointense area seems to be characteristic of ependymomas in our limited study, it has also been reported, although rarely, in intramedullary cavernous hemangiomas

Figure 3. Case 6. Ependymoma. (a) Sagittal Ti-weighted image (SE 600/40) shows an isointense mass with hypointense cysts at the cranial portion and at the level of C-6 to C-7. (b) On the sagittal 12-weighted image (SE 2,000/i20), the mass is relatively hyperintense and the cysts are hyperintense. Hypointense areas (arrows) within the tumor are recognized on both

TI- and 12-weighted well-demarcated medulla oblongata

images

but are seen

better

solid tumor associated was edematous.

with

face between the tumor and normal cord substance. At microscopy, many hemosiderin-laden macnophages were observed in the specimens taken from these areas. Hypointense areas within the tumor corresponded to intratumoral hematoma. In the seven surgically confirmed cases, histologic examination revealed that all these tumors were ependymomas. Microscopic examination showed no evi-

dence

of these

seven

more vascular than cases of ependymomas hypointense areas seven cases (64%).

tumors usual. were

being

Among 11 in our study, recognized in

DISCUSSION Most

intramedublary

are ependymomas,

spinal

astrocytomas,

tumors

or

hemangioblastomas. In general, hemangiobbastomas can be diagnosed before surgery on the basis of MR imaging and angiographic findings. On contrast-enhanced MR images, he-

Volume

182

Number

#{149}

2

on the T2-weighted

multiple

cysts

and

image.

Surgery

intratumoral

showed

hematoma.

mangiobbastoma will be demonstrated as a well-demarcated, enhanced mass that frequently accompanies syrinx and, less frequently, a curvilinear area of signal void indicating a vessel (13). Spinal angiography usually shows intense tumor stain and a draining

vein

that

is characteristic

of heman-

gioblastoma.

Differentiation

between

ependymo-

mas and astrocytomas before surgery is important for the surgeon because ependymomas of the spinal cord are so well circumscribed that they can apparently be completely removed (4), while astrocytomas have a propensity for infiltrating growth that makes complete removal difficult (5,6). It is not easy, even aging and other radiologic to differentiate one from

with

Panizeb

suggested

usefulness

et al (2) recently

MR immodalities, the other.

to show

the

of gadolinium-enhanced

MR imaging in differentiation. reported that ependymomas intense,

homogeneous,

mas. a

The

They tended and

(8). There

is no

description

in

the literature, to our knowledge, regarding a tendency toward bleeding in mntramedullary spinal ependymoWhy

did

hematomas

at the

tu-

mon margin so frequently accompany ependymomas in our cases? This phenomenon could be attributed to the following two factors: 1. One factor is the site of these tumors in the spinal cord. The cervical spinal cord seems to be the most motile during neck motion compared with other segments of the cord. In fact, Jirout (9) reported anteroposterior shift of the cord in the cervical canal with change in neck position by using air myebography. According to Breig and El-Nadi (10), the cervical dura and cord undergo axial compression and, hence, shortening and slackening in dorsal extension of the cervical

spine

with

the

head

tilted

backward, the cervical horizontal

and the nervous tissue of cord is under axial and tension in ventral flexion. 2. The other factor is the margin and mode of extension of intramedullary tumors. In neck motion, the tumors as well as the cervical cord sustain mechanical forces such as compression and stretching. Ependymomas are usually, but not always, well defined without intervening neural tissues, while most astrocytomas

ance, with

are

poorly

demarcated

in appear-

infiltrative, and intermingled nervous tissues (5). Radiology

795

#{149}

We speculate together seem between

cord neck

the

substance motion.

flexibility

that these two factors to make the interface tumor

and

the

normal

more vulnerable In other words,

in the

to since

well-demarcated

tu-

mor is slightly different from that in the adjacent normal cord, there will be a discrepancy in the amount of compression and stretching between them. Because ependymomas are usually well demarcated, there will be sliding at the interface of the tumor and the normal cord. This sliding will stretch and break either the feeding vessels or surface veins of the tumor, resulting

in a small

rhage. The axial ing forces seems top and bottom portion

of the

amount

of hemor-

sliding due to stretchto be greater at the than at the middle tumor.

Although hypointensity at mor margin was seen only in ependymomas in our limited this hypomntensity seems not pathognomonic

but

suggestive

ependymoma, because an MR of an intramedullary astrocytoma with hypointensity was shown

796

Radiology

#{149}

the tuthe study, to be

literature

tensity

no

special

at the

tumor

3.

comment

(11). hypoin-

margins

seen

on

MR images indicates intramedullary tumors to be relatively well demarcated from surrounding spinal cord tissue and that the frequency is higher among ependymomas. Further study should be performed to reinforce this statement, since our study is limited in its number of clinical cases. In conclusion, if an intramedullary tumor associated with hypointensity at the tumor margin can be seen on both Ti- and T2-weighted images, the tumor is relatively well demarcated from the adjacent normal cord and can be totally removed by means of surgery. Most of such tumors wifi be ependymomas when they are in the cervical spinal cord. #{149}

4.

Kaffenberger DA, Shah CP, Murtagh FR, Wilson C, Silbiger ML. MR imaging of spinal cord hemangioblastoma associated with syringomyebia. J Comput Msist Tomogr 1988; 12:495-498. Russell DS, Rubinstein U. Pathology of

of the nervous system. don: Arnold, 1989; 302-315. tumors

5.

6.

Malls mors.

References 1.

of 2.

Scotti C, Scialfa G, Cobombo N, Landom L. Magnetic resonance diagnosis of intramedullary tumors of the spinal cord. Neuroradiobogy i987; 29:130-135. Parizel PM, Baleriaux D, Rodesch C, et aL

Gd-DTPA-enhanced MR imaging tumors. AJNR i989; 10:249-258.

of spinal

LI.

Intramedullary

tramedullary

spinal

spinal

cord

Gomori Zimmerman

diology

Suppl

report

(Wien)

imaging

by high-field

MR. Ra-

1985; 157:87-93.

Fontaine S, Melanson trand G. Cavernous

D, Cosgrove hemangiomas

R, Berof the

cord: MR Imaging. Radiology 166:839-841. Jirout J. The mobility of the cervical spinal

9.

nal cord under normal diol 1959; 32:744-751. 10.

11.

tu-

JM, Grossman RI, Goldberg HI, PA, Bilaniuk LT. Intracranial

hematomas: 8.

cord

tumours:

of 22 cases. Acta Neurochir 1988; 43:9-12. 7.

5th ed. Lon-

Clin Neurosurg 1978; 25:512-539. Yasui T, Hakuba A, Katsuyama J, Nishimura S. Microsurgical removal of in-

Breig cervical

image in the

and

was presented on this matter Therefore, we can infer that

A, El-Nadi

spinal

AF.

conditions.

spiBr J Ra-

Biomechanics

cord. Acta Radiol

1988;

of the 1966;

4:602-624. Sze G, Krol Intramedulbary

G, Zimmerman RD, Deck MDF. disease of the spine: diag-

nosis using

gadolinium-DTPA-enhanced

MR imaging.

AJNR

i988;

9:847-858.