Spinal schwannoma with broad pial adhesion: A case report

Abstract

Background:

Typical spinal schwannomas are well-encapsulated intradural extramedullary tumors arising from sensory nerve roots. Schwannomas adherent to the spinal cord are rare and include both intramedullary (subpial) and combined intra- and extramedullary lesions. Here, a 60-year-old male initially presented with a combined intra/extramedullary schwannoma with dense adhesions to the spinal cord; at surgery, this proved to be a peripheral schwannoma with broad pial adhesions.

Case Description:

A 60-year-old male presented with severe paraparesis attributed to a dorsal thoracic T11 tumor. Chronic hemodialysis precluded performing a contrast magnetic resonance. Intraoperative ultrasonography showed a well-defined, multi-cystic, and dorsal lesion without intramedullary extension. After dural opening, the tumor was tightly adherent to the dorsal spinal cord/pia. A staged internal decompression improved tumor mobility, allowing the tumor to be progressively dissected away from its broad-based pial adhesion/vasculature. Finally, a clean cleavage plane between the tumor capsule and spinal cord confirmed that the tumor was an extramedullary, broad-based pial schwannoma that was totally resected without neurological sequelae.

Conclusion:

Peripheral spinal schwannomas may occasionally exhibit broad-based pial adhesions that mimic intramedullary (subpial) or combined intra/extramedullary lesions. Proceeding with a step-wise resection often reveals an increasingly clean cleavage plane facilitating gross total tumor resection.

INTRODUCTION

Typically, spinal schwannomas are well-encapsulated, intradural extramedullary tumors arising from sensory nerve roots. Rarely, schwannomas are adherent to the spinal cord (i.e., intramedullary [subpial] schwannomas vs. combined intra/extramedullary lesions). Here, a 60-year-old male presented with a T11 schwannoma that was originally thought to be a combined intra/extramedullary lesion with broad-based pial adhesions. Intraoperative findings, however, confirmed the extramedullary location of a schwannoma with broad pial adhesions.

CASE PRESENTATION

A 60-year-old male presented with progressive paraparesis, and sensory loss below the umbilical (T12) level. The non-contrast magnetic resonance (MR) imaging demonstrated a dorsal, intradural/extramedullary T11 tumor causing severe spinal cord compression [Figure 1a-c]. A contrast MR was contraindicated due to chronic hemodialysis.

Figure 1:

Preoperative and intraoperative imaging. (a and b) Sagittal T1- and T2-weighted MRI showing a dorsal T11 intradural extramedullary tumor. (c) Axial T2-weighted MRI showing severe spinal cord compression. (d) Intraoperative ultrasonography showing a well-defined, multicystic dorsal lesion. MRI: Magnetic resonance imaging.

Surgery and pathology

After a T11 laminectomy, intraoperative ultrasonography demonstrated a well-defined, multi-cystic, dorsal extramedullary lesion [Figure 1d]. After dural opening, a reddish-brown tumor beneath the arachnoid membrane was tightly adherent to the dorsal spinal cord [Figure 2a]. A staged internal decompression was performed, and as dissection proceeded, multiple feeders arising from the posterior spinal artery/pial arteries were identified, coagulated, and divided. Final division of the distal sensory root exposed a broad pial adhesion, confirming the extramedullary location of the lesion [Figure 2b and c]. Gross-total resection was achieved without incurring new neurological deficits. The histopathological examination confirmed schwannoma with Antoni A and Antoni B architecture.

Figure 2:

Sequential intraoperative findings. (a) Tumor tightly adherent to the dorsal spinal cord. (b) Broad pial adhesion after internal decompression and distal root division; multiple pial feeders were coagulated and divided. Asterisk indicates the pia-denuded spinal cord surface. (c) Final view after gross-total resection, showing no intramedullary tumor extension. Asterisk indicates the pia-denuded spinal cord surface .The dotted lines in Figure 2c delineate the area of pial denudation. PSA: Posterior spinal artery.

DISCUSSION

Spinal schwannomas are generally well-encapsulated intradural extramedullary tumors arising from sensory nerve roots that are usually readily separable from the spinal cord. When a spinal schwannoma is found to be firmly adherent to the spinal cord, intramedullary (subpial) schwannoma and combined intra- and extramedullary schwannoma should be considered. [1-4] In this case, the tumor initially appeared to be a combined intra/extramedullary schwannoma due to its broad pial adhesion and poor mobility. However, meticulous stepwise dissection demonstrated no intramedullary extension. Intramedullary schwannomas are extremely rare, accounting for approximately 1% of all spinal schwannomas.[4] Several reports described completely intramedullary schwannomas versus combined intra- and extramedullary schwannomas.

Their origin was variously attributed to the: (a) subpial origin (intramedullary schwannoma), or (b) through the dorsal root entry zone.[1-3] Here, we speculated that this patient’s tumor originated immediately distal to the pial penetration site of the proximal sensory nerve root and subsequently developed progressive adhesion between the perineurium and pia while remaining extramedullary [Figure 3].

Figure 3:

Proposed mechanism of epi-pial adhesion in a peripheral spinal schwannoma. (a) The tumor likely originated immediately distal to the pial entry site of the proximal sensory root; here, focal adhesions between the perineurium (sensory root sheath) and the pia mater probably developed. (b) Progressive tumor growth resulted in broad-based adhesions along the perineurium–pia interface. There was no intramedullary tumor extension. PSA: Posterior spinal artery.

CONCLUSION

Peripheral spinal schwannomas, despite exhibiting broad-based pial adhesions that mimic intramedullary (subpial) or combined intra/extramedullary schwannomas, may remain solely extramedullary. Careful staged internal decompression with meticulous tumor dissection and coagulation/cutting of spinal/pial feeding vessels allows for safe gross-total tumor removal.

Ethical approval:

The Institutional Review Board has waived the ethical approval for this study.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given consent for their images and other clinical information to be reported in the journal. The patient understands that the patient’s 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.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The author(s) confirms that they have used artificial intelligence (AI)-assisted technology for language editing and improvement of manuscript readability. The authors reviewed, edited, and take full responsibility for the final content of the manuscript.

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