INTRODUCTION
Intracranial dural arteriovenous fistulas (DAVFs) are abnormal connections between meningeal arteries and venous sinuses or pial vessels. While most DAVFs occur in the cavernous sinus (CS) or transverse/sigmoid sinuses, those involving the sphenoparietal sinus (SpS) are rare and often associated with high-risk venous drainage patterns, such as retrograde leptomeningeal drainage, which increases the risk of hemorrhage [1].
SpS DAVFs typically arise from the middle meningeal artery (MMA) and drain into the SpS, with further drainage through the superficial middle cerebral vein (SMCV), basal vein of Rosenthal (BVR), or CS. These lesions often present with symptoms such as proptosis or intracranial hemorrhage [2]. Endovascular embolization, using transarterial or transvenous approaches with agents like Onyx, n-butyl cyanoacrylate (nBCA) or coils, is the primary treatment modality [3].
We present a rare case of an SpS DAVF, highlighting its unique anatomy, clinical presentation, and successful endovascular management via the vein of Galen, along with a review of the relevant literature.
CASE REPORT
A patient in their early 60s presented to the emergency department with complaints of headache and right-sided numbness. Magnetic resonance imaging revealed a hemorrhagic lesion in the left thalamus, while magnetic resonance angiography (MRA) showed engorgement of the left SpS with drainage through an enlarged left BVR (Fig. 1A, B).
Under general anesthesia, digital subtraction angiography identified left-sided SpS DAVFs with multiple feeding arteries originating from branches of the left external carotid artery (ECA) (Fig. 1C, D) and the cavernous segment of the left internal carotid artery (ICA) (Fig. 1E, F). Venous drainage occurred retrogradely through the BVR and the vein of Galen, with a venous varix noted in the basal vein. Additionally, drainage was observed through the SMCV and the vein of Trolard. The DAVFs were classified as Cognard type IV. Following a detailed angiographic review, the decision was made to access the left BVR via the vein of Galen for coiling.
The approach was performed via the right common femoral vein using a triaxial system comprising a Neuron MAX 088 guiding catheter (Penumbra), a SOFIA 5F intermediate catheter (MicroVention), and a Headway 17 microcatheter (MicroVention). The guiding catheter was advanced into the right internal jugular vein, and the SOFIA 5F catheter was used to support the microcatheter at the junction of the straight sinus and the vein of Galen. Once access to the vein of Galen was achieved, the microcatheter was navigated retrogradely using a Runthrough microwire (Asahi Intecc) through the vein of Galen into the basal vein, bypassing the venous varix, and finally reaching the fistula sites. The fistulas were successfully obliterated with 2 Hypersoft coils (MicroVention) (Fig. 1G, H) without retrograde opacification of the BVR or SMCV on post-procedure left carotid angiography (Fig. 1I, J).
DISCUSSION
DAVFs involving the SpS are rare vascular anomalies that pose significant diagnostic and therapeutic challenges due to their complex anatomy and diverse clinical presentations. These lesions are typically fed by branches of the ECA, such as the MMA, and the ICA, including the inferolateral trunk and meningohypophyseal trunk. Venous drainage often involves the SMCV, BVR, or CS, with retrograde leptomeningeal drainage associated with a higher risk of hemorrhage and aggressive clinical behavior [2].
SpS is a critical venous structure located within the middle cranial fossa. Its anatomical architecture is highly complex, exhibiting significant variability in drainage pathways, including connections to the SMCV, BVR, and CS. Furthermore, bridging veins within the middle fossa establish additional interconnections among these structures, thereby contributing to the intricate and functionally significant venous network of the region [2]. In our case, the fistula drained retrogradely through the BVR and vein of Galen, with additional drainage via the SMCV and vein of Trolard, consistent with a Cognard type IV classification. This pattern highlights the importance of understanding venous anatomy in planning effective treatment strategies.
SpS DAVFs often present with headache, visual disturbances, or neurological deficits due to venous hypertension or cortical venous reflux [4]. Hemorrhage, though less common, is a severe complication linked to high-risk drainage patterns, particularly retrograde leptomeningeal drainage. Venous varices, resulting from chronic venous hypertension, further increase hemorrhage risk due to their structural vulnerability [5-7]. In high-risk DAVFs, such as Cognard type IV lesions, cortical venous reflux and venous varices are associated with aggressive clinical behavior [8]. In this case, the patient presented with a thalamic hemorrhage, likely due to retrograde drainage into the BVR and a venous varix. This underscores the importance of early intervention in high-risk SpS DAVFs to prevent catastrophic outcomes.
The management of SpS DAVFs has evolved significantly, with endovascular techniques now serving as the primary therapeutic approach. Transarterial embolization (TAE) using liquid embolic agents like Onyx or nBCA is effective for occluding arterial feeders, while transvenous embolization (TVE) is preferred for accessing and obliterating the venous side of the fistula [3]. In our case, a transvenous approach via the vein of Galen was successfully employed to coil the fistula, achieving complete occlusion without complications.
The literature underscores the efficacy of TAE, TVE, surgery, or a combination of these approaches in achieving complete occlusion of sphenoid wing DAVFs (Table 1). Treatment strategies often involve either direct arterial access or a more intricate venous route. While arterial access is less complex, it carries the risk of embolic reflux into adjacent vessels, which may require additional surgical intervention [2,6,9]. On the other hand, the venous route, though more complicated, facilitates controlled embolization [10-12]. The small venous pouch at the junction of arterial feeders is an advantageous anatomical feature, enhancing precision and improving treatment success. A combined approach using both arterial and venous access may reduce risks and improve outcomes [10]. Although surgical resection remains a viable option for fistulas with complex angioarchitecture or those inaccessible by endovascular methods [2,5-7,13-15], endovascular techniques are increasingly preferred due to their minimally invasive nature and high success rates.
Our case contributes to the growing body of literature on SpS DAVFs by demonstrating the feasibility of a trans-Galen approach for fistulas with deep venous drainage. The presence of a venous varix in the BVR and retrograde drainage into the vein of Galen posed significant challenges, necessitating precise navigation and coil deployment. The successful outcome underscores the importance of meticulous planning and the use of advanced imaging techniques, such as 3D angiography, to guide treatment.
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