Medial Lenticulostriate Artery Research Articles

Recurrent Artery of Heubner Guiding the Clip Application for Internal Carotid Artery Bifurcation Aneurysm: 2-Dimensional Operative Video.

Aneurysms of the bifurcation of the internal carotid artery (ICA) represent approximately 5% of intracranial aneurysms and tend to occur in younger patients.1-3 They typically have a superior orientation, in close relationship with the medial (branches of the anterior cerebral artery, segment A1) and lateral (branches of the middle cerebral artery, segment M1) lenticulostriate arteries (LSA), including recurrent artery of Heubner (RAH). RAH commonly originates in the junction of A1 and A2, courses medially to laterally between LSA and anterior cerebral artery, ICA bifurcation, and middle cerebral artery before entering the lateral portion of the anterior perforated substance.4-7 Damage to these arteries are catastrophic. This complex vascular anatomy makes treatment challenging, either endovascular or microsurgical.8-13 We present a video case of microsurgical clipping for the left ICA bifurcation aneurysm. This study was approved by the ethics committee of our institution. The patient, a 46-year-old man, was diagnosed with an unruptured ICA bifurcation aneurysm during workup for intermittent headache. Morphological characteristics of the aneurysm supported intervention over conservative treatment. Digital subtraction angiography showed a prominent proximal RAH crossing between the aneurysm neck and LSA, providing anatomical protection for clip application. Microsurgical clipping was chosen, and the procedure went uneventfully. The patient consented to the procedure and to the publication of his/her image. We discussed and demonstrated throughout the video how we used this anatomic variation and trajectory of the RAH to prevent clipping of LSA unwittingly and achieve complete occlusion of the aneurysm neck.

Arterial Supply of the Basal Ganglia: A Fiber Dissection Study.

The basal ganglia, a group of subcortical nuclei located deep in the insular cortex, are responsible for many functions such as motor learning, emotion, and behavior control. Nowadays, because it has been shown that deep brain stimulation and insular tumor surgery can be performed by endovascular treatment, the importance of the vascular anatomy of the basal ganglia is being increasingly recognized. To explain the arterial blood supply of the basal ganglia using white matter dissection. The Klingler protocol was used to prepare 12 silicone-injected human hemispheres. The dissections were performed from lateral to medial with the fiber dissection technique to preserve arteries. The globus pallidus blood supply came from the medial lenticulostriate, lateral lenticulostriate, and anterior choroidal arteries; the substantia nigra and subthalamic nucleus were supplied by the branches of posterior cerebral artery; the putamen was supplied by the lateral and medial lenticulostriate arteries; and the caudate nucleus was supplied by the lateral lenticulostriate and medial lenticulostriate arteries and the recurrent artery of Heubner. Knowledge of the detailed anatomy of the basal ganglia and its vascular supply is essential for avoiding postoperative ischemic complications in surgeries related to the insula. In addition, knowledge of this anatomy and vascular relationship opens the doors to endovascular deep brain stimulation treatment. This study provides a 3-dimensional understanding of the blood supply to the basal ganglia by examining it using the fiber dissection technique. Further studies could use advanced imaging modalities to explore the vascular relationships with critical structures in the brain.

Cerebrovascular complications in tuberculous meningitis-A magnetic resonance imaging study in 90 patients from a tertiary care hospital.

Cerebrovascular complications of tuberculous meningitis (TBM) are associated with increased morbidity and mortality. We retrospectively reviewed clinicoradiological findings of 90 TBM patients who presented to a tertiary care hospital, with emphasis on frequency and distribution of infarcts on diffusion imaging and pattern of vascular involvement on magnetic resonance (MR) angiography (MRA). MR images of 90 TBM patients at presentation (2012-2018) were coanalyzed by two radiologists for tuberculomas, leptomeningeal enhancement (LM), hydrocephalus, infarct and vascular abnormalities. Infarcts were categorized based on location ("tubercular" (TB) or "ischemic" zones) and arterial supply (perforators and cortical branches). Clinical and laboratory findings were correlated with imaging data. Ninety TBM patients (age 10-82 years) were enlisted after application of inclusion criteria. Tuberculomas were most common (100%) followed by LM (84.4%), cerebral infarcts (57.7%) and hydrocephalus (29%). Location-wise, 35% infarcts were in ischemic, 13% in TB and 15% in both zones. According to arterial supply, infarcts equally (50%) involved perforators from the lateral lenticulostriate and posterior cerebral (PCA)/basilar artery (BA) followed by medial lenticulostriate arteries (23%). MRA was available in 74.4% and abnormal in 43.2%. The middle cerebral artery was frequently involved (76%) followed by the anterior cerebral artery (38%), internal carotid artery (31%), PCA and BA. Six had diffuse narrowing with a paucity of distal vessels. Cerebral infarction was associated with hydrocephalus (p = .0019) and vasculitis (p < .001). In TBM, strokes are common and mainly involve the perforators and cortical branches. MR is the imaging modality of choice for early diagnosis and timely management.

Abstract WMP120: The Role of Age, Lesion Location and Volume in Predicting Long-Term Neurological Outcomes in Pediatric Ischemic Stroke

Introduction: The balance of plasticity versus vulnerability to acute ischemic injury in the immature brain across development remains controversial. We aimed to investigate the relationship between age at stroke and lesion location and volume with long-term outcomes following arterial ischaemic stroke (AIS). Hypothesis: Age at stroke onset interacts with lesion location and volume to predict long-term neurological outcomes. Methods: In a single-centre prospective study, children aged term birth to 18 years with acute symptomatic AIS from 1992 to 2016 who underwent neuroimaging (CT/MRI) within 14 days of stroke onset were studied. Long term outcomes were assessed with the Pediatric Stroke Outcome Measure (PSOM). Outcomes were defined as normal (score 0-0.5 on 1-5 PSOM subscales), otherwise abnormal. AIS lesions were classified based on major (anterior, middle, posterior, other) cerebral arteries and branch sub-territories (e.g. MCA-lateral lenticulostriate). For each vascular territory, the proportion of infarcted brain was estimated as ‘small’ (≤50% territory) or ‘large’ (&gt;50% territory). Factors predictive of long term outcomes were evaluated using logistic regression models. Results: Among 285 children, median age at stroke onset was 22 months (IQR: 0.03-101), 41% were females. PSOM scoring at median 9 years (IQR: 4-15) post-stroke was normal in 61%. Abnormal outcome was associated with age 1-4 years (OR=2.2, 95% CI: 1.02-4.9), ‘large’ proportion infarcts involving cortex within any major artery territory (OR=6.1, 95% CI: 2.6-14.4), and subcortical infarcts: OR= 2.7 (95% CI: 1.4-5.4) for small proportion infarcts; OR=8.3 (95% CI: 4.2-16.6) for large proportion infarcts in either medial or lateral lenticulostriate arteries; OR=15.8 (95% CI: 5-50.3) for large volume lesions in both lenticulostriate territories. In multivariate logistic regression, age, cortical and subcortical infarcts predicted long-term neurologic outcomes. Conclusions: In addition to age at stroke onset, infarct location including volume plays a key role in predicting long-term neurological outcomes in children. While the relationship between age and neurological outcomes seems to be bimodal, a linear effect of lesion volume on stroke outcomes is evident.

Microsurgical clipping of a large ruptured anterior communicating artery aneurysm.

Background:Anterior communicating artery (AComA) aneurysms are the most complex aneurysms of the anterior cerebral circulation. They mostly arise between the dominant A1 and the AComA, and are associated with intraventricular hemorrhage or other aneurysms in around 20%–30% of the cases. Giant and fusiform aneurysms are rare in this location in contrast to the common small ruptured aneurysms. Throughout the treatment, branches of A1–A2 complex such as the orbitofrontal artery, the frontopolar artery, the recurrent artery of Heubner, medial lenticulostriate arteries, and small perforators from the A1–A2 junction should be preserved. The orientation of the aneurysm, undefined in case of tortuous A1, but usually to the contralateral side of the dominant A1, might be downward, forward, upward, backward, or even of a complex morphology. Moreover, the evaluation of the chiasm and skull base, the site of possible rupture, the presence of intraluminal thrombosis, vascular calcifications, or anatomic variations of A1 and A2 segments is required. Since the angle between the AComA perforators and the A2s varies between 30° and 180°, parallel application of the clip along the AComA is unrecommended.Technique:The patient with large ruptured AComA aneurysm underwent supine position. The head, placed above the cardiac level, was minimal extended, and slightly tilted and rotated to the opposite side according to the projection of the aneurysm dome. A left lateral supraorbital approach was performed. The carotid cistern and the lamina terminalis were opened to release cerebrospinal fluid. Arachnoid bands extending from the olfactory triangle to the lateral side of the optic nerve were carefully dissected to find the ipsilateral A1 and the aneurysm. Skillful dissection of the AComA complex under repeated temporary and pilot clips allowed a safe definitive clipping. Occasionally, aneurysm remodeling and shrinking under bipolar coagulation might be required. Intraoperative angiography and/or Doppler ultrasound determine complete occlusion of the aneurysm and patency of the vessels.Conclusion:Skillful microneurosurgery is required for the management of challenging ruptured AComA aneurysms.Videolink:http://surgicalneurologyint.com/videogallery/ruptured-acoma-aneurysm-14

Cerebral infarction pattern in tuberculous meningitis.

Tuberculous meningitis (TBM) causes significant morbidity and mortality. The primary objective was to re-examine the concept of “TB zone” and “ischaemic zone” in cerebral infarction in patients with tuberculous meningitis. The secondary objective was to evaluate cerebral infarction, vasculitis and vasospasm in tuberculous meningitis infections. Between 2009 and 2014, TBM patients were recruited. Neuroimaging was performed and findings of cerebral infarction, vasculitis and vasospasm were recorded. Infarcts were classified based on arterial supply and Hsieh’s classification. Fifty-one TBM patients were recruited of whom 34 patients (67%) had cerebral infarction. Based on Hsieh’s classification, 20 patients (59%) had infarcts in both “TB zone” and “ischaemic zones”. 12 patients (35%) had infarcts in “ischaemic zone” and two (6%) patients had infarcts in “TB zone”. In terms of vascular supply, almost all patients (35/36) had infarcts involving perforators and cortical branches. 25 patients (73%) and 14 patients (41%) had infarcts supplied by lateral lenticulostriate and medial lenticulostriate arteries respectively. 15 patients (37%) had vasculitis. Vasospasm was present in six patients (15%). 29 patients (85%) with cerebral infarction also had leptomeningeal enhancement (p = 0.002). In summary, infarcts involved mainly perforators and cortical branches, rather than “TB zone” versus “ischaemic zone”.

Coil embolization in precommunicating (A1) segment aneurysms of anterior cerebral artery

Precommunicating (A1) segment aneurysms of the anterior cerebral artery are rare and often pose technical challenges for coil embolization due to their distinctive configurations. Clinical and radiologic outcomes of treating such aneurysms through endovascular coil embolization are presented herein. Data accruing prospectively from May 2002 to August 2013 yielded 48 patients harboring 50 A1 segment aneurysms, each classified as proximal, middle, or distal by location. Clinical outcome of the patients and morphological outcome of the aneurysms were assessed, with emphasis on technical aspects of treatment. The aneurysms studied occupied either proximal (n = 39), middle (n = 6), or distal (n = 5). Proximal aneurysms were largely directed posteriorly (80 %), and most (97 %) were devoid of branches. Middle and distal aneurysms were associated with the medial lenticulostriate artery, cortical branches, or fenestrations. The preshaped "S" and steam-shaped "S" microcatheters facilitated aneurysm selection in 60 % of lesions. Single-microcatheter technique was most commonly applied for coil embolization (62 %), followed by balloon protection (16 %). Successful aneurysmal occlusion could be achieved in 76 % of the patients, with no procedure-related morbidity and mortality. At final follow-up (mean interval, 29.9 months), stable aneurysmal occlusion was sustained in 93 % of the patients (40/43). A1 segment aneurysms are amenable to safe and efficacious endovascular coil embolization by adjusting procedural strategy to accommodate distinctive anatomic configurations.

Idiopathic Lenticulostriate Artery Pseudoaneurysm Protruding into the Lateral Ventricle: A Case Report

We report a rare case of an idiopathic pseudoaneurysm causing intraventricular hemorrhage (IVH). A 28-year-old man presented with sudden onset of severe headache. He underwent external ventricular drainage for an isolated IVH in the right lateral ventricle. Digital subtraction angiography (DSA) revealed that the aneurysm (7.5×4.5 mm) arose from the distal part of the medial lenticulostriate artery. Following removal of the external ventricular drainage catheter, the aneurysm decreased in size (4.0×2.3 mm). However, follow-up DSA revealed a slightly enlarged aneurysm (4.2×3.2 mm) with morphologic change. The aneurysm was clipped via the interhemispheric transcallosal approach, but postoperative DSA revealed a residual aneurysm sac beside the clips. Given the risk of rebleeding, a second operation was planned for complete resection of the aneurysm. After revised craniotomy and careful dissection of the caudate nucleus, the aneurysm sac was completely resected. Histopathological examination revealed that the aneurysm was a pseudoaneurysm. The patient recovered without any neurological sequel and was discharged.To the best of our knowledge, this is the first reported case of an idiopathic lenticulostriate artery pseudoaneurysm protruding into the right lateral ventricle and causing an IVH that was successfully treated with microsurgical resection.

The Variable Origin of the Recurrent Artery of Heubner: An Anatomical and Morphometric Study

The recurrent artery of Heubner (RAH) is the largest vessel of the medial lenticulostriate arteries. It supplies many deep structures, mainly the corpus striatum, the globus pallidus, and the anterior crus of the internal capsule. The aim of the present paper was studying the morphological variations of the RAH and its diameter in relation to different areas of origin. The series contained the records from 183 formalin-fixed adult human brains. The calibrated digital images of the studied brains were evaluated and measured by Image J, which can calculate the number of pixels and convert them to metric measures. The RAH arose most often from the postcommunicating part of the anterior cerebral artery (47.81%). It originated from the precommunicating part of the anterior cerebral artery in 3.55% and at the level of the anterior communicating artery in 43.4% of cases. The RAH was missing in 5.19% and doubled in 6.28% of cases. The mean outer diameter of the RAH was 0.6 mm. The maximal measured diameter was 1.34 mm, and the minimal diameter was 0.19 mm. The awareness of the various anatomical and morphometric variations of the RAH is essential in planning the neurosurgical procedures to avoid unexpected neurological complications.

Medial lenticulostriate artery aneurysm presenting with isolated intraventricular hemorrhage

Background:Isolated intraventricular hemorrhage (IVH) secondary to lenticulostriate artery aneurysm rupture is extremely rare. Thus, the diagnostic imaging modalities and therapeutic interventions utilized in the management of such cases are not clearly defined.Case Description:Here we describe a case of isolated or primary IVH (PIVH) in a 71-year-old woman presenting with severe headache. Emergent catheter cerebral angiography, performed after nondiagnostic computed tomography angiography (CTA), revealed the bleeding source to be a 4 × 2.6 mm distal medial lenticulostriate artery aneurysm that ruptured directly into the lateral ventricle. The poorly accessible location of the aneurysm for both endovascular and direct surgical treatment argued for conservative management. A good clinical outcome was obtained with rapid angiographic resolution of the ruptured aneurysm.Conclusion:Thus, lenticulostriate artery aneurysm rupture must be given diagnostic consideration in cases of isolated IVH. Emergent catheter cerebral angiography should be performed in cases such as this when noninvasive imaging is unrevealing. Conservative management may be a reasonable therapeutic option in patients with this kind of aneurysm, and spontaneous resolution can be observed.

Idiopathic distal lenticulostriate artery aneurysm in a child

The authors describe a rare case of idiopathic distal lenticulostriate artery (LSA) aneurysm in a 5-year-old boy who presented in the emergency department with a sudden onset of headache. Admission computed tomography scans revealed an intracerebral hemorrhage in the left caudate nucleus with intraventricular extension. Angiographic studies demonstrated a left medial LSA aneurysm. The patient underwent a left parasagittal frontal craniotomy, the lateral ventricle was accessed via the anterior transcallosal approach, and the aneurysm was removed after sectioning of the parent vessel. The child left the hospital after 5 days; at that time he was asymptomatic and without motor impairment. The optimum treatment of aneurysms involving small perforating arteries is controversial and depends mainly on the causative factors. The pathogenesis and treatment of these unusual aneurysms are discussed.

Microsurgical treatment of proximal anterior cerebral artery aneurysms

To explore clinic characteristics of proximal anterior cerebral artery aneurysms and analyzed operative techniques. A review was performed of a total of 362 patients whose aneurysms were surgically treated from June 1995 to December 2003, the morbidity of A(1) aneurysms was 2.2%. To reviewed clinical data of 8 proximal anterior cerebral artery aneurysms patients. All of the aneurysms developed at the takeoff point of perforating arteries, the recurrent artery of Heubner in three cases, the medial proximal lenticulostriate artery in five cases. Six cases aneurysms projected posteriorly, two cases projected inferiorly in the surgical field. The shape of the aneurysms was saccular in all cases and diameter no larger than 5 mm in six cases. Patients were clipped satisfactorily, excellent condition in 7 patient, good condition in one. It is important to preserve the perforating arteries and use suitable clip by avoiding cerebral ischemia.

Cerebral Infarction Following Pituitary Apoplexy-Case Report-

A 29-year-old man presented with lethargy, headache, high fever, and visual disturbance. Neurological examination showed mydriatic pupil, ptosis, diminished light reflex, and ophthalmoplegia on the left. Magnetic resonance (MR) imaging showed the typical findings of pituitary apoplexy, and cerebral angiography disclosed mild narrowing of the A1 segment of the left anterior cerebral artery (ACA). Transsphenoidal tumor resection was performed. Transient severe right hemiparesis occurred directly after the operation. Computed tomography demonstrated cerebral infarction in the territory of the left Heubner's and medial lenticulostriate arteries. Pituitary apoplexy followed by cerebral infarction is very rare. Vasospasm of the perforating arteries of the ACA probably caused the cerebral infarction. Subarachnoid blood or vasoactive agents released from the tumor were the most likely cause of the vasospasm. MR imaging findings of contrast enhancement around the vessels may indicate reactive processes around the vessels.

Characteristics of aneurysms arising from the horizontal portion of the anterior cerebral artery

BACKGROUND Aneurysms arising from the proximal portion of the anterior cerebral artery (A 1: horizontal portion) are quite rare and are considered to be unique, because they are usually connected with other vascular anomalies and are sometimes part of a multiple aneurysm occurrence. A 1 aneurysm cases experienced over the past seven and a half years are summarized in this paper. METHODS A total of 413 patients were surgically treated including 142 patients with subarachnoid hemorrhage (SAH); the remaining 271 patients had unruptured aneurysms. Among them, nine cases were categorized as constituent A 1 aneurysms, three with SAH and six with unruptured aneurysms. RESULTS The shape of the aneurysm was saccular in all nine cases. Three of the nine cases had associated vascular malformations. The average aneurysm diameter in the three cases with SAH was 4.0 mm, which is smaller than other common aneurysms presenting with SAH. Eight aneurysms developed at the takeoff point of perforating arteries—the medial lenticulostriate artery in five cases and the recurrent artery of Heubner in three cases. In the remaining case, the aneurysm originated from the proximal end of the associated A 1 fenestration. All nine patients had an excellent outcome after surgery. CONCLUSION A 1 aneurysms require surgical elimination even if they are small. We emphasize the importance of preserving the blood flow of these perforating arteries by avoiding compression with either the clip blade or the clip body itself.

Striatocapsular haemorrhage.

Haemorrhages in the striatocapsular area, or striatocapsular haemorrhages (SCHs), have been regarded as a single entity, although the area is composed of several functionally discrete structures that receive blood supply from different arteries. We analysed the morphological and clinical presentations of 215 cases of SCHs according to a new classification method we have designed on the basis of arterial territories. SCHs were divided into six types: (i) anterior type (Heubner's artery); (ii) middle type (medial lenticulostriate artery); (iii) posteromedial type (anterior choroidal artery); (iv) posterolateral type (posteromedial branches of lateral lenticulostriate artery); (v) lateral type (most lateral branches of lateral lenticulostriate artery); and (vi) massive type. The anterior type (11%) formed small caudate haematomas, always ruptured into the lateral ventricle, causing severe headache, and mild contralateral hemiparesis developed occasionally. The outcome was excellent. The middle type (7%) involved the globus pallidus and medial putamen, frequently causing contralateral hemiparesis and transient conjugate eye deviation to the lesion side. About 50% of the patients recovered to normal. The posteromedial type (4%) formed very small haematomas in the posterior limb of the internal capsule and presented with mild dysarthria, contralateral hemiparesis and sensory deficit, with excellent outcome in general. The posterolateral type (33%) affected the posterior half of the putamen and posterior limb of the internal capsule and presented with impaired consciousness and contralateral hemiparesis with either language dysfunction or contralateral neglect. The outcome was fair to poor but there were no deaths. The lateral type (21%) formed large elliptical haematomas between the putamen and insular cortex. Contralateral hemiparesis with language dysfunction or contralateral neglect developed frequently but resolved over several weeks. The clinical outcome was relatively excellent except when the haematoma size was very large. The massive type (24%) formed huge haematomas affecting the entire striatocapsular area. Marked sensorimotor deficits and impaired consciousness, ocular movement dysfunctions including the 'wrong-way' eyes were observed quite frequently. The outcome was very poor with a case fatality rate of 81%. The clinico-radiological presentations suggested its origin was the same as the posterolateral type.

Ruptured proximal anterior cerebral artery (A1) aneurysm located at an anomalous branching of the fronto-orbital artery--a case report

Cerebral aneurysms are occasionally associated with anomalies of cerebral arteries, that should be recognized pre- and intra-operatively. Most of the previous reports on the anomalies of the anterior cerebral artery have been concerned with hypoplasia, fenestration, and infra-optic course of the A1, variant A1 perforators or Heubner's artery, multi-channeled anterior communicating artery, and azygos anterior cerebral artery. The author experienced a patient with a ruptured proximal anterior cerebral artery (A1) aneurysm located at an anomalous origin of the fronto-orbital artery from the A1. The fronto-orbital artery normally branches off the anterior cerebral artery just distal to the anterior communicating artery (proximal A2). An anomalous branching of the fronto-orbital artery off the A1 seems very rare. This anomalous artery could be mistaken for an unusually large medial lenticulostriate artery, aberrant frontopolar artery, or the third A2. The author reviewed the literature on anomalies of the A1 and the fronto-orbital artery.

Deep Perforators From the Carotid System

Most reports on small infarcts in the territory of the deep perforators that arise from the internal carotid artery and its branches have focused on the anatomical structures. Recently, it has become possible to map the territories of the deep perforators from the carotid system, based on matching previous anatomical studies with recent data from computed tomographic and magnetic resonance imaging studies. The middle cerebral artery gives origin to two main groups of perforators: the medial and lateral lenticulostriate arteries. Rarely, the thalamotuberal artery may take origin from the middle cerebral artery but much more commonly it originates from the posterior communicating artery. The anterior cerebral artery gives origin to the anterior lenticulostriate arteries and the recurrent artery of Heubner. The anterior choroidal artery takes its origin from the internal carotid artery and exceptionally from the middle cerebral artery. In addition, a small group of perforators comes directly from the internal carotid artery. The anatomical structures supplied by these perforators are described, and a map of the territories is proposed.

An Enlarging Intraventricular Arteriovenous Malformation

A case is presented in which an enlargement of an intraventricular arteriovenous malformation (AVM) was noted over the period of two years. The patient, a 15-year-old male, was first admitted in December 1980, at the age of 13 years, when he had a sudden onset of headache. Computed tomography (CT) scan showed an intraventricular hemorrhage. Cerebral angiography revealed a small AVM in the left frontal lobe. He was treated conservatively and discharged. In October 1981, the patient was readmitted because of a recurrent intraventricular hemorrhage and was treated conservatively. The third admission was at the age of 15, in November 1982, at which time he suffered again from the intraventricular hemorrhage seen on CT scan. Cerebral angiography showed an enlarged AVM which was supplied by one of the medial lenticulostriate arteries. A right frontotemporal craniotomy was performed in December 1982. As the initial step, the feeding artery was clipped and the AVM located in the wall of the left frontal horn was completely resected microscopically through the transcallosal approach. The histological examination showed a typical AVM. Transcallosal surgery is a useful approach for lesions in the anterior ventricular system. It is assumed that the enlargement of the AVM occurred in the periventricular area which was weakened in resistance by recurrent hemorrhages. No neuropsychological complications were encountered following the section of the anterior part of the corpus callosum.

Technique of catheterization and embolization of the lenticulostriate arteries

✓ The technique of catheterization and embolization of the lateral and medial lenticulostriate arteries, using one or two balloon catheters of various designs, is described. A case of a bilateral thalamic arteriovenous malformation is presented and a further instance of an aneurysm of a striate artery is briefly discussed. Because of the high probability of proximal middle cerebral artery (MCA) thrombosis, care must be taken to determine tolerance to MCA occlusion prior to embolization.