CT finding of epidural gas indicates Intradural disc herniation?
Intradural disc herniation associated with epidural gas (1).
According to Hidalgo-Ovejero AM et al possibility of an intradural herniated disc must always be considered in a patient whose CT scan reveals the presence of epidural gas. They also suggest, in the event where no clear disc herniation is found to justify the clinical symptoms or the previous radiologic findings, an intradural exploration may be indicated.
The study by Hidalgo-Ovejero AM et al:
Hidalgo-Ovejero AM et al in the year1998, presented a case study that cautioned spine surgeons of the possible association of intradural disc herniation and epidural gas, to prevent overlooking intradural disc fragments during surgery. This spine presentation is so rarely studied that only 3 cases were published prior to this study.
In this study, spine surgeons Hidalgo-Ovejero AM et al performed open discectomy. During the open discectomy, after a negative epidural examination, an intradural examination was performed, which revealed a disc herniation, which was removed during the surgery.
Role of MRI in preoperative diagnosis of Intradural lumbar disc herniations (3)
According to the researchers D'Andrea G et al, radiologic diagnosis of intradural herniation is possible in carefully selected patients with MRI with gadolinium. D'Andrea G et al of Italy (2004) discussed the role of MRI in preoperative diagnosis.
D'Andrea G et al analyzed 9 patients of intradural lumbar disc hernia on whom hemilaminectomy was performed. In 6 cases, the diagnosis of intradural herniation was confirmed preoperatively but in 3 remaining, it was confirmed at surgery.
Comparision with CT & Myelography:
1. In 5 cases, CT (with no contrast medium) of the lumbar area revealed disc herniation, but none could it confirm its intradural location.
2. Myelography was performed in 2 cases but also could not prove intradural extrusion.
3. Magnetic resonance imaging study was used in 4 cases.
Is it possible to predict Intradural lumbar disc herniation preoperatively? (4)
To answer this question Choi JY et al of Korea reported study of two cases and they also have tried to explain how a correct preoperative diagnosis helps to aid in good surgical outcome and minimize the nurological deficits. The authors describe two patients with intradural lumbar disc herniations, one with and one without preoperative diagnosis, who had different postoperative outcomes.
The findings in these 2 patients:
Case no.1: (post operative diagnosis)
a. The first patient underwent an extended L3 subtotal laminectomy followed by bilateral medial facetectomy and foraminotomy at L3-L4.
b. A durotomy uncovered large disc fragments comprised of friable disc materials and end plates, after no clear disc herniation was found in the epidural space.
Outcome of surgery: The patient experienced a marked reduction of pain and progressive recovery of sensory disturbance, but neurologic examination showed right foot drop postoperatively. Two years after surgery, she can not walk without a cane because the neurologic deficit of the right ankle has shown no improvement.
Case no.2: (preoperative diagnosis)
The second patient underwent anterior lumbar interbody fusion after a preoperative diagnosis of intradural disc herniation.
Outcome of surgery: Two days after surgery, the second patient was allowed to ambulate with a lumbar orthosis. Neurologic examination showed no motor deficit. Twenty-one months after surgery, the patient reports minimal back pain when sitting on a chair for prolonged periods of time.
This group of researchers concluded:
1. "hawk-beak sign" on axial imaging & abrupt loss of continuity of the posterior longitudinal ligament (PLL) indicates potential presence of an intradural disc herniation. These signs must always be considered preoperatively.
2. This above said association on MRI should be guide; if followed it will result in an adequate surgical approach, thereby reducing the chance of postoperative neurologic deficit.
3. Finally, anterior lumbar interbody fusion can be a reasonable alternative in the treatment of intradural lumbar disc herniations.
However despite of above study describing the ease of diagnosing the disorder from "hawk-beak sign" & integrity of PPL; according to Oztürk A et al of Turkey preoperative diagnosis of intradural disc herniation is still difficult despite new neuroradiologic investigation possibilities including CT and MRI and it is usually diagnosed by during surgery (6).
Intradural herniation of intervertebral disc at the level of Lumbar 1-Lumbar 2 (6).
Oztürk A et al of Turkey presented an case study of intradural disc herniation at the level of L1-L2 with significant myelopathic neurologic deficits.
The case is as follows:
1. A 50-year-old female patient was admitted to the hospital in Turkey with pain and weakness in both legs.
2. Her neurological examination revealed paraparesis.
3. Magnetic resonance imaging showed an extruded disc hernia of central localization at the L1-L2 level.
This patient underwent total laminectomy at the level of L1-L2 and her intradural disc fragment was extirpated by microsurgical methods. Hence the surgery was a combination of ablative surgery & microsurgical methods.
Cervical intradural disc herniation (5).
Cervical intradural disc herniation is an extremely rare condition. The pathogenesis remains obscure. Iwamura Yet al of Japan presented a cervical intradural disc herniation. Including this case study only 17 cases of cervical intradural disc herniation have been reported.
The case study:
1. A 45-year-old man who had Brown-Sequard syndrome diagnosed on neurologic examination.
2. A cervical intradural disc herniation at C6-C7, with localized hypertrophy and segmentally ossified posterior longitudinal ligament, is reported in Neuroradiologic, operative, and histologic findings.
Upon en bloc resected posterior vertebral portion of C6 and C7, to evaluation for discussion of the pathogenesis.
Following are found:
1. Adhesion of dura mater and hypertrophic posterior longitudinal ligament was observed around a perforated portion of the herniated disc.
2. Histologic study showed irregularity in fiber alignment accompanied by scattered inflammatory cell infiltration and hypertrophy in the posterior longitudinal ligament.
Hence the salient points to be considered are the adhesion and fragility of dura mater and posterior longitudinal ligament. This was caused by hypertrophy, with chronic inflammation and ossification of the posterior longitudinal ligament sustaining chronic mechanical irritation to the dura mater, leading to perforation of the herniated disc by an accidental force.
The cervical intradural disc herniation was removed successfully and followed by C5-Th1 anterior interbody fusion with fibular strut graft.
Neurologic recovery was complete except for minor residual sensory disturbance in the leg 7 years after the surgery.
Report of 3 cases of intradural lumbar disc herniations from Germanany (2).
According to neurosurgeons Prestar FJ et al (1995) of Germany; Intradural lumbar disc herniation is a rare pathological entity. According to database of these researchers 3 new cases among a series of 5000 lumbar spine operations are added to the about 60 previous case reports in the literature.
Report of 3 cases:
1. In one patient the location of the free disc fragment was medial within the dural sac
2. In other two patients the free disc fragment had penetrated the dural sac from the axilla of the nerve root.
Prestar FJ et al suggested the pathogenesis as:
1. Congenital adhesions of the dura mater to the posterior longitudinal ligament at the lower lumbar spine.
2. Weakness of the dura mater ventrally and at the axilla of the nerve root.
Prestar FJ et al further suggested to include a multiplanar MRI to correctly investigate the free disc hernia within the dural sac preoperatively.
1. Hidalgo-Ovejero AM et al, Intradural disc herniation associated with epidural gas; Spine. 1998 Jan 15;23(2):281-3.
2. Prestar FJ et al, Intradural lumbar disc herniations: report of three cases; Minim Invasive Neurosurg. 1995 Sep;38(3):125-8.
3. D'Andrea G et al, Intradural lumbar disc herniations: the role of MRI in preoperative diagnosis and review of the literature; Neurosurg Rev. 2004 Apr;27(2):75-80; discussion 81-2. Epub 2003 Oct 15.
4. Choi JY et al, Intradural lumbar disc herniation--is it predictable preoperatively? A report of two cases; Spine J. 2007 Jan-Feb;7(1):111-7. Epub 2006 Nov 20.
5. Iwamura Y et al, Cervical intradural disc herniation; Spine. 2001 Mar 15;26(6):698-702.
6. Oztürk A et al, Intradural herniation of intervertebral disc at the level of Lumbar 1-Lumbar 2; Turk Neurosurg. 2007 Apr;17(2):134-7.