Parent artery encroachment after clipping of kissing middle cerebral artery bifurcation aneurysm: A case report

Changheon Kim; HyoJun Kim; Taesik Song; Seung Kon Huh

doi:10.7461/jcen.2025.E2025.08.002

Abstract

Background

Kissing middle cerebral artery bifurcation aneurysms (KMCBA) are rare vascular lesions. Their complex morphology and limited surgical experience may predispose patients to devastating complications.

Cases

Among 100 patients who underwent microsurgical clipping for cerebral aneurysms between May 2022 and April 2025, two were diagnosed with unruptured KMCBA. In Case 1, the two aneurysm sacs of a left KMCBA were clipped separately using interlocking and fenestrated clips without premature rupture. In Case 2, both aneurysm sacs of a right KMCBA were clipped simultaneously with a long J-shaped clip. Postoperatively, the patient developed left hemiparesis due to clip-induced encroachment of the superior trunk of M2. Revision clipping with a shorter L-shaped clip restored flow, and the patient was discharged with a modified Rankin scale (mRS) score of 4.

Conclusions

Successful microsurgical clipping of KMCBA requires meticulous surgical strategies to avoid parent artery encroachment, including separate clipping of each aneurysm neck whenever feasible, appropriate clip selection, and the use of multimodal intraoperative anatomical and physiological monitoring.

INTRODUCTION

Kissing aneurysms (KA) are defined as two adjacent aneurysms arising from the same parent artery, each with a distinct neck and dome, often partially adherent. They account for fewer than 1% of all intracranial aneurysms [1,2]. Preoperative diagnosis is challenging, as KA are frequently misinterpreted as multilobulated aneurysms or vascular irregularities, even with three-dimensional digital subtraction angiography (3D-DSA) [3,4,7,11,12, Accurate recognition is critical for planning clip application sequence and minimizing intraoperative complications.

We present two cases of middle cerebral artery-kissing aneurysms (MCA-KA) treated with microsurgical clipping, highlighting intraoperative pitfalls of parent artery encroachment (PAE), their underlying causes, and strategies for prevention.

CASE DESCRIPTION

Case 1

A 59-year-old woman presented with headache and dizziness. Magnetic resonance imaging (MRI) revealed a left middle cerebral artery (MCA) bifurcation aneurysm. Angiography demonstrated two aneurysms: an anteroinferior aneurysm measuring 4.2×2.5×2.4 mm and a posterior aneurysm measuring 2.1×2.0×2.0 mm (Fig. 1).

Through a standard left pterional approach, the aneurysm complex was exposed. Due to close adherence of the domes, premature rupture was anticipated [4,6]. The anteroinferior aneurysm was secured with interlocking clips (a 5-mm L-shaped clip and a fenestrated straight clip, 3.5 mm diameter/3 mm length), while the posterior aneurysm was clipped with an additional fenestrated straight clip of the same size (Fig. 2). Microvascular Doppler ultrasonography (MDU) and intraoperative evoked potentials (IEP) confirmed preserved flow without PAE [6,10]. The patient recovered uneventfully, and postoperative CT confirmed proper clip placement (Fig. 3). She was discharged without neurological deficits.

Case 2

A 72-year-old woman was diagnosed with a right kissing middle cerebral artery bifurcation aneurysms (KMCBA) consisting of a lateral aneurysm (2.9×2.3×2.0 mm) and a medial aneurysm (2.1×2.0×1.7 mm). Both necks were clipped simultaneously with a 7.4-mm J-shaped clip applied across the M2 branches, as separate clipping attempts carried a high risk of premature rupture [5] (Fig. 4). Intraoperative findings revealed kissing domes in contact and the clip applied in parallel (Fig. 5). MDU and evoked potentials showed no evidence of PAE [6,8,9].

Postoperatively, the patient developed left hemiparesis (grade 2). Transcranial Doppler revealed reduced flow in the superior trunk of M2. Revision surgery demonstrated clip-induced encroachment of the superior trunk. The J-shaped clip was replaced with a tangentially applied 5-mm L-shaped clip, leaving a small neck remnant but restoring flow, confirmed by intraoperative MDU [5] (Fig. 6). The patient was discharged with a modified Rankin scale (mRS) score of 4 and referred for rehabilitation.

DISCUSSION

Kissing aneurysms present unique diagnostic and surgical challenges due to their rarity, complex morphology, and frequent adherence [4,12]. They are often misdiagnosed as bilobulated aneurysms, and intraoperative findings may differ significantly from preoperative 3D-DSA imaging [7,11,12]. The close adherence of aneurysm domes increases the risk of premature rupture during clip application [4,6]. Preventive strategies include meticulous dissection to separate aneurysm walls, sequential exposure of both necks, and judicious use of temporary clipping when necessary [5].

In Case 1, careful dissection enabled safe separate clipping without rupture. In Case 2, dense adhesion precluded separation, necessitating simultaneous clipping, which resulted in PAE. Compared with single aneurysms, KA carry a higher risk of PAE due to the need for multiple clips in a restricted surgical field or the use of simultaneous clipping. Reported clip repositioning rates are ~12–19% for single aneurysms [3], but ~23% for KA [5]. Our Case 2 supports this elevated risk.

Multimodal intraoperative monitoring is essential to minimize complications. Anatomical tools include endoscopic inspection, indocyanine green angiography (ICGA), MDU, and intraoperative angiography [8,9]. Physiological monitoring with motor evoked potentials (MEP) and somatosensory evoked potentials (SSEP) is also valuable, though false negatives must be carefully excluded [6]. In our cases, reliance solely on microvascular mirror inspection, MDU, and EP monitoring was insufficient; the addition of ICGA or endoscopic inspection would likely have enhanced intraoperative assessment [6,8,9].

CONCLUSIONS

Successful management of KMCBA requires: complete dissection and separate clipping of each aneurysm neck whenever feasible, appropriate selection and orientation of clips to avoid PAE, and integration of multimodal intraoperative anatomical and physiological monitoring. These strategies are essential to minimize morbidity and achieve complete aneurysm occlusion while preserving parent artery flow.

Notes

Disclosures

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

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Fig. 1.

(A), (B) Internal carotid artery angiograms show that two different-shaped aneurysms at the middle cerebral arteries. (C) Preoperative 3D DSA rotational angiography. In a high-resolution image, two kissing aneurysms are seen at the bifurcation of left MCA. DSA, digital subtraction angiogram; MCA, middle cerebral artery

Fig. 2.

Intraoperative photographs show that two aneurysms are in contact (A), and two aneurysms have been clipped (B), (C), (D).

Fig. 3.

Postoperative CT scan shows clip placement. CT, computed tomography

Fig. 4.

(A) Internal carotid artery angiograms show that two different-shaped aneurysms at the middle cerebral arteries. (B) Preoperative 3D DSA rotational angiography. In a high-resolution image, two kissing aneurysms are seen on the bifurcation of the M1 segment of the right MCA. DSA, digital subtraction angiogram; MCA, middle cerebral artery

Fig. 5.

Intraoperative photographs show that two aneurysms are in contact (A), and two aneurysms have been clipped (B), (C). (B) In the first surgery, two aneurysms were clipped using the parallel-clipping method. (C) In revision surgery, two aneurysms have been clipped using the tangential-clipping method.

Fig. 6.

Postoperative CT scan shows clip placement. CT, computed tomography