Pial arteriovenous fistula as a cause of bilateral thalamic hyperintensities--an unusual case report and review of the literature.
Dear Editor, Pial arteriovenous fistula (AVF) is an extremely rare intracranial vascular lesion, consisting of one or more arterial supply in direct connection to venous drainage without intervening nidus . We present a rare case of pial AVF with giant varix and draining into dilated vein of Galen, which was managed by surgical clipping. This 1-year-old boy presented with visible protrusion of the eyeball and dilated scalp veins. Computer tomography (CT) and three-dimensional (3D) CT angiography revealed an AVF between A2 (infracallosal) segment of the anterior cerebral artery and anterior pericallosal vein (Fig. 1a). There was a varix continued to the AVF, and the enlarged varix drained into dilated vein of Galen (Fig. 1a, b). The child underwent pterional craniotomy. We found a pial AVF between an enlarged pericallosal artery and an associated varix under the corpus callosum. The varix lost turgidity immediately after clipping of the pericallosal artery near to the fistula. One week postoperatively, CT angiography found disappearance of AVF associated varix and distal part of draining vein in arterial phase (Fig. 1c). After discharge, the boy returned to normal childhood without any neurological deficits. Followup CT angiograms obtained at 14 months postprocedure showed total obliteration of the AVF, no perfusion of the varix, and remodeling of the vein of Galen (Fig. 1d, e). Enhancing CT showed shrinking of the AVF associated varix, and remolding of dilated vein of Galen (Fig. 1f). Supratentorial pial AVFs are most often diagnosed during the first 5 years of life. In this case, it is important to differentiate true vein of Galen malformation (VGAM) from vein of Galen aneurysmal dilation (VGAD). The VGAD describes an arterio-venous shunt that drains into a tributary of the vein of Galen, resulting in its overload and dilatation. The frequency of VGAD in neonates and infants is low and patients with VGAD often present at a later age during childhood . In a case reported by Tawk, the abnormality was a pial fistula with varix lying in posterior fossa . In the present case, the mass in the anterior fossa was a dilated venous pouch secondary to high flow fistula (Fig. 1a, b). The dilatation presumably occurs because the vein is the most proximal distensible venous structure to the shunt. Its nature as bridging structure between subarachnoid venous system and dural sinus confers it a characteristic anatomy. Being unfettered by dural walls, it dilates enormously with thickening of its wall in response to increased blood pressure and turbulent flow . Resection of varix and ligation of both arterial feeder and drainage have been performed for pial AVF. However, huge and partial calcified varix made complete resection extremely difficult. Hoh et al. have demonstrated that the goal of treatment in AVFs, is the rapid control of the AV shunt . The preferred treatment of AVF is obliteration of the fistula or interruption of all feeding vessels at the fistulous point while preserving venous drainage. In absence of a nidus, surgical disconnection of arterio-venous communication is considered to be a safe and rational option . This disconnection has been successfully achieved either by aneurysm clip application or cauterization of the vessel near the fistula . Endovascular therapy plays an important role in the treatment of intracranial AVF with giant varices. Review of literature revealed an obliteration rate of 86.5 % for endovascular treatment. Compared with an endovascular This job was partially supported by the National Natural Science Foundation of China (NO. 81101620), and National Key Clinical Specialty Construction Project. L. Han : J. Chen : T. Lei (*) Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science & Technology, 430030, Wuhan, China e-mail: firstname.lastname@example.org