Arteries of the insula

Surgery for Nontumoral Insular Epilepsy Explored by Stereoelectroencephalography

BACKGROUND

Hidden by the perisylvian operculi, insular cortex has long been underexplored in the context of epilepsy surgery. Recent studies advocated stereoelectroencephalography (SEEG) as a reliable tool to explore insular cortex and its involvement in intractable epilepsy and suggested that insular seizures could be an underestimated entity. However, the results of insular resection to treat pharmacoresistant epilepsy are rarely reported.

OBJECTIVE

We report 6 consecutive cases of right insular resection performed based on anatomoelectroclinical correlations provided by SEEG.

METHODS

Six right-handed patients (3 male, 3 female) with drug-resistant epilepsy underwent comprehensive presurgical evaluation. Based on video electroencephalographic recordings, they all underwent SEEG evaluation with bilateral (n = 4) or unilateral right (n = 2) insular depth electrode placement. All patients had both orthogonal and oblique (1 anterior, 1 posterior) insular electrodes (n = 4-6 electrodes). Preoperative magnetic resonance imaging findings were normal in 4 patients, 1 patient had right insular focal cortical dysplasia, and 1 patient had a right opercular postoperative scar (cavernous angioma). All patients underwent right partial insular corticectomy via the subpial transopercular approach.

RESULTS

Intracerebral recordings demonstrated an epileptogenic zone confined to the right insula in all patients. After selective insular resection, 5 of 6 patients were seizure free (Engel class I) with a mean follow-up of 36.2 months (range, 18-68 months). Histological findings revealed focal cortical dysplasia in 5 patients and a gliosis scar in 1 patient. All patients had minor transient neurological deficit (eg, facial paresis, dysarthria).

CONCLUSION

Insular resection based on SEEG findings can be performed safely with a significant chance of seizure freedom.

Intraparenchymal Hyperattenuations on Flat-Panel CT Directly After Mechanical Thrombectomy are Restricted to the Initial Infarct Core on Diffusion-Weighted Imaging

PURPOSE

The presence of intraparenchymal hyperattenuations (IPH) on flat-panel computed tomography (FP-CT) after endovascular recanalization in stroke patients is a common phenomenon. They are thought to occur in ischemic areas with breakdown of the blood-brain barrier but previous studies that investigated a mutual interaction are scarce. We aimed to assess the relationship of IPH localization with prethrombectomy diffusion-weighted imaging (DWI) lesions.

METHODS

This retrospective multicenter study included 27 acute stroke patients who underwent DWI prior to FP-CT following mechanical thrombectomy. After software-based coregistration of DWI and FP-CT, lesion volumetry was conducted and overlapping was analyzed.

RESULTS

Two different patterns were observed: IPH corresponding to the DWI lesion and IPH exceeding the DWI lesion. The latter showed demarcated infarction of DWI exceeding IPH at 24 h. No major hemorrhage following IPH was observed. Most IPH were manifested within the basal ganglia and insular cortex.

CONCLUSION

The IPH primarily appeared within the initial ischemic core and secondarily within the penumbral tissue that progressed to infarction. The IPH represent the minimum final infarct volume, which may help in periinterventional decision making.

Putamen involvement and survival outcomes in patients with insular low-grade gliomas

OBJECTIVE Insular glioma has a unique origin and biological behavior; however, the associations between its anatomical features and prognosis have not been well established. The object of this study was to propose a classification system of insular low-grade gliomas based on preoperative MRI findings and to assess the system's association with survival outcome. METHODS A total of 211 consecutively collected patients diagnosed with low-grade insular gliomas was analyzed. All patients were classified according to whether tumor involved the putamen on MR images. The prognostic role of this novel putaminal classification, as well as that of Yaşargil's classification, was examined using multivariate analyses. RESULTS Ninety-nine cases (46.9%) of insular gliomas involved the putamen. Those tumors involving the putamen, as compared with nonputaminal tumors, were larger (p < 0.001), less likely to be associated with a history of seizures (p = 0.04), more likely to have wild-type IDH1 (p = 0.003), and less likely to be totally removed (p = 0.02). Significant favorable predictors of overall survival on univariate analysis included a high preoperative Karnofsky Performance Scale score (p = 0.02), a history of seizures (p = 0.04), gross-total resection (p = 0.006), nonputaminal tumors (p < 0.001), and an IDH1 mutation (p < 0.001). On multivariate analysis, extent of resection (p = 0.035), putamen classification (p = 0.014), and IDH1 mutation (p = 0.026) were independent predictors of overall survival. No prognostic role was found for Yaşargil's classification. CONCLUSIONS The current study's findings suggest that the putamen classification is an independent predictor of survival outcome in patients with insular low-grade gliomas. This newly proposed classification allows preoperative survival prediction for patients with insular gliomas.

Isolated left posterior insular infarction and convergent roles in verbal fluency, language, memory, and executive function

The posterior insular cortex-a complex structure interconnecting various brain regions for different functions-is a rare location for ischemic stroke. We report a patient with isolated left posterior insular infarction who presented with multiple cognitive impairment, including impairment in semantic and phonemic verbal fluency.

Indocyanine green as an adjunct for resection of insular gliomas

Objective:

Many controversies exist regarding the extent of resection for insular gliomas and the timing of resection. Several techniques and adjuncts are used to maximize safety during resection of these tumors. We describe the use of indocyanine green (ICG) to identify the branches of the middle cerebral artery and discuss its utility to increase safety for resection for insular gliomas.

Materials and Methods:

Five patients with insular gliomas were surgically treated by the authors from June 2013 to June 2014. The patients presented with complaints of either a headache or recurring episodes of convulsions. All the patients were operated with the aid of neuronavigation and tractography. The long perforating branches of the middle cerebral artery course through the insula and pass onward to supply the corona radiata. It is essential to preserve these vessels to prevent postoperative neurological deficits. ICG (Aurogreen) was used to identify and preserve the long perforating arteries of the middle cerebral artery.

Results:

ICG dye correctly identified the long perforating branches of the middle cerebral artery and easily distinguished these vessels from the short perforating branches. All the branches of the middle cerebral artery that coursed through the tumor and had an onward course were preserved in all the patients. Only one patient developed a transient right sided hemiparesis that had improved at follow-up.

Conclusions:

Surgery for insular gliomas is challenging due to its location adjacent to eloquent areas, important white fiber tracts and the course of the middle cerebral artery within it. ICG is useful to identify and preserve the long perforating branches of the middle cerebral artery that course through the tumor and traverse onward to supply the corona radiata.

The transsylvian approach for resection of insular gliomas: technical nuances of splitting the Sylvian fissure

Insular gliomas represent a unique surgical challenge due to the complex anatomy and nearby vascular elements associated within the Sylvian fissure. For certain tumors, the transsylvian approach provides an effective technique for achieving maximal safe resection. The goal of this manuscript and video are to present and discuss the surgical nuances and appropriate application of splitting the Sylvian fissure. Our hope is that this video highlights the safety and efficacy of the transsylvian approach for appropriately selected insular gliomas.

A Digital Atlas of Middle to Large Brain Vessels and Their Relation to Cortical and Subcortical Structures

While widely distributed, the vascular supply of the brain is particularly prominent in certain anatomical structures because of the high vessel density or their large size. A digital atlas of middle to large vessels in Montreal Neurological Institute (MNI) coordinates is here presented, obtained from a sample of N = 38 healthy participants scanned with the time-of-flight (TOF) magnetic resonance technique, and normalized with procedures analogous to those commonly used in functional neuroimaging studies. Spatial colocalization of brain parenchyma and vessels is shown to affect specific structures such as the anteromedial face of the temporal lobe, the cortex surrounding the Sylvian fissure (Sy), the anterior cingular cortex, and the ventral striatum. The vascular frequency maps presented here provide objective information about the vascularization of the brain, and may assist in the interpretation of data in studies where vessels are a potential confound.

Visualization of lenticulostriate arteries during insular low-grade glioma surgeries by navigated 3D ultrasound power Doppler: technical note

OBJECTIVE Resection of insular gliomas is challenging. In cases of intraoperative injury to the lenticulostriate arteries (LSAs), the usual result is a dense hemiplegia. LSAs are usually localized just behind the medial tumor border but they can also be encased by the tumor. Thus, exact localization of these perforators is important. However, intraoperative localization of LSAs using conventional neuronavigation can be difficult due to brain shift. In this paper, the authors present a novel method of intraoperative LSA visualization by navigated 3D ultrasound (3DUS) power Doppler. This technique enables almost real-time imaging of LSAs and evaluation of their shift during insular tumor resections. METHODS Six patients harboring insular Grade II gliomas were consecutively operated on at the Department of Neurosurgery in Bratislava using visualization of LSAs by navigated 3DUS power Doppler. In all cases, the 3DUS data were repeatedly updated to compensate for the brain shift and display the actual position of LSAs and residual tumor. RESULTS Successful visualization of LSAs was achieved in all cases. During all surgeries, the distance between the bottom of the resection cavity and LSAs could be accurately evaluated; in all tumors the resection approached the LSAs and only a minimal amount of tissue covering these perforators was intentionally left in place to avoid injury to them. CONCLUSIONS Visualization of LSAs by navigated 3DUS power Doppler is a useful tool that may help to prevent injury of LSAs during removal of insular low-grade gliomas. However, reliability of this method has to be carefully evaluated in further studies.

Surgical assessment of the insula. Part 1: surgical anatomy and morphometric analysis of the transsylvian and transcortical approaches to the insula

OBJECT

Transcortical and transsylvian corridors have been previously described as the main surgical approaches to the insula, but there is insufficient evidence to support one approach versus the other. The authors performed a cadaveric comparative study regarding insular exposure, surgical window and freedom, between the transcortical and transsylvian approaches (with and without cutting superficial sylvian bridging veins). Surgical anatomy and skull surface reference points to the different insular regions are also described.

METHODS

Sixteen cadaveric specimens were embalmed with a customized formula to enhance neurosurgical simulation. Two different blocks were defined in the study: first, transsylvian without (TS) and with the superficial sylvian bridging veins cut (TSVC) and transcortical (TC) approaches to the insula were simulated in all (16) specimens. Insular surface exposure, surgical window and surgical freedom were calculated for each procedure and related to the Berger-Sanai insular glioma classification (Zones I–IV) in 10 specimens. Second, the venous drainage pattern and anatomical landmarks considered critical for surgical planning were studied in all specimens.

RESULTS

In the insular Zone I (anterior-superior), the TC approach provided the best insular exposure compared with both TS and TSVC. The surgical window obtained with the TC approach was also larger than that obtained with the TS. The TC approach provided 137% more surgical freedom than the TS approach. Only the TC corridor provided complete insular exposure. In Zone II (posterior-superior), results depended on the degree of opercular resection. Without resection of the precentral gyrus in the operculum, insula exposure, surgical windows and surgical freedom were equivalent. If the opercular cortex was resected, the insula exposure and surgical freedom obtained through the TC approach was greater to that of the other groups. In Zone III (posterior-inferior), the TC approach provided better surgical exposure than the TS, yet similar to the TSVC. The TC approach provided the best insular exposure, surgical window, and surgical freedom if components of Heschl’s gyrus were resected. In Zone IV (anterior-inferior), the TC corridor provided better exposure than both the TS and the TSVC. The surgical window was equivalent. Surgical freedom provided by the TC was greater than the TS approach. This zone was completely exposed only with the TC approach. A dominant anterior venous drainage was found in 87% of the specimens. In this group, 50% of the specimens had good alternative venous drainage. The sylvian fissure corresponded to the superior segment of the squamosal suture in 14 of 16 specimens. The foramen of Monro was 1.9 cm anterior and 4.42 cm superior to the external acoustic meatus. The M2 branch over the central sulcus of the insula became the precentral M4 (rolandic) artery in all specimens.

CONCLUSIONS

Overall, the TC approach to the insula provided better insula exposure and surgical freedom compared with the TS and the TSVC. Cortical and subcortical mapping is critical during the TC approach to the posterior zones (II and III), as the facial motor and somatosensory functions (Zone II) and language areas (Zone III) may be involved. The evidence provided in this study may help the neurosurgeon when approaching insular gliomas to achieve a greater extent of tumor resection via an optimal exposure.

The association of insular stroke with lesion volume

The insula has been implicated in many sequelae of stroke. It is the area most commonly infarcted in people with post-stroke arrhythmias, loss of thermal sensation, hospital acquired pneumonia, and apraxia of speech. We hypothesized that some of these results reflect the fact that: (1) ischemic strokes that involve the insula are larger than strokes that exclude the insula (and therefore are associated with more common and persistent deficits); and (2) insular involvement is a marker of middle cerebral artery (MCA) occlusion. We analyzed MRI scans of 861 patients with acute ischemic hemispheric strokes unselected for functional deficits, and compared infarcts involving the insula to infarcts not involving the insula using t-tests for continuous variables and chi square tests for dichotomous variables. Mean infarct volume was larger for infarcts including the insula (n = 232) versus excluding the insula (n = 629): 65.8 ± 78.8 versus 10.2 ± 15.9 cm³ (p < 0.00001). Even when we removed lacunar infarcts, mean volume of non-lacunar infarcts that included insula (n = 775) were larger than non-lacunar infarcts (n = 227) that excluded insula: 67.0 cm³ ± 79.2 versus 11.5 cm³ ± 16.7 (p < 0.00001). Of infarcts in the 90th percentile for volume, 87% included the insula (χ² = 181.8; p < 0.00001). Furthermore, 79.0% infarcts due to MCA occlusion included the insula; 78.5% of infarcts without MCA occlusion excluded the insula (χ² = 93.1; p < 0.0001). The association between insular damage and acute or chronic sequelae likely often reflects the fact that insular infarct is a marker of large infarcts caused by occlusion of the MCA more than a specific role of the insula in a range of functions. Particularly in acute stroke, some deficits may also be due to ischemia of the MCA or ICA territory caused by large vessel occlusion.

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The insula is the most commonly infarcted area in patients with a wide range of deficits.

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In 861 acute ischemic hemispheric strokes, mean infarct volume was much larger when infarct included the insula (p < 0.00001).

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Of infarcts in the 90th percentile for volume, 87% included the insula (χ² = 181.8; p < 0.00001).

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Nearly 80% of infarcts due to MCA occlusion included the insula

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Identified associations between insular infarct and deficits should control for lesion volume.

Arteries and Veins of the Sylvian Fissure and Insula: Microsurgical Anatomy

We present a vascular anatomical study of the arteries and veins of the sylvian fissure and insula.A good knowledge of the sylvian fissure, the insula, and their vascular relationship would seem mandatory before performing surgery in this area, whatever the type of surgery (aneurysms, arteriovenous malformations, insular tumors).We start with the sylvian fissure and insula morphology, followed by the MCA description and its perforators, with special attention paid to the insular perforators. We demonstrate that the long insular perforators penetrating in the superior part of the posterior short gyrus and long gyri vascularize, respectively, the corticonuclear and corticospinal fasciculi. We particularly insist too on three anatomical constants regarding the vascularization of the insula, already described in the literature: The superior periinsular sulcus is the only sulcus on the lateral surface of the brain without an artery along its axis; the superior branch of the MCA supplies the anterior insular pole and both the anterior and middle short gyri in 100 % of cases; in at least 90 % of cases, the artery that supplied the central insular sulcus continued on to become the central artery.We end with the anatomical study of the veins and cisterns.

[Review of surgical treatment of insular gliomas: challenges and opportunities]

Intracerebral tumors of the insular lobe are quite frequent, however treatment of patients with this pathology still remains a challenging and controversial issue of neurosurgery. First of all, this is associated with the localization of tumors in the area of eloquent anatomical structures: M1--M2 segment of the middle cerebral artery, lenticulostriate arteries, basal ganglia, and internal capsule, which causes a high rate of postoperative complications in these patients. Most insular tumors are amenable for resection with a reasonable rate of postoperative complications, although most of the surgery-related complications resulting in substantial deficits are due to lesions of eloquent anatomical structures located in this compact anatomical space. Therefore, the aim of this work was to analyze the literature regarding the issues of clinical presentation, diagnosis, and aspects of surgical treatment of insular tumors.

Results of re-exploration because of compromised distal blood flow after clipping unruptured intracranial aneurysms

BACKGROUND

One of the major causes for performing unplanned re-exploration of a craniotomy after microsurgery for unruptured intracranial aneurysms (UIAs) is compromised distal blood flow after clipping. Therefore, it is important to identify the causes of compromised distal blood flow after clipping and the factors that influence the prognosis for re-exploration in order to decrease ischemic complications related to clipping UIAs.

METHOD

Between January 2007 and December 2013, 1954 patients underwent microsurgery for UIAs. In this cohort, 20 patients (1.0%) required unplanned re-exploration of the craniotomy for several reasons, and 11 patients (0.6%) underwent unplanned re-exploration with clip repositioning or changing of the previous clip because of compromised distal blood flow after clipping. Patient characteristics, aneurysm properties, intraoperative findings, annual incidence and prognosis were analyzed in these 11 patients.

RESULTS

The annual incidence of re-exploration has gradually decreased since the introduction of several intraoperative monitoring techniques. In total, 3.0% of UIAs in the M1 trunk, 0.8% of UIAs at the origin of the anterior choroidal artery (AchA) and 0.5% of UIAs at the bifurcation of the middle cerebral artery (MCA) required re-exploration. Here, all 11 UIAs had broad necks, and atherosclerosis was identified around 10 UIAs. Six patients with compromised MCA flow demonstrated relatively better outcomes following re-exploration than five patients with a compromised lenticulostriate artery (LSA) or AchA flow. Four patients with delayed ischemic symptoms demonstrated relatively better outcomes than the seven patients who developed ischemic symptoms immediately postoperatively.

CONCLUSION

Clinicians need to be more careful not to compromise distal blood flow when clipping UIAs at the MCA and AchA origin. Various intraoperative monitoring techniques can help reduce the incidence of compromised distal blood flow after clipping.

Vascular consequences of operculoinsular corticectomy for refractory epilepsy

OBJECT

Surgery in the insular region is considered challenging because of its vascular relationships, the proximity of functional structures, and its deep location in the sylvian fissure. The authors report the incidence and consequences of ischemic lesions after operculoinsular corticectomy for refractory epilepsy.

METHODS

The authors retrospectively reviewed the data of all patients who underwent an insular resection with or without an opercular resection for refractory epilepsy at their center. All patients underwent postoperative MRI, enabling a radiological analysis of the ischemic lesions as a result of the corticectomies. The resections were classified according to the location and extent of the insular corticectomy and the type of operculectomy. Each patient underwent clinical follow-up.

RESULTS

Twenty patients underwent surgery. All patients underwent insular corticectomy with or without an operculectomy. Ischemic lesions were identified in 12 patients (60%). In these patients, 11 ischemic lesions (55%) were related to the insular corticectomy, and 1 was related to the associated periinsular resection. The ischemic lesions associated with the insulectomies were typically located in the corona radiata running from the insula to the periventricular region. Nine patients (45%) developed a postoperative neurological deficit, among whom 6 (67%) had an insular corticectomy–related ischemic lesion. All reported neurological deficits were transient. Five patients (25%) had ischemic lesions without neurological deficit.

CONCLUSIONS

Operculoinsular corticectomies are associated with ischemic lesions in approximately 60% of patients. However, given that no patient had a definitive postoperative deficit, these ischemic lesions have few clinical consequences. Therefore, this surgical procedure can be considered reasonably safe for the treatment of refractory epilepsy.

Hemispheric differences in malignant middle cerebral artery stroke

BACKGROUND

We recently reported that left versus right hemisphere cerebral infarctions patients more frequently have worse outcomes. However our clinical experience led us to suspect that the incidence of malignant middle cerebral artery infarctions (MMCA) was higher in the right compared to the left hemispheric strokes.

OBJECTIVE

To determine whether laterality in MMCA stroke is an important determinant of stroke sequelae.

METHODS

A systematic search was performed for publications in PubMed using "malignant middle cerebral artery and infarction". A total of 73 relevant studies were abstracted.

RESULTS

MMCA laterality data were available for 2673 patients, with 1687 (63%) right hemispheric involvement, thus right being more commonly associated with MMCA (binomial test, p<0.05). While mortality rates were similar, right hemispheric MMCA (n=271) had mortality of 31% (n=85) whereas left hemispheric MMCA (n=144) had mortality of 36% (n=53), morbidity rates were worse on the right.

CONCLUSION

MMCA stroke appears to be more common on the right, and this laterality is also associated with significantly higher morbidity. Further prospective studies are needed to more completely understand the nature of this laterality as well as test possible new treatments to reduce mortality and morbidity associated with MMCA.

Technical nuances for surgery of insular gliomas: lessons learned

Insular gliomas were traditionally considered a nonsurgical entity due to the high morbidity associated with resection. For the past 20 years, advances in microsurgical and brain mapping techniques have allowed neurosurgeons to resect insular gliomas with acceptable morbidity rates. Maximizing the extent of resection is nowadays the goal of surgery since this has proven to be an independent factor contributing to longer survival. Despite much progress, insular tumors remain a challenge for the neurosurgeon due to the complex anatomy of the region and technical expertise required to minimize morbidity during surgery. Herein, the authors describe the current surgical nuances, based on their experience and a literature review, that will allow the surgeon to achieve a thorough resection while ensuring patient safety. The key factors for successful surgery in the insular region include detailed knowledge of the surgical anatomy, mastery of the nuances of cortical and subcortical mapping methods, and meticulous microsurgical technique.

Transcranial color-coded duplex sonography of the middle cerebral artery: more than just the M1 segment

OBJECTIVES

Routine sonography of the middle cerebral artery in acute ischemic stroke usually focuses on the main stem (M1 segment). However, stenoses and occlusions affect not only proximal but also more distal vessel branches, such as the M2 segments. Transcranial color-coded duplex sonography allows visualization of these segments; however, a formal analysis and description of normal blood flow values are missing. The purpose of this study was to analyze middle cerebral artery branching patterns with transcranial color-coded duplex sonography and to establish reference flow velocity values in the detectable M2 branches as well as the early temporal M1 branch.

METHODS

Transcranial color-coded duplex sonography in the axial and coronal planes was performed in 50 participants without vascular disease and with a good temporal bone window (ie, fully visible M1 middle cerebral artery segment and A1 anterior cerebral artery segment). We analyzed the course and branching pattern of the M1 segment, including anatomic variants such as an early temporal M1 branch, and measured the length and flow parameters of the detectable M2 branches.

RESULTS

Assessment of 100 hemispheres allowed classification into 3 anatomic patterns: M1 bifurcation (63%), M1 trifurcation (32%), and medial M1 branching into 2 major segments (2%). A clear distinction was not possible in 3 cases (3%). An early temporal M1 branch was detected in the coronal plane in 26%.

CONCLUSIONS

Transcranial color-coded duplex sonography is a useful tool for analyzing anatomic variants and branching patterns of the middle cerebral artery as well as flow characteristics of M2 segments. Therefore, it also has potential to increase the diagnostic yield for the detection of middle cerebral artery disease in these vessel segments.

Surgical anatomy of the insular cortex

OBJECTIVE

The objective of the study was to investigate the surgical anatomy of the insular cortex, morphology and vascularization of the insula and adjacent opercula in terms of transsylvian and transcortical approaches, and identification of the permissible anatomical boundaries for resection of glial tumors of the insula.

MATERIAL AND METHODS

The study was conducted on 18 anatomical specimens fixed in an alcohol-glycerol solution. Perfusion of the internal carotid artery with red latex was used to study the arterial system. Dissection of the arteries and Sylvian fissure, investigation of the morphological features of the opercula as well as simulation of the transsylvian and transcortical approaches to the insula were performed using a surgical microscope, in a certain sequence.

RESULTS

In the trassylvian approach, the anteroinferior part of the insula (including the limen insulae) is the most technically easy-to-reach area, whereas the superior parts of the insula are the most difficult-to-reach areas. With the tumor localized in the superior insula, the transcortical approach may be recommended that, unlike the transsylvian approach, does not require a significant retraction of the brain matter and provides a larger surgical corridor. The transcortical approach, regardless the insular region, provides a better surgical view and workspace compared to the transsylvian approach. However, the previous approach is characterized by less access to the important anatomical landmarks such as the peri-insular sulci, limen insulae, and lateral lenticulostriate arteries. Furthermore, the approach requires dissection of the brain matter of the frontal and temporal lobes.

CONCLUSION

Detailed knowledge of the surgical anatomy of the insular region provides correct intraoperative identification of a number of the major anatomical landmarks (limen insulae, peri-insular sulci, most distal lenticulostriate artery) and facilitates choosing the proper surgical approach.

Percentage insula ribbon infarction of >50% identifies patients likely to have poor clinical outcome despite small DWI infarct volume

BACKGROUND AND PURPOSE

Large admission DWI infarct volume (>70 mL) is an established marker for poor clinical outcome in acute stroke. Outcome is more variable in patients with small infarcts (<70 mL). Percentage insula ribbon infarct correlates with infarct growth. We hypothesized that percentage insula ribbon infarct can help identify patients with stroke likely to have poor clinical outcome, despite small admission DWI lesion volumes.

MATERIALS AND METHODS

We analyzed the admission NCCT, CTP, and DWI scans of 55 patients with proximal anterior circulation occlusions on CTA. Percentage insula ribbon infarct (>50%, ≤50%) on DWI, NCCT, CT-CBF, and CT-MTT were recorded. DWI infarct volume, percentage DWI motor strip infarct, NCCT-ASPECTS, and CTA collateral score were also recorded. Statistical analyses were performed to determine accuracy in predicting poor outcome (mRS >2 at 90 days).

RESULTS

Admission DWI of >70 mL and DWI-percentage insula ribbon infarct of >50% were among significant univariate imaging markers of poor outcome (P < .001). In the multivariate analysis, DWI-percentage insula ribbon infarct of >50% (P = .045) and NIHSS score (P < .001) were the only independent predictors of poor outcome. In the subgroup with admission DWI infarct of <70 mL (n = 40), 90-day mRS was significantly worse in those with DWI-percentage insula ribbon infarct of >50% (n = 9, median mRS = 5, interquartile range = 2-5) compared with those with DWI-percentage insula ribbon infarct of ≤50% (n = 31, median mRS = 2, interquartile range = 0.25-4, P = .036). In patients with admission DWI infarct of >70 mL, DWI-percentage insula ribbon infarct did not have added predictive value for poor outcome (P = .931).

CONCLUSIONS

DWI-percentage insula ribbon infarct of >50% independently predicts poor clinical outcome and can help identify patients with stroke likely to have poor outcome despite small admission DWI lesion volumes.

Neuroanatomic correlates of poststroke hyperglycemia

OBJECTIVE

A study was undertaken to determine associations between ischemic stroke sites and poststroke hyperglycemia (PSH).

METHODS

Nondiabetic patients with first ever ischemic stroke confirmed by imaging were prospectively included. Blood glucose level (BGL), National Institute of Health Stroke Scale (NIHSS) score, and clinical parameters were assessed on admission. BGL was dichotomized for elevated versus normal levels using a cutoff value of >7.0 mmol/l. Clinical parameters were correlated with BGL and were compared between patient groups with elevated versus normal glucose values. A voxel-based lesion symptom mapping (VLSM) analysis adjusted for confounding variables was performed correlating sites of ischemic lesions with PSH.

RESULTS

Of 1,281 stroke patients screened, 229 (mean age = 66.3 ± 15.9 years) met the inclusion criteria. Patients with elevated BGL were older, had higher NIHSS scores, and had larger infarcts compared to those without elevated glucose levels. Spearman rank analysis showed correlations between BGL and age, infarct size, heart rate (HR), and NIHSS scores (p ≤ 0.05). The VLSM analysis adjusted for these confounding factors demonstrated associations between PSH and damaged voxels in right hemispheric insular and opercular areas.

INTERPRETATION

The data indicate that damage in the right insulo-opercular areas contributes to PSH. The association between sympathetically mediated increase of HR and BGL suggests disinhibition of sympathetic outflow as a possible mechanism for PSH.

Scoring flow restoration in cerebral angiograms after endovascular revascularization in acute ischemic stroke patients

Endovascular revascularization techniques are increasingly used to treat arterial occlusions in patients with acute ischemic stroke. To monitor and communicate treatment results, a valid, reproducible, and clinically relevant, yet easy to use grading scheme of arterial recanalization and tissue reperfusion for digital subtraction angiography is needed. An ideal scoring system would consider the target arterial lesion, the perfusion deficit, and the collateral status before treatment and measure recanalization, reperfusion, early venous shunting, vasospasm, as well as distal embolization after flow restoration. Currently, a variety of different flow restoration scales are in use, including the Thrombolysis in Myocardial Infarction scoring system, the Thrombolysis in Cerebral Infarction score, and the Arterial Occlusive Lesion score, which describe the local recanalization result. These scores are not used homogeneously throughout the literature, are often modified and not fully documented, which make them inept to compare treatment effects across studies. In addition, none of these scores cover all of the above-mentioned aspects, nor are they able to describe satisfactorily all relevant angiographic findings, and data on their reliability and predictive power regarding clinical outcome are sparse. We aimed to review and illustrate the different revascularization scales, discuss their advantages and limitations as well as the available data regarding standardization, reliability testing, and outcome prediction. In addition, we give examples for the use of the scales and show potential pitfalls.

Practical surgical indicators to identify candidates for radical resection of insulo-opercular gliomas

Object

Maximum resection of gliomas with minimum surgical complications usually leads to optimum outcomes for patients. Radical resection of insulo-opercular gliomas is still challenging, and selection of ideal patients can reduce risk and obtain better outcomes.

Methods

This retrospective study included 83 consecutively treated patients with newly diagnosed gliomas located at the insulo-opercular region and extending to the sylvian fissure around the primary motor and somatosensory cortices. The authors selected 4 characteristics as surgical indicators: clear tumor boundaries, negative enhancement, intact lenticulostriate arteries, and intact superior extremity of the central insular sulcus.

Results

Univariate analysis showed that tumors with clear boundaries were associated with higher rates of gross-total resection than were tumors with ambiguous boundaries (75.7% vs 19.6%). Tumors with negative enhancement compared with enhanced tumors were associated with lower frequency of tumor progression (32.0% vs 81.8%, respectively) and lower rates of surgical complications (14.0% vs 45.5%, respectively). Tumors with intact lenticulostriate arteries were associated with higher rates of gross-total resection than were tumors with involved lenticulostriate arteries (67.3% vs 11.8%, respectively). Tumors with intact superior extremity of the central insular sulcus were associated with higher rates of gross-total resection (57.4% vs 20.7%, respectively) and lower rates of surgical complications (18.5% vs 41.4%, respectively) than were tumors with involved anatomical structures. Multivariate analysis showed that clear tumor boundaries were independently associated with gross-total resection (p < 0.001). Negative enhancement was found to be independently associated with surgical complications (p = 0.005), overall survival times (p < 0.001), and progression-free survival times (p = 0.004). Independent associations were also found between intact lenticulostriate arteries and gross-total resection (p < 0.001), between intact lenticulostriate arteries and progression-free survival times (p = 0.026), and between intact superior extremity of the central insular sulcus and gross-total resection (p = 0.043). Among patients in whom all 4 indicators were present, prognosis was good (5-year survival rate 93.3%), resection rate was maximal (gross-total resection 100%), and surgical complication rate was minimal (6.7%). Also among these patients, overall rates of survival (p = 0.003) and progression-free survival (p = 0.005) were significantly higher than among patients in whom fewer indicators were present.

Conclusions

The authors propose 4 simple indicators that can be used to identify ideal candidates for radical resection of insulo-opercular gliomas, improve the outcomes, and promote maximum resection without introducing neurological complications. The indicators are clear tumor boundaries, negative enhancement, intact lenticulostriate arteries, and intact superior extremity of the central insular sulcus.

Microanatomical study of the insular perforating arteries

BACKGROUND

The insular perforating arteries originate from the middle cerebral artery. They have only been very partially described up to now. In the literature, they come from the M2 segment and three types are listed: the short, medium and long perforators. The first two types supply the claustrum as well as the external and extreme capsules.

OBJECTIVE

We describe the anatomy of long perforating insular arteries and their arterial contribution to the main white matter bundles of the oval center of Vieussens.

MATERIALS AND METHOD

Twenty adult cadaveric hemispheres were studied after perfusion of the arteries and veins with colored latex. The arteries were dissected and photographed under an operating microscope.

RESULTS

The long insular perforating arteries come from the M2 segment or from the junction of the M2 and M3 segments and sometimes from the M3 segment. They often perforate the insular cortex on the top of the posterior short insular gyrus and the insular long gyri, or in the superior peri-insular sulcus, before coming together in the oval center. At this level, they give arterial contribution to the main white matter bundles such as corticospinal and corticonuclear tracts for motricity, and the arcuate fasciculus and the occipitofrontal tract for language in the dominant hemisphere.

CONCLUSION

These perforating arteries have to be carefully respected during insular surgery to avoid neurologic weakness.

Innervation of the brain, intracerebral Schwann cells and intracerebral and intraventricular schwannomas

The cerebral vasculature and the choroid plexus are innervated by peripheral nerves. The anatomy of the vascular supply to the brain and its related perivascular nerves is reviewed. Intracerebral and intraventricular schwannomas most likely come from neoplastic transformation of Schwann cells investing the perivascular nerves and nerves within the choroid plexus.

Microsurgical anatomy of the transsylvian translimen insula approach to the mediobasal temporal lobe: Technical considerations and case illustration

Background:

Various vascular, neoplastic, and epileptogenic pathologies occur in the mediobasal temporal region. A transsylvian translimen insula (TTI) approach can be used as an alternative to temporal transcortical approach to the mediobasal temporal region. The aim of this study was to demonstrate the surgical anatomy of the TTI approach, including the gyral, sulcal, and vascular anatomy in and around the limen insula. The use of this approach is illustrated in the resection of a complex arteriovenous malformation.

Methods:

The TTI approach to the mediobasal temporal region was performed on three silicone-injected cadaveric heads. The gyral, sulcal, and arterial anatomy of the limen insula was studied in six formalin-fixed injected hemispheres.

Results:

The TTI approach provided access to the anterior and middle segments of the mediobasal temporal lobe region as well as allowing access to temporal horn of the lateral ventricle. Using this approach we were able to successfully resect an arteriovenous malformation of the dominant medial temporal lobe.

Conclusion:

The TTI approach provides a viable surgical route to the region of mediobasal temporal lobe region. This approach offers an advantage over the temporal transcortical route in that there is less risk of damage to optic radiations and speech area in the dominant hemisphere.

Admission insular infarction >25% is the strongest predictor of large mismatch loss in proximal middle cerebral artery stroke

BACKGROUND AND PURPOSE

Previous univariate analyses have suggested that proximal middle cerebral artery infarcts with insular involvement have greater severity and are more likely to progress into surrounding penumbral tissue at risk. We hypothesized that a practical, simple scoring method to assess percent insular ribbon infarction (PIRI score) would improve prediction of penumbral loss over other common imaging biomarkers.

METHODS

Of consecutive acute stroke patients from 2003 to 2008, 45 with proximal middle cerebral artery-only occlusion met inclusion criteria, including available penumbral imaging. Infarct (diffusion-weighted imaging), tissue at risk (magnetic resonance mean transit time), and final infarct volume (magnetic resonance/computed tomography) were manually segmented. Diffusion-weighted imaging images were rated according to the 5-point PIRI score (0, normal; 1, <25%; 2, 25%-49%; 3, 50%-74%; 4, ≥75% insula involvement). Percent mismatch loss was calculated as an outcome measure of infarct progression. Receiver operating characteristic curve and multivariate analyses were performed.

RESULTS

Mean admission diffusion-weighted imaging infarct volume was 30.9 (±38.8) mL and median (interquartile range) PIRI score was 3 (0.75-4). PIRI score was significantly correlated with percent mismatch loss (P<0.0001). When percent mismatch loss was dichotomized based on its median value (30.0%), receiver operating characteristic curve area under curve was 0.89 (P=0.0001) with a 25% insula infarction optimal threshold. After adjusting for time to imaging and treatment, binary logistic regression, including dichotomized PIRI (25% threshold), age, National Institutes of Health Stroke Scale score, diffusion-weighted imaging infarct volume, and computed tomography angiography collateral score as covariates, revealed that only dichotomized insula score (P=0.03) and age (P=0.02) were independent predictors of large (68.2%) versus small (8.1%) mismatch loss. There was excellent interobserver agreement for dichotomized PIRI scoring (κ=0.91).

CONCLUSIONS

Admission insular infarction >25% is the strongest predictor of large mismatch loss in this cohort of proximal middle cerebral artery occlusive stroke. This outcome marker may help to identify treatment-eligible patients who are in greatest need of rapid reperfusion therapy.

Preservation of the long insular artery to prevent postoperative motor deficits after resection of insulo-opercular glioma: technical case reports

Resection of insulo-opercular gliomas carries the risk of postoperative hemiparesis caused by ischemia of the corona radiata resulting from injury to the long insular arteries. However, intraoperative identification of these perforating arteries is challenging. We attempted intra-operative motor evoked potential (MEP) monitoring under temporary occlusion of the suspected long insular artery arising from the opercular portion of middle cerebral artery in two patients with insulo-opercular gliomas. Temporary occlusion of the artery caused decrease in MEP amplitude, which recovered after release in one patient, who had no postoperative motor deficits or ischemic lesion in the corona radiata. Temporary occlusion of the artery caused no changes in MEP amplitude, so that the artery was sacrificed for tumor removal in the other patient, who had no motor deficits but ischemic lesion was present in the corona radiata in the territory of the long insular artery sparing the descending motor pathway. These cases show that great care should be taken during surgical manipulations near the posterior part of the superior limiting sulcus to preserve the perforating branches to the corona radiata, and temporary occlusion of the branches under MEP monitoring is useful to identify the arteries supplying the pyramidal tract.

Long insular artery infarction: characteristics of a previously unrecognized entity

BACKGROUND AND PURPOSE

The infarctions arising in the long insular arteries of the M2 segment have been poorly described in the past. The purpose of this study was to investigate the incidence, clinical characteristics, and pathogenesis of long insular artery infarcts.

MATERIALS AND METHODS

Patients with acute isolated infarcts in territories of the long insular arteries and lenticulostriate arteries were retrospectively reviewed. The long insular artery territory was defined as the area above the lenticulostriate artery territory at the level of centrum semiovale. On the coronal section, it lies between the tip of the anterior horn and the top of the superior limb of the insular cleft. Clinical features and prevalence of embolic sources were compared between the 2 groups.

RESULTS

Of 356 consecutive patients with acute ischemic stroke, 8 (2.2%) had a long insular artery infarct (long insular artery group) and 50 (14.0%) had a lenticulostriate artery infarct (lenticulostriate artery group). There were no differences in age, sex, prevalence of risk factors, neurologic deficit, or incidence of lacunar syndromes between these groups. Abrupt onset was more common in the long insular artery than in the lenticulostriate artery group (P = .004). The prevalence of embolic high-risk sources (eg, atrial fibrillation) was not significantly different between these groups, but the combined prevalence of all embolic sources, including moderate-risk sources, was significantly higher in the long insular artery group (P = .048).

CONCLUSIONS

Isolated infarction caused by long insular artery occlusion is not rare. Abrupt onset is more common for long insular artery infarction, and this finding could be attributed to the higher incidence of an embolic etiology as the pathogenesis of infarction.

Definition of a stereotactic 3-dimensional magnetic resonance imaging template of the human insula

BACKGROUND

This study proposes a 3-dimensional (3-D) template of the insula in the bicommissural reference system with posterior commissure (PC) as the center of coordinates.

OBJECTIVE

Using the bicommissural anterior commissure (AC)-PC reference system, this study aimed to define a template and design a method for the 3-D reconstruction of the human insula that may be used at an individual level during stereotactic surgery.

METHODS

Magnetic resonance imaging (MRI)-based morphometric analysis was performed on 100 cerebral cortices with normal insulae based on a 3-step procedure: Step 1: AC-PC reference system-based reconstruction of the insula from the 1-mm thick 3-D T1-weighted MRI slices. Step 2: Digitalization and superposition of the data obtained in the 3 spatial planes. Step 3: Representation of pixels as colors on a scale corresponding to the probability of localization of each insular anatomic component.

RESULTS

The morphometric analysis of the insula confirmed our previously reported findings of a more complex shape delimited by 4 peri-insular sulci. A very significant correlation between the coordinates of the main insular structures and the length of AC-PC was demonstrated. This close correlation allowed us to develop a method that allows the 3-D reconstruction of the insula from MRI slices and only requires the localization of AC and PC. This process defines an area deemed to contain insula with 100% probability.

CONCLUSION

This 3-D reconstruction of the insula should be useful to improve its localization and other cortical areas and allow the differentiation of insular cortex from opercular cortex.

A New, More Accurate Classification of Middle Cerebral Artery Aneurysms

BACKGROUND:

Classification of middle cerebral artery (MCA) aneurysms is sometimes difficult because the identification of the main MCA bifurcation, the key for accurate classification of MCA aneurysms, is inconsistent and somewhat subjective.

OBJECTIVE:

To use the meeting point of the M1 and M2 trunks as an objective, generally accepted, and angiographically evident hallmark for identification of MCA bifurcation and more accurate classification of MCA aneurysms.

METHODS:

We reviewed the computed tomographic angiography data of 1009 consecutive patients with 1309 MCA aneurysms. The M2 trunks were followed proximally until their meeting with the M1 trunk at the main MCA bifurcation. The aneurysms were classified according to their relative location: proximal, at, or distal to the MCA bifurcation. The M1 aneurysms were further subgrouped into M1 early cortical branch aneurysms and M1 lenticulostriate artery aneurysms, extending the classic 3-group classification of MCA aneurysms into a 4-group classification.

RESULTS:

The main MCA bifurcation was the most common location for MCA aneurysms, harboring 829 aneurysms (63%). The 406 M1 aneurysms comprised 242 M1 early cortical branch aneurysms (60%) and 164 M1 lenticulostriate artery aneurysms (40%). We found 106 MCA aneurysms (8%) at the origin of large early frontal branches simulating M2 trunks liable to be misclassified as MCA bifurcation aneurysms. Even though 51% of the 407 ruptured MCA aneurysms were associated with an intracerebral hematoma, this did not affect the classification.

CONCLUSION:

Studying MCA angioarchitecture and applying the 4-group classification of MCA aneurysms is practical and facilitates the accurate classification of MCA aneurysms, helping to improve surgical outcome.

Delineation of the safe zone in surgery of sylvian insular triangle: morphometric analysis and magnetic resonance imaging study

BACKGROUND

Surgery within the insula carries significant risk of morbidity, particularly hemiparesis, because of the difficulty in detecting the internal capsule boundaries.

OBJECTIVE

We analyzed the anatomy of the insula and identified landmarks anticipated to facilitate surgery for intrinsic insular lesions.

METHODS

Insular region anatomy was studied in 11 cadaveric brains harvested within 72 hours postmortem. MRI of the specimens was acquired using 3.0 T with T2-weighting and 25 directions of diffusion tensor imaging. Landmarks easily recognizable during surgery were identified on the surface of the insula. The interrelationships between surface landmarks and critical structures were analyzed.

RESULTS

The posterior inferior insular point (PIIP) and the upper central insular point (UCIP) were newly established as landmarks on the insula. The PIIP corresponded to the obvious bend in the posterior long insular gyrus. The UCIP is the meeting point between the central insular sulcus and superior peri-insular sulcus. The corticospinal tract was identified as a high-intensity area in the posterior limb of the internal capsule on T2-weighted imaging and its course confirmed with diffusion tensor imaging tractography. The corticospinal tract took a course deep to the posterosuperior insula on T2-weighted imaging, 4.8 mm from the UCIP and 6.2 mm from the PIIP.

CONCLUSION

The posterosuperior part of the insula forms the region at greatest risk to corticospinal tract injury. The PIIP and UCIP are crucial to understanding the relationship of the insula with the posterior limb of the internal capsule including the corticospinal tract.

Insular ischemic stroke: clinical presentation and outcome

Background

The insula is a small but complex structure located in the depth of the sylvian fissure, covered by the frontal, parietal and temporal operculum. Ischemic strokes limited to the insula are rare and have not been well studied. Our objective is to better define the clinical presentation and outcome of insular ischemic strokes (IIS).

Methods

We reviewed the institutional prospective, consecutive stroke database from two centers to identify patients with IIS seen between 2008 and 2010. We also searched the Medline database using the keywords insula(r), infarction and stroke to identify previously published IIS cases confirmed by MRI. Minimal extension to an adjacent operculum or subinsular area was accepted. Clinicoradiological correlation was performed by distinguishing IIS involving the anterior (AIC) or posterior insular cortex (PIC). We collected clinical, demographic and radiological data. The outcome was determined using the modified Rankin Scale (mRS).

Results

We identified 7 patients from our institutions and 16 previously published cases of IIS. Infarcts were limited to the AIC (n = 4) or the PIC (n = 12) or affected both (n = 7). The five most frequent symptoms were somatosensory deficits (n = 10), aphasia (n = 10), dysarthria (n = 10), a vestibular-like syndrome (n = 8) and motor deficits (n = 6). A significant correlation was found between involvement of the PIC and somatosensory manifestations (p = 0.04). No other statistically significant associations were found. IIS presentation resembled a partial anterior circulation infarct (n = 9), a lacunar infarct (n = 2) or a posterior circulation infarct (n = 2). However, most cases presented findings that did not fit with these classical patterns (n = 10). At the 6 month follow up, mRS was 0 in 8/23 (35%) patients, 1–2 in 7/23 (30%) and unknown in 8/23 (35%).

Conclusions

IIS presentation is variable. Due to the confluence of functions in a restricted region, it results in multimodal deficits. It should be suspected when vestibular-like or motor but especially somatosensory, speech or language disturbances are combined in the same patient. The outcome of IIS is often favorable. Larger prospective studies are needed to better define the clinical presentation and outcome of IIS.

Surgery of insular nonenhancing gliomas: volumetric analysis of tumoral resection, clinical outcome, and survival in a consecutive series of 66 cases

BACKGROUND

Despite intraoperative technical improvements, the insula remains a challenging area for surgery because of its critical relationships with vascular and neurophysiological functional structures.

OBJECTIVE

To retrospectively investigate the morbidity profile in insular nonenhancing gliomas, with special emphasis on volumetric analysis of tumoral resection.

METHODS

From 2000 to 2010, 66 patients underwent surgery. All surgical procedures were conducted under cortical-subcortical stimulation and neurophysiological monitoring. Volumetric scan analysis was applied on T2-weighted magnetic resonance images (MRIs) to establish preoperative and postoperative tumoral volume.

RESULTS

The median preoperative tumor volume was 108 cm. The median extent of resection was 80%. The median follow-up was 4.3 years. An immediate postoperative worsening was detected in 33.4% of cases; a definitive worsening resulted in 6% of cases. Patients with extent of resection of > 90% had an estimated 5-year overall survival rate of 92%, whereas those with extent of resection between 70% and 90% had a 5-year overall survival rate of 82% (P < .001). The difference between preoperative tumoral volumes on T2-weighted MRI and on postcontrast T1-weighted MRI ([T2 - T1] MRI volume) was computed to evaluate the role of the diffusive tumoral growing pattern on overall survival. Patients with preoperative volumetric difference < 30 cm demonstrated a 5-year overall survival rate of 92%, whereas those with a difference of > 30 cm had a 5-year overall survival rate of 57% (P = .02).

CONCLUSION

With intraoperative cortico-subcortical mapping and neurophysiological monitoring, a major resection is possible with an acceptable risk and a significant result in the follow-up.

The hybrid operculo-insular electrode: a new electrode for intracranial investigation of perisylvian/insular refractory epilepsy

BACKGROUND

Precise localization of an epileptic focus in the perisylvian/insular area is a major challenge. The difficult access and the high density of blood vessels within the sylvian fissure have lead to poor coverage of intrasylvian (opercular and insular) cortex by available electrodes.

OBJECTIVE

To report the creation of a novel electrode designed to record epileptic activity from both the insular cortex and the hidden surfaces of the opercula.

METHODS

The hybrid operculo-insular electrode was fabricated by Ad-Tech Medical Instrument Corporation (Racine, Wisconsin). It was used in combination with regular subdural and depth electrodes for long-term intracranial recordings. The hybrid electrode, which contains both a depth and a strip (opercular) component, is inserted after microsurgical opening of the sylvian fissure. The depth component is implanted directly into the insular cortex. The opercular component has 1 or 2 double-sided recording contacts that face the hidden surfaces of the opercula.

RESULTS

The hybrid operculo-insular electrode was used in 5 patients. This method of invasive investigation allowed including (2 patients) or excluding (3 patients) the insula as part of the epileptic focus and the surgical resection. It also allowed extending the epileptogenic zone to include the hidden surface of the frontal operculum in 1 patient. There were no complications related to the insertion of this new electrode.

CONCLUSION

The new hybrid operculo-insular electrode can be used for intracranial investigation of perisylvian/insular refractory epilepsy. It can contribute to increasing cortical coverage of this complex region and may allow better definition of the epileptic focus.

The branching pattern of the middle cerebral artery: is the intermediate trunk real or not? An anatomical study correlating with simple angiography

OBJECT

The branching structure of the middle cerebral artery (MCA) remains a debated issue. In this study the authors aimed to describe this branching structure in detail.

METHODS

Twenty-seven fresh, human brains (54 hemispheres) obtained from routine autopsies were used. The cerebral arteries were first filled with colored latex and contrast agent, followed by fixation with formaldehyde. All dissections were done under a microscope. During examination, the trunk structures of the MCA and their relations with cortical branches were demonstrated. Lateral radiographs of the same hemispheres were then obtained and comparisons were made. Angles between the MCA trunks were measured on 3D CT cerebral angiography images in 25 patients (50 hemispheres), and their correlations with the angles obtained in the cadaver brains were evaluated.

RESULTS

A new classification was made in relation to the terminology of the intermediate trunk, which is still a subject of debate. The intermediate trunk was present in 61% of cadavers and originated from a superior trunk in 55% and from an inferior trunk in 45%. Cortical branches supplying the motor cortex (precentral, central, and postcentral arteries) significantly originated from the intermediate trunk, and the diameter of the intermediate trunk significantly increased when it originated from the superior trunk. In measurements of the angles between the superior and intermediate trunks, it was found that the intermediate trunk had significant dominance in supplying the motor cortex as the angle increased. The intermediate trunk was classified into 3 types based on the angle values and the distance to the bifurcation point as Group A (pseudotrifurcation type), Group B (proximal type), and Group C (distal type). Group A trunks were seemingly closer to the trifurcation structure that has been reported on in the literature and was seen in 15%. Group B trunks were the most common type (55%), and Group C trunks were characterized as the farthest from the bifurcation point. Group C trunks also had the smallest diameter and fewest cortical branches. Similarities were found between the angles in cadaver specimens and on 3D CT cerebral angiography images. Beyond the separation point of the MCA, trunk structures always included the superior trunk and inferior trunk, and sometimes the intermediate trunk.

CONCLUSIONS

Interrelations of these vascular structures and their influences on the cortical branches originating from them are clinically important. The information presented in this study will ensure reliable diagnostic approaches and safer surgical interventions, particularly with MCA selective angiography.

Current surgical management of insular gliomas

The insula is a functionally and anatomically complex cortical structure that can be affected by both low-grade and high-grade gliomas. This complexity often prevents many neurosurgeons from attempting to surgically manage insular gliomas. This article reviews the anatomic and functional uniqueness of the insula and the surgical outcomes and lessons learned from previously reported surgical series. Successful management of insular gliomas, defined as maximal resection of the tumor without postoperative neurologic morbidity, can be achieved through a sophisticated understanding of the neurovascular structure of the insular region and an intraoperative functional mapping using cortico-subcortical electrical stimulation.

The sub-pial resection technique for intrinsic tumor surgery

BACKGROUND

The technique of sub-pial resection, first described in the early 1900s, was later refined by Penfield and Jasper for removal of supratentorial epileptic cortex. This technique has not been widely adopted for intrinsic tumor resection, for which the most widely used technique involves piecemeal aspiration of the tumor. This technique of "staying within the tumor" results in persistent bleeding, with obscuration of the tumor/brain interface, potentially yielding less than satisfactory results. In our experience, the sub-pial technique is useful for resections of supratentorial intrinsic tumor. We report the use of sub-pial resection technique and present illustrative cases.

METHODS

The sub-pial resection technique is described along with important clinical decision-making guidelines. Representative cases are presented to discuss application of the sub-pial technique and to demonstrate surgical results.

RESULTS

The sub-pial technique preserves the pia during cortical resections and makes it easier to protect and identify normal anatomy, including sulci, gyri, cranial nerves, and major vascular structures. This reduces bleeding, making surgery safer and more efficient. In most cases, an en bloc resection can be accomplished, permitting more accurate histopathology and more extensive tissue acquisition for research purposes.

CONCLUSION

The sub-pial technique can be incorporated into strategies for supratentorial intrinsic tumor resections, including temporal, frontal, occipital, and insular tumors, at para-Sylvian or para-insular-sulcus locations.

Ischemic involvement of the primary motor cortex is a prognostic factor in acute stroke

BACKGROUND

The location of the primary motor cortex can be detected in healthy adults using the findings of 'T2 hypointensity' and the 'double layer sign' on 3 T diffusion-weighted imaging. The aim of this study was to assess whether ischemic involvement of the primary motor cortex can be identified on 3 T diffusion-weighted imaging within six-hours after stroke onset and to evaluate whether this finding could predict clinical outcome three-months after ischemic stroke.

METHODS

Sixty-five patients who had paralysis and ischemia of the anterior circulation underwent 3 T magnetic resonance imaging within six-hours of symptom onset. Follow-up MRI was obtained at 72 h. Anatomic localization and ischemic involvement of the primary motor cortex were evaluated on diffusion-weighted imaging by two investigators. Ischemic involvement on the primary motor cortex was classified into three grades. Ischemic lesion volumes were measured. We compared the favorable outcomes at three-months between subjects with and without ischemic involvement on the primary motor cortex using the NIHSS and modified Rankin Scale.

RESULTS

Ischemic involvement on the primary motor cortex was identified in 52% of patients. Interrater agreement coefficients were 0·93 for the identification of ischemic involvement of primary motor cortex. As defined by scores on the modified Rankin Scale, among the patients with ischemic involvement of the primary motor cortex were worse than the patients without ischemic involvement of the primary motor cortex (P = 0·01). The mean ischemic lesion volume at baseline diffusion-weighted imaging was 38·7 ± 41·7 cm(3) and was 89·8 ± 93·6 cm(3) at follow-up T2-WI. Ischemic involvement on the primary motor cortex (odds ratio: 14·7) was a determinant for worse outcome.

CONCLUSIONS

3T diffusion-weighted imaging can identify ischemic involvement on the primary motor cortex and may provide useful information for predicting outcome during the hyperacute stage. Ischemic involvement on the primary motor cortex has a significant negative impact on recovery.

Altered neural activity and emotions following right middle cerebral artery stroke

Stroke of the right MCA is common. Such strokes often have consequences for emotional experience, but these can be subtle. In such cases diagnosis is difficult because emotional awareness (limiting reporting of emotional changes) may be affected. The present study sought to clarify the mechanisms of altered emotion experience after right MCA stroke. It was predicted that after right MCA stroke the anterior cingulate cortex (ACC), a brain region concerned with emotional awareness, would show reduced neural activity. Brain activity during presentation of emotional stimuli was measured in 6 patients with stable stroke, and in 12 age- and sex-matched nonlesion comparisons using positron emission tomography and the [(15)O]H(2)O autoradiographic method. MCA stroke was associated with weaker pleasant experience and decreased activity ipsilaterally in the ACC. Other regions involved in emotional processing including thalamus, dorsal and medial prefrontal cortex showed reduced activity ipsilaterally. Dorsal and medial prefrontal cortex, association visual cortex and cerebellum showed reduced activity contralaterally. Experience from unpleasant stimuli was unaltered and was associated with decreased activity only in the left midbrain. Right MCA stroke may reduce experience of pleasant emotions by altering brain activity in limbic and paralimbic regions distant from the area of direct damage, in addition to changes due to direct tissue damage to insula and basal ganglia. The knowledge acquired in this study begins to explain the mechanisms underlying emotional changes following right MCA stroke. Recognizing these changes may improve diagnoses, management and rehabilitation of right MCA stroke victims.

Angiographic characteristics of unruptured middle cerebral artery aneurysms predicting perforator injuries

PURPOSE

The aim of the present study was to delineate preoperative factors that may predict perforator injuries following open surgery for an unruptured middle cerebral artery (MCA) aneurysm.

METHODS

The authors conducted a retrospective review of 85 consecutive patients who underwent surgical clipping of 91 unruptured MCA aneurysms. In addition to demographic profiles, angiographic characteristics of aneurysms, which included the side, size, projection, height from the origin of the ophthalmic artery, and distance between the internal carotid artery (ICA) bifurcation and the aneurysm origin, were analysed and correlated with perforator injuries. Compared with the preoperative CT and/or MRI, any newly-developed infarctions in the striatocapsular area were regarded as perforator injuries even if they were very small and asymptomatic.

RESULTS

A perforator injury was found in 14 out of 91 cases (15%). Although the majority of them remained asymptomatic, neurological deterioration occurred in four patients. Of the analysed variables, both the height (from the origin of the ophthalmic artery) and the distance (between the ICA bifurcation and the aneurysm origin) were significantly associated with perforator injuries. A stepwise increment of the risk was observed as the position of aneurysms became higher or as the distance to the ICA bifurcation became shorter.

CONCLUSIONS

These results would be helpful in estimating surgical risks for an unruptured MCA aneurysm, one of the most commonly encountered aneurysms in the neurosurgical field.

Analysis of multiple factors affecting surgical outcomes of proximal middle cerebral artery aneurysms

OBJECTIVE

We analyzed multiple factors including anatomical characteristics that influence the surgical outcomes of proximal middle cerebral artery (M1) aneurysms.

METHODS

Between January 1999 and February 2007, 189 patients had middle cerebral artery aneurysms and 60 had M1 aneurysms. Eleven patients were excluded from this study. The aneurysms were classified into two groups (superior- and inferior-wall type). Retrospectively, we evaluated characteristics of these patients and investigated factors affecting surgical outcomes.

RESULTS

Of the 49 patients, 28 had ruptured aneurysms and 43 had aneurysms sized less than 10mm in diameter. There were no giant aneurysms, the incidence of multiple aneurysms was high (22 patients, 45%), and intracerebral hematomas (ICH) were recognized in 13 patients (27%). The superior-wall group included 29 patients (59.2%) and the inferior-wall group had 20 (40.8%). Overall mortality and morbidity rates were 6.1% and 24.5%, respectively. Thirty-four patients (69%) showed good outcomes (GOS 4-5). Eleven and five patients showed unfavorable outcomes from the superior- and inferior-wall group, respectively. Of the four operation-related morbidity patients, three were from the superior-wall and one from the inferior-wall group. There were no statistically significant differences with respect to clinical outcome between the superior- and inferior-wall groups. Patients with poor Hunt-Hess (H-H) grades on admission showed worse outcomes than those with good H-H grades (p=0.002) and those patients without ICH revealed better outcomes than those with ICH (p=0.004).

CONCLUSIONS

In patients with M1 aneurysms, clinical status on admission and the presence of ICH were significant factors for surgical outcome. Surgical morbidity seems to be related to the direction of the aneurysm. It is critical to save the lenticulostriate arteries and their branches in patients with superior-wall type aneurysms. Thorough preoperative angiographic evaluation, careful brain retraction, and meticulous inspection for hidden small branches are crucial to successful outcomes.

Three-dimensional morphometrical analysis of the M1 segment of the middle cerebral artery: potential clinical and neurosurgical implications

With an increase in the understanding of the formation and treatment of cerebral aneurysms and an improvement in imaging technology, actual standardized measurement values for the cerebral arteries are necessary. Therefore, the aim of this study was to provide a detailed assessment of the three-dimension (3D) morphology (vessel's curvature and trajectory) and 3D-morphometry of the M1 segment of the middle cerebral artery using computer tomography angiography (CTA) images. The DICOM files from CTA of 40 male and 75 female individuals with a mean age of 50.1 years were analyzed using an interactive postprocessing 3D volume-rendering algorithm. Specifically, the M1 segment was evaluated. Calculations included the length, internal diameter, volume, deviation (DI) and tortuosity indices (TI). The M1 segment had a mean internal diameter of 2.23 mm and was greater in men. M1 asymmetry was identified in 23.4% of the individuals and was more common in women. The mean length was 15.62 mm and the left M1 segments were a little longer. The mean volume of the M1 segments was 63.92 mm(3) , and this was typically greater in men and on the left sides. The mean TI and DI for the M1 segment were 0.91 and 2.17 mm, respectively. Therefore, the M1 segments are only slightly curved or straight in their course. In addition, the longest vascular M1 segments are more deviated (curved) and more tortuous. Such standardized data as presented herein may be useful in the preprocedural evaluation of patients with intracranial vascular pathology of the M1 segment.