Atypical slow-flow paramedian AVM with venous varix

Abstract

Background: Cerebral arteriovenous malformations (CAVMs) are either clinically silent or symptomatic. The most common presentation in more than half of all CAVMs presenting patients is hemorrhage which is accompanied by long-standing neurological morbidity and mortality. This report presents a case of an atypical large, slow-flow paramedian AVM with a dilated venous varix managed with surgery. The impact of the intraoperative findings on the diagnosis and the operative technique will be discussed.

Case description: In otherwise, healthy 26-year-old male complained of repeated episodes of generalized seizures and loss of consciousness. Brain magnetic resonance imaging (MRI) revealed a right parietal paramedian arteriovenous malformation (AVM) with signs of an old hemorrhagic cavity beneath it. Digital subtraction angiography demonstrated a slow-filling AVM with dilated venous varix drains into the superior sagittal sinus. However, the exact point of drainage cannot be appreciated. The filling of the AVM occurred precisely with the beginning of the venous phase. Intraoperatively, we noticed a whitish spherical mass, thick hemosiderin tissue, and a large cavity below the nidus; then, a complication-free complete microsurgical resection of this high-grade AVM was performed. Postoperatively, the patient suffered two attacks of seizures in the first few hours after the surgery, for which he received antiepileptics. MRI was clear during follow-up, and the patient was seizure-free and neurologically intact.

Conclusion: Parietal convexity AVMs are challenging lesions to tackle. However, the chronicity and the slow-filling of the AVM, in this case, can render the surgical pathway more direct and accessible.

Keywords: Cerebral arteriovenous malformation; Microsurgical resection; Venous varix.

Figure 1:

(a) Axial T2 magnetic resonance imaging (MRI) weighted image demonstrated a linear and round flow void features of a vascular lesion and an area of parenchymal hypointensity indicating a previous hemorrhage. (b) Sagittal view flair MRI demarcates a cavity and hemosiderin accumulation.

Figure 2:

Artistic depiction of the paramedian arteriovenous malformation (AVM), in this case showing, arterial feeders, the AVM nidus position, venous varix (red arrow), and the draining vein (yellow arrow).

Figure 3:

Serial angiography of the right carotid artery reveals a slow-filling vascular lesion in the parietal lobe. It appears to be fed by the M4 segment of the middle cerebral artery, giving branches to its base. The draining vein appears exceedingly enlarged, forms varix (red arrow), and ends in the superior sagittal sinus.