1239
Synovial Cysts of the Lumbosacral
Spine: Diagnosis by MR Imaging
Shih S. Liu 1
Kenneth D. Williams2
Burton P. Drayer-2
Robert F. Spetzler1
Volker K. H. Sonntag 1
Intraspinal synovial or ganglion cysts are uncommon lesions associated with degenerative lumbosacral spine disease. CT usually reveals cystic lesions adjacent to a facet
joint, and they may show calcification. MR imaging of four surgically confirmed cases
of intraspinal synovial cysts revealed subtle signal changes compared with CSF. Short
TR/TE images showed the lesions to be slightly hyperintense in three cases and
isointense in one case. Long TR/TE sequences revealed a hyperintense appearance in
two cases and a hypointense appearance in the others. A peripheral rim of decreased
signal on long TR/TE images probably reflects fine calcification or hemorrhage in the
margins of the cysts.
The multiplanar and contrast characteristics of MR make this technique well suited to
the diagnosis of herniated disk, degenerative facet disease, and synovial cyst.
AJNR 10:1239-1242, November/December 1989; AJR 154: January 1990
Intraspinal synovial or ganglion cysts are associated with degenerative lumbosacral spine disease. The increasing number of recent reports [1-8] probably
reflects the improved diagnostic accuracy afforded by CT. The characteristic CT
appearance is usually a calcified, cystic lesion adjacent to a facet joint, as first
reported by Hemminghytt et al. [9]. There are two reports of MR imaging in the
diagnosis of synovial cysts. Granat et al. [1 OJ first reported that MR was diagnostic
in one case but noncontributory in a second. Azzam [11] has recently described
the MR diagnosis of a midline lumbar ganglionfsynovial cyst. We present four
surgically treated cases of lumbar intraspinal synovial cysts that were diagnosed
preoperatively by MR.
Case Reports
Case 1
Received December 1, 1988; revision requested
January 31 , 1989; revision received March 15,
1989; accepted March 21, 1989.
'Department of Neurological Surgery, Barrow
Neurological Institute, 350 W. Thomas Rd., Phoenix, AZ 85013. Address reprint requests to R. F.
Spetzler.
• Department of Radiology, Barrow Neurological
Institute, Phoenix, AZ 85013.
0195-61 08/89/1 006- 1239
cc American Society of Neuroradiology
A 57-year-old man presented with numbness of the left anterior thigh that he had
experienced for 31 years. Intermittent pain in his left calf became persistent and severe about
7 weeks before hospitalization. He denied any trauma, although he had been involved in
multiple sports injuries. On examination, his left thigh was atrophied but the calf muscles
were normal. Patellar reflex was absent on the left and hypoactive on the right. Sensory
examination revealed diminished sensation to light touch and pin prick on the anterior aspect
of the left thigh.
The spine was examined with a 1.5-T MR imager. Short TR/TE (T1-weighted) axial images
at L4-L5 (Fig. 1A) revealed bilateral severe facet joint degeneration with bony hypertrophy
and large posterolateral extradural impressions upon the thecal sac, which was markedly
narrowed. These extradural lesions were centered on the facet joints and were slightly
hyperintense relative to CSF. A hypointense rim was best seen on a sagittal long TRfTE (T2weighted) image (Fig. 1B). The synovial cyst was mildly hypointense relative to CSF on the
long TR/TE image. The decreased signal intensity of the L3-L4 and L5-S1 intervertebral
disks reflected disk desiccation resulting from degenerative disk disease. Signal hyperintensity
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A
LIU ET AL.
B
c
AJNR:10, November/December 1989
D
Fig. 1.-Case 1. MR images at 1.5 T.
A, 5-mm-thick axial T1-weighted SE image (800/20/2) at L4-L5.
B, 5-mm-thick sagittal T2-weighted SE image (2000/80/2) of lumbosacral spine.
C, Anteroposterior radiograph from lumbar myelogram.
D, Axial postmyelogram CT image at L4-L5.
of the adjacent endplates of LS and 51, due to increased marrow fat,
was a consequence of degenerative disk disease. Lumbar myelography confirmed bilateral extradural masses compressing the thecal
sac (Fig. 1C). The postmyelogram CT demonstrated arthropathy with
vacuum phenomenon involving the left facet joint; the cysts were
located laterally, adjacent to the facet joints (Fig. 1 D).
Bilateral L4-L5 laminectomies were performed. Synovial cysts,
arising bilaterally from the L4-L5 facet joints, were totally excised.
Histologic examination revealed that the cyst wall was composed of
reactive synovial membrane. The patient has done well 8 months
postoperatively.
Case2
A 67-year-ok:l man presented with a history of chronic low back
and right leg pain for 1 year. The pain radiated along the posterolateral
aspect of the thigh to the midcalf. On examination he was tender
over the right sciatic notch. The straight leg-raising test was positive
at 20° on the right. His sensory examination was normal.
An MR axial image at L4-L5 showed a right posterolateral mass
near the facet joint compressing the thecal sac. The mass had a
greater signal intensity than adjacent CSF on a short TR{TE sequence
(Fig. 2A). The peripheral hypointensity of the synovial cyst was
accentuated on the long TR{TE sagittal image, while the more central
portion of the cyst had greater signal intensity than CSF (Fig. 28).
Images were acquired at 0.35 T.
The patient had a right L4-L5 laminectomy with excision of the
synovial cyst, which arose from the right L4-L5 facet joint. The cyst
wall was composed of reactive fibrous connective tissue.
The patient did well for 8 months postoperatively. He returned with
complaints of left-sided leg pain. Physical examination revealed weakness of plantar flexion on the left and decreased sensation to pin
prick and light touch along the sacral one dermatome. He had an
absent ankle jerk on the left. MR revealed lumbar stenosis at L4-L5.
He underwent a lumbar laminectomy and fusion 20 months after his
initial surgery. He is asymptomatic a month after his second surgery.
Case3
A 58-year-old woman presented with right leg pain of 3 months
duration, which radiated along the posterolateral aspect of the thigh
A
B
Fig. 2.-Case 2. MR images at 0.35 T.
A, 5-mm-thick axial T1-weighted SE image (600/20/2) at L4-L5. Arrow
indicates medial margin of right extradural mass.
B, 5-mm-thick sagittal lumbosacral T2-weighted SE image (1500/
120/2).
to the calf. Examination revealed mild lumbosacral tenderness with a
positive straight leg-raising maneuver on the right at 40°. She had no
objective motor weakness or sensory deficits. The right Achilles reflex
was absent.
Short TR{TE axial MR images at 1.5 T demonstrated a right
posterolateral mass compressing the thecal sac and encroaching
upon the right intervertebral foramen at LS-51 (Fig. 3). This synovial
cyst was slightly hyperintense relative to CSF and was approximately
centered at the right facet joint. A sagittal long TR{TE sequence (not
shown) revealed hypointensity of the cyst relative to CSF, with a
more subtly hypointense peripheral margin.
Right L5 and 51 hemilaminectomies with decompression of the
right 51 nerve root were performed. A cyst with 1 ml of xanthochromic
fluid arose from the facet joint, adhering to the hypertrophic ligamentum flavum and compressing the S 1 nerve root. The cyst was totally
excised. Histologic examination showed a cyst wall of dense fibrous
connective tissue with multiple foci of dystrophic calcification. The
patient has no complaints 11 months postoperatively.
AJNR:1 C, November/December 1989
MR OF SYNOVIAL CYSTS
1241
Fig. 3.-case 3. MR images at 1.5 T. 5-mm-thick
axial T1-weighted SE images (800/20/2) at and just
cephalad to L5-S1.
Case4
A 63-year-old woman presented with a 2-year history of progressive right leg pain in the distribution of the L4 nerve root. No history
of trauma was obtained.
Although sensory examination was normal, the right quadriceps
and hamstrings were weak, with absent right patellar and Achilles
reflexes.
Spinal MR at 1.5 T disclosed, in the right lateral recess at the L4L5 level, a lesion that extended into the intervertebral foramen (Fig.
4A). The epidural fat ventrolateral to the thecal sac was observed,
and the right lateral aspect of the thecal sac was compressed. The
mass effect was centered on the facet joint and appeared contiguous
with the joint space. A subtle hypointensity, best seen on the long
TRfTE image, demarcated the borders of this cyst, which was
isointense with CSF on the short TRfTE sequence and slightly
hyperintense relative to CSF on the long TRfTE sagittal image (Fig.
48). The sagittal image assisted in clarifying that the lesion was not
a herniated nucleus pulposus, as it showed no continuity with the
normal-appearing L4-L5 intervertebral disk.
The patient underwent a partial right L4-L5 hemilaminectomy with
total excision of a 1 x 1-cm cyst arising from the right L4-L5 facet
joint. Histologic examination revealed that the cyst wall was composed of hyperplastic synovial membrane. The patient has no complaints 9 months postoperatively.
Discussion
Intraspinal synovial or ganglion cysts are uncommon. A
review of 54 reported cases (including the present four cases)
reveals a female predominance (38 females, 16 males) [1-1 0,
12-23]. Their ages range from 33 to 76 years, with a mean
of 58 years. Most patients are symptomatic at the time of
diagnosis. Incidental synovial cysts have been described [9,
21 ). Motor deficits were observed in 44.2%, sensory deficits
in 28%, reflex changes in 31 %, and no neurologic deficits in
38.5%.
In these 54 cases, 61% (33 cases) were located at the L4L5 interspace, 17% (nine cases) at the L3-L4 interspace,
13% (seven cases) at the L5-S1 interspace, and 9% (five
cases) in the cervical region. Bilateral synovial cysts have
been reported in three cases (Mercader et al. [6], Shushan et
al. [22], and case 1 in the series reported here).
The origin of synovial cysts remains controversial. Most
develop as a consequence of degenerative joint disease or
trauma [17-19]. This is further supported by the frequency
of these cysts at the L4-L5 and L5-SIIevels, which represent
the most mobile segments of the lumbar spine and are the
most common locations for degenerative disease.
Myelography is usually inconclusive, revealing an extradural
defect not immediately adjacent to the disk space. CT shows
a cystic lesion with or without calcification located laterally
adjacent to the facet joint. In 11 of 23 cases, calcification has
been identified on CT [1-4, 6-10, 14, 23]. These cysts may
be difficult to differentiate from other intraspinal cysts or from
cystic neurofibroma and large herniated disks with free fragments.
MR in our four cases revealed minimal signal intensity
difference between the cyst and CSF on either short or long
TR{TE sequences. In three cases the lesions were slightly
hyperintense relative to CSF on the short TR{TE images; in
the fourth case, the cyst was isointense with CSF. In two
cases the cysts were slightly hyperintense relative to CSF on
the long TR{TE sequences and in two cases they were
Fig. 4.-Case 4. MR images at 1.5 T.
A, 5-mm-thick axial T1weighed SE images (1000/
20/4) through L4-L5 Intervertebral foramina. Arrow
identifies mass lesion in
right intervertebral foramen.
8, 5-mm-thick sagittal
T2-weighted SE image
(2500/80/1) just to right of
midline.
A
B
1242
LIU ET AL.
hypointense. These signal intensity changes may require careful manipulation of width and level of the image display
window to avoid overlooking the lesion. All of our cases had
a peripheral hypointensity accentuated on the long TR{fE
images. This finding most likely represents fine calcification
or hemorrhage in the margins of the cyst [7]. Joint capsule
ligaments and dura are also of low signal intensity and may
contribute to this appearance. The lateral location of the mass
effect and its relationship to the facet joint is helpful in
suggesting the diagnosis of a synovial cyst. Careful interpretation of both the axial and sagittal images is necessary to
distinguish clearly a synovial cyst from a herniated nucleus
pulposus. Facet joint degeneration, an associated finding,
may be seen with MR.
We conclude that a lateral location adjacent to a degenerated facet joint will assist in differentiating synovial cysts from
other extradural disorders. The multiplanar and contrast characteristics of MR make this technique well suited to the
diagnosis of herniated disk as well as to the diagnosis of
degenerative facet disease and synovial cyst.
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