An intracranial arteriovenous fistula with a large pial venous varix in a young female: A case report and review of the literature.

Dear Sir,

The intracranial arteriovenous fistulas (AVFs) with direct communication to a pial venous varix are rare vascular lesions, represent a specific group of arteriovenous shunt and constitute about 5% of all brain arteriovenous malformation.[12] Arteriovenous shunts with direct communication between a pial venous plexus without any intervening nidus is quite uncommon. Pial AVFs are often high-flow lesions, and often associated with dilated venous pouches.[3] They differ from dural AVFs as they are not located within the leaflets of the dura and acquire feeders from pial or cortical arteries.[4]

A 16-year-old female was admitted with complain of intermittent headache, seizures, vomiting and blurring of vision for 1-year duration. On clinical examination, her vital signs were normal. No bruit over the cranium was heard. There was no neurological deficit except bilateral mild papilledema. The magnetic resonance (MR) imaging angiography of brain showed about 3 × 3 cm size venous aneurysm in left fronto-parietal lobe with multiple varicose venous channels draining to dilated superior sagittal sinus with a single arterial feeder from dilated left middle cerebral artery (MCA) as shown in Figure 1. The AVF and venous aneurysm show signal void in all sequences suggestive of high-flow vascular lesion. She opted for neurosurgical treatment in our hospital as she was very poor and unable to afford the cost of endovascular coiling treatment in higher center.

Figure 1

T2-weighted coronal, (a) three-dimensional time of flight (3DTOF) arterial magnetic resonance (MR) image and (b) 3DTOF venous MR imaging (c and d) about 3 × 3 cm size flow void in left fronto-parietal lobe suggestive of venous aneurysm, which is fed by single arterial feeder from left middle cerebral artery and drained by two predominant dilated venous channels to superior sagittal sinus

A left fronto-parietal craniotomy was done. The dura was cut open and reflected toward sagittal sinus. Under microscopic vision, the single arterial feeder from MCA was identified, which looks dilated and thick. A temporary clip was applied over it, and the vessel was dissected further till it's merging into the venous varix. Then the feeder was ligated and cut. The dilated draining veins were identified, dissected, ligated and cut. Then the whole venous varix along with cut end of feeding artery and draining vein was taken out [Figure 2]. The temporary clips were removed; hemostasis achieved and wound closed in layers. The patient had no neurological deficit except mild aphasia on immediate postoperative period, which recovered on follow-up. Postoperative MR angiogram showed absence of AVF and residual postoperative chronic hemorrhage in the left fronto-parietal lobe [Figure 3].

Figure 2

Picture showing excised arteriovenous fistula with ligated MC feeder and draining veins

Figure 3

Postoperative three-dimensional time of flight arterial (a) and venous (b) magnetic resonance imaging showing nonvisualization of arteriovenous fistula and venous aneurysm

Intracranial pial AVFs can result from trauma or may be congenital. Congenital pial AVFs are very rare, and little is known regarding their pathophysiological mechanisms. Abnormal expression of various angiogenic factors such as vascular endothelial growth factor, basic fibroblast growth factor, and alpha transforming growth factor and suppression of vascular cell growth modulators, including endoglin1, have also been found in case of AVF.[567] Cases of acquired pial AVFs in MoyaMoya disease and following cerebral vein thrombosis[8] suggest ischemia or hypoxia is an important etiological factor.

Patient with pial AVFs usually presents with seizures, hemorrhage, headache, focal neurological deficit, symptoms of increased intracranial pressure, and intracranial bruit.[9] Neonates and infants may present with high output cardiac failure, increased head circumference, and bruit.[10] Our case presented with headache, occasional vomiting and temporary blurring of vision.

Pial AVF can be imaged by computed tomography angiography, MR imaging angiography or digital subtraction angiography. Clues to the diagnosis of pial AVFs at cross-sectional imaging include the presence of (a) dilated vessels, mainly at the brain surface; and (b) asymmetric dilatation of the pial feeding artery – either the MCA, anterior cerebral artery, or posterior cerebral artery which is best seen at the level of the circle of Willis. These findings can be used to differentiate pial AVFs from dural AVFs and may be accompanied by dilated venous pouches outside the brain parenchyma.[11]

Hoh et al.[10] state that surgical or endovascular intervention for disconnection of the shunt was sufficient and resection of the entire vascular malformation was unnecessary, which can be understood by the pathophysiologic mechanism of the AVF, namely, the high-flow nature of the communication between an arterial feeder and draining vein. The venous varices associated with AVFs are produced by the high, turbulent flow caused by arteriovenous shunting. Surgically inaccessible lesions are best treated by endovascular embolization. However, the treatment failure rate has been known to be 40% in endovascular embolization and 7.8% in surgical disconnection.[10] In our case, the patient opted for surgical disconnection of AVF as she could not afford endovascular coiling/embolization in higher center.

Intracranial pial AVF with an intervening large venous aneurysm is a rare vascular lesion and should be ideally managed by endovascular coiling/embolization as morbidity is less in comparison to surgery. However, with single feeding artery that can be well sacrificed at the junction of venous aneurysm, surgery can yield a good result.