Quantifying post-treatment vascular remodeling in brain aneurysms using WEKA-based machine learning: a pilot study

Microsurgical Clipping Compared with New and Most Advanced Endovascular Techniques in the Treatment of Unruptured Middle Cerebral Artery Aneurysms: A Meta-Analysis in the Modern Era

Введение. Эффективность хирургического лечения пациентов с артериальными аневризмами (АА) головного мозга складывается из полноты выключения аневризмы из кровотока и появления неврологических нарушений после клипирования аневризмы, связанных с компрессией клипсом афферентных, эфферентных и перфорирующих артерий. Для повышения эффективности хирургического лечения пациентов с АА необходимо применять методы интраоперационной оценки кровотока и контроля клипирования АА. Цель. Изучить эффективность хирургического лечения пациентов с нервавшимися аневризмами супраклиноидного отдела внутренней сонной артерии (ВСА), средней мозговой артерии (СМА) при применении методов интраоперационной оценки кровотока, контроля клипирования аневризм. Материалы и методы. В исследование были включены 213 пациентов с нервавшимися аневризмами супраклиноидного отдела ВСА (71 пациент), СМА (142 пациента), которым проводилось микрохирургическое клипирование аневризм и которые были разделены на 6 групп по методам использования интраоперационной диагностики кровотока и контроля микрохирургического клипирования аневризм сосудов головного мозга. Использовали шкалу NIHSS для оценки неврологических нарушений; послеоперационное контрольное обследование пациентов осуществлялось с помощью СКТ-АГ головного мозга, МРТ-АГ головного мозга с оценкой радикальности клипирования и наличия ишемии головного мозга. Результаты. Установлено, что комплексное применение ультразвуковой флоуметрии и интраоперационной флуоресцентной видеоангиографии в группе пациентов при микрохирургическом клипировании нервавшихся аневризм СМА, в сравнении с группой пациентов, у которых не использовали данный комплекс, уменьшает возникновение ишемии головного мозга, приводящей к неврологическим нарушениям, с 28,6% до 0% (p=0,003), повышает радикальность клипирования АА с 77,1% до 97,5% (p=0,01) и, соответственно, повышает эффективность хирургического лечения с 60% до 97,5% (р<0,001). Комплексное применение видеоэндоскопической ассистенции, интраоперационной флуоресцентной видеоангиографии с использованием микрозеркала в группе пациентов при микрохирургическом клипировании нервавшихся аневризм супраклиноидного отдела ВСА, в сравнении с группой пациентов, у которых не использовали данный комплекс, уменьшает возникновение ишемии головного мозга, приводящей к неврологическим нарушениям, с 16,7% до 0% (p=0,01), повышает радикальность клипирования АА с 77,2% до 97,6% (p=0,04) и, соответственно, повышает эффективность хирургического лечения с 70% до 97,6% (p=0,001). Комплексное использование интраоперационной флуоресцентной видеоангиографии и интраоперационной ультразвуковой доплерографии при клипировании нервавшихся аневризм СМА уменьшает возникновение ишемии головного мозга, приводящей к неврологическим нарушениям, с 28,6% до 6% (p=0,05), повышает радикальность клипирования АА с 77,1% до 97% (p=0,03) и, соответственно, повышает эффективность хирургического лечения с 60% до 94% (p=0,001). Заключение. Комплексное применение интраоперационной ультразвуковой флоуметрии, интраоперационной флуоресцентной видеоангиографии для интраоперационной оценки церебрального кровотока у пациентов при микрохирургическом клипировании нервавшихся аневризм СМА и видеоэндоскопической ассистенции, интраоперационной флуоресцентной видеоангиографии с использованием микрозеркала при микрохирургическом клипировании нервавшихся аневризм супраклиноидного отдела ВСА достоверно повышает эффективность хирургического лечения пациентов с АА. Introduction. The effectiveness of surgical treatment of patients with cerebral arterial aneurysms (AA) is determined by the extent of aneurysm exclusion from blood flow and neurological disorders after aneurysm clipping associated with afferent, efferent and perforating arteries compression by clips. To enhance the effectiveness of surgical treatment of AA patients, methods of intraoperative blood flow assessment and AA clipping control should be applied. Purpose. To study the efficacy of surgical treatment of patients with unruptured supraclinoid internal carotid artery (ICA) aneurysms and middle cerebral artery (MCA) aneurysms using of intraoperative blood flow assessment and aneurysm clipping control methods. Materials and methods. The study included 213 patients with unruptured supraclinoid internal carotid artery (ICA) aneurysms (71 patients) and middle cerebral artery (MCA) aneurysms (142 patients), who underwent microsurgical clipping of aneurysms. The patients were divided into 6 groups by intraoperative blood flow diagnostics and microsurgical clipping of cerebral vascular aneurysms control methods. The NIHSS scale was used to assess neurological disorders; postoperative control examination of the patients was performed by brain SCT-AG, brain MRI-AG with assessment of clipping radicality and cerebral ischemia evidence. Results. It was established that a comprehensive use of ultrasound flowmetry and intraoperative fluorescent video angiography in the group of patients with microsurgical clipping of unruptured MCA aneurysms, as compared to the group of patients without using this combination, reduced the emergence of cerebral ischemia leading to neurological disorders from 28.6% to 0% (p=0.003), increased the radicality of AA clipping from 77.1% to 97.5% (p=0.003), and, consequently, enhanced the efficiency of surgical treatment from 60% to 97.5% (p<0.001). A combined use of video endoscopic assistance and intraoperative fluorescent video angiography with micromirror in the group of patients with unruptured supraclinoid ICA aneurysms microsurgical clipping in comparison with the group of patients in which this combination was not used, decreased the occurrence of cerebral ischemia leading to neurological disorders from 16.7% to 0% (p=0.01), increased the radicality of AA clipping from 77.2% to 97.6% (p=0.04) and, consequently, enhanced surgical treatment efficiency from 70% to 97.6% (p=0.001). A comprehensive use of intraoperative fluorescent video angiography and intraoperative ultrasound Doppler ultrasonography in clipping unruptured MCA aneurysms reduced the occurrence of cerebral ischemia leading to neurological disorders from 28.6% to 6% (p=0.05), increased the radicality of AA clipping from 77.1% to 97% (p=0.03), and, consequently, enhanced surgical treatment efficiency from 60% to 94% (p=0.001). Conclusion. The comprehensive use of intraoperative ultrasound flowmetry and intraoperative fluorescent video angiography for intraoperative assessment of cerebral blood flow in patients with microsurgical clipping of unruptured MCA aneurysms, and video endoscopic assistance and intraoperative fluorescent video angiography with micromirror in microsurgical clipping of unruptured supraclinoid ICA aneurysms significantly enhances surgical treatment the efficiency in AA patients.

Predictors of recurrence and complications for the endovascular treatment of unruptured middle cerebral artery aneurysm: A high-volume center experience over 12 years

ObjectiveThis study used the intradural procedural time to assess the overall technical difficulty involved in surgically clipping an unruptured middle cerebral artery (MCA) aneurysm via a pterional or superciliary approach. The clinical and radiological variables affecting the intradural procedural time were investigated, and the intradural procedural time compared between a superciliary keyhole approach and a pterional approach.MethodsDuring a 5.5-year period, patients with a single MCA aneurysm were enrolled in this retrospective study. The selection criteria for a superciliary keyhole approach included : 1) maximum diameter of the unruptured MCA aneurysm <15 mm, 2) neck diameter of the MCA aneurysm <10 mm, and 3) aneurysm location involving the sphenoidal or horizontal segment of MCA (M1) segment and MCA bifurcation, excluding aneurysms distal to the MCA genu. Meanwhile, the control comparison group included patients with the same selection criteria as for a superciliary approach, yet who preferred a pterional approach to avoid a postoperative facial wound or due to preoperative skin trouble in the supraorbital area. To determine the variables affecting the intradural procedural time, a multiple regression analysis was performed using such data as the patient age and gender, maximum aneurysm diameter, aneurysm neck diameter, and length of the pre-aneurysm M1 segment. In addition, the intradural procedural times were compared between the superciliary and pterional patient groups, along with the other variables.ResultsA total of 160 patients underwent a superciliary (n=124) or pterional (n=36) approach for an unruptured MCA aneurysm. In the multiple regression analysis, an increase in the diameter of the aneurysm neck (p<0.001) was identified as a statistically significant factor increasing the intradural procedural time. A Pearson correlation analysis also showed a positive correlation (r=0.340) between the neck diameter and the intradural procedural time. When comparing the superciliary and pterional groups, no statistically significant between-group difference was found in terms of the intradural procedural time reflecting the technical difficulty (mean±standard deviation : 29.8±13.0 min versus 27.7±9.6 min).ConclusionA superciliary keyhole approach can be a useful alternative to a pterional approach for an unruptured MCA aneurysm with a maximum diameter <15 mm and neck diameter <10 mm, representing no more of a technical challenge. For both surgical approaches, the technical difficulty increases along with the neck diameter of the MCA aneurysm.

Successful surgical treatment of cerebral aneurysms requires complete occlusion of the aneurysm lumen while maintaining patency of the adjacent branching and perforating arteries. Intraoperative flow assessment allows aneurysm clip repositioning in the event these requirements are not met, avoiding the risk of postoperative rehemorrhage or infarction. A number of modalities have been proposed for primarily intraoperative qualitative blood flow assessment, including microdoppler ultrasonography, intraoperative digital subtraction angiography (DSA), and more recently noninvasive fluorescent angiography including indocyanine green (ICG) fluorescent imaging. Puncture of the aneurysm dome to exclude aneurysm sac filling may also assess the efficacy of clip placement. Although a high concordance between ICG and DSA has been reported, there remains an important subset of aneurysms for which negative ICG study may erroneously suggest aneurysm occlusion. A high-risk situation for such a false-negative study is an atherosclerotic middle cerebral artery (MCA) aneurysm in which vessel wall plaque interferes with the ICG signal. Furthermore, a decreased flow within the aneurysm may not allow enough emission light for detection under the current technology. In this report, we describe our experience with cases of MCA aneurysms with false-negative ICG-VA studies requiring clip adjustment for optimal surgical treatment and discuss two illustrative cases of MCA aneurysms with intraoperative fluorescence studies that were falsely negative, requiring puncture of the aneurysm to correctly identify incomplete aneurysm occlusion.

We report a 64-year-old woman who developed symptomatic vasospasm on postoperative day 7 after clipping of an unruptured right middle cerebral artery (MCA) aneurysm. Imaging revealed right MCA vasospasm, which resolved with oral antiplatelets and intravenous vasodilators. She was discharged without neurological deficits. Although a few reports describe vasospasm after clipping unruptured aneurysms, this is the first to detail the clinical course, radiological findings, and treatment response. Potential risk factors include female sex, age 40–60, smoking, trigeminal neuralgia, and complex aneurysms. This case underscores the need to consider vasospasm even without subarachnoid hemorrhage for timely intervention.

Background We report a case of 39-year-old male patient with an unruptured middle cerebral artery aneurysm associated with moyamoya disease (MMD) treated by surgical clipping combined with encephalo-duro-myo-synangiosis surgery. Case description A 39-year-old male patient with a history of intraventricular hemorrhage was admitted to our hospital. Preoperative digital subtraction angiography (DSA) showed the aneurysm, arising from a collateral branch of the right middle cerebral artery (RMCA), had an extremely thin neck. Also present were an occlusion of the RMCA main trunk, and moyamoya vessels. Microsurgical aneurysm clipping was performed for the aneurysm, while encephalo-duro-myo-synangiosis was performed for ipsilateral MMD. At the 4-month follow-up, the patient had recovered well and DSA indicated improved cerebral perfusion with no de novo aneurysms. Conclusions For ipsilateral moyamoya disease accompanied with intracranial aneurysm (IA), simultaneous surgery combining microsurgical clipping and encephalo-duro-myo-synangiosis can be a good treatment option.

In February 2013, results of two key clinical trials assessing clinical efficacy of endovascular management in acute ischemic stroke were presented at annual meeting of International Stroke Conference (ISC) in Honolulu. The trials, SYNTHESIS expansion and IMS-III, had received great attention from many neurologists and neurointerventionalists, as they were multicenter, randomized, controlled trials comparing clinical results of endovascular approach versus standard intravenous (IV) recombinant tissue plasminogen activator (tPA) alone. Although it had already been demonstrated that endovascular treatment had higher recanalization rates than standard medical care (IV tPA), clinical outcomes of two methods had not yet been compared directly. The SYNTHESIS expansion trial, led by Alfonso Ciccone (Carlo Poma Hospital, Mantua, Italy), randomly assigned 362 acute ischemic stroke patients within 4.5 hours of symptom onset to receive IV tPA or intraarterial endovascular treatment, including intraarterial thrombolysis with tPA, mechanical clot disruption or retrieval, or a combination of these interventions. This study was initiated under hypothesis that the disadvantage of endovascular treatment in terms of time spent may be offset by more effective recanalization achieved with endovascular This hypothesis was supported by preliminary results of SYNTHESIS study. The primary outcome of survival (free from disability, modified Rankin score (mRS) ≤ 1) was assessed at 3 months. 30.4% of 181 patients given endovascular therapy and 34.8% of 181 patients given tPA were free of disability (mRS ≤ 1). This result demonstrated that intraarterial intervention was not superior to standard medical care for patients with acute ischemic stroke. In addition, there were no between-group differences in mortality at 90 days (14.4% in endovascular group versus 9.9% in IV tPA group, p = 0.22) or symptomatic intracranial hemorrhage within 7 days (6% in each group). Notably, patients in endovascular group did not undergo treatment initiation until one hour after tPA group, with median onset-to-treatment times of 3.75 hours and 2.75 hours, respectively. In conclusion, clinical benefit of endovascular treatment of acute stroke, when compared with IV tPA, could not be proven by SYNTHESIS expansion trial. However, Ciccone and colleagues presented that generalizability of results may be limited because demonstrating presence of an occlusion was not necessary for inclusion in trial. They said that selection of patients on basis of demonstration of vascular occlusion with noninvasive method may provide endovascular treatment superiority. Another recent trial, IMS III, is a randomized, multicenter, open-label clinical trial that examined whether combined intravenous and endovascular treatment is superior to standard IV tPA treatment alone for patients with acute stroke. Subjects were randomly assigned to combined or standard therapy within 3 hours of stroke onset in a 2:1 ratio. Endovascular treatment included a choice of catheters and devices or intraarterial tPA based upon lesion characteristics, experience and training of investigator, and specified use of devices. At outset, only one device was available, Concentric Merci retriever, but trial leadership recognized that endovascular technology would evolve. In order to keep trial clinically relevant and optimize endovascular approach, additional devices including stent retriever, Penumbra system, and microsonic SV infusion system were allowed as each became cleared for clinical use by Food and Drug Administration. Contrary to SYNTHESIS trial, computed tomography angiography (CTA) was routinely used in identification of occlusion except at beginning of trial. According to journal articles, IMS III study was stopped after 656 participants had been randomized, because it was clear there was no significant difference between two approaches. In overall analysis, 90 day rate of survival free from disability (mRS < 2) was 30.4% in endovascular group and 34.8% in IV tPA group, an insignificant difference (OR 0.71; 95% confidence CI, 0.44 to 1.14). There was no statistically significant difference between interventions for primary endpoint. The absolute difference between groups was 1.5% (95% CI, -6.1% to 9.1%) when adjusted for stroke severity by National Institutes of Health Stroke Scale (NIHSS) score. Although high recanalization rates using endovascular approach were achieved with active use of a thrombectomy device in this study, clinical outcome was disappointing. This result of IMS III also demonstrated that effective recanalization rate of endovascular therapy cannot offset time required for completion of endovascular treatment. Additionally, it was concluded that bridging therapy should not be considered routine protocol but instead should be thought of as a highly-selective therapeutic option. Despite fact that these two trials comprise research on extended application of endovascular approach in overcoming standard medical treatment, management guidelines for acute ischemic stroke have remained unchanged. However, merit of bridging method, which has been commonly used to recanalize large artery occlusions, was brought into question by these trials. The window of time during which endovascular approach may be attempted (4.5-6h) is so narrow that amount of patients for which this procedure may be indicated was significantly decreased. With fewer patients receiving endovascular recanalization therapy, there is less opportunity for trainees to gain experience in intraarterial thrombectomy, and hospitals or medical insurance companies may hesitate to use willingly money for maintenance of emergent neuroendovascular system. Even more damaging, ability to recruit patients to new trials that assess superiority of endovascular treatment will be difficult. Not every result was unfriendly to endovascular treatment, however. In IMS III, for predefined subgroups of patients with an NIHSS score of 20 or higher, indicating severe stroke (endovascular therapy, 23.5%; IV tPA alone, 16.7%, p = 0.07), comparison of functional outcomes between endovascular and medical groups showed a tendency toward a better outcome in endovascular group. This result may indicate that more severe stroke associated with proximal arterial occlusion, including carotid T and proximal M1, would potentially have a greater benefit with endovascular approach, as these clot locations may be highly amenable to endovascular therapy. The role of endovascular therapy is considered to be more critical in proximal artery occlusion than distal artery occlusion. To this end, it would be helpful if IMS III investigators additionally report rescult of subgroup comparisons using CTA. Each time encountering patients with acute stroke, we will be conflicted between our empirical knowledge and verified evidence. The myth has been debunked, but challenge is still present. The endovascular therapy system that is able to start endovascular approach as soon as patient come to hospital and more effective thrombectomy device such as stentriever, will allow endovascular treatment to play critical role in treatment of stroke.

Our aim was to investigate the feasibility of digital variance angiography (DVA) in lower extremity CO2 angiography and to compare the quantitative and qualitative performance of the new image processing technique with that of the current reference standard digital subtraction angiography (DSA). This prospective study enrolled 24 patients (mean age ± SD, 65.5 ± 9.2 years; 14 males, 65.1 ± 7.5 years; 10 females, 66.1 ± 11.6 years) undergoing lower-limb CO2 angiography between December 2017 and April 2018 at 2 clinical centers: The Heart and Vascular Center (HVC) of Semmelweis University, Budapest (7 patients), and the Bács-Kiskun County Hospital (BKCH) in Kecskemét (17 patients). The interventional protocol was similar at both sites, but the image acquisition instruments and protocols were different, which allowed us to investigate DVA in different settings. For comparison, the signal-to-noise ratio (SNR) of DSA and DVA images were calculated. The visual quality of DSA and DVA images were compared by independent clinical specialists using an online questionnaire. Interrater agreement was characterized by percent agreement and Fleiss kappa. The specialists also evaluated in a random and blinded manner the individual DSA and DVA images on a 5-grade scale ranging from poor (1) to outstanding (5) image quality, and the mean ± standard error of mean (SEM) was calculated. A total of 4912 regions of interest were carefully selected in 110 image pairs to determine the SNRs. The ratio of SNRDVA/SNRDSA was calculated. At HVC, it ranged between 2.58 and 4.16 in the anatomical regions (abdominal, iliac, femoral, popliteal, crural, talar), and the overall median value was 3.53, whereas at BKCH the range was 2.71 to 4.92 and the overall median value was 4.52. During the visual evaluation, 120 DSA and DVA image pairs were compared. At HVC in 78%, although at BKCH in 90% of comparisons, it was judged that DVA provided higher quality images. The interrater agreement was 88% (P < 0.001) and 90% (P < 0.01), respectively. DVA images received consistently higher individual rating than DSA images, regardless of the research site and anatomical region. At HVC, the overall DSA and DVA scores (mean ± SEM) were 2.75 ± 0.12 and 3.23 ± 0.16, respectively (P < 0.05), whereas at BKCH these values were 2.49 ± 0.10 and 3.03 ± 0.09, respectively (P < 0.001). These data show that lower-limb CO2 angiography DVA, regardless of the image acquisition instruments and protocols, produces higher SNR and significantly better image quality than DSA; therefore this new image processing technique might help the widespread use of CO2 as a safer contrast agent in clinical practice.

To describe a case of combined duplicate origin and early bifurcated middle cerebral artery (MCA) incidentally diagnosed using magnetic resonance (MR) angiography. A 51-year-old woman with an unruptured left MCA aneurysm underwent cranial MR angiography with a 3-Tesla scanner for presurgical evaluation. MR angiography was performed using a standard 3-dimensional time-of-flight technique. An unruptured left MCA aneurysm at the M1-M2 junction was identified. The maximum aneurysm diameter was 9mm. Two almost equally sized right MCAs arose from the terminal segment of the right internal carotid artery. These two channels soon anastomosed, and the temporal branch arose from the inferior channel. The aneurysm was successfully treated with coil embolization. We herein report a case of a combined duplicate origin and early bifurcated MCA. This variation can also be regarded as anastomosis between the main MCA and the duplicated MCA. This variation has been previously reported as segmental duplication of the MCA. This is the third case of this rare MCA variation reported in the relevant English-language literature. The term "segmental duplication" may be confused with duplicate origin of the MCA, in which only one artery is located distal to the fusion.

Anatomical variations of the middle cerebral artery (MCA) are an important clinical issue, due to high prevalence of intracranial aneurysms. Anatomical variations of vessels can lead to higher shear stress, which is thought to be the main factor leading to aneurysm formation and consequently to higher prevalence of aneurysms. The aim of this study was to evaluate anatomy of the MCA; to classify MCA aneurysms using computed tomography angiography and to correlate anatomical variations of MCA and circle of Willis with prevalence of MCA aneurysms. Two hundred and fifty patients without MCA aneurysms and 100 patients with unruptured MCA aneurysms were qualified for the study, with exclusion of patients after MCA clipping. Four aspects of MCA anatomy were evaluated: division point, its relation to the genu, distance to M1 division and the genu and domination of post-division trunks. Middle cerebral artery bifurcation was found in 86.2% and trifurcation in 13.8% of the cases. 78.4% of MCAs divided before the genu, 19.2% in the genu and 2.4% after the genu. Upper branch domination was seen in 26%, lower branch in 25.4%, middle branch in 4% and no domination in 44.6% of the cases. In the study group 116 aneurysms were found. 86.2% of the aneurysms were located in M1 division point, 6.9% in M2 segment, 3.4% near lenticulostriatae arteries and 3.4% near early cortical branches. The only anatomical variation, which had significantly higher prevalence in patients with left MCA aneurysms, was domination of upper post-division trunk of MCA. No other statistically significant differences in circle of Willis and MCA variations were found between patients with aneurysms and without them. The most common configuration of MCA is bifurcation before the genu with no dominating post-division trunk. Incidence of MCA aneurysms is not correlated with anatomical variations of MCA and the circle of Willis.

Surgical Revascularization Versus Endovascular Therapy to Treat Chronic Limb-Threatening Ischemia: Perhaps Less Invasive Is Not Always Better

Surgery or endovascular therapy for patients with chronic limb-threatening ischemia requiring infrapopliteal interventions

Background: Giant intracranial aneurysms pose significant challenges in treatment due to a high risk of postoperative complications, including delayed rupture, cerebral edema, and aggravation of mass effect. Endovascular approaches, such as adjunctive coiling and flow diverter (FD) procedures, have become increasingly recommended for wide-necked, large, and giant aneurysms. Case Description: In this report, we present a challenging case of a staged coiling and FD procedure in a giant unruptured middle cerebral artery (MCA) aneurysm. The patient, a 26-year-old adult female, was admitted to our hospital with a history of convulsions. Digital Subtraction Angiography (DSA) revealed a massive aneurysm measuring 40 mm × 27 mm in the M1 segment of the MCA. To mitigate the risk of mass effect aggravation, we performed a two-staged procedure with a seven-day interval between the interventions. The first step involved partial endovascular coiling to shrink the aneurysm, followed by successful flow diversion. The patient did not experience further convulsions or neurologic deficits, and the follow-up angiogram showed no residual flow to the aneurysm. Conclusion: We report one of the very first cases of adjunctive coiling and FD in ‘unruptured’ giant aneurysms. Our neurovascular intervention provides valuable insights into the approach and treatment of unruptured giant aneurysms in cerebral arteries. By employing a staged procedure, effective flow diversion can be achieved even in giant unruptured aneurysms. Although further research is necessary to confirm its superiority and address critical issues, our findings may contribute to the future management of giant aneurysms and inspire avenues for research in the neurosurgical community. Bang. J Neurosurgery 2023; 12(2): 129-136

Introduction: Improved imaging modalities have led to an increased detection of intracranial aneurysms, many of which are small. While studies have shown that many ruptured intracranial aneurysms are small (≤7 mm), the natural history of tiny (≤3 mm) aneurysms, particularly in certain locations such as the middle cerebral artery (MCA) is thought to be relatively benign with a reported rupture rate of less than 0.5% per year. The objective of this study is to evaluate the safety and efficacy of treatment of tiny unruptured MCA aneurysms. Methods: The NVQI-QOD registry was queried for patients with tiny unruptured MCA aneurysms who underwent either microsurgical or endovascular repair. Tiny size was defined as an aneurysm with a maximum dimension of ≤3 mm. Demographics, aneurysm characteristics and treatment safety were queried. Safety data included intra-operative and post-operative complications. Outcomes included modified Rankin Score (mRS) at discharge and last follow up as well as aneurysm occlusion status at discharge. Results: Of 670 treated, unruptured MCA aneurysms, 43 were tiny (6.4%). The mean aneurysm width was 1.9 mm with a mean patient age of 56.3 years. The median pre-operative mRS was 0 (range 0-4). The majority of patients underwent microsurgery (27/43). The overall intra-operative complication rate was 7% (3/43) with an intra-operative rupture rate of 4.7% (2/43). The post-operative complication rate was 9.3% (4/43). New intracerebral hemorrhage occurred in 7% of patients (3/43) and unplanned return to OR occurred in 14.8% of patients who underwent microsurgery (4/27). There were no mortalities. 16.3% (7/43) of patients were discharged to inpatient rehabilitation or a skilled nursing facility. At discharge, 37 (88.1%) patients had complete aneurysm occlusion. In the subgroup of patients with recorded follow up data, only 40% (10/25) had a mRS of 0 at discharge and 40% (6/15) had an mRS of 0 at last follow up (median follow up: 165 days). Conclusions: Our analysis showed that treatment of tiny unruptured MCA aneurysms is associated with a high rate of complications. We suggest that many tiny, unruptured MCA aneurysms should be observed given that the morbidity associated with treatment is likely significantly higher than the risk of rupture.