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77i
Pictorial
MR Imaging Louis
H. Wetzel1
of Sacral
and Errol
and Presacral
and
(three),
proved
chordoma
aneurysmal
bone
primary
sacral
neoplasms
(two),
giant-cell
tumor
cyst
(one),
and malignant
with sacral and Eleven had his-
including
(two),
schwannoma
had sacral arachnoid of
lesions
with
medium
Both
reprint
October
authors:
requests
AJR 154:771-775,
Axial and sagittal images were always obtained and were often supplemented by coronal oblique sacral images. A body coil with a 50-cm field of view was used in 1 2 patients and a 37-cm elliptical surface coil was used in 38 patients.
1 9, 1 989; accepted Department
21
in six patients
by One
,
Schwannomas
544-0771
neoplasm the lesion
primary
sacral neoplasm.
that arises from notochordal rembegins in the midline and involves
1)[i].
Tumor enlarge-
are usually benign.
Metastases are the most common reach the sacrum hematogenously
sacral neoplasms. They or via the subarachnoid
1989. the University
of Kansas
Medical
Center,
to L. H. Wetzel. April 1990 0361-803X/90/1
is the most common
ment ultimately causes destruction of adjacent sacral segments and a presacral mass (Fig. 2). Giant-cell tumor is the second most common primary sacral neoplasm (Fig. 3) [1]. These tumors are often unresectable because of their large size or strategic location (Fig. 3) [i]. Neural tumors originating in the sacral canal include ependymoma and schwannoma. They have a mainly longitudinal intracanalicular growth pattern (Figs. 4 and 5). Ependymomas are malignant and arise from ependymal cell clusters in the filum terminale [i].
myelography.
Radiology,
Chordoma It is a malignant nants. Typically
the fourth and fifth sacral vertebrae(Fig.
during
November
of Diagnostic
Neoplasms
(one).
(one).
1
4-i 0 mm and intersection spacing of 0-5 mm. Two pulse sequences were always used: 500-600/i 7-30 (TRITE) and 2100-2500/30,90.
(two),
patient had a surgically confirmed anterior sacral meningocele. Two patients had surgically proved presacral teratomas. Four patients had presacral extension of pelvic carcinoma including recurrent rectal carcinoma (two), bladder carcinoma (one), and carcinoma of the cervix
Received
magnet (Mag-
histiocytoma
fibrous
cysts. These were confirmed contrast
with a superconductive
ependymoma
Fourteen patients had secondary sacral neoplasms originating from breast carcinoma (three), lung cancer (two), rectal carcinoma (two), thyroid carcinoma (one), renal cell carcinoma (two), malignant melanoma (one), lymphoma (two), and multiple myeloma (one). Eight patients had surgically confirmed spinal dysraphism. Ten patients filling
MR studies were performed
netom, Siemens Medical Systems, Iselin, NJ) operated at 1 .0 T. Multisection spin-echo imaging was used with section thicknesses of
Sacral
Methods
Between May 1986 and August 1989, 50 patients presacral lesions were examined with MR imaging. tologically
Lesions
Levine
Sacral lesions are frequently overlooked because of the nonspecificity of associated symptoms and because the postenor curvature of the sacrum and the presence of overlying bowel gas cause difficulties in plain film evaluation [i]. CT is an excellent technique for imaging the sacrum and presacral space [i]. MR imaging has many of the advantages of CT, but adds multiplanar capability and improved soft-tissue contrast. This essay illustrates the use of MR imaging in evaluating sacral disorders.
Materials
Essay
C American
Roentgen
Ray Society
39th
St. and Rainbow
Blvd.
,
Kansas City, KS 661 03. Address
772
WETZEL
AND
LEVINE
AJR:154,
April 1990
Downloaded from www.ajronline.org by 193.0.65.67 on 10/07/15 from IP address 193.0.65.67. Copyright ARRS. For personal use only; all rights reserved
Fig. 1.-Small chordoma (arrow) on sagittal MR image, 500/30. Lesion arises in 54 but also involves contiguous parts of 53 and 55. Slight presacral extension (arrowheads) indents posterior rectal wall (A). Distal sacrectomy was successfully performed through S2-S3 junction.
Fig. 2.-Chordoma. Sagittal MR image, 500/30, shows extensive neoplasm (arrowheads) with obliteration of sacral canal and pre- and postsacral extension. Note preservation of 51-52 disk (arrow). Lack of involvement of disk indicates potential for radical resection. High-intensity areas in neoplasm (asterisks) corresponded to areas of hemorrhage in surgical specimen. Lesion was resected at mid 51 level.
Fig. 3.-Giant-cell
tumor.
A, Axial MR image, 500/17, shows tumor (arrowheads) replacing normal marrow fat in left sacral ala and body of Si. Tumor surrounds neural canal containing first left ventral sacral nerve root (arrow). B, Tumor (arrows) is inhomogeneous and of
intermediate
intensity
2100/90. There is tumor across left sacroiliac joint
Fig. 4.-Ependymoma. Sagittal MR image, 500/ 30, shows neoplasm (arrowheads) filling most of sacral canal. Lesion has penetrated sacral cortex at S3-S5, resulting in presacral mass (arrow). Growth pattern of lesion is mainly longitudinal in sacral canal, suggesting neural origin.
on T2-weighted extension
image,
(arrowhead)
Fig. 5.-Schwannoma. A, Sagittal MR image, 500/17, shows tumor (arrowheads) causing erosion of posterior surface of 52. High-intensity areas (arrows) corresponded to hemorrhage in surgical specimen. Confinement of lesion to sacral canal suggests neoplasm of neural origin. B, T2-weighted sagittal MR image, 2100/90, reveals high intensity of neoplasm (arrows). lncomplete low-intensity ring (arrowhead) in lower part of tumor probably represents hemosiderin and femtin deposition around hemorrhage.
AJR:154,
MR
April 1990
Fig. 6.-Metastatic
rectal carcinoma
OF
SACRAL
AND
PRESACRAL
LESIONS
773
in patient
who had previous abdominoperineal rectal resection. Sagittal MR image, 500/17, shows oval neoplasm (arrowheads) involving distal sacrum. There
were no other metastases,
and lesion probably
Downloaded from www.ajronline.org by 193.0.65.67 on 10/07/15 from IP address 193.0.65.67. Copyright ARRS. For personal use only; all rights reserved
reached sacrum via vertebral venous plexus of Batson. Note enlarged neurogenic bladder (B) and absence of rectum. Distal sacrectomy was performed.
Fig. 7.-Metastatic
malignant
melanoma
in pa-
tient with brain metastasis from previously resected cutaneous melanoma. Patient had recent onset of bladder incontinence. Sagittal MR Image, 500/17, shows metastasis (arrows) involving thecal sac at L5 and in sacrum. Lesion probably reached thecal sac via subarachnoid space.
Fig. 8.-Solitary sacral metastasis from occult renal cell carcinoma. Coronal oblique MR Image, 600/25, shows metastasis (arrows) involving Si and 52 and invading left first and second ventral neural canals.
Fig. 9.-Sacral noma in patient
metastases from lung carciwith rectal incontinence. Saglttal MR image, 500/17, shows metastases (asterisks) involving L4 and L5 and most of sacrum. Expansile midsacral lesion (arrowheads) narrows sacral canal. Sacral radiation produced relief from symptoms.
Fig.
10.-Spinal
dysraphism
with
tethered
conus medullans, partial sacral agenesis, and intradural lipoma. A, Sagittal MR image, 500/17, shows absence of sacrum below level of Si. Conus (arrow) Is tethered by intradural liporna (L). B, T2-weighted image, 2100/90, shows extenslon of neural tissue of tethered conus (arrow) Into lipoma (arrowheads). Note thecal sac ectasia.
space (Figs. 6 and 7). Occult renal cell carcinoma or thyroid carcinoma may present with solitary, symptomatic sacral metastases (Fig. 8). Sacral metastases may also be encountered on MR imaging when patients with known primary neoplasms develop symptoms suggesting cauda equina compression (Figs. 7 and 9).
Developmental
Abnormalities
Spinal dysraphism is a developmental anomaly that includes various combinations of spina bifida, meningocele, myelomeningocele, lipomyelomeningocele, intradural lipoma, intradural dermoid cyst, and tethering of the spinal cord [2]. MR imaging
WETZEL
Downloaded from www.ajronline.org by 193.0.65.67 on 10/07/15 from IP address 193.0.65.67. Copyright ARRS. For personal use only; all rights reserved
774
Fig. 1 1.-Sacral
arachnoid
AND
LEVINE
AJR:154,
cyst.
A, Sagittal MR image, 500/17, shows lesion (arrows) of intensity similar to CSF causing erosion (arrowhead). Note degeneration of L5/S1 disk and spondylolisthesis of U on 51. B, T2-weighted image, 2100/90, shows that cyst (arrowheads) remains isointense relative
sacral to CSF.
Fig. 12.-Sacral arachnoid cyst shown in coronal oblique MR image, 600/25. Cyst (solid arrow) arises from left 53 nerve sheath and causes medial displacement of adjacent left 54 nerve (open arrow). Generalized decrease in bone-marrow signal intensity was from myelofibrosis.
Fig. 13.-Anterior
sacral
year-old woman. A, Axial MR image,
500/17,
low-intensity
fluid collection
to sacrum. B, Sagittal
MR image,
reveals
narrow
channel
from meningocele thecal sac.
is invaluable in showing these abnormalities (Fig. i 0) and often obviates myelography in suspected spinal dysraphism. Sacral arachnoid cysts most commonly arise as diverticula of the second and third sacral nerve sheaths [i ]. Most are asymptomatic but some cause sacral erosion and back pain (Fig. i i). They are readily diagnosed on MR images (Figs. i i and 1 2). An anterior sacral meningocele results from herniation of the caudal meninges through an anterior sacral defect. These lesions are often asymptomatic but may cause symptoms by compressing pelvic viscera [i ]. MR imaging may show the connection between the cyst and the thecal sac (Fig. i3).
Presacral
Lesions
A wide variety of lesions occur in the presacral space. Sacrococcygeal teratomas are developmental in origin and are the most frequently encountered presacral masses in
April 1990
(M)
meningocele
in 47-
shows well-defined, (arrowheads) anterior
500/17, just left of midline (arrowheads) extending via defect in S4 to distal
children. They rarely first present in adult life (Fig. i 4) [i]. Most patients with sacrococcygeal teratomas have no evidence of bony sacrococcygeal abnormalities [i ]. Presacral extension of rectal, uterine, bladder, and prostatic carcinoma is readily diagnosed by CT and MR imaging. Diagnosis is more difficult when patients with pelvic carcinoma develop
presacral
masses
after surgery
or radiation
tion between tumor recurrence and fibrosis both CT and MR imaging (Fig. i 5) [3J.
therapy.
Distinc-
is difficult
with
Discussion
Although MR imaging can usually distinguish sacral neoplasms of neural origin (Figs. 4 and 5) from those of bone origin (Figs. i -3), it cannot distinguish among the various primary neoplasms and it cannot distinguish primary neoplasms from solitary metastases (Figs. 3 and 8). MR imaging is of great value in planning the management of sacral neo-
Downloaded from www.ajronline.org by 193.0.65.67 on 10/07/15 from IP address 193.0.65.67. Copyright ARRS. For personal use only; all rights reserved
AJR:154,
MR
April 1990
OF
SACRAL
AND
PRESACRAL
LESIONS
775
Fig. 14.-Benign presacral teratoma in 35-year-old woman. A, CT scan shows presacral mass without evidence of sacral erosion. Note posterior calcification (arrowhead) and fat/fluid level (arrow) in lesion. B, Axial MR image, 500/17, shows presacral mass (arrowheads). Note high-intensity fat (solid arrow) layering on lower-intensity fluid in lesion. Lowintensity area posteriorly (open arrow) represents calcification. C, T2-weighted image, 2100/90, shows reversal of signal intensities at fat/fluid interface (solid arrow). Posterior calcification (open arrow) remains of low intensity. C = ovarian cyst; U = uterus.
Fig. 15.-Local
recurrence
of rectal carcinoma
after abdominoperineal
resection
of rectum.
A, CT scan shows mass (arrows) anterior to lower sacrum. Distinction between postoperative B, Axial MR image, 500/17, shows low-intensity presacral mass (arrowheads). C, T2-weighted image, 2100/90, shows that intensity of most of mass (arrowheads) remains central area (arrow) represents recurrent neoplasm.
plasms because it accurately determines and intrasacral extent. If a lesion extends
both their soft-tissue proximal to the Si
S2 disk space, it is usually unresectable.
Patients
fibrosis low,
siS and recurrent -
surgery
or radiation
and recurrent suggesting
pelvic
neoplasm
fibrous
carcinoma [3].
tissue.
Is not possible. However,
in patients
high-intensity
managed
with
therapy
with known
bone metastases and symptoms suggesting cauda equina compression are often referred for spinal MR imaging. In this setting, sacral metastases are often responsible for the symptoms, therefore, the sacrum should be included in the MR study. MR imaging is more sensitive than CT in diagnosing spinal dysraphism; its use often obviates myelography in this disorder. MR also helps in the characterization of sacral arachnoid cysts. Benign and malignant presacral masses and their relationship to pelvic structures are well shown on MR images. However, MR often cannot distinguish between fibro-
REFERENCES 1 . Levine lesions.
E, Batnitzky S. Computed tomography of sacral CRC Crit Rev Diagn imaging 1984;21 :307-374
and
perisacral
2. Scatliffe JH, Kendall BE, Kingsley DPE, Britton J, Grant DN, Hayward AD. Closed spinal dysraphism: analysis of clinical, radiological, and surgical findings in 1 04 consecutive patients. AJR 1989;1 52: 1 049-i 057 3. De Lange EE, Fechner RE, Wanebo HJ. Suspected recurrent rectosigmoid carcinoma after abdominoperineal resection: MA imaging and histopathologic findings. Radiology i989;170:323-328
77i
Pictorial
MR Imaging Louis
H. Wetzel1
of Sacral
and Errol
and Presacral
and
(three),
proved
chordoma
aneurysmal
bone
primary
sacral
neoplasms
(two),
giant-cell
tumor
cyst
(one),
and malignant
with sacral and Eleven had his-
including
(two),
schwannoma
had sacral arachnoid of
lesions
with
medium
Both
reprint
October
authors:
requests
AJR 154:771-775,
Axial and sagittal images were always obtained and were often supplemented by coronal oblique sacral images. A body coil with a 50-cm field of view was used in 1 2 patients and a 37-cm elliptical surface coil was used in 38 patients.
1 9, 1 989; accepted Department
21
in six patients
by One
,
Schwannomas
544-0771
neoplasm the lesion
primary
sacral neoplasm.
that arises from notochordal rembegins in the midline and involves
1)[i].
Tumor enlarge-
are usually benign.
Metastases are the most common reach the sacrum hematogenously
sacral neoplasms. They or via the subarachnoid
1989. the University
of Kansas
Medical
Center,
to L. H. Wetzel. April 1990 0361-803X/90/1
is the most common
ment ultimately causes destruction of adjacent sacral segments and a presacral mass (Fig. 2). Giant-cell tumor is the second most common primary sacral neoplasm (Fig. 3) [1]. These tumors are often unresectable because of their large size or strategic location (Fig. 3) [i]. Neural tumors originating in the sacral canal include ependymoma and schwannoma. They have a mainly longitudinal intracanalicular growth pattern (Figs. 4 and 5). Ependymomas are malignant and arise from ependymal cell clusters in the filum terminale [i].
myelography.
Radiology,
Chordoma It is a malignant nants. Typically
the fourth and fifth sacral vertebrae(Fig.
during
November
of Diagnostic
Neoplasms
(one).
(one).
1
4-i 0 mm and intersection spacing of 0-5 mm. Two pulse sequences were always used: 500-600/i 7-30 (TRITE) and 2100-2500/30,90.
(two),
patient had a surgically confirmed anterior sacral meningocele. Two patients had surgically proved presacral teratomas. Four patients had presacral extension of pelvic carcinoma including recurrent rectal carcinoma (two), bladder carcinoma (one), and carcinoma of the cervix
Received
magnet (Mag-
histiocytoma
fibrous
cysts. These were confirmed contrast
with a superconductive
ependymoma
Fourteen patients had secondary sacral neoplasms originating from breast carcinoma (three), lung cancer (two), rectal carcinoma (two), thyroid carcinoma (one), renal cell carcinoma (two), malignant melanoma (one), lymphoma (two), and multiple myeloma (one). Eight patients had surgically confirmed spinal dysraphism. Ten patients filling
MR studies were performed
netom, Siemens Medical Systems, Iselin, NJ) operated at 1 .0 T. Multisection spin-echo imaging was used with section thicknesses of
Sacral
Methods
Between May 1986 and August 1989, 50 patients presacral lesions were examined with MR imaging. tologically
Lesions
Levine
Sacral lesions are frequently overlooked because of the nonspecificity of associated symptoms and because the postenor curvature of the sacrum and the presence of overlying bowel gas cause difficulties in plain film evaluation [i]. CT is an excellent technique for imaging the sacrum and presacral space [i]. MR imaging has many of the advantages of CT, but adds multiplanar capability and improved soft-tissue contrast. This essay illustrates the use of MR imaging in evaluating sacral disorders.
Materials
Essay
C American
Roentgen
Ray Society
39th
St. and Rainbow
Blvd.
,
Kansas City, KS 661 03. Address
772
WETZEL
AND
LEVINE
AJR:154,
April 1990
Downloaded from www.ajronline.org by 193.0.65.67 on 10/07/15 from IP address 193.0.65.67. Copyright ARRS. For personal use only; all rights reserved
Fig. 1.-Small chordoma (arrow) on sagittal MR image, 500/30. Lesion arises in 54 but also involves contiguous parts of 53 and 55. Slight presacral extension (arrowheads) indents posterior rectal wall (A). Distal sacrectomy was successfully performed through S2-S3 junction.
Fig. 2.-Chordoma. Sagittal MR image, 500/30, shows extensive neoplasm (arrowheads) with obliteration of sacral canal and pre- and postsacral extension. Note preservation of 51-52 disk (arrow). Lack of involvement of disk indicates potential for radical resection. High-intensity areas in neoplasm (asterisks) corresponded to areas of hemorrhage in surgical specimen. Lesion was resected at mid 51 level.
Fig. 3.-Giant-cell
tumor.
A, Axial MR image, 500/17, shows tumor (arrowheads) replacing normal marrow fat in left sacral ala and body of Si. Tumor surrounds neural canal containing first left ventral sacral nerve root (arrow). B, Tumor (arrows) is inhomogeneous and of
intermediate
intensity
2100/90. There is tumor across left sacroiliac joint
Fig. 4.-Ependymoma. Sagittal MR image, 500/ 30, shows neoplasm (arrowheads) filling most of sacral canal. Lesion has penetrated sacral cortex at S3-S5, resulting in presacral mass (arrow). Growth pattern of lesion is mainly longitudinal in sacral canal, suggesting neural origin.
on T2-weighted extension
image,
(arrowhead)
Fig. 5.-Schwannoma. A, Sagittal MR image, 500/17, shows tumor (arrowheads) causing erosion of posterior surface of 52. High-intensity areas (arrows) corresponded to hemorrhage in surgical specimen. Confinement of lesion to sacral canal suggests neoplasm of neural origin. B, T2-weighted sagittal MR image, 2100/90, reveals high intensity of neoplasm (arrows). lncomplete low-intensity ring (arrowhead) in lower part of tumor probably represents hemosiderin and femtin deposition around hemorrhage.
AJR:154,
MR
April 1990
Fig. 6.-Metastatic
rectal carcinoma
OF
SACRAL
AND
PRESACRAL
LESIONS
773
in patient
who had previous abdominoperineal rectal resection. Sagittal MR image, 500/17, shows oval neoplasm (arrowheads) involving distal sacrum. There
were no other metastases,
and lesion probably
Downloaded from www.ajronline.org by 193.0.65.67 on 10/07/15 from IP address 193.0.65.67. Copyright ARRS. For personal use only; all rights reserved
reached sacrum via vertebral venous plexus of Batson. Note enlarged neurogenic bladder (B) and absence of rectum. Distal sacrectomy was performed.
Fig. 7.-Metastatic
malignant
melanoma
in pa-
tient with brain metastasis from previously resected cutaneous melanoma. Patient had recent onset of bladder incontinence. Sagittal MR Image, 500/17, shows metastasis (arrows) involving thecal sac at L5 and in sacrum. Lesion probably reached thecal sac via subarachnoid space.
Fig. 8.-Solitary sacral metastasis from occult renal cell carcinoma. Coronal oblique MR Image, 600/25, shows metastasis (arrows) involving Si and 52 and invading left first and second ventral neural canals.
Fig. 9.-Sacral noma in patient
metastases from lung carciwith rectal incontinence. Saglttal MR image, 500/17, shows metastases (asterisks) involving L4 and L5 and most of sacrum. Expansile midsacral lesion (arrowheads) narrows sacral canal. Sacral radiation produced relief from symptoms.
Fig.
10.-Spinal
dysraphism
with
tethered
conus medullans, partial sacral agenesis, and intradural lipoma. A, Sagittal MR image, 500/17, shows absence of sacrum below level of Si. Conus (arrow) Is tethered by intradural liporna (L). B, T2-weighted image, 2100/90, shows extenslon of neural tissue of tethered conus (arrow) Into lipoma (arrowheads). Note thecal sac ectasia.
space (Figs. 6 and 7). Occult renal cell carcinoma or thyroid carcinoma may present with solitary, symptomatic sacral metastases (Fig. 8). Sacral metastases may also be encountered on MR imaging when patients with known primary neoplasms develop symptoms suggesting cauda equina compression (Figs. 7 and 9).
Developmental
Abnormalities
Spinal dysraphism is a developmental anomaly that includes various combinations of spina bifida, meningocele, myelomeningocele, lipomyelomeningocele, intradural lipoma, intradural dermoid cyst, and tethering of the spinal cord [2]. MR imaging
WETZEL
Downloaded from www.ajronline.org by 193.0.65.67 on 10/07/15 from IP address 193.0.65.67. Copyright ARRS. For personal use only; all rights reserved
774
Fig. 1 1.-Sacral
arachnoid
AND
LEVINE
AJR:154,
cyst.
A, Sagittal MR image, 500/17, shows lesion (arrows) of intensity similar to CSF causing erosion (arrowhead). Note degeneration of L5/S1 disk and spondylolisthesis of U on 51. B, T2-weighted image, 2100/90, shows that cyst (arrowheads) remains isointense relative
sacral to CSF.
Fig. 12.-Sacral arachnoid cyst shown in coronal oblique MR image, 600/25. Cyst (solid arrow) arises from left 53 nerve sheath and causes medial displacement of adjacent left 54 nerve (open arrow). Generalized decrease in bone-marrow signal intensity was from myelofibrosis.
Fig. 13.-Anterior
sacral
year-old woman. A, Axial MR image,
500/17,
low-intensity
fluid collection
to sacrum. B, Sagittal
MR image,
reveals
narrow
channel
from meningocele thecal sac.
is invaluable in showing these abnormalities (Fig. i 0) and often obviates myelography in suspected spinal dysraphism. Sacral arachnoid cysts most commonly arise as diverticula of the second and third sacral nerve sheaths [i ]. Most are asymptomatic but some cause sacral erosion and back pain (Fig. i i). They are readily diagnosed on MR images (Figs. i i and 1 2). An anterior sacral meningocele results from herniation of the caudal meninges through an anterior sacral defect. These lesions are often asymptomatic but may cause symptoms by compressing pelvic viscera [i ]. MR imaging may show the connection between the cyst and the thecal sac (Fig. i3).
Presacral
Lesions
A wide variety of lesions occur in the presacral space. Sacrococcygeal teratomas are developmental in origin and are the most frequently encountered presacral masses in
April 1990
(M)
meningocele
in 47-
shows well-defined, (arrowheads) anterior
500/17, just left of midline (arrowheads) extending via defect in S4 to distal
children. They rarely first present in adult life (Fig. i 4) [i]. Most patients with sacrococcygeal teratomas have no evidence of bony sacrococcygeal abnormalities [i ]. Presacral extension of rectal, uterine, bladder, and prostatic carcinoma is readily diagnosed by CT and MR imaging. Diagnosis is more difficult when patients with pelvic carcinoma develop
presacral
masses
after surgery
or radiation
tion between tumor recurrence and fibrosis both CT and MR imaging (Fig. i 5) [3J.
therapy.
Distinc-
is difficult
with
Discussion
Although MR imaging can usually distinguish sacral neoplasms of neural origin (Figs. 4 and 5) from those of bone origin (Figs. i -3), it cannot distinguish among the various primary neoplasms and it cannot distinguish primary neoplasms from solitary metastases (Figs. 3 and 8). MR imaging is of great value in planning the management of sacral neo-
Downloaded from www.ajronline.org by 193.0.65.67 on 10/07/15 from IP address 193.0.65.67. Copyright ARRS. For personal use only; all rights reserved
AJR:154,
MR
April 1990
OF
SACRAL
AND
PRESACRAL
LESIONS
775
Fig. 14.-Benign presacral teratoma in 35-year-old woman. A, CT scan shows presacral mass without evidence of sacral erosion. Note posterior calcification (arrowhead) and fat/fluid level (arrow) in lesion. B, Axial MR image, 500/17, shows presacral mass (arrowheads). Note high-intensity fat (solid arrow) layering on lower-intensity fluid in lesion. Lowintensity area posteriorly (open arrow) represents calcification. C, T2-weighted image, 2100/90, shows reversal of signal intensities at fat/fluid interface (solid arrow). Posterior calcification (open arrow) remains of low intensity. C = ovarian cyst; U = uterus.
Fig. 15.-Local
recurrence
of rectal carcinoma
after abdominoperineal
resection
of rectum.
A, CT scan shows mass (arrows) anterior to lower sacrum. Distinction between postoperative B, Axial MR image, 500/17, shows low-intensity presacral mass (arrowheads). C, T2-weighted image, 2100/90, shows that intensity of most of mass (arrowheads) remains central area (arrow) represents recurrent neoplasm.
plasms because it accurately determines and intrasacral extent. If a lesion extends
both their soft-tissue proximal to the Si
S2 disk space, it is usually unresectable.
Patients
fibrosis low,
siS and recurrent -
surgery
or radiation
and recurrent suggesting
pelvic
neoplasm
fibrous
carcinoma [3].
tissue.
Is not possible. However,
in patients
high-intensity
managed
with
therapy
with known
bone metastases and symptoms suggesting cauda equina compression are often referred for spinal MR imaging. In this setting, sacral metastases are often responsible for the symptoms, therefore, the sacrum should be included in the MR study. MR imaging is more sensitive than CT in diagnosing spinal dysraphism; its use often obviates myelography in this disorder. MR also helps in the characterization of sacral arachnoid cysts. Benign and malignant presacral masses and their relationship to pelvic structures are well shown on MR images. However, MR often cannot distinguish between fibro-
REFERENCES 1 . Levine lesions.
E, Batnitzky S. Computed tomography of sacral CRC Crit Rev Diagn imaging 1984;21 :307-374
and
perisacral
2. Scatliffe JH, Kendall BE, Kingsley DPE, Britton J, Grant DN, Hayward AD. Closed spinal dysraphism: analysis of clinical, radiological, and surgical findings in 1 04 consecutive patients. AJR 1989;1 52: 1 049-i 057 3. De Lange EE, Fechner RE, Wanebo HJ. Suspected recurrent rectosigmoid carcinoma after abdominoperineal resection: MA imaging and histopathologic findings. Radiology i989;170:323-328
