Arteriovenous malformation with unique drainage through the emissary vein of the foramen ovale: illustrative case

Abstract

Background: As part of the laterotrigeminal venous system (LTVS), the emissary vein of the foramen ovale (EVFO) is an underrecognized venous structure communicating between the cavernous sinus and pterygoid plexus. The sphenobasal sinus is an anatomical variation of the sphenoparietal sinus that drains directly into the EVFO. The authors present the case of a ruptured arteriovenous malformation (AVM) with a unique drainage pattern through the sphenobasal sinus and EVFO.

Observations: A 9-year-old female initially presented with loss of consciousness and was subsequently found to have a ruptured AVM in the left basal frontal area. She underwent an immediate decompressive hemicraniectomy, with a computed tomography angiogram demonstrating a unique anatomical variation in which the sphenobasal sinus communicated with the EVFO and LTVS. The final venous drainage returned to the pterygoid plexus and external jugular vein. Postoperatively, the patient made a substantial recovery, with generalized right-sided weakness remaining as the sole deficit.

Lessons: The authors present the case of a ruptured AVM with unique venous drainage into the sphenobasal sinus and EVFO, for which the current literature remains limited. As exemplified by this illustrative case, technique modification may be warranted in the setting of this unique anatomical variation to avoid venous sinus injury.

Keywords: arteriovenous malformation; emissary vein of the foramen ovale; sphenoparietal sinus.

FIG. 1

Axial CT scan (A) demonstrated a large intracerebral hemorrhage in the left frontal and temporal lobes, measuring up to 76 mm anteroposteriorly. Lateral view of the left internal carotid artery (ICA) injection on an angiogram (B), during the arterial phase, demonstrated a nidus (red circle) in the basal frontal area and draining to the abnormally early filling vein. An intranidal aneurysm was also visible (asterisk). The capillary phase of the lateral left ICA injection (C) demonstrating abnormally early filling to the draining vein. The nidus drained into the sphenoparietal sinus, sphenobasal sinus, EVFO, and pterygoid plexus. The anteroposterior view of the angiogram (D) again demonstrated the nidus (red circle) with the aneurysm (asterisk). The nidus received arterial feeders from the MCA superiorly. A sagittal view of a CT angiogram (E) demonstrated filling of the sphenoparietal and sphenobasal sinuses (arrowheads), which drained into the EVFO through the foramen ovale; the EVFO was shown to be significantly dilated. An axial view of the CT angiogram (F) demonstrated the dilated pterygoid plexus (blue circle) within the infratemporal fossa. Postoperative lateral (G) and anteroposterior (H) angiograms showed no residual of the previously demonstrated nidus, no abnormally early filling vessels, and no significant filling defect.

FIG. 2

A: A cadaveric dissection of the middle fossa floor on the right side. After extradural subtemporal dissection, the LTVS is demonstrated in proximity to the GG and V3. B: Illustration of the normal anatomy of the LTVS, which contains the following components: GG, the V3, the communicating vein to the superior petrosal sinus, the middle meningeal vein coursing through the foramen spinosum, and the EVFO. The LTVS provides venous communication to the cavernous sinus, superior petrosal sinus, and pterygoid plexus. C: Illustration of the sphenobasal variation, where the sphenoparietal sinus drains into the LTVS and EVFO. Cav. = cavernous; em. = eminence; FO = foramen ovale; For. = foramen; FR = foramen rotundum; GSPN = greater superficial petrosal nerve; IPS = inferior petrosal sinus; Intercav. = intercavernous; LPN = lesser petrosal nerve; sin. = sinus; SPS = superior petrosal sinus; SS = sigmoid sinus; TT = tagmen tympani; V2 = maxillary nerve.