DOI:10.2214/AJR.07.2195
AJR 2008; 190:W310-W314
© American Roentgen Ray Society
Midterm Results of Percutaneous CT-Guided Aspiration of Symptomatic Lumbar Discal Cysts
Hoyeong Kang1,
Wei Chiang Liu1,
Sang-Ho Lee2 and
Sung Suk Paeng3
1 Department of Radiology, Wooridul Spine Hospital, Seoul, Republic of
Korea.
2 Department of Neurosurgery, Wooridul Spine Hospital, 47-4, Cheongdam-dong,
Gangnam-gu, Seoul 135-100, Republic of Korea.
3 Department of Pathology, Wooridul Spine Hospital, Gangnam-gu, Seoul, Republic
of Korea.
Received March 8, 2007;
accepted after revision July 18, 2007.
Address correspondence to S. H. Lee
(shlee{at}wooridul.co.kr).
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Abstract
OBJECTIVE. Lumbar intervertebral discal cysts are rarely reported.
To our knowledge, only 12 cases have been reported in the literature. The
symptoms are indistinguishable from those of typical discal herniation. Our
aim is to report the imaging characteristics, method of percutaneous CT-guided
aspiration, and clinical outcome after management of lumbar intervertebral
discal cysts.
CONCLUSION. Percutaneous CT-guided aspiration is an effective method
for the management of lumbar intervertebral discal cysts.
Keywords: cyst • disk herniation • intervertebral cyst • lumber disk • percutaneous CT-guided aspiration
Introduction
Lumbar radiculopathy is commonly caused by degenerative conditions such as
a herniated nucleus pulposus and lumbar spinal stenosis. Less common causes
include intraspinal cysts such as perineural cysts, synovial cysts
[1,
2], arachnoid cysts
[3], epidural hematoma
[4], cyst of the ligamentum
flavum [5], ganglion cysts
[6], intraspinal gas
[7], and discal cysts
[8]. Intraspinal extradural
cysts that communicate with the intervertebral disk are a rare entity and thus
an uncommon cause of lumbar radiculopathy. Surgical removal of the cyst has
usually been performed for the management of this disorder
[8]. We report the imaging
characteristics, method of percutaneous CT-guided aspiration, and clinical
outcome after management of lumbar intervertebral discal cysts.
Materials and Methods
Patient Population
We retrospectively reviewed the clinical outcome and imaging studies of
eight men (mean age, 29.8 years; range, 18–41 years) with symptomatic
lumbar intervertebral discal cysts. These patients were referred to the
radiology department for CT-guided percutaneous management of discal cysts.
This study was approved by our ethics panel. Written informed consent for the
CT-guided aspiration procedure and for use of related data for the study was
obtained from all patients after the nature of the procedures was fully
explained.
MRI
MR images were obtained in the sagittal and axial planes with the use of
spinal surface coils on a 1.5-T unit (Intera, Achieva, Philips Medical
Systems). The parameters were as follows: 512 x 256 matrix, 30-cm field
of view, four signals averaged, and 4-mm section thickness with a 0.4-mm
intersection gap. Fast T1-weighted (TR/TE, 438/8) and T2-weighted (3,670/120)
spin-echo sequences were performed on all patients. Gadopentetate dimeglumine
(0.1 mmol/kg body weight) was administered IV to six patients, and images were
obtained with parameters identical to those for the unenhanced T1-weighted
sequences.
Technique of CT-Guided Aspiration
Patients were placed in the prone position. According to the requirements
of the radiologist performing the procedure and the availability of the CT
suite, the procedure was performed in aseptic conditions with CT (Somatom
Sensation Open scanner, Siemens Medical Solutions) imaging guidance. After
confirmation of the discal cyst level on axial and sagittal CT multiplanar
projection reconstructions, an 18-gauge 9-cm spinal needle was inserted
through the posterolateral route at the disk level. Ten to 15 mL of nonionic
contrast medium (300 mg I/mL iohexol, Omnipaque 300, GE Healthcare) was
injected into the epidural space by means of positioning the needle. During
puncture of the epidural space, the needle was slowly advanced with constant
spillage of contrast material that not only enabled clear visualization of the
cyst and nerve root but also displaced the thecal sac laterally, giving a
sufficient route for puncture of the discal cyst and avoidance of puncture of
the thecal sac.
CT was repeated for confirmation of the location of the needle. Under CT
guidance, an 18-gauge spinal needle was inserted into the cyst through the
interlaminar space (Fig. 1A,
1B). If the needle tip reached
the cyst, a small amount of air or contrast material was injected into the
cyst. That the tip of the needle was in the cyst was confirmed on the CT
images. If the tip of the 18-gauge 9-cm needle did not reach the cyst, a
22-gauge 15-cm spinal needle was inserted into the cyst through the coaxial
system. A small amount of serous or bloody fluid was aspirated from the cyst
(mean volume, 3.4 mL; range, 2–5 mL). Immediately after the procedure,
lower back pain, radiculopathy, and numbness in the dorsal aspect of the foot
disappeared. The straight-leg-raising test returned a negative result, and
muscle weakness and sensory abnormality were relieved.
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Fig. 1A —35-year-old man with left radiculopathy. Images show
insertion of needle tip under CT guidance. After epidurography performed at
L5–S1, needle tip is placed in cyst through interlaminar space. CT scan
shows general appearance of cyst.
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Fig. 1B —35-year-old man with left radiculopathy. Images show
insertion of needle tip under CT guidance. After epidurography performed at
L5–S1, needle tip is placed in cyst through interlaminar space. CT scan
shows appearance of cyst at bone setting.
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Follow-Up
Preoperative evaluations included detailed neurologic examinations, dynamic
radiologic studies of the lumbosacral spine, lumbosacral MRI, and subjective
ratings of back and radicular pain. Postoperative neurologic examinations and
telephone surveys were conducted for all patients at the follow-up times shown
in Table 1 to determine whether
new symptoms had developed since the previous clinic visit. Pain level was
evaluated with a visual analog scale (VAS) of 0–10. A score of 0
represented no pain, and a score of 10 indicated severe pain. Preprocedural
and postprocedural clinical assessments were focused primarily on the severity
of pain. Follow-up MRI was performed at varying intervals (mean, 13.2 months;
range, 3–27 months). Clinical follow-up examinations were performed a
mean of 14.7 months (range, 6–27 months) after therapeutic
aspiration.
Statistics
The degree of VAS score improvement in each patient was calculated by
subtracting the postprocedural VAS score from the preprocedural score. The
degree of VAS score improvement was statistically assessed. A paired Student's
t test was used to compare preprocedural and postprocedural VAS
scores. These statistical analyses were conducted with SAS software version
8.1 (SAS Institute) for Microsoft Windows, and p < 0.05 was
considered to indicate a statistically significant difference.
Results
The clinical results are summarized in
Table 1. The lumbar
intervertebral discal cysts were located at the L4–L5 level in six
(75%), at the L5–S1 level in one (12%), and at the L3–L4 level in
one (12%) of the patients. Five (62%) of the lumbar discal cysts were on the
left side, two (25%) on the right side, and one (12%) on the midline. All
discal cysts manifested as sharply marginated epidural masses. All cysts were
located outside the thecal sac. A round or ovoid mass was found in all
patients (Figs. 2A,
2B,
2C and
3A,
3B). The mean diameter of the
lesions was 11.1 mm (range, 6–14 mm).
In all patients, the signal intensity of the lumbar intervertebral discal
cysts on the T1- and T2-weighted MR images was equal to or slightly greater
than that of CSF. At aspiration, these cysts were seen to be filled with
serous or bloody content. Lumbar intervertebral discal cysts manifested with
high signal intensity on T2-weighted images, a finding consistent with
accumulation of serous fluid (Figs.
2A and
2C). All discal cysts had a
low-signal-intensity rim at the periphery that was accentuated on long TR/TE
sequences. Rim enhancement of the discal cysts after administration of
gadolinium was seen in all patients who received contrast material
(Fig. 2B). The cyst walls were
firm at aspiration. The cyst wall had a smooth surface in all patients.
The mean improvement in VAS score, defined as the preprocedural to
postprocedural difference, was 7.6 ± 1.0 (SD). Excellent pain relief
was achieved in seven (88%) of eight patients during 6–27 months of
follow-up. The VAS score decreased from 8.0 ± 1.2 before the procedure
to 00.4 ± 0.8 after the procedure (improvement of 7.6 ± 1.0)
(p < 0.001). Three (38%) of eight patients had eight-point; two
(25%), seven-point; one (12%), nine-point; and one (12%), six-point pain
improvement (Table 1). One
(12%) of the patients reported recurrent radiculo pathy at the 3-month
follow-up evaluation. MRI evidence confirmed the presence of recurrent disk
herniation, and the patient underwent surgical treatment. In none of the eight
patients did rupture of the discal cyst occur at aspiration. No complications
occurred during 6–27 months of follow-up.
Discussion
Intraspinal extradural cysts that communicate with the intervertebral disk
are a rare entity and therefore are an uncommon cause of lumbar radiculopathy.
To our knowledge, only 12 cases have been reported in the English language
literature [9]. Chiba et al.
[8] proposed that this clinical
entity be called discal cyst and proposed a variety of characteristic factors
associated with lumbar discal cysts. Clinically, this disease is typified by
symptoms indistinguishable from those of typical disk herniation. The primary
process that eventually gives rise to a lumbar discal cyst may be a tear of
the annulus fibrosis with subsequent disk herniation. Lumbar discal cysts are
said [10] to occur at a
slightly younger age (mean, 32 years) and at a higher vertebral level than
typical discal herniation. In our study, all patients were of a younger age
(mean, 29.1 years; range, 18–41 years), but the vertebral level was
equal to that of typical disk herniation (75% of cases at the L4–L5
level).
The cause and pathogenesis of lumbar discal cysts remain unknown. Two
hypotheses for the formation of these cysts have been suggested. Chiba et al.
[8] proposed that an epidural
hematoma initially formed from hemorrhage of the epidural venous plexus
results from either disk herniation or an underlying disk injury. The discal
cyst develops as a result of unspecified impairment in hematoma resorption.
Those authors proposed this epidural hematoma theory from findings that most
of the cysts they detected contained either hemorrhagic fluid or hemosiderin.
In our study, histopathologic examination of the discal cysts showed small
deposits of hemosiderin, and the findings serve to support the epidural
hematoma theory. Kono et al.
[11] reported two cases of
operatively confirmed discal cysts and proposed that the pathogenesis of
discal cysts is similar to that of meniscal cysts of the knee and synovial
cysts of facet joints. Those authors hypothesized that a discal cyst results
when focal degeneration of an intervertebral disk causes herniation of the
disk with subsequent spilling of fluid from the herniated disk. The extruded
fluid incites an inflammatory response that leads to reactive pseudomembrane
formation and development of a discal cyst.
The clinical and radiologic differential diagnosis of an extradural
space-occupying mass in the spinal canal is extensive and includes both benign
and malignant entities. Several benign intraspinal cysts manifest symptoms and
signs resembling those of lumbar discal herniation. Examples are synovial
cysts, gas-containing ganglion cysts, and postsurgical pseudocysts. Imaging
evaluation is important in the evaluation of suspected lesions because if the
diagnosis can be made prospectively, minimally invasive therapy with needle
puncture, as opposed to open surgical intervention, may be appropriate.
Radiography is of little diagnostic value in the evaluation of lumbar
intervertebral discal cysts but can be useful for excluding other conditions
in the differential diagnosis. MRI is helpful for visualizing the cystic
nature of the lesion and its relation to the disk and the thecal sac,
narrowing the differential diagnostic possibilities. MRI reveals that an
intervertebral discal cyst is a well-defined homogeneous cyst located in the
ventral or ventrolateral extradural space adjacent to a herniated disk. The
cyst displaces the dural sac dorsally and may even erode an adjacent vertebral
body. MRI shows a lesion similar or identical to intervertebral disk
herniation with low signal intensity on T1-weighted and high signal intensity
on T2-weighted images. These findings are compatible with a cyst but not with
disk herniation.
Management options for lumbar intervertebral discal cysts range from
nonoperative to operative, depending on the symptoms. Nonoperative techniques
generally involve symptomatic relief or steroid injections into the cyst.
Operative management of a discal cyst is reserved for patients with persistent
neurologic symptoms or severe leg pain refractory to nonoperative treatment.
Decompression of the cyst contents and resection of the cyst lining and stalk
have resulted in immediate and complete resolution of pain and of motor
strength and sensory deficits. Successful percutaneous management of an
intervertebral discal cyst has been reported
[12], but the report described
only one case. In our series, more cases were available. We do not use steroid
injections because no strong evidence corroborates the effectiveness of
steroid injections in the treatment of patients with lumbar discal cysts. When
steroid injections are administered in the management of these cysts, the
treatment effect of steroid cannot be differentiated from that of aspiration
of the cyst.
As for the limitations of our study, all lumbar discal cysts were not
confirmed with discography or surgery. We believe discography carries risk of
cyst rupture, and all discal cysts had typical findings on MR images.
Aspirated fluid was sent for pathologic analysis in all cases. Examination of
aspirated content can confirm the presence of a discal cyst, but the lack of
pathologic proof can be a serious limitation in analysis of individual lumbar
discal cysts. The small sample size also was a limitation of our study. A
larger number of cases and long-term follow-up are needed.
In this study, we found that CT-guided percutaneous aspiration is effective
in the management of lumbar discal cysts, 88% of patients experiencing
complete resolution of radiculopathy and back pain due to lumbar discal cysts.
In five (71%) of seven cases, follow-up imaging more than 1 year after treat
ment showed complete regression of the lumbar discal cyst. In the other two
(29%) of the seven, 6-month follow-up imaging showed decreased cyst volume. In
conclusion, percutaneous CT-guided aspiration is effective for the management
of lumbar discal cysts.
Acknowledgments
We are grateful for the editorial assistance provided by Joel Encinas and
Youngshin Rho.
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Abstract
Introduction
