Clinical Implications of Basilar Artery Plaques in the Pontine Infarction with Normal Basilar Angiogram: A High-Resolution Magnetic Resonance Imaging Study.

BACKGROUND: Using high-resolution magnetic resonance imaging (HR-MRI), we investigated the impact of basilar artery plaques that were not detected by magnetic resonance angiography (MRA) on the functional outcomes of patients with acute pontine infarction. METHODS: A total of 40 patients with acute pontine infarction and normal basilar findings on MRA prospectively underwent HR-MRI for detection of basilar artery plaques. A relevant plaque was defined as one on the dorsal side of basilar artery, the same side of the ischemic lesion, and the same axial slices of the ischemic lesion. We analyzed the relationship between the relevant basilar artery plaques and the functional outcomes at 3 months. RESULTS: The initial National Institutes of Health Stroke Scale score (3.5 versus 2.0, P = .012), and the incidences of neurological deterioration (42.9% versus 6.3%, P = .031) and unfavorable functional outcome (71.4% versus 12.5%, P = .001) were higher in patients with relevant basilar artery plaques than in those without. On multiple regression analysis, the relevant basilar artery plaque was a significant and independent predictor of unfavorable functional outcome (odds ratio, 6.662; 95% confidence interval, 1.117-39.735; P = .037). CONCLUSIONS: The presence of a relevant basilar artery plaque was closely related with unfavorable functional outcome in patients with acute pontine infarction even if the patients' MRA showed normal basilar findings.

Silent Embolic Infarction after Neuroform Atlas Stent-Assisted Coiling of Unruptured Intracranial Aneurysms.

OBJECTIVE: There is still controversy regarding whether neck remodeling stent affects the occurrence of silent embolic infarction (SEI) after aneurysm coiling. Thus, the aim of the present study is to investigate the incidence of SEI after stent-assisted coiling (SAC) using Neuroform Atlas Stent (NAS) and possible risk factors. This study also includes a comparison with simple coiling group during the same period to estimate the impact of NAS on the occurrence of SEI. METHODS: This study included a total of 96 unruptured intracranial aneurysms in 96 patients treated with SAC using NAS. Correlations of demographic data, aneurysm characteristics, and angiographic parameters with properties of SEI were analyzed. The incidence and characteristics of SEI were investigated in 28 patients who underwent simple coiling during the same period, and the results were compared with the SAC group. RESULTS: In the diffusion-weighted imaging obtained on the 1st day after SAC, a total of 106 SEI lesions were observed in 48 (50%) of 96 patients. Of these 48 patients, 38 (79.2%) had 1-3 lesions. Of 106 lesions, 74 (69.8%) had a diameter less than 3 mm. SEI occurred more frequently in older patients (≥60 years, p=0.013). The volume of SEI was found to be significantly increased in older age (≥60 years, p=0.032), hypertension (p=0.036), and aneurysm size ≥5 mm (p=0.047). The incidence and mean volume of SEI in the SAC group (n=96) were similar to those of the simple coiling group (n=28) during the same period. CONCLUSION: SEIs are common after NAS-assisted coiling. Their incidence in SAC was comparable to that in simple coiling. They occurred more frequently at an older age. Therefore, the use of NAS in the treatment of unruptured intracranial aneurysm does not seem to be associated with an increased risk of thromboembolic events if antiplatelet premedication has been performed well.

Rotational vertebral artery occlusion: mechanisms and long-term outcome.

BACKGROUND AND PURPOSE: To elucidate the mechanisms and prognosis of rotational vertebral artery occlusion (RVAO). METHODS: We analyzed clinical and radiological characteristics, patterns of induced nystagmus, and outcome in 21 patients (13 men, aged 29-77 years) with RVAO documented by dynamic cerebral angiography during an 8-year period at 3 University Hospitals in Korea. The follow-up periods ranged from 5 to 91 months (median, 37.5 months). Most patients (n=19; 90.5%) received conservative treatments. RESULTS: All the patients developed vertigo accompanied by tinnitus (38%), fainting (24%), or blurred vision (19%). Only 12 (57.1%) patients showed the typical pattern of RVAO during dynamic cerebral angiography, a compression of the dominant vertebral artery at the C1-2 level during contralateral head rotation. The induced nystagmus was mostly downbeat with horizontal and torsional components beating toward the compressed vertebral artery side. None of the patients with conservative treatments developed posterior circulation stroke, and 4 of them (21.1%) showed resolution of symptoms during the follow-ups. CONCLUSIONS: RVAO has various patterns of vertebral artery compression, and favorable long-term outcome with conservative treatments. In most patients with RVAO, the symptoms may be ascribed to asymmetrical excitation of the bilateral labyrinth induced by transient ischemia or by disinhibition from inferior cerebellar hypoperfusion. Conservative management might be considered as the first-line treatment of RVAO.

Erratum: Contralateral Transverse Sinus Occlusion After Treatment of Transverse-Sigmoid Sinus Dural Arteriovenous Fistula: A Case Report.

[This corrects the article on p. 104 in vol. 18, PMID: 35557632.].

Additional rescue stenting with Neuroform Atlas stents during stent-assisted coiling of saccular aneurysms.

OBJECTIVE: Overlapping stenting is sometimes attempted during endovascular treatment of cerebral aneurysm as a rescue for coil herniation, stent mal-positioning, or in-stent thrombosis. We retrospectively evaluated the efficacy and safety of additional rescue stenting (ARS) in telescoping fashion with Neuroform Atlas stent (NAS) during stent-assisted coiling of saccular aneurysms. METHODS: We collected clinical and radiological data of patients with saccular aneurysms treated with ARS using NASs between March 2018 and December 2021. Y or X-stent-assisted coiling technique was excluded. RESULTS: Eighteen unruptured and 5 ruptured aneurysms in 23 patients were treated with ARS using NASs. Sizes of aneurysms ranged from 2.0 mm to 10.0 mm (mean: 5.0 mm). Immediate angiographic results were complete occlusion in 11 aneurysms, residual neck in 4 aneurysms, and residual sac in 8 aneurysms. Peri-operative morbidity was 4.3 %. Nineteen of 23 patients underwent follow-up conventional angiography (mean, 9.9 months). Results showed progressive occlusion in 10 (52.6 %) cases and asymptomatic in-stent stenosis in 3 (15.8 %) cases. At the end of the observation period (mean, 17.4 months), all 18 patients without subarachnoid hemorrhage had excellent clinical outcomes (mRS of 0), except one (mRS of 1). Of five patients with subarachnoid hemorrhage, four had a favorable outcome (mRS of 0-1), while the other one was dependent (mRS of 4). CONCLUSION: In this report on 23 patients, ARS with NASs for treating saccular aneurysms showed good technical safety with favorable clinical and angiographic outcomes. However, delayed in-stent stenosis was not uncommon. Thus, regular imaging follow-up is required.

Contralateral Transverse Sinus Occlusion After Treatment of Transverse-Sigmoid Sinus Dural Arteriovenous Fistula: A Case Report.

A dural arteriovenous fistula (DAVF) is a pathologic arteriovenous shunt located within the dural wall of a venous sinus. In addition, DAVFs are associated with sinus thrombosis. Consequently, sinus occlusion may occur near DAVF lesions, making treatment challenging. However, there are few reports of sinus occlusion unrelated to lesions. In this study, we present a rare case of contralateral transverse sinus occlusion in a patient who underwent endovascular treatment and stereotactic radiosurgery for DAVF in the transverse-sigmoid sinus with ipsilateral sigmoid sinus occlusion.

Stacking ensemble learning model to predict 6-month mortality in ischemic stroke patients.

Patients with acute ischemic stroke can benefit from reperfusion therapy. Nevertheless, there are gray areas where initiation of reperfusion therapy is neither supported nor contraindicated by the current practice guidelines. In these situations, a prediction model for mortality can be beneficial in decision-making. This study aimed to develop a mortality prediction model for acute ischemic stroke patients not receiving reperfusion therapies using a stacking ensemble learning model. The model used an artificial neural network as an ensemble classifier. Seven base classifiers were K-nearest neighbors, support vector machine, extreme gradient boosting, random forest, naive Bayes, artificial neural network, and logistic regression algorithms. From the clinical data in the International Stroke Trial database, we selected a concise set of variables assessable at the presentation. The primary study outcome was all-cause mortality at 6 months. Our stacking ensemble model predicted 6-month mortality with acceptable performance in ischemic stroke patients not receiving reperfusion therapy. The area under the curve of receiver-operating characteristics, accuracy, sensitivity, and specificity of the stacking ensemble classifier on a put-aside validation set were 0.783 (95% confidence interval 0.758-0.808), 71.6% (69.3-74.2), 72.3% (69.2-76.4%), and 70.9% (68.9-74.3%), respectively.

Erratum: Transiting Nerve Rootlet Abnormalities on MRI after Lumbar Laminectomy: Associations with Persistent Postoperative Pain.

This corrects the article on p. 225 in vol. 22, PMID: 32901462.

Transiting Nerve Rootlet Abnormalities on MRI after Lumbar Laminectomy: Associations with Persistent Postoperative Pain.

OBJECTIVE: To determine whether changes in the transiting nerve rootlet or its surroundings, as seen on MRI performed after lumbar hemilaminectomy, are associated with persistent postoperative pain (PPP), commonly known as the failed back surgery syndrome. MATERIALS AND METHODS: Seventy-three patients (mean age, 61 years; 43 males and 30 females) who underwent single-level partial hemilaminectomy of the lumbar spine without postoperative complications or other level spinal abnormalities between January 2010 and December 2018 were enrolled. Two musculoskeletal radiologists evaluated transiting nerve rootlet abnormalities (thickening, signal alteration, distinction, and displacement), epidural fibrosis, and intrathecal arachnoiditis on MRI obtained one year after the operations. A spine surgeon blinded to the radiologic findings evaluated each patient for PPP. Univariable and multivariable analyses were used to evaluate the association between the MRI findings and PPP. RESULTS: The presence of transiting nerve rootlet thickening, signal alteration, and ill-distinction was significantly different between the patients with PPP and those without, for both readers (p ≤ 0.020). Conversely, the presence of transiting nerve rootlet displacement, epidural fibrosis, and intrathecal arachnoiditis was not significantly different between the two groups (p ≥ 0.128). Among the above radiologic findings, transiting nerve rootlet thickening and signal alteration were the most significant findings in the multivariable analyses (p ≤ 0.009). CONCLUSION: On MRI, PPP was associated with transiting nerve rootlet abnormalities, including thickening, signal alterations, and ill-distinction, but was not associated with epidural fibrosis or intrathecal arachnoiditis. The most relevant findings were the nerve rootlet thickening and signal alteration.

Isolated bilateral abducens nerves palsy due to traumatic delicate arteriovenous fistula.

BACKGROUND: Ocular motor dysfunction is common in patients with head trauma. Also, traumatic lateral gaze palsy is usually associated with brain stem lesion, peripheral nerve injury with or without basilar skull fracture and lateral rectus muscle injury or entrapment. However, isolated bilateral abducens nerve palsy is extremely rare. CASE STUDY: This study describes a case of isolated bilateral abducens nerve palsy in a 35-year-old male with head trauma without cervical and skull fractures. He was diagnosed with mild diffuse axonal injury. During his assessment, he developed mild limb weakness, an ataxic gait and impaired abductive movement in both eyes. Angiography of the left common carotid artery revealed multiple small arteriovenous fistulae in both inferior nasal conchae. After embolization, lateral gaze palsy of his eyes was significantly improved. CONCLUSIONS: Based on this case, arteriovenous fistula should be considered as a cause of bilateral isolated abducens nerve palsy.

Result of coiling versus clipping of unruptured anterior communicating artery aneurysms treated by a hybrid vascular neurosurgeon.

OBJECTIVE: This study will evaluate the outcomes of coiling versus clipping of unruptured anterior communicating artery (A-com) aneurysms treated by a hybrid vascular neurosurgeon to suggest the best protocol of management for these conditions. METHODS: We retrospectively reviewed the records of 70 patients with an unruptured A-com aneurysm treated with coiling or clipping performed by a hybrid vascular neurosurgeon between March 2012 and December 2019. The patients were dichotomized, into the coil group or clip group. Treatment-related complications, clinical and radiological results were evaluated. RESULTS: Of the 70 patients identified, 37 underwent coiling and 33 clipping. Procedure-related symptomatic complications occurred in 2 patients (5.4%) in the coil group and 3 patients (9.1%) in the clip group. Poor clinical outcome (modified Rankin Scale [mRS] of 3 to 6) at 6 months of follow-up was seen in only one patient (2.7%) for the coil group, and none for the clip group. The one poor outcome was the result of intra-procedural rupture during coiling. Follow-up conventional angiography data (mean duration, 15.0 months) revealed that the major recanalization rate is 5.6% for the coil group and 10.0% for the clip group. CONCLUSIONS: Management of A-com aneurysms requires more collaboration between microsurgical clipping and endovascular therapy. Evaluation of patient and aneurysm characteristics by considering the advantages and disadvantages of both techniques could provide an optimal treatment modality. A hybrid vascular neurosurgeon is expected to be a proper solution for the management of these conditions.

Endovascular treatment of the vertebral artery origin stenosis by using the closed-cell, self-expandable Carotid Wallstent.

BACKGROUND: Endovascular treatment has been considered a good alternative to surgery for symptomatic vertebral artery origin stenosis (VAOS) due to the high risk of morbidity associated with surgery. The purpose of this study was to evaluate the feasibility and efficacy of insertion of the closed-cell, self-expandable Carotid Wallstent for the treatment of VAOS. METHODS: The records of 72 patients with VAOS refractory to adequate medication who were treated by endovascular treatment with the Carotid Wallstent from December 2006 to November 2018 were retrospectively evaluated. RESULTS: Of the 72 patients, 43 presented with transient ischemic attacks. Forty-seven patients (65.3%) manifested other brachiocephalic stenoses; of these, 40 patients had occlusion, hypoplasia, or stenosis of the contralateral vertebral artery. Overall technical success (defined as 20% or less residual stenosis) was 100%. Procedure-related complications (n = 8, 11.1%) included sudden asystole (n = 1), acute in-stent thrombosis (n = 3), minor stroke (n = 3), and stent shortening (n = 1). All complications were resolved without permanent neurological deficit. Angiographic follow-up (mean, 13.0 months) was achieved in 49 patients and revealed in-stent restenosis in 1 patient (2.0%) and stent malposition by shortening in 2 patients (4.1%). Follow-up records were available in 57 patients (mean 15.6 months). Three of the 57 patients (n = 3, 5.3%) had recurrent symptoms of vertebrobasilar ischemia and none was retreated. CONCLUSIONS: Endovascular treatment of symptomatic VAOS using the closed-cell, self-expandable Carotid Wallstent is technically feasible and effective in alleviating patient symptoms and for improving vertebrobasilar blood flow.

Radiological and clinical outcomes of endovascular coiling of proximal A1 aneurysms.

Aneurysms of the proximal anterior cerebral artery (A1) are rare. Of these A1 aneurysms, proximal A1 aneurysms are among the most challenging for endovascular coiling. This study aimed to evaluate the angiographic features and radiological and clinical outcomes of endovascular coiling of proximal A1 aneurysms. We recruited 38 patients with 38 proximal A1 aneurysms treated with endovascular coiling between September 2005 and April 2016. Baseline patient characteristics, aneurysm morphology, endovascular treatment techniques, immediate post-procedural radiological outcome, and follow-up clinical and radiological outcomes were evaluated, as were risk factors for recurrence. Sixteen proximal A1 aneurysms ruptured (42.1%). Six procedural complications (15.8%), including 5 thromboembolisms and 1 coil migration, were noted. There was no procedural morbidity or mortality. Immediate post-procedural radiological outcomes showed complete occlusion in 23, residual necks in 12, and residual sacs in 3 lesions. Follow-up angiographic outcomes were possible for 28 lesions (73.7%). Follow-up angiography showed sac recurrence in 3 (10.7%) and neck recurrence in 3 (10.7%) lesions. Retreatment was performed in 4 lesions (14.3%); all were treated by endovascular coiling. The presence of aneurysmal ruptures was only significant regarding recurrence in univariate logistic regression analysis. In our study, endovascular coiling of proximal A1 aneurysms was associated with a relatively high rate of procedural complications but not with procedural morbidity and mortality. The recurrence and retreatment rates of endovascular coiling of proximal A1 aneurysms were relatively high, and presence of rupture was significant for recurrence.

Vascular response to the vasa vasorum in a carotid artery dissecting aneurysm.

Collateralization of a hemodynamically compromised internal carotid artery (ICA) by the vasa vasorum is rare. We report the serial radiologic findings of an apparent hypertrophied vasa vasorum of the cervical ICA, which was secondary to arterial dissection.

Endovascular reconstructive treatment using a fill-and-tunnel technique for a fusiform vertebral artery dissecting aneurysm with ipsilateral dominance.

BACKGROUND: Fusiform dissecting aneurysms involving the dominant vertebral artery with poor collaterals are challenging to treat. The purpose of this study was to present an initial experience with a fill and tunnel technique for reconstructive endovascular treatment of these conditions. METHODS: A total of 13 patients, 11 men and 2 women, each with a fusiform vertebral artery dissecting aneurysm not amenable to internal trapping of the parent artery, underwent reconstructive endovascular treatment using a fill and tunnel technique between January 2012 and December 2015. The safety, feasibility, and clinical and angiographic outcomes of these procedures were retrospectively evaluated. RESULTS: The average maximum diameter of the fusiform aneurysms was 12.1 mm. Five were ruptured. Three aneurysms were treated with a single stent and the remaining 10 aneurysms required double-stent placement. Treatment was technically successful in all 13 patients, achieving complete occlusion (n = 10, 76.9%) and near-complete occlusion (n = 3, 23.1%). No procedure-related complications occurred in any patient. There were no delayed thromboembolic or hemorrhagic complications during the follow-up period (mean, 19.0 months). Angiographic follow-ups (mean, 9.1 months) showed stable occlusion in 90.9% (10/11) and asymptomatic in-stent occlusion in one patient (9.1%, 1/11). At the end of the observation period (mean, 19.0 months), all patients had excellent clinical outcomes (modified Rankin Scale (mRS) 0, 92.3%, 12/13), except one (mRS 4), resulting from poor preoperative status. CONCLUSIONS: This retrospective study demonstrated that endovascular reconstruction using a fill-and-tunnel technique was a technically safe, feasible, and clinically effective treatment method for fusiform vertebral artery dissecting aneurysms with ipsilateral dominance.

Endovascular treatment of ruptured tiny aneurysms.

OBJECTIVE: Endovascular coiling of ruptured tiny aneurysms (RTAs) in the brain has been known to be technically challenging owing to the higher rate of adverse events, such as thromboembolism and intraoperative rupture. The aim of this study was to report our ex-periences of endovascular treatment of RTAs (size, ≤3 mm). METHODS: From January 2006 to December 2017, 35 RTAs in 35 patients were treated at our institution with an endosaccular coiling. Procedural data and clinical and angiographic results were retrospectively reviewed. RESULTS: The mean size of the RTAs was 2.53 mm (SD: 0.38). The neck remodeling technique was applied to 14 aneurysms, including stent-assisted coiling (n=7) and balloon-assisted coiling (n=7). Procedure-related complications included intraprocedural rupture (n=2), thromboembolic event (n=1), and early rebleeding (n=2), which needed recoiling. Regarding immediate angiographic control, complete occlusion was achieved in 25 aneurysms (71.4%), small neck remnant in 5 (14.3%), and definite remnant in 5 (14.3%). At the end of follow-up, 31 of the 35 patients (88.6%) were able to function independently. Twenty-two of the 35 patients underwent follow-up conventional angiography (mean, 468 days). Stable occlusion was achieved in 20 of the 22 patients (90.9%), minor recanalization in 1 (4.5%), and major recanalization, which required recoiling, in 1 (4.5%). CONCLUSION: Our experiences demonstrate that endovascular treatment for RTAs is both feasible and effective. However, periprocedural rebleedings were found to occur more often (11.4%) than what is generally suspected.

Feasibility and efficacy of coil embolization for middle cerebral artery aneurysms.

Background: The anatomy of middle cerebral artery (MCA) aneurysms has been noted to be unfavorable for endovascular treatment. The purpose of this study was to assess the feasibility and efficacy of coiling for MCA aneurysms. Methods: From January 2004 to December 2015, 72 MCA aneurysms (38 unruptured and 34 ruptured) in 67 patients were treated with coils. Treatment-related complications, clinical outcomes, and immediate and follow-up angiographic outcomes were retrospectively analyzed. Results: Aneurysms were located at the MCA bifurcation (n=60), 1st segment (M1, n=8), and 2nd segment (M2, n=4). Sixty-nine aneurysms (95.8%) were treated by neck remodeling techniques using multi-catheter (n=44), balloon (n=14), stent (n=8), or combination of these (n=3). Only 3 aneurysms were treated by single-catheter technique. Angiographic results were 66 (91.7%) complete, 5 (6.9%) remnant neck, and 1 (1.4%) incomplete occlusion. Procedural complications included aneurysm rupture (n=1), asymptomatic coil migration to the distal vessel (n=1), and acute thromboembolism (n=10) consisting of 8 asymptomatic and 2 symptomatic events. Treatment-related permanent morbidity and mortality rates were 4.5% and 3.0%, respectively. There was no bleeding on clinical follow-up (mean, 29 months; range, 6-108 months). Follow-up angiographic results (mean, 26 months; range, 6-96 months) in patients included 1 major and 3 minor recanalizations. Conclusion: Coiling of MCA aneurysms could be a technically feasible and clinically effective treatment strategy with acceptable angiographic and clinical outcomes. However, the safety and efficacy of this technique as compared to surgical clipping remains to be ascertained.

Transvenous Stent-assisted Coil Embolization for Management of Dehiscent High Jugular Bulb With Tinnitus and Contralateral Hypoplastic Venous Sinuses.

OBJECTIVES: This study aimed to evaluate the safety and efficacy of transvenous stent-assisted coil embolization for dehiscent high jugular bulb (HJB) with tinnitus and contralateral hypoplastic venous sinus. STUDY DESIGN: Case series with chart review. SETTING: Tertiary academic medical center. METHODS: From September 2008 to October 2018, a series of patients with dehiscent HJB presenting with intractable pulsatile tinnitus abated only by ipsilateral jugular vein compression were included. Patients underwent transvenous stent-assisted coil embolization for selective obstruction to the dome of the HJB due to hypoplastic contralateral transverse or sigmoid venous sinus. Technical safety and clinical efficacy were retrospectively analyzed. Clinical outcome measurements included pure-tone audiogram, tinnitus character, and tinnitus handicap inventory and evaluated based on the change during the first 6 months after the procedure. RESULTS: Subjects included five patients with dehiscent HJB and troublesome pulsatile tinnitus who refused surgery (n = 4), or who experienced recurrence after surgical covering and reinforcement using autologous cartilage (n = 1). The mean age of the five patients (only female) was 45 years. Transvenous stent-assisted coil embolization was technically successful in all patients with symptomatic dehiscent HJB, with no procedure-related complications. Temporary postprocedural headache was observed in two patients, but resolved within 3 days. Symptoms were completely resolved in all cases. There was no recurrence or aggravation of tinnitus during follow-up period. CONCLUSIONS: Transvenous stent-assisted coil embolization for dehiscent HJB with tinnitus and contralateral hypoplastic transverse or sigmoid venous sinus could be a technically safe and clinically effective treatment strategy while preserving cranial venous drainage.

Probabilistic anatomic mapping of cerebral blood flow distribution of the middle cerebral artery.

UNLABELLED: Probabilistic atlases are more representative of the population than single brain atlases. They allow anatomic and functional labeling of the results of group studies in stereotactic space and, hence, the automated anatomic labeling of individual brain imaging data. METHODS: In the current study, probabilistic maps of the blood flow distribution of the middle cerebral artery (MCA) were developed using the basal and MCA brain SPECT images. Twenty-nine patients (mean age +/- SD, 54.6 +/- 6.1 y) who previously received placement of a stent for MCA stenosis (right MCA stenosis, 15 patients; left MCA stenosis, 14 patients) were included in the current study. Of the 29 MCA SPECT images, 18 were analyzed for the final result because 11 MCA SPECT images revealed an uneven uptake distribution of (99m)Tc-ethylcysteinate dimer in the brain. MCA brain SPECT images were coregistered to basal brain SPECT images, and spatial normalization parameters used for basal brain SPECT images were reapplied to MCA brain SPECT for anatomic standardization. Pixel counts of the MCA brain SPECT images were then normalized, and the probabilistic map of cerebral perfusion distribution (perfusion probabilistic map) for each hemisphere was determined by averaging the spatial- and count-normalized MCA brain SPECT images. Population-based probabilistic maps representing the extent of MCA territory (extent probabilistic map) were also composed by averaging the binary images obtained by thresholding the spatially normalized MCA brain SPECT images. RESULTS: The blood supply from the MCA to the basal ganglia area was largest (probability, 0.6 approximately 0.8), followed by the insular cortex (probability, 0.3 approximately 0.5), and various cerebral cortical areas (probability, 0.2 approximately 0.4). The MCA reached to deep structures of the brain, including the internal capsule, caudate nucleus, putamen, globus pallidus, insular cortex, and thalamus with a high-extent probability. CONCLUSION: A population-based probabilistic map of MCA flow distribution was generated by using MCA brain SPECT images. This map could be a potential tool for the analysis of major cerebral artery distribution, especially the MCA. Furthermore, the probabilistic MCA atlas could be used to define the object delineation of the MCA territory, to quantify ischemic disease affecting the MCA, to predict prognosis, and to risk stratification of cerebrovascular diseases, especially affecting the MCA.