Thursday, March 19, 2009

Intra-radicular disc prolapse (review of 11 papers)

History & prevalence:
According to Mut M et al of Turkey Intraradicular disc herniation is a special type of intradural disc herniations (7). The mechanism of the tearing of the dura mater by a herniated disc is not known with certainty (6). Akdemir H et al (1997) presented case in which a fragment of herniated lumbar disc was found within the sheath of the right S1 nerve root (5). How ever before 1997 there have been reports of such cases. According to a paper by Nazzal MM et al in journal of spinal disorder (1995) Intradural disc herniation accounts for < 0.3% of all disc herniations. Intraradicular disc herniation accounts for 4.1% of all such cases.

Clinical signs & symptoms:
The Intraradicular disc herniations may present from no symptoms (!!!) to symptoms presenting with profound neurological deficits (see the case studies below). Lakshmanan P presented 2 case studies one of them presented with no neurological deficit. Hence they have concluded that diagnosis of posterior epidural migration of the sequestrated discs may be difficult even it may be present with subtle clinical features even though the disc transgresses through numerous anatomic restraints including the nerve roots in such cases (10).

Case studies:
Finkel HZ also reported a case of intraradicular, intervertebral disc herniation L5-S1 intervertebral disc into the left S1 nerve root & S1 nerve root was found to be adherent to the underlying disc space. The diagnosis was made at the time of surgery during exploration of the L5-S1 disc space but before surgery this condition was believed to represent a large extradural and extraradicular disc herniation (2).

Nazzal MM et al revealed in 1995 that preoperative diagnosis of Intraradicular disc herniation is difficult, and must be thoroughly examined during surgery for the diagnosis. Back in 1995 when probably myelogram was the examination available at hand showed a block at the involved nerve root in a case presentation discussed by them in journal of spinal disorder (3).

A case study by Süzer T et al is as follows (6):
A 41-year-old man was admitted with a 3-year history of low back pain and sciatica. A neurological examination revealed motor weakness during plantar flexion, positive Lasègue's sign, sensory deficit on the S1 dermatoma, and loss of Achilles reflex. Magnetic resonance imaging revealed disc protrusion at the L5-S1 level.

Report of surgery in this case is as follows:
A standard hemilaminotomy and foraminotomy for a removal of the L5-S1 disc was followed. Interestingly there was no disc protrusion or extruded fragment. The left S1 nerve root was observed to be swollen and immobile. A longitudinal incision was made on the radicular sheet of the S1 root, and a free disc fragment, approximately 2 x 1 x 1 cm, was extirpated in one piece.
The patient was immediately relieved of pain and was discharged on the 7th day after the operation with normal muscle strength. The authors like other group of researchers Ozdemir N et al (8) have presumed that failed back cases are due to such disorders and mostly associated with failed back cases.

A case study by Mut M et al is as follows (7):
A 32-year-old male was admitted to hospital having experienced pain in the lower back and right leg for 1 month prior to admission. Neurological examination revealed weakness of the extensor hallucis longus, positive Laségue's sign, decreased ankle reflex in his right lower extremity, and bilateral paravertebral muscle spasm. MRI revealed a disc herniation with a posterolateral extruded fragment on the right at the level of the L5-S1 space.

Report of surgery in this case is as follows: He underwent L5 laminectomy. During the operation, the right S1 root was found to be swollen and immobile. A longitudinal incision was made in the dura of the right S1 root and an intradural free disc fragment was removed, and the S1 root was relieved. The patient was free of pain postoperatively (7).

According to Lakshmanan P at al (UK) Posterior epidural migration is an interesting but rare path taken by a prolapsed intervertebral disc fragment. There are only seven cases reported of a similar migration of the disc fragment in the lumbar spine (10).

Lakshmanan P at al presented 2 case studies.
1. In one patient there was weakness of the ankle dorsiflexors, foot invertors, and toe extensors of the left foot, with sensory loss over the back of the calf and over the lateral three toes. The left ankle jerk was also absent.
2. However, in the other case, there was no objective evidence of neurological deficit distally.

Lakshmanan P at al’s second study biopsy of the specimen taken from surgery confirmed it to be sequestrated disc fragment. Hence they concluded that diagnosis of posterior epidural migration of the sequestrated discs may be difficult even it may be present with subtle clinical features even though the disc transgresses through numerous anatomic restraints including the nerve roots in such cases (10).

An extensive case studies of 9 cases (4).
Schisano G et al doing a retrospective clinical examination on 9 cases found that Intraradicular or intradural disc herniation is a very rare complication of spinal degenerative processes. Lateral perforations of the dural sac are more common than the ventral perforation. 9 cases studied by Schisano G et al ware having intradural disc herniation. Among these, 6 were associated with lateral perforation, the remaining three with intradural herniation and ventral perforation.
According to the data base o these Italian authors
1. Nine cases of intradural herniations comprise 1.51% of the 593 cases of ruptured lumbar disc that underwent surgery from 1980 to 1992.
2. The site most frequently involved is at level L4-L5.
3. 30% of their patients have previously undergone surgery for lumbar disc herniation.
4. Most patients have been complaining of a chronic history of sciatica, complicated later by bilateral neurologic signs. There is no typical neuroradiologic picture of intraradicular herniation, while a total or subtotal block is frequently observed in intradural ventral perforations. Dural perforation is often an unexpected intraoperative finding.

Investigations followed by Schisano G et al to diagnose are by means of myelography and CT; magnetic resonance imaging was performed in one case. Surgery has good to excellent result in these cases. Interlaminar approach (for lateral perforations) or bilateral laminectomy (for ventral perforations) was used.

Association of Intraradicular disc herniation Failed back surgeries:
Ozdemir N et al have presumed that failed back cases are due to such disorders and mostly associated with failed back cases(8). Turgut M et al reported an unusual case of intradural intraradicular lumbar disc herniation, in which an extruded fragment of disc was found within the sheath of the left S1 nerve root after a failed back surgery. This diagnosis of intraradicular extruded disc herniation was only possible at time of surgical exploration of the L5-S1 disc space. Although MRI is a useful diagnostic tool in all patients with lumbar disc herniation, preoperative correct diagnosis is usually difficult in such cases. A careful observation of the root during surgery is indicated to detect such an anatomical abnormality. Bloom B of UK reported the case of a man who underwent urgent surgery to relieve compression of the cauda equina caused by a large L4/5 disc protrusion. A post-operative but not pre-operative MRI scan showed appearances suggestive of intradural migration of a disc fragment, confirmed at re-operation. The authors found that this event happened during the first operation and not before it (11).

What MRI Clue may help diagnosing such cases?
MRI is the “gold standad” in diagnosis of lumbar discogenic pathologies. However it is not efficient in diagnosing Intraradicular extruded disc herniations. Ozer E et al have suggested that the round shape of the sequestrated fragment, as seen on MRI, may help to establish the correct diagnosis (9) of Intraradicular extruded disc herniations.

Reference:
1. Neurol Neurochir Pol. 2008 May-Jun;42(3):251-4; discussion 254.
2. Spine. 1997 May 1;22(9):1028-9.
3. J Spinal Disord. 1995 Feb;8(1):86-8.
4. Surg Neurol. 1995 Dec;44(6):536-43.
5. Neurosurg Rev. 1997;20(1):71-4.
6. Neurosurgery. 1997 Oct;41(4):956-8; discussion 958-9.
7. Spinal Cord. 2001 Oct;39(10):545-8.
8. Br J Neurosurg. 2004 Dec;18(6):637-43.
9. Spine J. 2007 Jan-Feb;7(1):106-10. Epub 2006 Sep 11.
10. Spine J. 2006 Sep-Oct;6(5):583-6.
11. Br J Neurosurg. 2007 Aug;21(4):417-8.





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