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Acta Radiologica

ISSN: 0284-1851 (Print) 1600-0455 (Online) Journal homepage: http://www.tandfonline.com/loi/iard20

Spinal Gas Collection Demonstrated at CT

J. Hjarbæk, P. W. Kristensen & P. Hauge

To cite this article: J. Hjarbæk, P. W. Kristensen & P. Hauge (1992) Spinal Gas Collection
Demonstrated at CT, Acta Radiologica, 33:2, 93-96
To link to this article: http://dx.doi.org/10.1080/02841859209173138

Published online: 04 Jan 2010.
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Download by: [50.116.19.84] Date: 29 January 2016, At: 02:01

Acta Radiologica 33 (1992) Fare.2

FROM THE DEPARTMENTS O F RADIOLOGY AND ORTHOPEDIC SURGERY, VEJLE COUNTY HOSPITAL, VEJLE,
DENMARK

SPINAL GAS COLLECTION DEMONSTRATED AT CT

J. HJARBIEKP., W. KRISTENSEaNnd P.HAUGE

Downloaded by [50.116.19.84] at 02:01 29 January 2016 Abstract Routine supine transaxial 2-mm CT scans were obtained
using a Somatom 2 (Siemens). A lateral scanogram was
In 234 consecutive CT examinations of the lumbar spine, gas used to obtain parallel scans through each disk spaceinclud-
collection was observed in 4 cases with disk herniation, and in 6 ing the vertebral end-plates with gantry angulation varying
casesof disk protrusion. In 3 casesfree gas was found in the epidural from 0 to 20”. In all cases the CT images were reviewed,
space, and one patient presented an intraspinal gas-filled “bleb”. and the position and type of gas collection registered. Hemi-
Gas collection in intervertebral disk spaces and facet joints was laminectomywas performed in 15patients, and the findings
at CT compared to operative findings. The postoperative
found in a total of 60 patients. The CT findings and surgical results condition was followed in pertinent cases.

were compared to determine whether gas collection contributes to Results
clinicalsymptoms. In most cases the presenceof gas was not clinical-
ly important, but in one patient it presented as a spinal mass, Varying degrees of gas collection were present in 60 pa-
causing pain and radiculopathy. tients (25.6%), aged 30 to 83 years (mean 57.6 years), 36
males and 24 females.’
Key words: Spine, CT; -, intervertebral disks; spinal canal, CT.
In 54 patients the gas collection was found to involve the
Gas in closed joint spaces, in intervertebral disks, or in intervertebral disk space (Fig. 1). In 3 of these cases a small
bone is commonly referred to as a “vacuum phenomenon”, amount of gas was found in a herniated disk (Fig. 2), and
first observed in 1910 by FICK(S), and first described radio- surgery verified the presence of a herniated disk fragment,
logically by KNUTSSONin 1942 (11). In CT these gas collec- but the presence of gas could not be confirmed with cer-
tions present with Hounsfield units (HU) equivalent to air tainty.
(- 1000 HU). Of the gas, 90 to 95% is nitrogen and prob-
ably evolves from the surrounding extracellular fluid (6). A In 6 patients with gas near the periphery of a bulging
gaseous lucency within a disk is a common finding observed disk verified on CT (Fig. 3), the patients improved on con-
in one to 20% of spinal radiographs and in 50% of CT servative treatment and none needed surgery. In one case a
examinations of the spine in patients older than 40 years of 8 x 4 x 3 mm gas collection occupying the right lateral recess
age (8, 13, 14).
between L4 and L5 was observed (Fig. 4). The sheath of
A vacuum phenomenon is commonly associated with the left L5 nerve root was displaced by a focal gas collection
preexisting degenerativechanges of the spine, such as osteo-
chondrosis, spondylosis deformans, or Schmorl’s nodes. It (-904 HU) surrounded by a thin rim of tissue. An interver-
has also been reported in patients with metastatic spinal tebral gas collection was seen in the adjacent disk.
disease (12, 16).
The patient suffered from severe radiating pain consistent
Material and Methods
with compression of the right L5 nerve. Based on the lumbo-
During one year (October 1988-September 1989)234 pa- sacral CT, decompressive hemilaminectomyof L4 was per-
tients, 115males and 119females, aged 18 to 83 years (mean formed. Exploration of the disk space between L4 and L5
50.5 years) had a lumbosacralCT examination from the 4th
lumbar vertebral body to the 5th disk space, for suspected Accepted for publication 26 September 1991.
spinal stenosis or disk herniation.

93

94 J. HJARBRK ET AL.

Downloaded by [50.116.19.84] at 02:01 29 January 2016 Fig. 1. Multiple lucent areas in the intervertebral disk produced by
the vacuum phenomenon (transverse section).

b
Fig. 3. Vacuum phenomenon in a bulging disk (+) demonstrated
in transverse (a) and reformatted sagittal CT (b). Concomitant
intervertebral vacuum phenomenon is seen.

b b
Fig. 2. Vacuum phenomenon in a median disk herniation demon- Fig. 4. An 8 x 4 x 3 mm large gas “bleb” in the right lateral recess
strated in a transverse section (a) and in reformatted sagittal section (+), in transverse section (a). No sign of herniated disk tissue. The
(b). reformatted sagittal section (b) shows the gas bubble (-904 HU).

revealed an air-filled indulgent thin-walled bubble, without surgery. Exploration at the L5/S1 disk level revealed a
evidence of disk protrusion or herniation. degenerated disk with a lateral protrusion. A small amount
of disk material was removed, but the presence of gas could
The bubble collapsed at biopsy, and the tissue close to not be confirmed.
the base of the bubble was dissected and removed. Histology
revealed nonspecific fibrous tissue. The patient obtained Epidural gas can be differentiated from gas in a herniated
immediate relief from his radicular pain. disk as the epidural gas assumes the exact contour of the
epidural space, and has no surrounding soft tissue rim (Fig.
Another patient with a left disk herniation between LA 6). This was demonstrated in 3 patients who additionally
showed a concomitant gas collection involving the corre-
and L5 showed evidence of concomitant ipsilateral extrafor- sponding intervertebral disk.

aminal disk herniation/protrusion between L5 and S1. A Gas within degenerated facet joints was demonstrated in

degenerated disk with an intervertebral gas collection was
observed between L5 and S1. A small amount of gas was
found immediately cranial to this disk in close contact with
the left L5 nerve just lateral to the neural foramen (Fig. 5).
The herniated disk at the U I L 5 level was removed by

SPINAL GAS COLLECTION AT CT 95

Downloaded by [50.116.19.84] at 02:01 29 January 2016 b Fig. 7. Bilateral facet joint degeneration with vacuum phenomenon
Fig. 5. Vacuum phenomenonjust lateral to the neural foramen (+) (- 577 HU). Concomitant intervertebral vacuum phenomenon is
seen.
in a bulging disk, demonstrated in transverse (a) and reformatted
sagittal section (b). In 234 lumbar CT scans we found 3 cases of gas within
a herniated disk and 6 cases with gas in a bulging but not
b herniated disk.

Fig. 6. Free epiduralgas assuming contour of the right lateral recess ANDAet al. (2) reported one case of suspected extrafora-
(+), in transverse section (a) and reformatted sagittal section (b). minal disk herniation associated with a vacuum phenome-
No sign of disk herniation or protrusion. non and spinal nerve compression. The diagnosis was not
surgically verified. In one case we found a lateral protrusion
9 patients (Fig. 7), in whom 6 had no other manifestation of the disk with a small amount of gas just lateral to the
of gas collection. neural foramen. The protrusion was verified by surgery, but
an extraforaminal herniation could not be confirmed. The
Discussion presence of gas near the periphery of a disk may indicate
Although gas is often observed in degenerated interverte- a disk herniation, but we found no evidence of clinical
bra1 disks (6, 8, 11-14, 16-18), the presence of gas in the connection.
spinal canal is reported to be a rare finding. In a series of
2 500 CT scans spinal gas was observed in only 7 cases (17). Gas in the epidural space was found in 3 cases. According
Other case reports have been published in the past years (1, to GULAT&I WEINSTEIN(9) this phenomenon is due to a
3, 4, 7, 9, 10, 15). tear in the ligament of the apophyseal joint or the anulus
fibrosus. Our findings’support this hypothesis as all 3 pa-
tients also presented gas in the corresponding intervertebral
disk. There was no indication that gas acted as a mass lesion
in these cases.

In 9 cases we demonstrated gas within a degeneratedfacet
joint. YETKINet al. (18) reported one case of gas within a
medial synovial “cyst” arising from a facet joint. We did
not find any such lesion.

In 2 reports a symptomatic spinal canalicular collection
of a gas-filled “bleb or bubble” has been described (4, 7).
In one case we made an identical observation, where a
“bleb” with no sign of disk herniation caused great radicular
pain. The histologic examination of the “bleb” revealed
nonspecific fibrous tissue, and the symptoms were relieved
after removal of the “bleb”. DEMIEReRtEal. (4) suggested
that this thin layer of nonspecific fibrous tissue represented
the posterior longitudinal ligament, and that the gas prob-
ably had penetrated from the intervertebral gas collection.
Intradural disk herniations with vacuum phenomenon re-
ported by others (1, 10) could not be demonstrated in our
material.

This study describes a variety of spinal gas collections

96 J. HJARBRK ET AL.

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The phantom nucleus pulposus. Radiology 62 (1954), 383.
Request for reprints: Dr. John Hjarbzk, Vibekevej 15, DK-5250 9. GULATIA. N. & WEINSTEINZ. R.: Gas in the spinal canal in
Odense SV, Denmark. association with the lumbosacral vacuum phenomenon. CT
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