Year : 2005 | Volume
: 15 | Issue : 4 | Page : 489--491
Role of contrast enhanced MR in diagnosis of a sequestered disc : A case report and review of literature
R Birla, A Singh, A Kharat, U Phalke
Department of Radiodiagnosis and Surgery, Pad. Dr. D. Y. Patil, Medical College & Hospital, Pimpri, Pune - 18., India
Flat No 2, Building No 34, Ranakpur Darshan Society, New Alandi Road, Vishrantwadi, Yerawada, Pune - 411006
A 38 years old female presented with complaints of radiating pain on lateral aspect of left thigh and leg. Clinical examination revealed signs of L 4 and L5 radiculopathy. Contrast enhanced MRI of the lumbosacral spine revealed degenerative disc disease with a contrast enhancing lesion with a non enhancing center on the left posterolateral portion of the L4 vertebral body. Differentials considered were a solitary epidural abscess, neurofibroma and a sequestered disc. Post operatively lesion was confirmed to be a sequestered disc material, which had migrated caudally from L2-L3 intervertebral disc space anterolateral to the thecal sac. Contrast enhancement was a feature secondary to associated epidural inflammation -a sign typically associated with a long standing sequestered disc.
|How to cite this article:|
Birla R, Singh A, Kharat A, Phalke U. Role of contrast enhanced MR in diagnosis of a sequestered disc : A case report and review of literature.Indian J Radiol Imaging 2005;15:489-491
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Birla R, Singh A, Kharat A, Phalke U. Role of contrast enhanced MR in diagnosis of a sequestered disc : A case report and review of literature. Indian J Radiol Imaging [serial online] 2005 [cited 2020 Sep 19 ];15:489-491
Available from: http://www.ijri.org/text.asp?2005/15/4/489/28781
A 38-year-old female presented with complaints of pain in her left hip radiating to thigh and leg since last one month. There was no significant past history of diabetes, hypertension or tuberculosis. No prior history of trauma.
On clinical examination power was grossly grade 4 in left lower limb with a sensory loss corresponding to L4 and L5 dermatomes. Reflexes were normal. Straight leg raising was restricted to 60 degrees on left as compared to 90 degrees on right.
Pre and post contrast enhanced MRI of the lumbar spine was done on a 0.2 tesla Siemens Magnetom Open MRI with Numaris software.
Sequences: Axial FSE and SE, sagittal T1W and T2W sequences, Sagittal STIR and MR Myelogram and contrast enhanced T1W axial, sagittal and coronal images.
MRI revealed the following
A rounded, nodular 1.1 x 0.9 cms lesion posterior to the L4 vertebra partially encasing and minimally indenting the thecal sac on the left lateral aspect with a small foraminal component [Image 1]. On contrast enhanced MRI the lesion displayed significant peripheral enhancement with a central non-enhancing dot [Image 2],[Image 3],[Image 4].
No evidence of obvious bone erosion or foraminal widening. No obvious continuity was demonstrated with the parent disc. Following differentials were considered: Neurofibroma, abscess, and sequestered disc.
Associated degenerative changes in the lumbar spine were as follows:
Loss of lumbar lordosis with minimal kyphotic deformity at L2/L3 vertebral level. Broad based posterocentral disc herniation with minimal inferior migration at L2/L3 vertebral level. The soft tissue density lesion was completely masked by the high signal intensity CSF on the T2W sagittal images [Image 5]. Herniated disc at the L2/L3 level with facetal arthropathy was seen to cause significant cauda equina compression.
L3-L4 fenestration was done. A vascular mass lesion was found in the anterolateral portion of the spinal canal adjacent to the thecal sac. The lesion coagulated with bipolar. The free fragment was excised and closure was done.
SEQUESTERED L3-L4 DISC MATERIAL.
The ability to differentiate extrusion and sequestration has importance for planning invasive and minimally invasive surgery. Extrusion of disc refers to extension of nuclear material completely through the outer annulus into the epidural space. Sequestration of disc can be considered as a special type of extrusion in which there is free fragment of the disc. The sequestered portion may or may not be confined by the posterior longitudinal ligament, it may lie adjacent to the disc of origin, or may migrate cranially or caudally to a different interspace both in midline and in lateral recess or in rare case even penetrate the dura. ,,. Free fragments also tend to look like the parent disc on both CT scans and short TR MRI .On long TR gradient-echo MRI they may be of a higher signal than the disc of origin.
The most important distinction however is the lack of connection between the extruded component and parent disc. Sometimes sequestration may remain in continuity with the parent disc and thus be inseparable by MRI especially when surrounded by an epidural inflammation, this contributes to the mass effect. (Increase in signal intensity of herniated nuclear material on T2 and T2* W images may be secondary to inflammation or increase in water content in extruded disc ,. When there is penetration of posterior longitudinal ligament, a low signal intensity (i.e. dark) line between a sequestered disc fragment and parent disc called as double fragment sign may be seen (6). An intradural disc herniation may demonstrate higher signal intensity than CSF on T1W images.
Gadolinium may be used to enhance granulation tissue around the peripheral border of a free fragment. Contrast enhancement is useful for excluding diagnoses such as neurofibroma, epidural fibrosis, abscess, conjoined nerve roots, Tarlov cyst (dilated nerve root sleeve), calcified cyst of facet joint, etc. After Gd-DTPA administration, the central portion of a free fragment of a sequestered disc maintains low signal intensity, whereas periphery is enhanced producing a Bull's eye sign.
Such an appearance could also be appreciated in our case. This parallels the documentation by Yamashita K., Hiroshima K., Kurala A., (SPINE 1994, 19: 479-82).
In cases of non operative spine, contrast enhanced MRI have been useful in identifying increased signal intensity in annular rents or tears, presumably due to ingrowths of blood vessels, granulation tissue or both (7). It should be noted that calcified cyst of the facet joint may mimic a calcified free fragment, but usually can be differentiated by their location posterolateral to the thecal sac as opposed to the anterolateral location of disc fragment. Conjoined nerve roots appear as symmetric masses in anterolateral epidural space and can be mistaken for disc fragments. The mistake can be avoided by tracing the course of nerve root bilaterally at each level. It is imperative to know presence of this normal variant in conjunction with an adjacent disc fragment is significant, since the surgeon should be alerted to its pressure to prevent unnecessary traction at the time of laminectomy.
High resolution MR/ contrast enhanced MR thus proves to be an excellent modality to diagnose a sequestered disc free fragment, its course of migration and the complication due to its mass effect on adjacent structures. Certain diagnostic signs like bull's eye appearance, central dot sign, double fragment sign aid in diagnosis of a sequestered disc.
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