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|LETTER TO EDITOR
|Year : 2017 | Volume
| Issue : 3 | Page : 650-652
Post-discectomy annular pseudocyst: A rare cause of failed back syndrome
G Lakshmi Prasad, Girish R Menon
Department of Neurosurgery, Kasturba Medical College, Manipal University, Manipal, Karnataka, India
|Date of Web Publication||9-May-2017|
G Lakshmi Prasad
Department of Neurosurgery, Room 12, OPD Block, Kasturba Hospital, Manipal - 576 104, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Prasad G L, Menon GR. Post-discectomy annular pseudocyst: A rare cause of failed back syndrome. Neurol India 2017;65:650-2
Lumbar discectomy is one of the most commonly performed spinal surgeries worldwide. With the classical presentation of sciatica, microdiscectomy is the preferred treatment, when the patient is not responding to a trial of conservative management. Pseudocysts causing recurrence of pain constitute a rare sequel of discectomy. This entity was first described in 2009. Till date, only 3 reports can be found in English literature regarding these symptomatic pseudocysts.,, Management is either conservative or surgery. This report briefly analyses all the reported cases in terms of demographic factors, level of disc herniation, time to relapse, management, and outcome. In addition, one such case managed at our institute has been described.
A 30-year old male patient was referred to our institute with a prior history of L4-5 discectomy done 2 months back at another hospital. At that time, he had complained of low backache with radiation of the pain along the posterolateral aspect of the right leg for 3 months. A L4 laminectomy and L4-5 discectomy was performed. No other intraoperative details were available. He had modest improvement of pain following his initial surgery. However, the pain recurred within 25 days of the surgery with increased severity [Visual Analog Scale (VAS) 9/10]. There was restriction of the right lower limb movement because of pain, and he developed mild great toe and ankle dorsiflexion weakness. There was no evidence of systemic or local infection. Preoperative magnetic resonance (MR) images were not available. At this present admission, MR imaging showed a T1-hypointense and T2-hyperintense lesion in the right posterolateral aspect of the previously operated L4-5 disc, conforming to the shape of the disc, with evidence of significant compression on the traversing nerve root [Figure 1]a,[Figure 1]b,[Figure 1]c,[Figure 1]d. There was mild enhancement of the cyst wall [Figure 1]e. The erythrocyte sedimentation rate was 16 mm/h and C-reactive protein was 0.4 mg/L. The probability of discitis was less likely. He was managed conservatively for 2 weeks with complete bed rest, analgesics, and antibiotics (considering a remote possibility of discitis). He had no relief of pain, and hence, was taken up for exploration. A L5 laminectomy and right-sided medial facetectomy was performed. There were mild adhesions between the L5 nerve root and the annulus, which were released and the nerve root was mobilized carefully. A thin-walled cyst containing clear fluid, similar to spinal fluid, that was compressing the traversing L5 nerve root, was present over the postero-lateral aspect of the annulus at the site of the previously operated L4-5 disc. Dissection of the cyst was tried, however, because of its thin wall, there was rupture of the cyst. The cyst wall was removed along with residual disc material. The nerve root was freed adequately and there was no dural tear. He had an excellent relief of the sciatica pain immediately after surgery (VAS 3/10). At the last follow up of 17 months, he had persistent relief of pain with no recurrence and had improvement in ankle and great toe weakness.
|Figure 1: Postoperative MRI of the lumbosacral spine with L4 laminectomy. Axial and sagittal cuts showing a lobulated cystic lesion, which is hypointense on T1 (a and b) and hyperintense on T2 sequences (c and d) located over the right posterolateral aspect of annulus at the site of previously operated L4-5 disc compressing the nerve root (circles). Axial post-contrast MR images showing enhancement of the pseudocyst (arrow in e)|
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Lumbar degenerative disease is one of the most common causes of low backache and radiculopathy. It can be in the form of disc herniation, canal stenosis, or spondylolisthesis. Intraspinal cysts causing radiculopathy are uncommon. Of the many types of spinal cysts, discal cysts are rare.,, They communicate with the corresponding intervertebral disc, as noted on discography, and are formed spontaneously because of an occult injury to the disc and subsequent cyst formation. Post-discectomy pseudocysts, also termed as annular pseudocysts, are similar to discal cysts, except that they occur after surgery. They are very rare causes of recurrent pain after lumbar spine surgery. After their first description in 2009 by Young et al., in a series of 2 cases, 2 more reports have furnished details about these lesions in terms of demographic factors, treatment options, and outcome.,, Altogether, a total of 29 cases have been reported till date. Due to their rarity, their exact incidence is unknown; however, Kang et al., quoted a figure of 1% among their initial cases operated for a disc prolapse. [Table 1] summarizes the available literature on annular pseudocysts. It is suggested that the surgical site connective tissue inflammation, particularly that of the posterior longitudinal ligament and annulus, results in a pseudocyst formation. The enlargement of the cyst is most likely due to loss of connection between the cyst space and extradural space, with resultant adjacent nerve root compression. Kang et al., proposed that physical activity pumps fluid from a mildly degenerated nucleus through the annular defect resulting in a pseudomembrane, and later, pseudocyst formation. They also believed that the surgical trajectory of endoscope is related to pseudocyst formation because of the heat generated by diathermy. A confirmation of this assumption needs further evaluation.
MR imaging is the modality of choice because of its excellent soft tissue visualization. Imaging findings are similar to that seen in discal cysts and have been summarized by Lee et al. They include the presence of a ventrolateral extradural cyst attached to a lumbar disc, rim enhancement on contrast administration, occasional lateral recess extension, a hypointense rim on T2-weighted images, no midline crossing, and a serous content of the cyst. Pseudocysts are similar to discal cysts, which show hypointensity and hyperintensity on T1 and T2-weighted images, respectively. Minimal rim enhancement is seen on post-contrast images. They are located at the site of the previous discectomy over the posterolateral aspect of annulus, confined to one side; however, on a few occasions, they may cross the midline, depending upon the dead space available for the cyst. Synovial cysts form a rare differential diagnosis for these pseudocysts and present with radiculopathy and neurological deficits. On MRI, they are slightly more proteinaceous than cerebrospinal fluid, and hence exhibit a higher signal intensity on T1 and T2 sequences. They are typically extradural, well-circumscribed lesions located adjacent to the facet joints. Furthermore, the density on computed tomography (CT) may vary depending on the content (calcification versus hemorrhage).,
Management of annular pseudocysts may be conservative or may involve surgery. Percutaneous CT-guided aspiration is also a viable option. Of the 29 reported cases, 17 were managed conservatively, and the rest, surgically. Of the surgically managed cases, one patient underwent percutaneous CT-guided aspiration with steroid injection, and another, a simple aspiration of the cyst., Similar to disc herniation, even for symptomatic annular pseudocysts, conservative treatment should be offered initially and surgery should be contemplated in non-responders because the cysts are known to regress spontaneously in a few patients. However, in our case, the patient had a severe, unbearable pain which prevented him from even lying flat on bed. He received a trial of conservative treatment for 14 days but later underwent exploration; the surgery offered excellent pain relief almost immediately. A problem with the conservative management is the propensity for the enlargement of the cyst, as reported in 1 case. Whether this enlargement leads to recurrence or persistence of pain is not known. Moreover, long-term outcomes cannot be commented upon because of the relatively short follow-up duration of the reported cases. Outcome is good-to-excellent in a majority of the cases, as assessed by VAS, and the outcome is not dependent on the type of management administered. However, as seen in [Table 1], the time to improvement is relatively longer with conservative rather than with surgical treatment. Further, with the exception of 1 case who had a fair outcome (out of available 10 cases), all the cases managed by surgery had good-to-excellent outcomes, whereas 3 cases (out of 15 cases) had a fair outcome on conservative treatment. Due to the rarity of these lesions, further studies with a larger number of patients and a longer follow-up duration are required to confirm the above mentioned findings and suggest optimal treatment strategies.
Post-discectomy annular pseudocysts are very rare causes of recurrent pain after lumbar spine surgery, with young males being the most susceptible. Endoscopic discectomy leads to a better outcome in these cases. A non-enhancing/mildly enhancing cystic lesion at the site of previous discectomy is the classical imaging finding. Irrespective of the cyst size, conservative treatment should be tried first, and surgery should be contemplated only in non-responders. Outcome appears to be good in a majority of cases.
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