Assessment for Carotid Atherosclerotic Plaque Using Vessel Wall Magnetic Resonance Imaging: A Multireader ROC Study to Determine Optimal Sequence for Detecting Vessel Wall Calcification.

INTRODUCTION: We aimed to compare conventional vessel wall MR imaging techniques and quantitative susceptibility mapping (QSM) to determine the optimal sequence for detecting carotid artery calcification. METHODS: Twenty-two patients who underwent carotid vessel wall MR imaging and neck CT were enrolled. Four slices of 6-mm sections from the bilateral internal carotid bifurcation were subdivided into 4 segments according to clock position (0-3, 3-6, 6-9, and 9-12) and assessed for calcification. Two blinded radiologists independently reviewed a total of 704 segments and scored the likelihood of calcification using a 5-point scale on spin-echo imaging, FLASH, and QSM. The observer performance for detecting calcification was evaluated by a multireader, multiple-case receiver operating characteristic study. Weighted κ statistics were calculated to assess interobserver agreement. RESULTS: QSM had a mean area under the receiver operating characteristic curve of 0.85, which was significantly higher than that of any other sequence (p < 0.01) and showed substantial interreader agreement (κ = 0.68). A segment with a score of 3-5 was defined as positive, and a segment with a score of 1-2 was defined as negative; the sensitivity and specificity of QSM were 0.75 and 0.87, respectively. CONCLUSION: QSM was the most reliable MR sequence for the detection of plaque calcification.

Impact of immediate general anesthesia in the emergency room on prevention of rebleeding after subarachnoid hemorrhage.

BACKGROUND: Aneurysm rebleeding is fatal in patients with aneurysmal subarachnoid hemorrhage (aSAH). We aimed to investigate whether immediate general anesthesia (iGA) management in the emergency room, upon arrival, prevents rebleeding after admission and reduces mortality following aSAH. METHODS: The clinical data of 3033 patients with World Federation of Neurosurgical Societies (WFNS) grade 1, 2, or 3 aSAH from the Nagasaki SAH Registry Study between 2001 and 2018 were retrospectively analyzed. iGA was defined as sedation and analgesia using intravenous anesthetics and opioids combined with intubation induction. We calculated crude and adjusted odds ratios to evaluate the associations between iGA and the risk of rebleeding/death using multivariable logistic regression models with fully conditional specification for multiple imputations. In the analysis of the relationship between iGA and death, we excluded patients with aSAH who died within 3 days after the onset of symptoms. RESULTS: Of the 3033 patients with aSAH who met the eligibility criteria, 175 patients (5.8%) received iGA (mean age, 62.4 years; 49 were male). Heart disease, WFNS grade, and lack of iGA were independently associated with rebleeding in the multivariable analysis with multiple imputations. Among the 3033 patients, 15 were excluded due to death within 3 days after the onset of symptoms. After excluding these cases, our analysis revealed that age, diabetes mellitus, history of cerebrovascular disease, WFNS grade, Fisher grade, lack of iGA, rebleeding, postoperative rebleeding, no shunt operation, and symptomatic spasm were independently associated with mortality. CONCLUSIONS: Management by iGA was associated with a 0.28-fold decrease in the risks of both rebleeding and mortality in patients with aSAH, even after adjusting for the patient's history of diseases, comorbidities, and aSAH status. Thus, iGA can be a treatment for the prevention of rebleeding before aneurysmal obliteration treatment.

A Spontaneous Extracranial Internal Carotid Artery Dissection with Autosomal Dominant Polycystic Kidney Disease: A Case Report and Literature Review.

Background and Objectives: Non-cystic manifestation of autosomal dominant polycystic kidney disease (ADPKD) is an important risk factor for cerebral aneurysms. In this report, we describe a rare spontaneous internal carotid artery (ICA) dissection in a patient with ADPKD. Observations: A 38-year-old woman with a history of ADPKD and acute myocardial infarction due to coronary artery dissection experienced severe spontaneous pain on the left side of her neck. Magnetic resonance imaging (MRI) revealed a severe left ICA stenosis localized at its origin. Carotid plaque MRI showed that the stenotic lesion was due to a subacute intramural hematoma. Close follow-up by an imaging study was performed under the diagnosis of spontaneous extracranial ICA dissection, and spontaneous regression of the intramural hematoma was observed uneventfully. Conclusions: When patients with a history of ADPKD present with severe neck pain, it is crucial to consider the possibility of a spontaneous ICA dissection. A carotid plaque MRI is beneficial in the differential diagnosis. Conservative management may benefit patients without ischemic symptoms.

Characteristics of aneurysmal subarachnoid hemorrhage associated with rheumatic disease.

Spontaneous subarachnoid hemorrhage (SAH) occurs due to intracranial aneurysm rupture in most cases. Rheumatic disease may cause vessel wall inflammation, which can increase the risk of rupture. However, the characteristics of SAH with rheumatic disease are unknown. This study aimed to evaluate SAH features in patients with rheumatic disease. We retrospectively analyzed clinical data of 5066 patients from the Nagasaki SAH Registry Study who had been diagnosed with aneurysmal SAH between 2001 and 2018. We evaluated the SAH characteristics in patients with rheumatic disease using multivariable logistic regression analysis. In total, 102 patients (2.0%, 11 men and 91 women, median age 69.0 [57.0-75.5]) had rheumatic disease. In these patients, univariate logistic regression analysis showed that sex, hypertension, family history of SAH, smoking history, World Federation of Neurosurgical Societies grade on admission, aneurysm size, multiple aneurysms, treatment, and symptomatic spasms were associated with SAH. Multivariable logistic regression analysis showed that characteristics independently associated with SAH in rheumatic disease were female sex (odds ratio [OR] 3.38; 95% confidence interval [CI] 1.81-6.93, P < 0.001), hypertension (OR 0.60; 95% CI 0.40-0.90, P = 0.012), family history of SAH (OR 0.18; 95% CI 0.01-0.80, P = 0.020), small ruptured aneurysms (OR 1.50; 95% CI 1.02-2.24, P = 0.048), and multiple aneurysms (OR 1.69; 95% CI 1.09-2.58, P = 0.021) in comparison with SAH without rheumatic disease. In conclusion, SAH in patients with rheumatic disease was characterized by small multiple aneurysms, regardless of the low incidence of hypertension and family history of SAH.

Moyamoya Disease Associated with Graves' Disease and Down Syndrome: A Case Report and Literature Review.

BACKGROUND: Moyamoya vessels are cerebral vasculopathies characterized by net-like collateral vessel formation at the cerebral basal area and stenosis of the terminal internal carotid artery, proximal middle cerebral artery, and anterior cerebral artery. A diagnosis of Moyamoya disease depends on the bilateral presence of Moyamoya vessels. Moyamoya disease associated with Graves' disease has rarely been reported to be a cause of ischemic events due to hyperthyroidism. However, there are extremely rare cases of Moyamoya disease with concurrent Graves' disease and Down syndrome. We aimed to report such a case, and to compare these cases' clinical features, pathogenesis, and treatment effects to those of the cases of concurrent Moyamoya disease and Graves' disease alone. METHODS: We performed an English literature search using the PubMed database and the keywords Moyamoya, quasi-Moyamoya, Graves' disease, thyrotoxicosis, Down syndrome, and trisomy 21. RESULTS: Only five cases of Moyamoya disease with Graves' disease and Down syndrome have been reported, including our own. Four patients were female (80%), and all underwent antithyroid therapy and experienced ischemic episodes, including transient ischemic attacks. At the time of their vascular accident, two patients were in a thyrotoxic state; only our patient was in a euthyroid state. The mean age was 15.6 years (standard deviation: 6.1), which was younger than the mean age of 31.4 years (standard deviation: 13) in patients with Moyamoya disease and Graves' disease alone. Down syndrome is commonly associated with abnormal vascular networks due to increased endostatin concentrations or immunological abnormalities such as those that occur in Graves' disease. Graves' disease accelerates the progression of Moyamoya disease and ischemic attacks due to atherosclerosis, enhances sympathetic nervous system activity and immunological changes. As compared to Moyamoya disease patients, patients with concurrent Graves' disease only and Moyamoya disease patients with concurrent Graves' disease and Down syndrome may experience accelerated disease progression or more frequent ischemic attacks. CONCLUSION: Early imaging follow-ups and strict control of thyroid function are necessary in such cases; if ischemic attacks have already occurred, revascularization surgery may be effective.

Correction to: Intra-Arterial Transplantation of Low-Dose Stem Cells Provides Functional Recovery Without Adverse Effects After Stroke.

The original version of this article unfortunately contained an error in affiliation of Yuhtaka Fukuda.

Pericytes Suppress Brain Metastasis from Lung Cancer In Vitro.

Metastasis of lung cancer to the brain is associated with poor outcomes and limited therapeutic options. The blood-brain barrier (BBB) plays a major role in brain metastasis. However, little is known about the role of pericytes in brain metastasis formation. This study aimed to reveal the interaction between pericytes and cancer cells. We established in vitro BBB models with rat primary cultured BBB-related cells (endothelial cells, astrocytes, and pericytes) and investigated the relationship between BBB-related cells and metastatic cancer cell lines. We observed a significant decrease in transendothelial electrical resistance with metastatic cancer cells in monolayer and coculture models with astrocytes. In contrast, the coculture model with pericytes showed inhibition of the decrease in transendothelial electrical resistance with metastatic cancer cells. In addition, the expression of tight junction protein was preserved only in the coculture model with pericytes. The conditioned medium of pericytes with metastatic cancer cells suppressed the proliferation of the cancer cells significantly. This study revealed that brain pericytes are the major regulators of the resistance of the BBB to lung cancer metastasis to the brain. Pericytes exert an anti-metastatic effect and thus have potential for the preventive treatment of brain metastasis.

Comparison of the rate of dedifferentiation with increasing passages among cell sources for an in vitro model of the blood-brain barrier.

Cell culture-based blood-brain barrier (BBB) models are useful experimental tools for developing central nervous system drugs. Several endothelial cell sources exist for BBB models, including primary cultured brain endothelial cells and immortalized cell lines. Among them, primary cell-based models are considered suitable for the functional analysis of the BBB; however, little is known about the utility of low-passage brain endothelial cells for this purpose. In this study, we investigated the effect of passage on brain endothelial cells from human, mouse and rat brain tissue as BBB models. We established in vitro BBB models using primary brain endothelial cells (Passage 1-Passage 4) from humans, mice, and rats. To analyze the effect of cell type on BBB function, we evaluated transendothelial electrical resistance (TEER) and performed immunofluorescence staining of tight junction proteins. Among the brain endothelial cell models, TEER was highest in the Passage 1 (P1) cell-based BBB model. There was no adequate increase in TEER in other low-passage cultures (P2-P4). A confluent, non-overlapping, uniform monolayer of cells in all P1 cell-based models was visible on immunostaining of tight junction proteins, whereas it was weak or undetectable in more passaged cultures. Increasing passages cultured of brain endothelial cells did not exhibit restrictive BBB function regardless of the cell source and despite culturing with pericytes and astrocytes. Among the tested culture models, only the lowest cultured cell-based models are suitable for functional analysis of the BBB.

Lower serum calcium and pre-onset blood pressure elevation in cerebral hemorrhage patients undergoing hemodialysis.

BACKGROUND: Asymptomatic blood pressure (BP) elevation may be associated with cerebral hemorrhage (CH); however, few studies have investigated this association. We aimed to evaluate BP elevation before CH in hemodialysis (HD) patients and elucidate its associated factors. METHODS: We reviewed HD patients treated for CH at our hospital between 2008 and 2019 (CH group). The control group comprised HD patients treated at Nagasaki Renal Center between 2011 and 2012. Data were obtained from medical records and three consecutive HD charts, made immediately before CH. HD1 was the session closest to onset, followed by HD2 and HD3. Systolic and mean BP were evaluated at the beginning of HD, and factors associated with BP elevation were investigated. RESULTS: The CH and control groups included 105 and 339 patients, respectively. Systolic and mean BP at HD1 were significantly higher than those at baseline (HD2 + HD3) in the CH group by 5 and 3 mmHg, respectively (P < 0.001). Multiple linear regression analysis showed that lower calcium levels were significantly associated with BP elevation in the CH group (P < 0.05). The CH group was sub-divided by June 2013; the latter group had lower calcium levels (9.2 mg/dL) and a marked systolic BP difference from baseline (+ 10 mmHg) compared with the former (9.5 mg/dL and - 4 mmHg). CONCLUSION: Asymptomatic BP elevation was observed in HD patients before CH; this elevation was associated with lower serum calcium levels and observed more frequently in the recent era. The precise mechanism underlying this effect remains unknown.

First Bite Syndrome Following Carotid Endarterectomy.

A 67-year-old man with a high position carotid plaque presented with severe pain in ipsilateral parotid region several days after carotid endarterectomy (CEA). The pain occurred at the first bite of each meal and resolved as further bite. We diagnosed the pain as first bite syndrome (FBS). FBS is infrequent but known as a complication associated with parapharyngeal space surgery. The pain is characterized by sharp pain in the parotid region associated with mastication. The cause is unclear but thought to the result from sympathetic denervation of the parotid gland, followed by parasympathetic nerve hypersensitivity. Only five cases associated with carotid endarterectomy (CEA) have been reported. We should be in mind that CEA for high position plaque is one of the risk factors to cause FBS associated with CEA. Neurologists and vascular surgeons as well as otolaryngologists should all be informed FBS as one of the complications after carotid endarterectomy.

Hyperhomocysteinemia Causes Severe Intraoperative Thrombotic Tendency in Superficial Temporal Artery-middle Cerebral Artery Bypass.

CASE: Two years ago, annual magnetic resonance imaging for unruptured right internal carotid artery aneurysm of a 47-year-old woman detected a cerebral infarct in her right occipital lobe which was unknown etiology and antiplatelet therapy was initiated. She presented with sensory disorder of her left fingers 4 months ago. Infarction in right parieto-occipital cortex and severe stenosis of right middle cerebral artery was revealed. Her laboratory test was normal except remarkably high homocysteine value. Regardless of dual anti-platelet therapy, she suffered from repeated minor stroke and the stenosis was progressing. Therefore, right superficial temporal artery - middle cerebral artery bypass was undertaken. Aspirin and clopidogrel were withdrawn 1 week before the surgery. Two branches were anastomosed with 2 separate frontal M4 branches. Although patency was confirmed immediately after the anastomosis, thrombus formation was revealed after 10 minutes. We needed to perform removal of the thrombus and re-anastomosis twice. Intraoperative administration of aspirin and ozagrel alleviated thrombotic tendency. After surgery, antiplatelet therapy and supplementation with folate and vitamin B were performed. Her postoperative course was uneventful and patency of both anastomoses was confirmed. DISCUSSION: Controversy still exists regarding preoperative antiplatelet therapy before superficial temporal artery-middle cerebral artery bypass, and folates and B6-12 vitamins supplementation for hyperhomocysteinemia. Considering intraoperative thrombo tendency in our case, it is recommended to evaluate the homocysteine level before bypass surgery for intracranial stenosis especially for young patients or patients with unknown etiology. Before bypass surgery of the patient with hyperhomocysteinemia, continuation of perioperative antiplatelet drugs and supplementation with folates and B6-12 vitamins are mandatory.

[A Case of Dural Arteriovenous Fistula at the Craniocervical Junction with High Signal Intensity Localized to the Thoracic Spinal Cord on T2-weighted MRI].

An 82-year-old man presented with lower extremity weakness, paresthesia, and gait disturbance. At the previous hospital, spinal MRI had demonstrated a high-intensity area confined to the thoracic spinal cord on T2-weighted images and prominent dorsal venous flow voids that were suggestive of a thoracolumbar dural arteriovenous fistula(dAVF). Spinal digital subtraction angiography(DSA)failed to detect the shunt point. MRDSA of the head revealed a dAVF at the craniocervical junction(CCJ). Cranial DSA demonstrated feeders from the left vertebral artery and left radicular artery, a shunting point on the dura at the CCJ, and drainers into the anterior and posterior spinal veins descending to the sacral level. Surgery improved his symptoms, and the abnormal imaging findings were resolved. Observation of a dAVF at the CCJ with myelopathy is rare, and the diagnosis of this type of dAVF might be challenging. MRDSA might be a useful tool for detecting this uncommon dAVF.

[Anomalous Origin of the Ophthalmic Artery from the Anterior Cerebral Artery Associated with the Paraclinoid Internal Carotid Artery Aneurysm].

The ophthalmic artery usually arises from the supraclinoid portion of the internal carotid artery. Here, we present an extremely rare case of abnormal origin of the ophthalmic artery from the anterior cerebral artery associated with the paraclinoid internal carotid artery aneurysm. As the embryology of the ophthalmic artery is complex, this case provides additional insight into the variation of the ophthalmic artery.

Arterial Spin Labeling Magnetic Resonance Imaging Can Identify the Occlusion Site and Collateral Perfusion in Patients with Acute Ischemic Stroke: Comparison with Digital Subtraction Angiography.

BACKGROUND AND OBJECTIVES: Determining the occlusion site and collateral blood flow is important in acute ischemic stroke. The purpose of the current study was to test whether arterial spin labeling (ASL) magnetic resonance imaging (MRI) could be used to identify the occlusion site and collateral perfusion, using digital subtraction angiography (DSA) as a gold standard. METHOD: Data from 521 consecutive patients who presented with acute ischemic stroke at our institution from January 2012 to September 2014 were retrospectively reviewed. Image data were included in this study if: (1) the patient presented symptoms of acute ischemic stroke; (2) MRI was performed within 24 h of symptom onset; and (3) DSA following MRI was performed (n = 32 patients). We defined proximal intra-arterial sign (IAS) on ASL as enlarged circular or linear bright hyperintense signal within the occluded artery and distal IAS as enlarged circular or linear bright hyperintense signals within arteries inside or surrounding the affected region. The presence or absence of the proximal IAS and distal IAS were assessed, along with their inter-rater agreement and consistency with the presence of occlusion site and collateral flow on DSA images. RESULTS: The sensitivity and specificity for identifying occlusion site with ASL were 82.8 and 100%, respectively. Those for identifying collateral flow with ASL were 96.7 and 50%, respectively. The inter-rater reliability was excellent for proximal IAS (κ = 0.92; 95% CI 0.76-1.00) and substantial for distal IAS detection (κ = 0.78; 95% CI 0.38-1.00). CONCLUSIONS: Proximal IAS and distal IAS on ASL imaging can provide important diagnostic clues for the detection of arterial occlusion sites and collateral perfusion in patients with acute ischemic stroke.

Biomarkers of Cardiac Dysfunction as Risk Factors in Cryptogenic Stroke.

BACKGROUND: It is unclear whether biomarkers of cardiac dysfunction are associated with cryptogenic stroke (CS). METHODS: We retrospectively evaluated consecutive ischemic stroke patients. Patients underwent transthoracic echocardiography to evaluate left atrial diameter and the peak transmitral filling velocity/mean mitral annular velocity during early diastole (E/e'). Patent foramen ovale (PFO) and left atrial appendage flow velocity were evaluated by transesophageal echocardiography. We compared clinical characteristics and biomarkers of cardiac dysfunction (brain natriuretic peptide [BNP], left atrial diameter, E/e', and left atrial appendage flow velocity) between CS or CS without large PFO and other causative stroke subtypes. RESULTS: Among 1,514 patients with ischemic stroke, 264 patients were classified as having CS. Of these, transesophageal echocardiography revealed 27/158 (17%) large PFOs. In comparison, for the noncardioembolic stroke group, which consisted of large artery and small vessel subtypes, patients with CS without large PFO had higher log10 BNP (adjusted OR 2.70; 95% CI 1.92-3.78; p < 0.001), higher log10 E/e' (3.41; 1.21-13.15; p = 0.019), and lower left atrial appendage flow velocity (0.98; 0.97-1.00; p = 0.031). Left atrial diameter was similar for noncardioembolic stroke and CS without large PFO (p = 0.380). Cutoff values of BNP, E/e', and left atrial appendage flow velocity capable of distinguishing CS without large PFO from noncardioembolic stroke were 65.0 pg/mL (sensitivity 55.3%; specificity 70.9%), 13.0 (45.5%; 68.0%), and 46.0 cm/s (37.1%; 87.5%), respectively. CONCLUSION: Patients with CS without large PFO could have biomarkers of cardiac dysfunction.

Association between serum calcium levels and prognosis, hematoma volume, and onset of cerebral hemorrhage in patients undergoing hemodialysis.

BACKGROUND: High serum calcium levels should be avoided in patients on hemodialysis (HD) because they can induce cardiovascular diseases and worsen the patient's prognosis. In contrast, low serum calcium levels worsen the prognosis of patients with cerebral hemorrhage in the general population. So far, whether serum calcium levels in patients on HD are associated with cerebral hemorrhage remains unknown. This study aimed to reveal the association between serum calcium and cerebral hemorrhage in patients on HD, including in-hospital death, volume of hematoma, and onset of cerebral hemorrhage. METHODS: This cross-sectional case-control study included 99 patients on HD with cerebral hemorrhage at a single center between July 1, 2007 and December 31, 2017. Controls included 339 patients on HD at a single HD center between July 1, 2011 and June 30, 2012. Data on serum calcium level, patient demographics, and comorbid conditions were collected, and associations between cerebral hemorrhage and subsequent death were evaluated by multivariate logistic regression analysis. Further, the association of these backgrounds and hematoma volume was evaluated by multiple regression analysis. RESULTS: Of the 99 patients, 32 (32%) died from cerebral hemorrhage. The corrected serum calcium level (odds ratio [OR], 2.49; 95% confidence interval [CI], 1.43-4.35; P < 0.001) and antiplatelet drug use (OR, 3.95; 95% CI, 1.50-10.4; P = 0.005) had significant effects on the prognosis. Moreover, the corrected serum calcium (P = 0.003) and antiplatelet drug use (P = 0.01) were significantly correlated with hematoma volume. In the patients, the corrected serum calcium level (OR, 1.54; 95% CI, 1.07-2.22; P = 0.02) was associated with the onset of cerebral hemorrhage, as was pre-hemodialysis systolic blood pressure (per 10 mmHg) (OR, 1.40; 95% CI, 1.23-1.59; P < 0.001). CONCLUSIONS: Although the precise mechanisms remain unknown, a high serum calcium level is associated with cerebral hemorrhage in patients on HD. Thus, we should pay attentions to a patient's calcium level.

[Progression of Endovascular Treatment for Acute Ischemic Stroke].

OBJECTIVE: Percutaneous transluminal recanalization(PTR)has been performed for more than 20 years and progressing because of the development of endovascular devices. However, the results have been changing dramatically since PTR was first introduced owing to dynamic social environments. Thus, we evaluated the progression of the treatment by reviewing the medical records of patients who received the treatment. MATERIALS AND METHODS: The present author has worked in three hospitals and performed PTR for 39 cases of acute ischemic stroke from 1996 to 1998. From 2012 to 2014, PTR was performed for 57 cases, and results were compared between the early and recent periods by using patient medical files and records. RESULTS: Elderly patients were treated with PTR in the recent period. The main target of PTR was the M1 segment of the middle cerebral artery in the early period. The internal carotid artery-to-posterior circulation ratio increased in the recent period. Regarding the methods of PTR, mechanical retrieval devices were mainly used in the recent period and resulted in a significantly more complete recanalization. The recovery rate based on the Glasgow outcome scale score increased, and the mortality rate decreased significantly in the recent period. CONSLUSIONS: Along with the development of endovascular devices, the results of PTR have been improving.

[Surgery for a Refractory Chronic Subdural Hematoma Using an Exoscope:A Technical Case Report].

Burr hole irrigation and drainage is effective in most cases of chronic subdural hematoma(CSDH). However, we sometimes encounter refractory cases that need further procedures or other interventions. Here we report a case with a disturbance of consciousness and left hemiparesis. CT of the head showed a right CSDH, which recurred three times in spite of repeated burr-hole irrigation surgeries. We performed a mini-craniotomy and evacuation of the hematoma under the exoscope to remove the hematoma effectively. The post-operative course was uneventful and no recurrence was found at the last follow up. A mini-craniotomy with an exoscope might be a useful option for treating cases of refractory CSDH.

[Open Surgery Following Transarterial Embolization for Cavernous Sinus Dural Arteriovenous Fistula].

Cavernous sinus(CS)dural arteriovenous fistula with cortical venous drainage often have a malignant presentation and require urgent treatment. Endovascular embolization is the primary treatment of choice, but failure to catheterize the CS may occur due to vessel tortuosity, hypoplasia, or stenosis. In the absence of venous access to the lesion, a careful surgical approach should be considered. Here we describe a patient who underwent open surgery following an unsuccessful transvenous embolization due difficulties in venous access.

[Middle Cerebral Artery Fenestration with M2 Fusion Detected during Aneurysm Clipping:A Case Report].

We report a unique case of middle cerebral artery fenestration with M2 fusion detected during an aneurysm clipping. A 72-year-old woman was diagnosed with an unruptured aneurysm of the right middle cerebral artery, and middle cerebral artery fenestration with M2 fusion was detected during the aneurysm clipping surgery. It was difficult to identify this unusual vascular anomaly before the surgery. Therefore, neurosurgeons should be cautious of such hidden vascular anomalies and be prepared for the possible complications during surgery.