Intradural-extramedullary Spinal Cavernoma

Cavernomas are dilated capillary vessels without intervening neural tissue.¹ Most cavernomas are intracranial; of the 5% located in the spine, most are extradural or intramedullary.¹ Intradural-extramedullary cavernomas are quite rare. Here, we present a unique case of an intradural-extramedullary cavernoma exclusively associated with a thoracic dorsal nerve root and review the clinical presentation, imaging features, surgical management, and postoperative outcomes of these rare lesions.

Case Report

A 45-year-old male patient presented with a gradual six-month history of decreased sensitivity to heat and a burning sensation to cold temperatures on his left leg, numbness, and paresthesia affecting the medial aspects of his lower extremities bilaterally, and leg weakness worse on the right side, consistent overall with a Brown-Sequard hemi-cord syndrome. He denied bowel, bladder, or sexual dysfunction. Clinical examination revealed mild thoracic myelopathy: his patellar and Achilles reflexes were increased bilaterally (3+) with two beats of ankle clonus and upgoing plantar response on the right. The remainder of the exam was unremarkable.

MRI demonstrated a 16 mm intradural-extramedullary lesion at T3-4 level, displacing and compressing the spinal cord (Figure 1A, 1B). The lesion appeared hyperintense on T1 and centrally hypointense (with surrounding high signal) on T2-weighted images, consistent with hemosiderin deposition. There was faint contrast enhancement. There was no identifiable abnormal vessels or abnormal intradural vascular enhancement seen on contrast-enhanced MR angiography.

Figure 1: Thoracic spine MRI (A, B) displaying an intradural-extramedullary lesion at T3-T4. Axial T1-weighted image with gadolinium demonstrates a hyperintense lesion (A); and sagittal T2-weighted image demonstrates central area of hypointensity consistent with hemosiderin deposition (B). Post-operative imaging (C, D) on axial T2-weighted image demonstrates resolution of the previously seen T2 hyperintense signal (C); and sagittal T1-weighted image of the thoracic spine demonstrating no abnormal enhancement or suggestion of residual tumor (D). Intraoperative images (E, F) following T3-4 laminectomy and durotomy: the extramedullary lesion can be seen displacing the spinal cord to the left (E); following en-bloc excision the mulberry-like appearance of the cavernoma with an attached nerve root (arrow) (F). Pathology slides (G, H) with H&E stain (G) demonstrating multiple vascular channels with hyalinized walls of varying thickness, size and shape and no intervening neural or connective tissue. Intraluminal blood clots with both recent and remote evidence of recanalization is observed. A spinal nerve rootlet is seen attached to the lesion, highlighted by S100 protein stain (H).

The patient underwent a T3-4 laminectomy and complete excision of the lesion. Significant epidural venous engorgement was noted intraoperatively. Following durotomy, a dark, mulberry-like lesion separate from the spinal cord and associated with a dorsal sensory nerve root was encountered (Figure 1E). With sacrifice of this root, a complete en-bloc excision was achieved (Figure 1F).

Permanent pathology was consistent with cavernoma, demonstrating a spinal nerve root attached to the lesion (Figure 1G, 1H). The patients’ symptoms completely resolved following surgery and he remained asymptomatic at 3-month follow-up (post-operative Figures 1C, 1D).

Literature Review

Intradural-extramedullary cavernomas are quite rare, including the current report, 71 cases have been reported to-date (Table 1). Fifty of these were associated with nerve roots, while in 21 cases the lesion was associated with other structures (e.g. dura), or its origin was not specified. Thirty-eight (54%) cases were located in the lumbar spine, 18 (25%) thoracic, 4 (6%) thoracolumbar, 8 (11%) cervical, and 3 (4%) with no level reported. Most patients presented between the ages of 40–59 (41%), followed by 60–79 (34%), 20–39 (20%), and rarely ≦19 (3%).

Table 1: Published cases of spinal intradural extramedullary cavernous malformation associated with a nerve root (No. 1-50) and with no documented nerve root involvement (No. 51-71)

NR = Not reported; Total = Total resection; Subtotal = subtotal resection; RR = Nerve root resection; SAH = subarachnoid hemorrhage.

See Supplemental Materials for additional references.

Cases reviewed from the literature demonstrated various patterns of homogenous and heterogenous enhancement on imaging, which may be attributed to mixed subacute and chronic hemorrhage.² Given that the classic hemosiderin ring of hypointensity was present only in some cases,³ these lesions may be difficult to identify preoperatively without a high index of suspicion.

Ten patients (14%) presented with confirmed subarachnoid hemorrhage (SAH) and one with intramedullary hemorrhage, as might be expected for intradural-extramedullary lesions. Although an annual hemorrhage rate has not yet been reported given limited available data, a comparable reported annual hemorrhage rate for intramedullary spinal cavernomas is 2.1%.⁴ All SAH cases reviewed demonstrated acute onset, whereas the unique case of intramedullary hemorrhage (Kivelet et al., 2008) displayed chronic progression (myelopathy, 5 months). However, 16 patients (23%) presented with acute onset of symptoms and 8 (11%) with a mixed acute-on-chronic presentation, indicating the true rate of hemorrhage at presentation may be higher. Comparably, in a 2014 meta-analysis, 45.4% of intramedullary cavernomas presented acutely or in a stepwise fashion, with 54.6% presenting with chronic progression.⁴ Roughly half (49%) of cases reviewed here presented solely with longstanding or progressive symptoms (weeks to years). Thirty-seven percent presented primarily with radiculopathy, 21% with myelopathy, and 11% with pain only. The tendency of intradural-extramedullary cavernomas to present with radiculopathy may be a distinguishing feature of their presentation, reinforced by the fact that the majority occurred at the lumbar level.⁵

Complete lesion resection was achieved in 65 cases (92%), with the remaining having subtotal resection, nonoperative management, or no reported intervention. Of cases with nerve root involvement, 44% documented nerve root sacrifice. Good postoperative recovery (partial or complete resolution of symptoms without major complication) was documented in 80% of all cases (with 31% achieving complete resolution of preoperative symptoms), and among 90% of cases with nerve root involvement (of which 36% completely recovered).^6–8 Although it is not possible to draw definitive conclusions, all cases published after 2000 reported postoperative improvement, which may indicate superior outcomes with advances in surgical technique.

In considering literature review findings and insights from our own case, we provide several recommendations regarding management of these lesions. Conservative approaches, including expectant management, do not offer symptom improvement and risk further deterioration and complications associated with SAH. Endovascular treatments are unfavorable given high chances of recurrence and progression of myelopathy following embolization.⁹ For symptomatic patients, we recommend prompt surgical excision. For lesions uniquely attached to a nerve root, root sacrifice may be necessary; outcomes are likely still to be favorable, with opportunity for complete resolution of symptoms.

Significance and Conclusions

Although additional data are required, intradural-extramedullary cavernomas may demonstrate a unique propensity for radiculopathy or myelopathy at presentation. Excellent postoperative outcomes in our case and others support the role of surgical resection over conservative approaches, particularly in symptomatic patients, in order to prevent further neurological deterioration.