Successful treatment of a recurrent dissecting aneurysm with flow diverter placement following occipital artery–posterior inferior cerebellar artery bypass

Abstract

Branch involvement can serve as a predicting factor of incomplete occlusion after flow diverter (FD) treatment, including pipeline embolization device. This study reports a case of subarachnoid hemorrhage owing to bilateral vertebral artery dissection with parent artery occlusion to the left side and stent-assisted coiling to the right side. However, a marked enlargement of the dissected lesion was observed at the right dissecting aneurysm at 6 months. Considering that the posterior inferior cerebellar artery (PICA) originating from the aneurysm could prevent aneurysm occlusion after the FD, we first conducted open surgery to perform a bypass from the occipital artery to the PICA and occluded the PICA origin to eliminate blood flow from the dissection site. Subsequently, we placed a pipeline embolization device at the same location. Complete occlusion of the aneurysm was confirmed after 6 months. Thus far, only one case report of a recurrent middle cerebral artery aneurysm treated with an FD following bypass has been reported. This is the first report of a similar procedure applied to the posterior circulation and dissecting aneurysm. This report highlights the potential for successful outcomes when branches arising from an aneurysm are occluded via bypass prior to the placement of an FD.

Introduction

Treatment of unruptured intracranial aneurysms using flow diverter (FD) results in a good prognosis [1]. Vertebral artery (VA) aneurysms larger than 5 mm have been treated, and dissections of aneurysms have also been conducted, with reports of their resolution published [2]. However, multiple factors have been reported to cause incomplete occlusion after FD treatment, one of them being the branches emanating from the aneurysm [3]. Some studies have suggested that aneurysms in the ophthalmic artery and those in internal carotid posterior communicating artery are difficult to cure when flow-out is observed [4]. Here we report a case of successful pipeline embolization device treatment of VA dissecting aneurysm involving posterior inferior cerebellar artery (PICA), following an occipital artery (OA)-PICA bypass. This case highlights that combining bypass with FD placement can be effective in the treatment of dissecting aneurysms in the posterior circulation.

Case report

A 43-year-old male was brought to our hospital for emergency medical services after experiencing a seizure. Upon arrival at the hospital, the patient’s consciousness was clear, with no apparent neurological deficits. The primary symptom was a headache, and head computed tomography (CT) revealed a subarachnoid hemorrhage (Fig. 1). Cerebral angiography revealed pearl-and-string signs in the left VA (Fig. 2A, B and Fig. 3A blue arrows). A slight dilation was observed in a portion of the right VA (Fig. 2C, D and Fig. 3A red arrow). Despite some uncertainty, the left VA, which clearly exhibited the pearl-and-string signs, was identified as the source of the hemorrhage. On day 0, lumbar drainage and parent artery occlusion using endovascular therapy were performed under local anesthesia to preserve the origin of the left PICA. After the procedure, the patient received 200 mg aspirin, followed by a daily dose of 100 mg for at least 30 days starting the next day. However, an expansion in the right VA was observed (Fig. 3A red arrow); therefore, the patient was followed up carefully. On day 5, the patient again experienced a strong headache, and the cerebrospinal fluid drained from the spinal drain became bloodier. CT revealed an increase in the size of the hematoma, and angiography revealed deformation of the tip of the dilated part of the right VA (Fig. 3B red arrow). Since the left VA had already undergone parent artery occlusion, 300 mg of clopidogrel was loaded, and a stent-assisted coil was placed on the dilated part of the right VA on day 8. The origin of the right PICA was contralateral to the dilated area (Fig. 3B yellow arrow). To avoid occlusion of the PICA, a low-profile visualized intraluminal support (LVIS) stent 4.0 mm × 22 mm (MicroVention Inc., Aliso Viejo, CA, USA) was placed in proximity to the origin of the PICA, and the aneurysm was embolized with a coil. Posttreatment cone-beam CT revealed that the stent-assisted coil was in good condition, with only a gap of approximately or less than 1 mm at the PICA origin (Fig. 4). The patient progressed well during the acute phase and was discharged from the hospital.

Fig. 1.

Initial computed tomography scan on admission showing diffuse subarachnoid hemorrhage, with slightly left-dominant accumulation in the posterior aspect of the midbrain.

Fig. 2.

Frontal (A) and lateral (B) views of left vertebral angiography on day 0, demonstrating a pearl-and-string sign, along with frontal (C) and lateral (D) views of right vertebral angiography on day 0.

Fig. 3.

(A) Three-dimensional rotational angiogram on day 0, showing the pearl-and-string sign at the left VA (blue arrows) and the expansion at the right VA (red arrow). (B) Three-dimensional rotational angiogram on day 5, revealing deformation of the tip of the dilated part of the right VA (red arrow). The posterior inferior cerebellar artery and its origin are identified on the contralateral side of the dilated segment (yellow arrows).

Fig. 4.

(A) Frontal view of the left vertebral angiography, performed immediately after stent-assisted coil embolization on day 5, demonstrating antegrade flow through the posterior inferior cerebellar artery (yellow arrow), with a vessel diameter of 1.15 mm. (B) Sagittal view of cone-beam CT, obtained on the same day confirming that the gap at the origin of the posterior inferior cerebellar artery (yellow arrowhead) measured less than approximately 1 mm. No residual aneurysm was visualized.

After 6 months, basiparallel anatomical magnetic resonance imaging revealed an enlarged dissecting aneurysm in the right VA (Fig. 5A and B). Angiography also showed an enlarged dissection space outside the LVIS, with a branch from the dissection cavity leading to the right PICA (Fig. 6A). We speculated that it would be challenging to preserve the right PICA and completely coil the dissection space outside the stent. Considering that surgical treatment alone would be challenging, we opted to perform an OA-PICA bypass followed by the placement of an FD from the vertebrobasilar junction, through the LVIS, and extending to the proximal right VA. One month after the OA-PICA bypass, the patient was administered 100 mg aspirin and 75 mg clopidogrel for 2 weeks. After confirming platelet function the previous day, a pipeline embolization device Flex with Shield Technology 4.0 mm × 25 mm was placed under general anesthesia (Fig. 6C). Postoperatively, dual antiplatelet therapy was continued for 6 months. Follow-up angiography revealed that the dissection cavity was no longer visible (Fig. 6B and D), which led to the discontinuation of aspirin. Clopidogrel was subsequently discontinued 6 months later. The basiparallel anatomical magnetic resonance imaging performed 6 months after FD placement demonstrated a reduction in the enlargement associated with the dissection of the right VA (Fig. 5C).

Fig. 5.

Basiparallel anatomic scanning magnetic resonance images showing progressive enlargement associated with the dissection of right VA. (A) Two months after LVIS stent-assisted coiling. (B) Six months after the procedure. (C) Six months after flow diverter placement.

Fig. 6.

(A-C) Frontal views of right vertebral angiography. (A) Angiography obtained at the time of re-enlargement of the vertebral artery dissection, 6 months after the initial LVIS stent-assisted coiling. The angiogram shows the PICA originating from the dissected and enlarged segment. Angiograms obtained 6 months after flow diverter placement. (B) Angiogram confirming the resolution of the dissection’s enlargement. (C) High-resolution cone-beam computed tomography showing the pipeline device deployed from the distal to the proximal end of the previously inserted LVIS stent. (D) Posterior view of a three-dimensional rotational angiogram illustrating fusion of the left VA (red) with the occipital branch of the left external carotid artery (yellow). Coil embolization and the clip occluding the left PICA are indicated in blue, and the flow diverter is visualized within the dissected segment.

Discussion

We encountered a case in which the FD was placed after performing an OA-PICA bypass for a dissecting aneurysm with a branch, and the results were favorable both clinically and radiologically.

To the best of our knowledge, only one previous case report has described the performance of bypass surgery in combination with FD placement—specifically, a superficial temporal artery to M2 bypass for a recurrent MCA aneurysm [5], there have been no prior reports of using an OA-PICA bypass to eliminate branches from an aneurysm, followed by the placement of an FD. This case represents the first report of such a combined approach. It has been reported that, to achieve complete occlusion of an aneurysm using FD, elimination of the branches that drain from the aneurysm and isolation of the aneurysm may play important roles [6]. We emphasize that FD, in combination with bypass, may be an effective treatment not only in cases involving PICA but also in aneurysms involving other bypass-feasible branches. In this case, cone-beam CT after stent-assisted coil placement with LVIS did not reveal any large residual false lumen (Fig. 4). However, 6 months later, the dissection cavity expanded around the circumference, and branch to the PICA was observed. We considered that additional transcell coiling while preserving the PICA would not provide a complete cure and carried a high risk of recurrence. There have also been reports of FD retreatment after stent-assisted coiling, with many favorable outcomes [7,8]. One study demonstrated that, when an FD is appropriately sized to the vessel wall and deployed within the VA, flow through the covered PICA can often be preserved [9]. However, several studies have reported that FD is difficult to treat when it involves the branch from the aneurysm [10,11]. The outcomes of using FDs in dissecting aneurysms with branch involvement have been insufficient in terms of both safety and efficacy, particularly concerning branch occlusion and aneurysm closure rates [10]. Another report described that, even in aneurysms incorporating branch vessels, favorable treatment outcomes could be achieved with FD placement alone when the branch vessel was small. However, in cases involving branches approximately 1 mm in diameter, the results were suboptimal without additional coil embolization [12]. In the present case, the PICA also measured approximately 1 mm, and sufficient aneurysm occlusion with FD placement alone was unlikely. Considering these possibilities, we chose to first perform an OA-PICA bypass, which was expected to be minimally invasive and carry a low risk of recurrence, followed by FD placement under dual antiplatelet therapy. The stent length was selected to sufficiently cover not only the proximal portion but also the distal portion to prevent continued blood flow into the aneurysm owing to an end leak [7]. Its diameter was selected based on the diameter of the VA proximal to the dissected segment. Consequently, a favorable outcome was obtained after FD placement combined with OA-PICA bypass for a dissected aneurysm that recurred after stent-assisted coil placement.

In addition, the treatment strategy for bilateral VA dissection in this case warrants reconsideration. The left VA was initially identified as the rupture site based on the presence of a pearl-and-string sign. However, subsequent hemorrhage from the right VA raised the possibility that the right side may have been the true source of bleeding from the outset. In recent years, an increasing number of studies have demonstrated the utility of vessel wall imaging in evaluating arterial wall pathology and identifying rupture points [13]. Although vessel wall imaging was not available at our institution, contrast-enhanced MRI—although limited in spatial resolution and specificity—might have contributed to more accurate localization of the rupture site in this patient [14]. A different treatment strategy may have been selected based on such findings.

In conclusion, even in cases of recurrent dissecting aneurysms of the posterior circulation involving vessels that cannot be embolized, FD placement after bypass surgery is a promising treatment strategy with favorable outcomes.

Patient consent

Informed consent was obtained from the patient for the publication of this case report and accompanying images.