Flow diverter for a dissecting aneurysm of the AICA serving as a feeding artery to a transverse-sigmoid sinus DAVF

Abstract

Involvement of the anterior inferior cerebellar artery (AICA) as a feeding artery in a transverse‑sigmoid sinus (TSS) dural arteriovenous fistula (DAVF) is uncommon, and the coexistence of a flow‑related aneurysm on this vessel is exceedingly rare. Flow diverter (FD) reconstruction of the AICA, followed by DAVF embolization, represents a feasible treatment strategy. Such a case is reported. A 53‑year‑old male patient presented with headache and dizziness. Computed tomography angiography (CTA) revealed a TSS DAVF, but neurological examination showed no positive signs. Endovascular treatment was performed. Under general anesthesia, digital subtraction angiography revealed a left TSS DAVF supplied by the well-developed left AICA, the bilateral middle meningeal arteries (MMAs), and the bilateral occipital arteries, among others. The DAVF drained into multiple cortical veins, with a Cognard grade of III. On the proximal AICA trunk, a dissecting aneurysm was identified. A Surpass Evolve FD was deployed to cover this lesion. Subsequently, the DAVF was obliterated with Onyx via the MMA. After the procedure, the patient exhibited no new neurological deficits. One month postoperatively, CTA confirmed complete DAVF obliteration and patency of the AICA with favorable reconstruction. Six months postoperatively, the patient had an uneventful recovery and returned to normal activities. The present findings, together with a review of similar cases from the literature, suggest that in carefully selected cases in which the AICA is sufficiently large, FD reconstruction of the AICA can be performed prior to DAVF embolization.

Introduction

Dural arteriovenous fistulas (DAVFs) commonly occur in the transverse‑sigmoid sinus (TSS) region [1]. They have various feeding artery origins. The main feeding arteries arise from the external carotid artery, through which endovascular treatment (EVT) is performed [2]. Less commonly, the anterior inferior cerebellar artery (AICA) can be involved as a feeding artery and may even develop a flow‑related aneurysm [[3], [4], [5]]. For an AICA aneurysm, it is preferable to preserve the AICA and its meningeal branch (the subarcuate artery) to avoid unpredictable ischemic complications. However, it is difficult to reconstruct the AICA, and the parent artery along with the aneurysm often requires occlusion [6].

In extremely rare cases, a flow diverter (FD) may be considered to reconstruct the AICA. Kass‑Hout et al. [7] reported the first case of FD use in the AICA to treat a dissecting aneurysm. FD deployment for a dissecting aneurysm of the AICA serving as a feeding artery to a TSS DAVF is even rarer. The present case report describes such an instance, thereby broadening the indications for FD deployment.

Case presentation

Patient’s onset and diagnosis

A 53-year-old male patient presented with a 1-year history of headache and dizziness. Computed tomography (CT) angiography (CTA) revealed an arteriovenous shunting lesion in the left occipital region, suggestive of a DAVF (Fig. 1A). Ten years prior to presentation, the patient underwent mitral valve replacement surgery. His postoperative course was uneventful, and he had since been maintained on long-term oral warfarin (Orion Corporation, Espoo, Finland) therapy (3 mg/d). At this admission, laboratory examination revealed an international normalized ratio of 1.07 (range 0.8-1.2). In addition, he had a 4-year history of hypertension and was on regular antihypertensive medication, with blood pressure well controlled. He had a 30-year smoking history, averaging approximately 10 cigarettes per day. He had no history of stroke, diabetes mellitus, intracranial infection, or trauma, and there was no family history of cerebrovascular disease. Neurological examination revealed that he was alert and able to follow commands, with full strength (5/5) in all extremities.

Fig. 1.

Diagnostic images. (A) In the upper and middle panels, CTA images demonstrate cortical venous dilation (arrowheads) arising from the left TS. In the lower panel, CTA shows that the left AICA is thickened and has a proximal aneurysm (arrow). (B) DSA of the right vertebral artery in anteroposterior (left panel) and lateral (middle panel) views reveals a left TS DAVF (asterisks). It is supplied by the right PMA, which crosses the midline, and by the left AICA. In the right panel, 3-dimensional DSA depicts that the BA gives off 2 left AICAs: a minor branch (number 1) and a major branch (number 2). The upper minor AICA shows a normal anatomical course and morphology. The lower major AICA has a fusiform dissecting aneurysm (arrow) in the proximal segment, and its distal segment supplies the DAVF. (C) DSA images of the right ECA in anteroposterior (left panel) and lateral (right panel) views show the right MMA and OA crossing the midline to supply the DAVF (asterisks). (D) DSA images of the left ECA in anteroposterior (left panel) and lateral (right panel) views show the left MMA, OA, and AphA supplying the DAVF (asterisks). (E) Venous phase DSA images of the left ECA in anteroposterior (upper panel) and lateral (lower panel) views identify the DAVF located at the left TS. Venous drainage is directed into the SSS, the left TS appears occluded, and the right TS is hyperplastic and patent. AICA, anterior inferior cerebellar artery; AphA, ascending pharyngeal artery; BA, basilar artery; CTA, computed tomography angiography; DAVF, dural arteriovenous fistula; DSA, digital subtraction angiography; ECA, external carotid artery; L, left; MMA, middle meningeal artery; OA, occipital artery; PMA, posterior meningeal artery; R, right; SSS, superior sagittal sinus; TS, transverse sinus.

All preoperative laboratory and imaging findings were within normal limits, supporting the safety of general anesthesia and EVT. In addition to warfarin, dual antiplatelet therapy (DAPT) with aspirin 100 mg and clopidogrel 75 mg was administered for 1 week, after which EVT for the DAVF was performed.

Therapeutic process

Under general anesthesia, digital subtraction angiography (DSA) revealed a TSS DAVF, supplied by the left AICA, the right posterior meningeal artery (PMA), the bilateral middle meningeal arteries (MMAs), the bilateral occipital arteries (OAs), and the left ascending pharyngeal artery (AphA). The DAVF drained into multiple cortical veins and subsequently into the superior sagittal sinus (Fig. 1B–E). The AICA gave off the subarcuate artery to supply the DAVF. On the proximal AICA trunk, which measured 2.5 mm in diameter, there was a fusiform dissecting aneurysm measuring 4 mm (Fig. 1B). The Cognard grade of the DAVF was III. Due to the flow-related aneurysm and the high Cognard grade of the DAVF, FD reconstruction of the proximal AICA and embolization of the DAVF were planned.

After a 6F long sheath and a 5F distal access catheter established the transarterial route of the right VA, an XT-27 microcatheter (Stryker Neurovascular, Fremont, CA) was navigated into the left AICA, guided by a Synchro-14 MicroGuidewire (Stryker Neurovascular, Fremont, CA) (Fig. 2A). A Surpass Evolve FD (2.5 mm × 20 mm) (Stryker Neurovascular, Fremont, CA) was then deployed to cover the dissecting aneurysm of the proximal AICA trunk (Fig. 2B and C). During FD deployment, tirofiban was administered as an intravenous bolus (5 mL), followed by a continuous infusion at 5 mL/h, which would be continued until the following day. Then, the 6F long sheath and the 5F distal access catheter established access to the left external carotid artery. A Marathon microcatheter (Medtronic, Minneapolis, MN) was navigated into the left MMA, guided by a Synchro-10 MicroGuidewire (Stryker Neurovascular, Fremont, CA). Then, 2.5 mL of Onyx-18 liquid embolic system (Medtronic, Irvine, CA) was injected, and the DAVF was obliterated (Fig. 3).

Fig. 2.

FD treatment for the AICA aneurysm. (A) Left panel: DSA of the right VA demonstrates a fusiform dissecting aneurysm (arrow) of the proximal left AICA. Right panel: Roadmap image reveals catheterization of the left AICA trunk using an XT-27 microcatheter (arrow). (B) DSA images of the right VA in anteroposterior (left panel) and lateral (right panel) views illustrate that the left AICA remains patent after FD deployment, still supplying the DAVF (asterisk). (C) Left panel: Unsubtracted DSA of the right VA depicts the FD (arrow) in the proximal left AICA with adequate opening. Right panel: DSA shows contrast stasis in the aneurysm (arrow). AICA, anterior inferior cerebellar artery; BA, basilar artery; DAVF, dural arteriovenous fistula; DSA, digital subtraction angiography; FD, flow diverter; L, left; R, right; VA, vertebral artery.

Fig. 3.

Embolization for the DAVF. (A) Upper 2 panels: Roadmap images of the left external carotid artery in anteroposterior (left) and lateral (right) views demonstrate that the left MMA can serve as the transarterial route to access the DAVF. Lower left panel: Roadmap image confirms microcatheter access to the DAVF (asterisk). Lower right panel: X-ray image shows Onyx casting within the DAVF and MMA. (B) Arterial (upper 2 panels) and venous (lower 2 panels) phases of DSA images of the left carotid artery in anteroposterior (left 2 panels) and lateral (right 2 panels) views reveal complete obliteration of the DAVF. (C) DSA images of the right VA (upper panel) and left VA (lower panel) confirm complete obliteration of the DAVF and patency of the right AICA. (D) DSA images of the right brachiocephalic artery in anteroposterior (upper panel) and lateral (lower panel) views verify complete obliteration of the DAVF. AICA, anterior inferior cerebellar artery; DAVF, dural arteriovenous fistula; DSA, digital subtraction angiography; L, left; MMA, middle meningeal artery; R, right; VA, vertebral artery.

Postoperative and follow-up outcomes

After EVT, the patient exhibited no new neurological deficits. On the following day, intravenous tirofiban was discontinued. His symptoms, including headache and dizziness, improved significantly. DAPT was prescribed for a planned duration of at least 3 months, and warfarin was prescribed for lifelong use.

One month postoperatively, follow‑up CT showed no abnormality, and CTA revealed that the abnormal cortical vein drainage had disappeared, indicating DAVF obliteration (Fig. 4A and B); the aneurysm was no longer visualized, and the proximal AICA had been reconstructed (Fig. 4C). At the 3‑month follow‑up, the patient had recovered well and had resumed normal activities. Clopidogrel was discontinued, while warfarin (3 mg/d) and aspirin 100 mg daily were continued long‑term, with regular monitoring confirming that the international normalized ratio remained consistently within the target therapeutic range. At the 6‑month follow‑up, the patient remained well.

Fig. 4.

Follow-up CT and CTA images. (A) CT images of different axial slices demonstrate no hemorrhage, edema, or infarction. In the upper panel, the FD is indicated (arrow). (B) CTA (left panel) and maximum intensity projection images (right 2 panels) in posteroanterior and lateral views reveal no sign of arteriovenous shunting in the left occipital region (frames). (C) Left panel: CTA depicts the FD reconstructing the AICA, and the proximal AICA aneurysm is not seen. Right panel: CTA confirms that the AICA trunk is patent (zigzag arrows). AICA: anterior inferior cerebellar artery; CT: computed tomography; CTA: CT angiography; FD: flow diverter; L: left.

Discussion

TSS is the most common location for DAVFs [2]. TSS DAVFs have a wide range of feeding artery origins. Four main meningeal arteries exist: the petrosquamosal or petrous branches of the MMA, the mastoid transosseous branch of the OA, the jugular and hypoglossal branches of the AphA, and the PMA. Other minor meningeal arteries include transosseous branches of the posterior auricular artery and the superficial temporal artery, the tentorial branches of the internal carotid artery, the artery of the falx cerebelli, and the meningeal branches of the posterior inferior cerebellar artery and the AICA [1].

Normally, the AICA does not supply the dura of the TSS region; it supplies only the dura of the posterior petrous surface above the internal acoustic meatus and the area surrounding the subarcuate fossa [8]. Therefore, the AICA is less involved in TSS DAVFs. However, when TSS DAVFs with extensive involvement are located close to the petrous region, the AICA may be recruited as a feeding artery via the subarcuate artery, albeit extremely rarely [1]. The subarcuate artery usually originates from the lateral pontine (a2) segment of the AICA medial to the porus of the internal acoustic meatus. It then pierces the dura covering the subarcuate fossa to enter the subarcuate canal. The subarcuate artery may also arise from the labyrinthine artery (itself an AICA branch) or from a cortical branch of the AICA (the cerebellosubarcuate artery) [9]. Occasionally, the subarcuate artery, together with its origin from the AICA, becomes incorporated into the dura on the posterior face of the temporal bone [10].

When involved in a DAVF, the subarcuate artery can anastomose with the branches of the MMA, OA, AphA, and tentorial artery of the ICA [8]. The AICA is subjected to flow‑related hemodynamic stress from high‑flow arteriovenous shunts. Consequently, the AICA and its subarcuate branch may become hyperplastic and dilated and exhibit dissecting changes [11,12]. In addition, aneurysms can occur along the AICA and the subarcuate artery. Aneurysms of the AICA and subarcuate artery in tentorial DAVFs have been reported by Kaech et al. [13], Gross et al. [14], and Tong et al. [11].

Similarly, in TSS DAVFs, the AICA, as a feeding artery, may also develop an aneurysm as summarized in Table 1. When the AICA serves as the feeding artery for a TSS DAVF that harbors an aneurysm, EVT becomes complex. The key clinical question is how to manage the aneurysm and whether it should be prioritized. Su et al. found an additional pial arterial supply in 259 of 1101 patients (23.5%). Their results suggest that embolizing this supply before DAVF closure may significantly increase the risk of both hemorrhagic and ischemic complications. Thus, routine embolization of the pial arterial supply prior to DAVF obliteration is not supported, especially given the very low incidence of presumed hemorrhagic complications from an unobliterated "pure" pial supply [15].

Table 1.

Reported cases of an aneurysm of the AICA serving as a feeding artery to a transverse‑sigmoid sinus DAVF.

Study	Age/Sex	Presentation	DAVF location	AICA aneurysm	AICA status	Other feeding arteries	Treatment	Complication and prognosis
Kan et al. [3]	27/M	Headache and vomiting due to TSS thrombosis, followed by DAVF‑related pulse‑synchronous tinnitus	Right TS, torcula, left TSS	Distal AICA, unruptured	Single trunk, normal size	Bilateral MMAs, OAs, PMA, and muscular branch of VA	Embolization and surgery; AICA aneurysm left untreated; later spontaneous regression	No complications; good outcome
Suzuki et al. [4]	67/F	Headache and vomiting due to SAH, later coma	TSS	Multiple tandem aneurysms on the subarcuate artery; proximal aneurysm ruptured	AICA‑PICA common trunk, normal size	MMA, OA, tentorial artery of the ICA, PMA	Cerebroventricular drainage; parent artery occlusion to occlude the aneurysm by casting Onyx; DAVF untreated	No complications; SAH led to brain damage; no long‑term follow‑up
Kim et al. [5]	71/F	Vertigo and headache due to SAH, intraventricular hemorrhage	Sigmoid sinus	Middle AICA, ruptured	Single trunk, normal size	MMA, OA	VP shunt; DAVF embolization by casting precipitating hydrophobic injectable liquid; aneurysm clipping	No complications; good outcome

AICA, anterior inferior cerebellar artery; DAVF, dural arteriovenous fistula; F, female; ICA, internal carotid artery; M, male; MMA, middle meningeal artery; OA, occipital artery; PICA, posterior inferior cerebellar artery; PMA, posterior meningeal artery; SAH, subarachnoid hemorrhage; TS, transverse sinus; TSS, transverse‑sigmoid sinus; VA, vertebral artery; VP, ventriculoperitoneal.

However, when the AICA harbors a flow‑related aneurysm, the management becomes complex. If the hemorrhage is due to a ruptured aneurysm, this aneurysm should be prioritized given the higher likelihood of re‑rupture [6]. For example, in Table 1, Suzuki et al. [4] and Kim et al. [5] reported that the flow‑related aneurysm of the AICA as a feeding artery of the TSS DAVF was given priority treatment. For unruptured aneurysms, the optimal treatment and priority remain uncertain. In theory, after embolizing the DAVF, the aneurysm may regress. This phenomenon has been observed in brain arteriovenous malformations (AVMs) [16]. The explanation relates to the pathophysiology of aneurysm development under hemodynamic stress [6]. It is postulated that obliteration of the brain AVM reduces blood flow through the feeder vessels, thereby decreasing intravascular pressure and vessel wall stress, allowing for vascular remodeling and subsequent aneurysm resolution [17]. In Table 1, Kan et al. [3] reported a TSS DAVF with a flow‑related AICA aneurysm. After embolization and surgery for the DAVF, the untreated aneurysm later regressed.

However, Gutiérrez et al.’s systematic review found that spontaneous aneurysm regression after AVM treatment is a recognized but variable and low-frequency phenomenon, with the highest observed probability being 23% [17]. Rarely, even after embolization of a brain AVM, acute rupture of a flow-related aneurysm on a feeding artery may occur [18]. This is because an increase in brain AVM feeding artery pressure following EVT may contribute to the rupture of a flow-related aneurysm. Therefore, it is reasonable to give priority to treating the flow‑related AICA aneurysm in TSS DAVFs.

The AICA aneurysm poses unique challenges due to the small diameter of the parent vessel and the limited depth of the surgical corridor. Unlike extracranial vascular territories, where open surgery is a standard approach [19], EVT often plays a key role in the management of an AICA aneurysm. Occlusion of the AICA may be a viable option during EVT [6,20]. However, parent artery occlusion carries a risk of unpredictable neurological deficits, even with adequate collateral circulation from the posterior inferior cerebellar artery and superior cerebellar artery [4]. The subarcuate artery has traditionally been considered a nonessential vessel whose sacrifice is believed to produce no sequelae. However, injury to this artery can compromise inner ear perfusion through its anastomotic connections with the labyrinthine artery, especially in patients with anatomical variations. Therefore, this vessel should be preserved whenever possible to minimize the risk of postoperative hearing deficits [21].

In uncommon circumstances, when the AICA is not small, it can be reconstructed [22]. The present case represents such an instance, in which an unruptured AICA aneurysm was reconstructed with FD deployment. The AICA and subarcuate artery were preserved, no ischemic complication occurred. Subsequently, embolization via the MMA completed the treatment of the TSS DAVF. In general, the AICA is a minor feeding artery. EVT of TSS DAVFs cannot be performed completely via the AICA because of the short reflux distance and poor ability to cast Onyx, unlike the intradural or intraosseous branches of the MMA or OA, which can provide sufficient burden to deliver Onyx. In this case, follow‑up DSA showed that the AICA trunk was reconstructed and the dissecting aneurysm was invisible.

Conclusion

It is rare for the AICA to be involved in a TSS DAVF as a feeding artery, and even more rarely does it develop a flow‑related aneurysm. In carefully selected cases in which the AICA is sufficiently large and well‑developed, FD reconstruction of the AICA can be performed, followed by DAVF embolization via the middle meningeal artery.

Limitation

In this case report, the present findings suggest that this approach is feasible only in carefully selected patients and should not be considered a general recommendation. Furthermore, no 6‑ or 12‑month follow‑up DSA was available, which limits the ability to fully evaluate the long‑term efficacy of this treatment. Nonetheless, the 1‑month postoperative CTA showed satisfactory results, which might suggest favorable long‑term outcomes. However, this report holds clinical value, as it offers a novel perspective on the management of an aneurysm of the AICA that supplies a TSS DAVF.

Patient consent

Written and informed consent was obtained from the patient for publication of this case report.