Intradural lumbar disc herniation is rare, with an incidence of 0.3%-1%, but has been well reported in the literature. Transdural migration of the disc penetrating both ventral and dorsal dura is extremely rare, and there is a dearth of literature in the pathophysiology and surgical management of transdural herniation. Lack of knowledge on this type of presentation can cause intraoperative surprises and inadvertent cauda equina root injuries and lead to prolonged operative time. ¹⁾.

Intradural disc prolapse remains a diagnostic dilemma as it is very difficult to diagnose all the cases preoperatively. The presence of MRI findings of mass effect in the form of displacement of the traversing nerve roots due to large central disc with crumble disc sign were suggestive of early evidence of intradural disc herniation. Y sign in ventral dura due to splitting of ventral dura and arachnoid mater by disc material was a good diagnostic sign to suspect intradural extra-arachnoid disc. The presence of hypointense structure inside the dura with no continuity with the adjacent intervertebral disc on MRI was highly suggestive of an intradural disc, in patients having the large central disc on MRI, especially at L4-L5 levels, should raise suspicion of intradural herniation of disc. ²⁾.

Ducati et al. described five cases of this pathology and review the literature as well as some considerations about the difficulties in the preoperative diagnostic issues and the surgical technique.

They concluded that for intradural disc herniations the diagnosis is mainly intraoperative, and the surgical technique has some special aspects ³⁾.

A female patient with lumbosciatic pain who developed an incomplete cauda equina syndrome. An asymmetric discopathy of the L2-L3 space and a gas bubble with disc material within the spinal canal was noticed in the radiologic explorations. The literature and the authors’ experience are reviewed with the aim of confirming the frequency of intradural herniation in association with gas in the spinal canal.

A laminoarthrectomy of the involved space was performed followed by direct intradural examination, which revealed a disc fragment that was excised. An instrumented L2-L3 arthrodesis was performed. Postoperative evolution was satisfactory. To date, the authors have found this association in 2% of the patients with intraspinal gas.

The potential presence of an intradural disc herniation must always be considered when performing an open discectomy on a patient whose CT scan study shows the presence of epidural gas. This association is particularly striking given the relative rarity of intradural herniations and intraspinal gas. In the event that no clear disc herniation was found, an intradural examination may be indicated to justify clinical signs and symptoms or previous radiologic studies ⁴⁾.

Intradural exploration and/or transdural sequestrectomy avoids traction on already compromised nerve roots and is often safer than extradural sequestrectomy. The onset of bladder paralysis is a most important indication for immediate surgery. The cases presented show that there is a highly significant difference in the outcome of those cases operated on within 24h of bladder paralysis compared to those operated on after this period ⁵⁾.

Sharma et al. presented a case series of six cases of intradural disc herniation at L4-L5 level diagnosed on the basis of intraoperative findings.

All the cases, on preoperative magnetic resonance imaging (MRI) were reported as having diffuse annular bulge with large posterocentral extrusion. The study comprised patients in age group of 30-60 years. Four cases out of six presented with cauda equina syndrome. In three cases, cauda equina was associated with sudden deterioration in the power of lower limb muscle groups.

They suspected that intradural herniation of disc was synchronous with cauda equina syndrome in these cases, which was very well documented in one of the cases. On retrospective analysis, MRI findings of mass effect in the form of displacement of the traversing nerve roots due to large central disc with crumble disc sign were suggestive of early evidence of intradural disc herniation. Y sign in ventral dura due to splitting of ventral dura and arachnoid mater by disc material was a good diagnostic sign to suspect intradural extra-arachnoid disc. The presence of hypointense structure inside the dura with no continuity with the adjacent intervertebral disc on MRI was highly suggestive of an intradural disc.

Intradural disc prolapse remains a diagnostic dilemma as it is very difficult to diagnose all the cases preoperatively. The presence of above-mentioned radiological signs on MRI in patients having the large central disc on MRI, especially at L4-L5 levels, should raise suspicion of intradural herniation of disc. ⁶⁾.

Ducati et al. described five cases of this pathology and review the literature as well as some considerations about the difficulties in the preoperative diagnostic issues and the surgical technique.

They concluded that for intradural disc herniations the diagnosis is mainly intraoperative, and the surgical technique has some special aspects ⁷⁾.

Intradural lumbar disc herniation is rare, with an incidence of 0.3%-1%, but has been well reported in the literature. Transdural migration of the disc penetrating both ventral and dorsal dura is extremely rare, and there is a dearth of literature in the pathophysiology and surgical management of transdural herniation. Lack of knowledge on this type of presentation can cause intraoperative surprises and inadvertent cauda equina root injuries and lead to prolonged operative time. Pedaballe et al. reported 1 such case, described the surgical experience, and discussed the pathological mechanisms and signs.

A 30-year-old woman presented to outpatient clinic with chronic cauda equina syndrome due to massive L4-L5 disc herniation. L4-L5 decompression and transforaminal lumbar interbody fusion were planned. Unexpectedly, however, surgery revealed a transdural herniation, which was effectively managed with laminectomy, extension of durotomy, discectomy, repair of both dorsal and ventral dura, and interbody fusion, but at the expense of prolonged surgical time.

Transdural herniation of a lumbar disc is very rare presentation. It can be effectively managed with laminectomy, extension of durotomy, discectomy and repair of both dorsal and ventral dura. It can be diagnosed by magnetic resonance imaging preoperatively only if read with suspicion of such presentation. ⁸⁾.

A 56-year-old man who developed cauda equina syndrome after several episodes of severe Valsalva maneuver.

The patient was found to have developed subacute urinary retention and leg weakness. Magnetic resonance imaging findings were concerning for an unusual-appearing lesion extending cranially at L2-3. Urgent decompression via an L2 laminectomy, exploration, and subsequent discectomy was performed. The patient recovered exceptionally well, regaining bladder function and ultimately being able to ambulate without assistance.

Cranially extending intrathecal disc herniations are a rare phenomenon and exceptionally uncommon above L3. The clinician should have a high level of suspicion for herniation when looking at the clinical and historical information consistent with such a diagnosis even in the presence of ambiguous imaging findings ⁹⁾

Nagaria et al. presented a case with intermittent symptoms and signs of cauda equina compression. They were unable to find in the literature, any previously described cases of intermittent cauda equina compression from a herniated intradural disc fragment leading to a “floppy disc syndrome” ¹⁰⁾.

A 73-year-old male presented with a rare dorsally sequestrated lumbar disc herniation manifesting as severe radiating pain in both leg, progressively worsening weakness in both lower extremities, and urinary incontinence, suggesting cauda equina syndrome. Magnetic resonance imaging suggested the sequestrated disc fragment located in the extradural space at the L4-L5 level had surrounded and compressed the dural sac from the lateral to dorsal sides. A bilateral decompressive laminectomy was performed under an operating microscope. A large extruded disc was found to have migrated from the ventral aspect, around the thecal sac, and into the dorsal aspect, which compressed the sac to the right. After removal of the disc fragment, his sciatica was relieved and the patient felt strength of lower extremity improved ¹¹⁾.

Mailleux et al. described a case of anterior transdural L4-L5 disc herniation presenting as a partial cauda equina syndrome without related back pain or history of back pain. MRI allowed presurgical diagnosis showing an irregular intradural mass that did not enhance. That lack of enhancement could be related to the fact that the disc herniation was relatively recent ¹²⁾.

A female patient with lumbosciatic pain who developed an incomplete cauda equina syndrome. An asymmetric discopathy of the L2-L3 space and a gas bubble with disc material within the spinal canal was noticed in the radiologic explorations. The literature and the authors’ experience are reviewed with the aim of confirming the frequency of intradural herniation in association with gas in the spinal canal.

A laminoarthrectomy of the involved space was performed followed by direct intradural examination, which revealed a disc fragment that was excised. An instrumented L2-L3 arthrodesis was performed. Postoperative evolution was satisfactory. To date, the authors have found this association in 2% of the patients with intraspinal gas.

The potential presence of an intradural disc herniation must always be considered when performing an open discectomy on a patient whose CT scan study shows the presence of epidural gas. This association is particularly striking given the relative rarity of intradural herniations and intraspinal gas. In the event that no clear disc herniation was found, an intradural examination may be indicated to justify clinical signs and symptoms or previous radiologic studies ¹³⁾.

A 59 year-old man with ILDH. It was the only case of ILDH among 960 patients surgically treated, during the period 1989-1996. Clinically the patient demonstrated an acute cauda equina syndrome. The diagnosis was established by radiculograms, which showed a total block at the L3-L4 level. There was a 3 days time interval between the diagnosed syndrome itself and the operation. At surgery the L3-L4 level was intact, whereas dense adhesions were found between the L4-L5 disc and the dura. Root retraction to expose the nucleus pulposus mass was impossible. A laminectomy of the L4 was undertaken. An incision was made in the dura and arachnoid, revealing an extruded discal mass, lying between the roots of the cauda equina. It was carefully removed. The state of the patient at follow-up 1 year after surgery was unsatisfactory. The patient has moderate flaccid paraparesis, bladder dysfunction improved. The prognosis appeared to be linked to the preoperative duration of symptoms ¹⁴⁾

One case of intradural lumbar disc herniation at the L3-L4 disc level with cauda equina syndrome is reported. Myelo-CT demonstrated an intradural tumor-like lesion with complete block. An intradural fragment of sequestrated disc material was found intraoperatively. Accurate preoperative diagnosis of the intradural nature of the disease and prompt surgical treatment resulted in a smooth recovery ¹⁵⁾.

A case of intradural disk herniation at L4-5 observed in a patient with longstanding low back pain and sciatica due to a herniated disk. After having undergone various surgical procedures for this disorder, the patient developed a multiradicular syndrome of the cauda equina ¹⁶⁾