A rare case of spinal dural arteriovenous fistula mimicking malignant glioma of the medulla oblongata: Significance of cerebral angiography for accurate diagnosis of brain stem region

Abstract

Background: The findings of a hyperintense sign on T2-weighted imaging (T2-WI) and gadolinium (Gd) contrast enhancement on magnetic resonance imaging (MRI) of the brain stem suggest malignant glioma. However, this pathological condition is probably uncommon, and it may be unknown that a dural arteriovenous fistula (DAVF) can imitate this radiological pattern. In addition, it is extremely rare to be caused by a spinal DAVF. Here, a rare case of spinal DAVF that mimicked malignant glioma of the medulla oblongata is presented.

Case description: A 56-year-old woman was admitted with a progressive gait disturbance, vertigo, and dysphasia. MRI showed a hyperintense signal in the medulla oblongata on fluid-attenuated inversion recovery (FLAIR) and moderate contrast enhancement on Gd-enhanced MRI. Interestingly, Gd-enhanced MRI demonstrated abnormal dilated veins around the brain stem and cervical spinal cord. Cerebral angiography showed spinal DAVF at the left C4/C5 vertebral foramen fed by the C5 radicular artery. The fistula drained into spinal perimedullary veins and flowed out retrograde at the cortical vein of the posterior cranial fossa. Therefore, surgical disconnection of the spinal DAVF was performed by a posterior approach. The patient's postoperative course was uneventful. Cerebral angiography showed complete disappearance of the DAVF, with marked reductions of the hyperintense sign of the medulla oblongata on FLAIR.

Conclusion: This important case illustrates MRI findings mimicking brain stem glioma. In cases with the hyperintense sign-on T2-WI associated with contrast enhancement suspicious of brainstem glioma, careful checking for perimedullary abnormal vessels and additional cerebral angiography should be performed.

Keywords: Cerebral angiography; Lower cranial nerve palsy; Mimicking medulla oblongata glioma; Spinal dural arteriovenous fistula; Venous congestion.

Figure 1:

Preoperative axial magnetic resonance imaging. (a) Diffusion-weighted image (DWI), (b) fluid attenuated inversion recovery (FLAIR), and (c) gadolinium (Gd)-enhanced T1-weighted images showing a lesion in the medulla oblongata. The lesion is hypointense on DWI hyperintense on FLAIR and shows moderate enhancement on Gd administration.

Figure 2:

Gadolinium (Gd)-enhanced T1-weighted MRI (a: axial and b: sagittal) clearly showing abnormal dilated veins around the brain stem and in front of the cervical spinal cord (white arrow). T2-weighted sagittal image showing hyperintensity of the medulla and an abnormal signal flow void extending to the cervical portion of the spinal cord (white dashed arrow) (c).

Figure 3:

Left vertebral artery angiographic findings. (a) Anteroposterior view and (b) lateral view showing a spinal dural arteriovenous fistula (red arrowhead) supplied by the C5 radicular artery arising from the left vertebral artery draining into the spinal perimedullary veins (black bald arrow) reaching the cortical vein localized along the left aspect of the medulla oblongata. Computed tomography three-dimensional fusion digital subtraction angiography demonstrating the exact location of the arterio-venous shunt point (red arrowhead). (c) Axial view, (d) coronal view, and (e) reconstruction fusion model (red blood vessels are arteries and blue are draining veins)

Figure 4:

Intraoperative views (opening of the dura mater, left side), showing the shunt location and the single draining vein (white arrow) (a and b), which is disconnected with bipolar coagulation (black arrow: disconnected vein) (c). The draining vein is degenerated with shunt disconnection (black dashed arrow) (d).

Figure 5:

Left vertebral artery angiographic findings. (a) Anteroposterior view and (b) lateral view demonstrating complete disappearance of the dural arteriovenous fistula. Postoperative MRI shows marked reductions of the hyperintense sign of the medulla oblongata on fluid- attenuated inversion recovery (c) and the disappearance of the atypical perimedullary vein on gadolinium-enhanced T1-WI (d).