Intraoperative ultrasound for localization of a ruptured M2–M3 middle cerebral artery aneurysm with temporal hematoma: A case report

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Korean J Cerebrovasc Surg. 2026;.jcen.2026.E2025.10.009

Publication date (electronic) : 2026 March 30

doi : https://doi.org/10.7461/jcen.2026.E2025.10.009

Taigen Sase^,1, Kiyotaka Wakatsuki¹, Gaku Hidaka¹, Homare Nakamura¹, Hidetoshi Murata²

¹Department of Neurosurgery, St. Marianna University School of Medicine, Yokohama Seibu Hospital, Yokohama City, Kanagawa, Japan

²Department of Neurosurgery, St. Marianna University School of Medicine, Kawasaki City, Kanagawa, Japan

Correspondence to Taigen Sase Department of Neurosurgery, St. Marianna University School of Medicine, Yokohama Seibu Hospital, Yokohama City, Kanagawa, Japan Tel +81-45-366-1111 Fax +81-45-366-6410 E-mail sasetaigen@marianna-u.ac.jp

Received 2025 October 23; Revised 2026 January 6; Accepted 2026 February 28.

Abstract

INTRODUCTION

Middle cerebral artery (MCA) aneurysms account for approximately 18% to 40% of all intracranial aneurysms, with the majority located at the M1-M2 bifurcation or trifurcation [2]. Distal MCA aneurysms, such as those in the M2 (insular), M2-M3 junction, M3 (opercular), and M4 (cortical) segments, are rare and represent only 1%–7% of MCA aneurysms [1,5]. These aneurysms are challenging to treat because of their deep location, variable branching patterns, and frequent association with intracerebral hematomas (ICH) [4,5,7]. Moreover, hematoma evacuation causes brain shift, which can reduce the accuracy of neuronavigation [13].

Intraoperative ultrasound (iUS) is a real-time, noninvasive imaging modality that can visualize deep-seated structures even after anatomical distortion [6], and its application in aneurysm surgery has been increasing [3,11,14]. Reports on iUS use for distal MCA aneurysms are rare [8-10]. To the best of our knowledge, no previous report has focused on the use of iUS through a hematoma cavity when neuronavigation was unreliable due to brain shift. Here, we presented a patient who had a ruptured distal MCA aneurysm at the M2-M3 junction with a large temporal lobe hematoma, in which iUS enabled precise localization and safe clipping.

CASE DESCRIPTION

The patient was an 80-year-old woman who was emergently transported to our hospital because of a sudden headache and impaired consciousness. She had a history of cerebral infarction. On hospital arrival, her Glasgow Coma Scale (GCS) was E1V1M1, and both pupils measured 2 mm with sluggish light reflexes. After endotracheal intubation, brain imaging revealed diffuse subarachnoid hemorrhage (SAH) and a large left temporal lobe hematoma on computed tomography (CT) and a 5-mm aneurysm at the left MCA M2-M3 junction, which was considered the source of bleeding, on CT angiography (CTA) (Fig. 1).

Fig. 1.

Preoperative imaging. (A) CT shows diffuse SAH and a large left temporal hematoma. (B) CTA reveals a 5-mm aneurysm at the left MCA M2–M3 junction (white arrow). CT, computed tomography; SAH, subarachnoid hemorrhage; CTA, computed tomography angiography; MCA, middle cerebral artery

Although the SAH was WFNS grade 5, the patient’s impaired consciousness was suspected to be mainly due to increased intracranial pressure from the hematoma, and emergent surgery was indicated. Although combined endoscopic hematoma evacuation and coil embolization were considered, our institutional strategy favors open clipping with decompressive craniectomy to achieve definitive treatment and intracranial pressure control for patients with grade 5 SAH. After obtaining informed consent from the family, a left frontotemporal craniotomy was performed under general anesthesia.

After opening the skull, the left frontal horn was punctured and an external ventricular drainage catheter was placed. The hematoma was evacuated through a small corticotomy on the temporal lobe. Neuronavigation was initially considered for aneurysm localization, but was not used because of the anticipated brain shift after hematoma evacuation. Instead, iUS was performed using a 7.0-MHz convex array transducer (Model PVT-745BPH, Toshiba Medical Systems Corporation, Japan) and a diagnostic ultrasound system (Model SSA-680A, Toshiba Medical Systems Corporation, Japan). After gently irrigating the hematoma cavity with sterile saline to improve acoustic coupling, the probe was placed on the cortical surface directly over the hematoma cavity, enabling real-time visualization of the aneurysm and inflow vessel (Fig. 2A).

Fig. 2.

Intraoperative findings. (A) Intraoperative ultrasound visualizes the aneurysm and inflow vessel through the hematoma cavity. (B) Microscopic view before clipping and after Sylvian fissure dissection. (C) After clipping, the microscopic view confirms complete aneurysm exclusion. (D) Final intraoperative view of the cortical surface after clipping and hematoma evacuation (Labels: (a) aneurysm, (b) MCA M2, (c) MCA M3, (d) frontal lobe, (e) temporal lobe, (f) clip, (g) cortical incision for hematoma evacuation, and (h) Sylvian fissure dissection) MCA, middle cerebral artery

Based on the iUS findings, the Sylvian fissure was widely opened from the distal opercular segment toward the proximal insular segment to obtain secure proximal control of the parent M2 segment before direct aneurysm manipulation. This strategy enabled the surgical team to minimize unnecessary dissection within the hematoma cavity and safely plan the dissection route toward the aneurysm neck. After identification of the aneurysm neck and surrounding branch vessels, a straight titanium clip (Sugita aneurysm clip, Mizuho Medical Co., Tokyo, Japan) was applied (Fig. 2B-2D). Temporary clipping of the parent vessel was not required because stable proximal control had already been established. After clipping, patency of the parent and branching vessels was confirmed using indocyanine green video angiography.

Postoperative CT confirmed adequate hematoma evacuation and complete clipping (Fig. 3A). During the vasospasm period, the patient was managed at the intensive care unit and administered clazosentan hydrochloride to prevent vasospasm. Digital subtraction angiography (DSA) on postoperative day 8 confirmed complete aneurysmal obliteration and no vasospasm (Fig. 3B). On day 17, tracheostomy was performed to facilitate mechanical ventilator weaning. On day 22, cranioplasty using the patient’s autologous bone flap was subsequently performed. Thereafter, the patient developed hydrocephalus, for which a ventriculoperitoneal shunt was placed on day 32. The patient was eventually transferred to a long-term care hospital with a GCS of E4VtM5 and a modified Rankin Scale score of 4 at discharge (Fig. 3C).

Fig. 3.

Postoperative imaging. (A) CT demonstrates adequate hematoma evacuation and no residual aneurysm. (B) DSA on postoperative day 8 confirms complete obliteration. (C) Final CT scan at our hospital after ventriculoperitoneal shunt placement. CT, computed tomography; DSA, digital subtraction angiogram

DISCUSSION

Distal MCA aneurysms are rare, representing only 1%–7% of all MCA aneurysms [5]. Their deep location, anatomical variability, and frequent association with ICH make intraoperative localization difficult [4,5,7]. In patients who undergo hematoma evacuation, the resulting brain shift can further reduce the accuracy of neuronavigation [13]. In this patient, iUS was used to localize the aneurysm through the hematoma cavity and allowed safe dissection, identification of the aneurysm neck, and successful clipping. Several authors have previously described the role of iUS in distal MCA aneurysm surgery. Payer et al. [10] used color-coded duplex sonography to localize distal MCA aneurysms. Onen et al. [9] reported the combined use of neuronavigation and iUS for M3 aneurysm clipping. Nerntengian et al. [8] described the real-time three-dimensional (3D) iUS findings in a ruptured mycotic M3 aneurysm. These studies demonstrated the feasibility of iUS in distal aneurysm surgery, but none specifically highlighted the use of iUS through a hematoma cavity after brain shift, which makes this present case report unique.

Our technique involved direct placement of the 7.0-MHz convex array transducer probe onto the hematoma cavity after gentle saline irrigation to optimize acoustic coupling. This approach provided a stable acoustic window and allowed real-time visualization of the aneurysm sac and inflow vessel despite brain shift-related distortion. Our findings suggested that when navigation is compromised, iUS can serve as a salvage modality that provides direct intraoperative feedback even in anatomically distorted settings. Moreover, iUS is cost-effective, widely available, and repeatable without radiation exposure, unlike intraoperative angiography [6]. Compared with extensive Sylvian fissure dissection, the use of iUS may reduce operative time and cortical injury by guiding the surgeon directly to the aneurysm.

With ongoing technological developments, the role of iUS in aneurysm surgery is expected to expand. In particular, navigated 3D power Doppler [14] and contrast-enhanced ultrasound [12] have improved vascular visualization and real-time hemodynamic assessment. These innovations, together with probe miniaturization and image integration, may broaden the applicability of iUS in cerebrovascular surgery.

To the best of our knowledge, this is one of the very few reports describing iUS-guided localization of a ruptured distal MCA aneurysm complicated by ICH and the first to emphasize its role when neuronavigation was unreliable due to brain shift. Our case underscored the clinical value of iUS as a practical and flexible adjunct that can complement or even replace navigation systems in selected scenarios, thereby improving surgical precision and safety in patients with aneurysms that are challenging to manage. However, iUS has several inherent limitations. Image quality may be affected by air-related artifacts within the surgical field, particularly after hematoma evacuation, which necessitates meticulous saline irrigation to optimize acoustic coupling. In addition, iUS is operator dependent, and accurate interpretation requires familiarity with ultrasound anatomy and experience, indicating the presence of a learning curve. Despite these limitations, iUS provides valuable real-time information in situations where conventional navigation systems are compromised by brain shift. Combining iUS with micro-Doppler, indocyanine green angiography, or intraoperative angiography may enhance safety and accuracy. Notably, this was a single case experience, and its reproducibility requires validation in a larger series. Nevertheless, in this patient, iUS provided useful real-time guidance that compensated for brain shift-related loss of neuronavigation accuracy.

CONCLUSIONS

iUS allowed safe localization and clipping of a ruptured M2–M3 MCA aneurysm through a hematoma cavity when neuronavigation became unreliable due to brain shift. iUS is a valuable adjunct in complex cases involving deep-seated aneurysms with associated ICH.

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