Rare sphenoid dural arteriovenous fistula treated with microsurgery: illustrative case

Abstract

BACKGROUND

Dural arteriovenous fistula (DAVF) in the sphenoid region is a rare condition. It develops following aberrant vascular connections between arterial branches of the external and internal carotid arteries with sphenoidal venous drainage. The treatment can be endovascular embolization or open surgery to obliterate the fistula.

OBSERVATIONS

A 62-year-old man was incidentally diagnosed with a DAVF located at the left lesser sphenoid wing during a routine checkup. Preoperative angiographic imaging revealed a high-grade fistula with arterial feeders originating from both the internal and external carotid arteries and venous drainage into the superficial middle cerebral vein (SMCV). Based on the angioarchitecture of the DAVF, surgery was performed, successfully obliterating the arterial feeders and disconnecting the fistula.

LESSONS

The authors present an asymptomatic case of a left lesser sphenoid wing DAVF with an atypical venous drainage pattern involving the SMCV, sparing the cavernous sinus. Recognition of the vascular architecture and the high-grade nature of this vascular malformation is crucial for ensuring proper treatment and preventing serious complications.

https://thejns.org/doi/10.3171/CASE2628

Dural arteriovenous fistulas (DAVFs) are vascular abnormalities characterized by pathological arteriovenous shunting within the leaflets of the dura mater. Their arterial supply commonly arises from branches of the internal or external carotid arteries or the vertebral arteries, while venous drainage occurs into dural venous sinuses or meningeal and cortical veins. DAVFs account for approximately 10%–15% of intracranial arteriovenous malformations,¹ with the transverse-sigmoid sinuses and cavernous sinus being the most frequently affected locations.^2,3 Sphenoid DAVFs are rare, representing roughly 1% of all intracranial DAVFs.⁴ The sphenoid bone is enveloped by dura extending across the central body and the greater and lesser wings. Its arterial supply derives from branches of the external carotid artery (ECA), primarily the middle and accessory meningeal arteries, as well as from the meningohypophyseal and inferolateral trunks of the cavernous internal carotid artery (ICA) and the recurrent meningeal branch of the ophthalmic artery.⁵ Venous drainage involves middle fossa sinuses such as the cavernous sinus, sphenoparietal sinus (SPS), and paracavernous sinus or the superficial middle cerebral vein (SMCV), which predisposes to cortical venous reflux.⁶

Cortical venous reflux is the principal determinant of DAVF aggressiveness and strongly correlates with an increased risk of intracranial hemorrhage and neurological deterioration.^7–9 This hemodynamic characteristic forms the basis for the widely adopted Borden and Cognard classification systems.^10,11

We report an exceptionally rare case of an asymptomatic left lesser sphenoid DAVF exhibiting cortical venous reflux, draining into the SMCV. The shunt was successfully obliterated by surgical disconnection of the arterial feeders. This case highlights the importance of recognizing rare DAVF vascular structures and the role of tailored treatment strategies in preventing potentially severe complications. The discussion includes literature review of DAVF in the sphenoid wing involving venous reflux in the SMCV and its management.

Illustrative Case

A 62-year-old male with well-controlled hypertension on amlodipine and no significant medical or surgical history presented to the neurosurgery department following an incidental finding of a left sphenoid DAVF during a routine checkup. The patient was asymptomatic, with a negative neurological examination and unremarkable blood tests on admission.

Cerebral angiography (Figs. 1 and 2) showed a high-flow DAVF in the left lesser sphenoid wing. The arterial feeders came from branches of the middle meningeal artery (MMA), internal maxillary artery (IMA), ophthalmic artery, and meningeal branches from the cavernous segment of the ICA. The venous drainage followed a pathway through the SMCV, with cortical vein varices, then into the superior petrosal sinus, and ultimately drained into the transverse and sigmoid sinuses.

FIG. 1.

Preoperative cerebral angiograms illustrating the arterial feeders. A: Lateral view, left ECA injection, showing the feeding arteries from the IMA (black arrows) and MMA (white arrow). B: Lateral view, selective left ICA, showing the feeding artery from the recurrent meningeal artery from the ophthalmic branch (arrowhead). C: Lateral view, 3D reconstruction of the arterial feeders from the branches of the IMA (asterisk), MMA (arrow), ophthalmic artery (arrowhead), and meningeal branch of the cavernous segment of the ICA.

FIG. 2.

Preoperative cerebral angiograms with selective ICA injection illustrating the venous drainage. Frontal (A) and lateral (B) views showing venous collection into the SMCV (asterisk) and drainage into the traverse and sigmoid sinuses (black arrow) via the superior petrosal sinus (white arrow).

The presence of DAVF with drainage into a cortical vein with venous ectasia was the indication for treatment. The patient underwent surgery. After the induction of general anesthesia, the patient was positioned supine with the head tilted 30° to the right. A Mayfield three-point skull clamp was applied to secure the head. A standard left pterional craniotomy was performed to access the sylvian fissure. Arachnoid dissection was carefully carried out along the sylvian fissure, which allowed identification of the arterialized cortical vein (Fig. 3A and B). The left temporal pole was gently retracted with a spatula, and the pathological cortical vein was traced; intraoperative indocyanine green was also used (Fig. 3C). Arterial feeders were then localized and coagulated, and the shunts in the SMCV were obliterated (Fig. 3D–G). Further coagulation of the adjacent dura was performed to ensure the complete disruption of any remaining arterial feeders. The main steps of the surgical procedure are documented in Video 1.

FIG. 3.

Intraoperative images. The fistula was accessed through a pterional approach. The dura opening reveal the temporal lobe on the left and the frontal lobe on the right. A and B: The temporal pole is gently retracted with a spatula, revealing the sphenoid ridge on top and the enlarged arterialized draining SMCV (asterisk). C: Indocyanine green was administrated, highlighting the arterialized cortical vein (asterisk). D and E: Exposure of the fistula, with arterial feeders (arrowhead) emerging from the dura. F and G: Coagulation of arterial feeders and dura at the fistula point (arrow). The change in color of the cortical vein (asterisk) after disconnection is noticeable.

VIDEO 1. Intraoperative video clip showing the main steps of the surgical execution of the DAVF obliteration. Click here to view.

The patient tolerated well the procedure. Postoperative angiography shows complete obliteration of the DAVF (Fig. 4).

FIG. 4.

Postoperative angiograms showing ECA (A) and ICA (B) injection confirming the complete obliteration of the DAVF.

Informed Consent

The necessary informed consent was obtained in this study.

Discussion

This case presents a unique fistula architecture, where venous drainage occurs through the SMCV, bypassing the cavernous sinus and flowing into the superior petrosal sinus before draining into the transverse sinus. Based on the Suzuki classification¹² of the SMCV, this case exhibits a superior petrosal type of SMCV, a pattern not seen in the other cases of lesser sphenoid DAVF involving SMCV drainage (Table 1).

TABLE 1.

Cases of sphenoid DAVF involving SMCV drainage treated with a surgical approach

Authors & Year	Sex/Age (yrs)	Clinical Presentation	Arterial Feeders	Venous Drainage	Varices Present	Treatment	Angiographic Outcome
Thompson et al., 199421	M/44	Ptosis	MMA	BVR, SMCV	No	TAE + surgery	Complete obliteration
Ezura et al., 199617	M/40	Global amnesia	MMA, OA	BVR, SMCV	Yes	TAE + surgery	Complete obliteration
Nomura et al., 200222	F/59	Subarachnoid hemorrhage	MMA, meningeal branches of cavernous ICA	SMCV	Yes	Surgery	Complete obliteration
San Millán Ruíz et al., 200419	F/47	Headache	MMA, OA via recurrent meningeal branch	SMCV	Yes	TAE + surgery	Complete obliteration
Zhou et al., 200723	M/42	Subarachnoid hemorrhage	IMA, MMA, OA	SMCV	Yes	TAE + surgery	Complete obliteration
Tanaka et al., 201218	M/61	Quadrantanopia	MMA	BVR, SMCV	Yes	Surgery	Complete obliteration
Shi et al., 201316	M/66	Optic neuropathy	MMA, OA, AMA, ILT, FRA	BVR, SMCV	Yes	TAE + surgery	Complete obliteration
Watanabe et al., 201524	M/69	Asymptomatic	MMA, OA via ethmoid artery branches	BVR, SMCV	Yes	Surgery	Complete obliteration
Present case	M/62	Asymptomatic	IMA, MMA, meningeal branches of cavernous ICA, OA	SMCV	Yes	Surgery	Complete obliteration

AMA = accessory meningeal artery; BVR = basal vein of Rosenthal; FRA = foramen rotundum artery; ILT = inferolateral trunk; OA = ophthalmic artery.

The natural history of DAVFs is primarily determined by their venous drainage patterns. According to the widely utilized Cognard classification, DAVFs of type I and IIa, which do not involve cortical venous reflux, typically exhibit a benign course. In fact, a study by the University of Toronto reported that 98% of such cases remained asymptomatic over a 3-year follow-up period.⁸ In contrast, higher-grade DAVFs exhibiting cortical venous reflux (Cognard classification types IIb, III, and IV) are associated with an annual intracranial hemorrhagic risk of 8.1%⁹ and an annual mortality rate of 10%.¹³ Cognard’s classification further indicates that hemorrhage occurs in 40% of type III DAVFs, which involve direct drainage into cortical veins, and in 65% of type IV DAVFs, which are additionally characterized by venous ectasia.¹¹

The case presented is a high-grade DAVF (Cognard type IV, Borden type III), characterized by cortical venous reflux and varices, which warranted intervention despite the patient being asymptomatic. DAVFs can be managed through either open surgery (arterial feeder obliteration or venous drainage clipping) or endovascular techniques, including transarterial embolization (TAE) and transvenous embolization (TVE). Given the accessible anatomical location of the fistula and the potential for complete obliteration through surgery, an open surgical approach was preferred. Endovascular intervention was deemed less favorable due to the involvement of feeder vessels from the ophthalmic artery, which posed a higher risk of complications and incomplete treatment. However, due to continuous improvement of endovascular techniques, safe and successful arterial and transvenous embolization of sphenoid DAVFs has been documented.^14,15 Rezende et al.¹⁴ reported a case of lesser sphenoid wing DAVF solely treated with TAE via the MMA injection of Onyx at the fistula point, combined with temporary balloon occlusion of the ICA near the ophthalmic artery, effectively preventing embolic agent reflux. Shi et al.¹⁶ presented a case series with 11 sphenoid DAVFs; 8 patients were treated with TAE using embolic agents, and 3 underwent TVE with coils. Surgical disconnection was required in 2 cases due to incomplete obliteration. They concluded that the endovascular approach can be considered the primary therapeutic strategy, with surgery reserved as adjunctive treatment for partial obliteration. Similarly, Fukada et al.¹⁵ suggested that the endovascular approach may be curative of sphenoid DAVF with cortical drainage. Based on the available literature, although endovascular approaches are generally less invasive and effective in most cases, TAE was considered suboptimal in this instance due to the presence of multiple arterial feeders, including branches from the ophthalmic artery, which could increase procedural risk and result in incomplete obliteration. In addition, the peculiar vascular anatomy and absent connection to the cavernous sinus further limited the feasibility of a transvenous endovascular access. In contrast, the relatively accessible surgical corridor and the potential for definitive cure supported microsurgical obliteration as the definitive treatment.

Lesser sphenoid DAVFs with venous drainage involving the SMCV are exceedingly rare, with only 9 surgically treated cases reported in the literature (Table 1). The mean age was 54.4 years (range 40–69 years), with a male predominance (78%). Preoperative TAE was performed in 5 cases. Ezura et al.¹⁷ performed drainer clipping, Tanaka et al.¹⁸ applied clips to the main feeder following microsurgical coagulation, and San Millán Ruíz et al.¹⁹ resected SMCV varices after clip placement.

DAVFs in the lesser sphenoidal wing are conventionally considered to be formed by abnormal arterial connection in the SPS with SMCV draining in this sinus along the sphenoid wing.¹⁶ However, recent anatomical investigations have challenged this view. San Millán Ruíz et al.¹⁹ suggested that the SPS is not a single venous channel but rather a combination of two distinct structures: the parietal segment of the anterior branch of the middle meningeal vein and a dural channel beneath the lesser sphenoid wing, termed the sinus of the lesser sphenoid wing (SLWS). Notably, they found no direct connection between the SPS and SMCV, suggesting the latter draining independently into either the cavernous sinus or the paracavernous sinus (including the laterocavernous sinus or a combination of the sphenobasal and sphenopetrosal sinuses). These findings were corroborated by Takahashi et al.,²⁰ who, using MRI, confirmed that the SPS is formed by the SLWS and the parietal portion of the middle meningeal vein and drains into the cavernous sinus, separately from the SMCV. Therefore, based on these anatomical considerations, fistulas beneath the lesser sphenoid wing can be classified according to involvement of the SMCV or SLWS. DAVF formation in the SMCV can occur due to its occasional attachment to the dura mater overlying the lesser sphenoid wing.¹⁴ Recognition of SMCV drainage is fundamental because it is associated with a higher risk of venous hypertension and hemorrhage compared to DAVF of the sphenoid sinuses with no involvement of cortical veins.

Observations

We present an asymptomatic case of a left lesser sphenoid wing DAVF with a unique fistula architecture characterized by an unusual venous drainage pattern. Venous drainage flows in the SMCV, bypassing the cavernous sinus. From the SMCV, the blood is directed into the superior petrosal sinus, which then drains into the transverse sinus. This atypical drainage pathway has not yet been described in similar cases reported in the literature.

Lessons

This case highlights the variability in the vascular architecture of sphenoid DAVFs. A careful evaluation of venous drainage patterns, particularly in atypical presentations, is crucial for determining the most appropriate treatment approach.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: all authors. Acquisition of data: Liao, Wu. Analysis and interpretation of data: Liao, Wu. Drafting the article: Wu. Critically revising the article: Liao, Wu. Reviewed submitted version of manuscript: Liao, Wu. Approved the final version of the manuscript on behalf of all authors: Liao.

Supplemental Information

Videos

  Video 1. https://vimeo.com/1184847137.

Correspondence

Yujun Liao: Huashan Hospital, Fudan University, Shanghai, China. nsliaoyujun@126.com.