Posterior longitudinal ligament and its implications in intradural cervical disc herniation: Case report and review of the literature.

BACKGROUND: Intradural disc herniations (IDH) are rare, particularly in the cervical spine, where they account for less than 5% of all discs. Adhesions between the ossified/calcified posterior longitudinal ligament (OPLL), dura, and ossified/calcified disc herniations increase the complexity of resecting these cervical lesions. CASE DESCRIPTION: A 42-year-old male presented with a rapidly progressive cervical myelopathy over a 2-month period. This was attributed to an ossified/calcified intradural cervical disc herniation in conjunction with OPLL. The anterior cervical discectomy and fusion (ACDF) resulted in a dural defect but there was no cerebrospinal fluid (CSF) fistula as the arachnoid membrane remained intact. Had there been a CSF leak, it would have warranted both wound-peritoneal (WP) and lumbo-peritoneal shunts (LP). The surgeons should have anticipated that a CSF leak would likely occur prior to performing the ACDF, and should have prophylactically prepared and draped the abdomen for a potential WP, followed by a LP shunt. Three months postoperatively, the patient's proprioceptive deficit improved, and he almost completely recovered motor function.
CONCLUSION: Performing an ACDF for resection of an intradural calcified/ossified disc with OPLL often results in both a dural defect and CSF fistula. As the arachnoid membrane rarely remains intact, the spine surgeon should be prepared to immediately perform both a WP shunt, and subsequently, an LP. In this case, following an ACDF, resection of an intradural ossified disc with OPLL resulted in an isolated dural defect without a CSF fistula and did not require no dural repair or shunting procedures.

INTRODUCTION

Intradural herniations (IDH) are rare and most commonly present in the lumbar (92%), followed by the thoracic (5%) and cervical spine (3%).[5] Since Marega first described a cervical IDH in 1959,[4] 30 such cases have been reported in the literature [Table 1].[13456789] When calcified/ossified IDH typically occur in conjunction with OPLL, they result in both durotomies and CSF fistulas.[68] Anticipation of such CSF leaks should prophylactically include preparation to perform a wound-peritoneal (WP) and subsequent lumbo-peritoneal (LP) shunts.[2]

Table 1

Historical review of the published cervical IDH cases[13456789]

Here, a patient with an ossified/calcified cervical IDH with OPLL underwent an ACDF with durotomy but without an accompanying cerebrospinal fluid (CSF) fistula that did not warrant any shunting procedures.

CASE REPORT

Clinical findings

A 42-year-old male presented with a 2-month history of a cervical myelopathy that had rapidly progressed over the past 2 weeks. He exhibited a left hemiparesis (2/5 motor) but normal function on the right side, which was accompanied by hypoesthesia in both lower extremities. Interestingly, reflexes remained intact bilaterally, and he retained normal sphincter function.

Radiographic evaluation

The cervical spine magnetic resonance imaging (MRI) showed a large ossified/calcified central disc herniation at the C4/5 level with OPLL contributing to marked ventral cord compression [Figure 1]. As no preoperative computed tomography (CT) was performed, no single-layer or double-layer signs could clearly signal the presence of OPLL.

Figure 1

Axial T2-weighted (a) and Sagital T2-weighted (b) images revealing central C4-C5 disc extrusion with effacement of the anterior subarachnoid space and compression / indentation of the spinal cord (hawk beak sign or Y sign, suggestive of intradural disc herniation – arrow)

When an ACDF was performed, they encountered a large calcified disc fragment with OPLL that was removed en bloc. Although there was a tear in the dura, the arachnoid remained intact; there was no accompanying cerebrospinal fluid (CSF) fistula [Figure 2]. Therefore, no shunting procedures were warranted. Postoperatively, the patient's left hemiparesis was partially resolved, however, the sensory deficit remained. Notably, the postoperative MRI scan revealed adequate spinal cord decompression, but a punctate intramedullary C4-C5 cord contusion [Figure 3]. There were no postoperative complications, and 3 months later, the patient's motor deficit fully resolved; however, he exhibited residual proprioceptive deficits.

Figure 2

(a) En bloc removal of the calcified disc fragment, protruding through the posterior longitudinal ligament and through the dura. (b) Central defect in the dura is observed, with arachnoid exposed. No CSF leak. Cord seen nicely pulsating through the arachnoid

Figure 3

Axial T2-weighted (a) and Sagital T2-weighted (b) images revealing status post-anterior discectomy and fusion (asterix) with repermeabilization of the anterior subarachnoid space and decompression of the spinal cord (punctate left paramedian spinal cord lesion is seen - arrow)

DISCUSSION

The pathogenesis of IDH include congenital narrowing of the spinal canal, chronic compression of a highly mobile segment of the spinal canal, and adhesions between the calcified/ossified ligaments, OPLL, and dura.[68] Here, the patient had a calcified/ossified IDH with OPLL and chronic cervical cord compression.

IDH with OPLL can be intra-arachnoidal (e.g. due to adhesions/calcification between the PLL and the dura) or extra-arachnoidal. Therefore, high CSF leak rates are reported for anterior OPLL surgery (e.g. 4.3–32%).[5] In this review [Table 1],[13456789] we report 6 CSF leaks for ACDF; 50% were due to OPLL. In this case, the potential for a CSF leak should have been anticipated, and prophylactically, the patient should have been prepared and draped for a possible immediate intraoperative WP shunt followed by a LP shunt.[2] Nevertheless, fortunately the C4-C5 calcified/ossified disc/OPLL excision resulted in a durotomy without a CSF fistula and no such shunts were required.

CONCLUSION

Here, a patient with a calcified/ossified cervical IDH/OPLL sustained a durotomy without a CSF fistula during an ACDF. No shunting procedures (WP and LP shunts) were required as the arachnoid remained intact. In the future, the spinal surgeon should obtain a preoperative CT to supplement MRI as this would best identify the classical single or double-layer signs indicating OPLL dural penetrance. This would have warned the surgeon of a potential anterior dural/arachnoidal fistula, and would have enabled them to prophylactically prepare and drape for and anticipate a CSF fistula requiring both an immediate WP, followed by an LP shunt.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.