This study summarizes the latest findings on the pathophysiology and prognosis of asymptomatic moyamoya disease, as presented at the STROKE2025 symposium “Appropriate Treatment Strategies for Moyamoya Disease.” Moreover, it incorporates relevant findings that could not be discussed due to time constraints. Asymptomatic moyamoya disease is not a stable condition and should be recognized as a preparatory stage for cerebrovascular events, such as transient ischemic attack (TIA), cerebral infarction, and intracranial hemorrhage. During this stage, the disease may be progressing, or microbleeds and cerebral infarctions may develop at a significant frequency.

With the increasing popularity of endovascular therapy, the number of traditional open surgical procedures has decreased, making conventional surgical training more difficult. At our institution, we overcome this challenge by using information technology (IT) to efficiently educate surgical trainees by using the following three methods: layered digital illustration (LDI), Multi-Viewing Surgical video recording, and mixed Reality (MR) surgical field reproduction.

The LDI method uses layer functions that are unique to digital illustration software to create detailed surgical field diagrams. This enables trainees to develop a deeper understanding of surgical anatomy and strategies by illustrating the different layers of anatomical structures. LDI enhances spatial comprehension and enables preoperative planning and education.

The Multi-Viewing Surgical Video Recording method integrates multiple audiovisual inputs into a single synchronized video. It captures the surgeon’s hands and posture, the environment of the operating room, and real-time audio, including the surgeon’s commentary and neuromonitoring data. This detailed recording enables trainees to relive their surgical experience virtually, making it an effective method for reviewing and planning for similar cases.

For the MR Surgical Field Reproduction, we convert actual surgical cases into 3D data and use goggle-based MR devices for 3D reproduction of the surgical field. This approach enables trainees to accurately understand the spatial depth and relationships of the operative field that textbooks and traditional videos frequently fail to convey. MR Surgical Field Reproduction is particularly useful for studying rare surgical approaches, such as skull-base surgery, and for creating advanced anatomical learning content.

Between July 2022 and December 2024, four trainees performed a total of 14 carotid endarterectomies (in seven symptomatic and seven asymptomatic cases). The median operating time was 194 min; no perioperative complications were observed; and patients were followed over a median 17-month period (range: 8-37 months).

Venous congestion (VC) due to retrograde leptomeningeal venous drainage (RLVD) in dural arteriovenous fistulas (dAVFs) can cause neurological symptoms and damage brain tissue. It can be identified as a fluid-attenuated inversion recovery hyperintense lesion (FHL) on magnetic resonance imaging (MRI). This study investigated the correlation between the FHL and preoperative ¹⁵O-positron emission tomography (PET) findings. We retrospectively analyzed the preoperative and postoperative MRI, digital subtraction angiography (DSA), and ¹⁵O-PET images of 14 patients with dAVF who underwent radical endovascular treatment between January 2017 and March 2024. The patients were classified into three groups: Group A (no FHL), Group B (preoperative FHL present, disappeared after treatment), and Group C (preoperative FHL present, persisted after treatment). ¹⁵O-PET parameters (cerebral blood flow [CBF], cerebral blood volume [CBV], cerebral metabolic rate of oxygen [CMRO₂], and oxygen extraction fraction [OEF]) were analyzed using the affected-to-unaffected side ratio. There was a significant correlation between the presence or absence of preoperative FHL and the decline in CBF and CMRO₂, and in Group B+C, CBF (0.69 ± 0.14) and CMRO2 (0.65 ± 0.13) were significantly lower than in Group A (CBF 0.98 ± 0.11, CMRO₂ 0.93 ± 0.09) (p = 0.001). On receiver operating characteristic curve analysis, a CBF cutoff value of 0.90 and CMRO₂ cutoff value of 0.85 exhibited high accuracy in predicting FHL. Regarding the reversibility of FHL, statistical analysis was not feasible because of the limited number of cases in Group C, comprising only two individuals; however, both CBF and CMRO₂ decreased. Further accumulation of cases and examination of long-term prognoses are needed.

We designed an individualized approach for endoscopic evacuation of intracerebral hematomas based on three-dimensional (3D) CT image analysis. We evaluated the clinical outcomes of patients treated using this method. Between April 2016 and March 2025, 61 patients with putaminal hemorrhage underwent endoscopic evacuation. Hybrid images combining the hematoma and skull were generated using a 3D imaging software. The entry point and trajectory were determined by prioritizing the hematoma’s long axis, while considering factors such as the shortest cortical distance. To ensure an accurate puncture according to the planned design, we used a custom-made guiding device aligned with the measured entry point and contralateral target. The median hematoma volume was 65.4 ml, and the mean removal rate was 78.4%. Hemorrhagic complications occurred in 3.3% of cases. A comparison between the long-axis approach group and the nonlong-axis group revealed no significant differences in the hematoma evacuation rate or functional outcomes, suggesting that a clinically appropriate approach was selected. 3D image analysis is useful for selecting an optimal trajectory that accounts for the spatial configuration of the hematoma. However, further case studies and investigations are required.

Objective: To investigate the long-term outcomes of surgical clipping for unruptured intracranial aneurysms through collaboration with large-scale medical examination facilities in Tokyo, focusing on retreatment rates and de novo aneurysm formation.

Methods: Among 379 patients who underwent surgical clipping for asymptomatic unruptured intracranial aneurysms at Showa University Hospital between 2012 and 2017, 248 patients (257 aneurysms) who were followed up for more than 5 years were analyzed. Long-term follow-up was conducted in collaboration with large-scale partner facilities in Tokyo by using magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) every 6 months and three-dimensional computed tomography angiography (3D-CTA) every 2–3 years.

Results: The mean follow-up period was 6.7 years (range: 5–10 years). During the observation period, three patients (1.21%, 3/248) required additional treatment, including one case of aneurysm recurrence (0.39%, 1/257 aneurysms) and two cases of growth of conservatively managed small aneurysms (0.81%, 2/248 patients). No de novo aneurysms were detected during the follow-up period.

Conclusions: Collaboration with large-scale medical examination facilities in urban areas enabled comprehensive long-term follow-up with a low retreatment rate of 1.21%. This study shows the high curative potential of clipping surgery and the critical importance of long-term postoperative surveillance.

Superficial temporal artery–superior cerebellar artery (STA–SCA) bypass represents an important revascularization procedure for posterior circulation lesions; however, it remains technically challenging due to the deep and narrow operative field. The conventional subtemporal approach frequently requires substantial temporal lobe retraction and carries a risk of venous injury.

To address these limitations, we employed an extended middle fossa approach that incorporates zygomatic arch resection, extradural dissection of the middle cranial fossa, and tentorial incision. Following spinal drainage to achieve brain relaxation, a temporal craniotomy with zygomatic arch removal was performed. The lateral wall of the cavernous sinus was dissected extradurally along the second (V2) and third (V3) divisions of the trigeminal nerve, enabling wide exposure of the middle cranial fossa. The tentorium was subsequently incised and extended anteriorly and posteriorly along the superior petrosal sinus (SPS), thereby creating a wide and shallow operative field and elevating the superior cerebellar artery (SCA) to a more superficial plane.

Additionally, the arteriotomy “lifting method, ” in which one edge of the recipient arteriotomy is elevated to enlarge the opening, facilitated safe and precise microanastomosis even within a deep surgical field.

The combination of the extended middle fossa approach and the lifting method provides a rational and effective strategy for establishing a wide and shallow operative field, thereby enabling safe and reliable STA–SCA bypass surgery.

There is no established treatment strategy for elongated styloid process syndrome. We report a case of elongated styloid process syndrome complicated by cerebral infarction, with favorable outcomes after endovascular and surgical treatment.

A 55-year-old man was referred to our hospital with a chief complaint of aphasia for several days. He was diagnosed with cerebral infarction. Detailed investigations revealed bilateral dissecting aneurysms of the internal carotid artery (ICA). Stent-assisted coil embolization was performed on the symptomatic side and styloid process resection on the contralateral side. The patient was discharged with an modified Rankin Scale (mRS) score of 0.

Elongated styloid process syndrome should be considered in the differential diagnosis of cerebral infarction. Definitive treatment involves resection of the elongated styloid process. Endovascular therapy is also effective for preventing cerebral infarction recurrence.