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Photographs of cadaveric specimens showing the anatomical correlation between the insular surface, underlying claustrum, and adjacent fiber tracts. A: The positions of the dorsal (blue) and ventral (dark green) claustrum are outlined on the insular surface. The ventral (or anteroinferior) portion of the external capsule (light green) is formed by the uncinate and the inferior occipitofrontal fascicles, which cross deep with respect to the anterior and middle short insular gyri. The ventral (or anteroinferior) claustrum consists of a group of diffuse or islandlike gray masses that are separated and fragmented by the uncinate and the inferior occipitofrontal fascicle. The dorsal (or posterosuperior) external capsule (orange) is composed predominantly of claustrocortical fibers, which are located deep with respect to the posterior short and anterior and posterior long gyri. The dorsal (or posterosuperior) claustrum is situated above and posterior to the limen insulae, posterior to the insular apex, and beneath the proximal part of the posterior short, anterior long, and posterior long gyri. The insular apex is the most prominent laterally projecting area on the insular surface. The central insular sulcus approximates the position of the center of the dorsal claustrum. B: Fiber dissection of the insular region showing the dorsal claustrum and external capsule, and the ventral claustrum and external capsule. The insular cortical gray matter and the extreme capsule have been removed. The uncinate fascicle forms most of the white matter of the limen insulae and passes beneath the anterior pole of the insula, connecting the temporal pole with the orbitofrontal region. The inferior frontaloccipital fascicle, which forms the most dorsal part of the limen insulae, is located deep with respect to the insular apex, and to the anterior and middle short gyri. It connects the frontal opercula and prefrontal region with the posterior temporal and occipital regions (panels C-F, coronal sections of the central core of the cerebral hemisphere at the level shown in panel F). The central core is the area (continued)
Source publication
The goal in this study was to examine the microsurgical and tractographic anatomy of the claustrum and its projection fibers, and to analyze the functional and surgical implications of the findings.
Fifteen formalin-fixed human brain hemispheres were dissected using the Klingler fiber dissection technique, with the aid of an operating microscope at...
Contexts in source publication
Context 1
... fragmented 59,60 prepiriform, amygdalar, or temporal claustrum. 22,46,67 The names dorsal and ventral claustrum were applied based on studies in ani- mals, and this nomenclature was carried over to humans. However, in humans the dorsal claustrum is posterosupe- rior, and the ventral claustrum is anteroinferior, as seen on our fiber dissection ( Fig. 1A and ...
Context 2
... dorsal (or posterosuperior) claustrum is a continuous irregular lamina of gray matter lying between the putamen (from which it is separated by the external capsule) and the insular cortex (from which it is separated by the extreme capsule) (Fig. 1D and E). It has the form of a plate, which narrows in the upward direction and widens in the down- ward direction, giving it a triangular form in coronal cross- section. This contrasts with the external capsule, which is widest above and narrow in the area adjacent to the low- er part of the dorsal claustrum, where it is separated from the ...
Context 3
... in the upward direction and widens in the down- ward direction, giving it a triangular form in coronal cross- section. This contrasts with the external capsule, which is widest above and narrow in the area adjacent to the low- er part of the dorsal claustrum, where it is separated from the putamen by a thin or even nonexistent external capsule (Fig. ...
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... and 2A and B). At this level, the fibers of the dorsal (or posterosuperior) external capsule appear at the periphery of the dorsal claustrum, forming a characteristic spoke-and-wheel pattern with its center at the dorsal claustrum ( Fig. 2C and D). Interestingly, the central insular sulcus crosses at or near to the center of the dorsal claustrum (Fig. 1A). Removal of the cortical gray matter overlying the limen insulae exposes the thick uncinate fas- cicle, with its characteristic hooklike shape, connecting the temporal pole with the orbitofrontal area (Figs. 1A and B and 2B-G) and forming the anterior part of the limen in- sulae. The posterior-most fibers at the level of the limen in- ...
Context 5
... et al. 72 stated that "the external capsule consists mostly of deeper fibers of the occipito-frontal fascicle" and "it is joined to the internal capsule at both ends of the putamen." Our study shows that the occipitofrontal and uncinate fascicles, including their deepest fibers, form exclusively the ventral (or anteroinfe- rior) part of the external and extreme capsules, whereas the corticoclaustral projection fibers form the dorsal (or poste- rosuperior) part of the external capsule ( Figs. 1 and 2). Our tractography studies showed that the latter is composed of multiple fiber bundles coming from the superior frontal, precentral, postcentral, superior parietal, and parietooccipi- tal regions, converging in the area of the dorsal claustrum. ...
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Citations
... Research in healthy subjects using diffusion tensor imaging (DTI) has revealed cortical connections with the claustrum, which possesses projections to A) prefrontal cortex, BA 8,9,10,11,12,and 34; B) visual cortex, BA 17, 18, 19 and 39; C) sensorimotor cortex, BA 7, 5, 1/2/3, 4, 6 and 8; and D) language areas BA 44, 45 and 31; as well as with orbitofrontal cortex, temporal cortex, basal ganglia and amygdala [3,7,8] using DTI in 100 healthy subjects, Torgerson et al. [8] found that the claustrum has the highest connectivity in the brain by regional volume. The literature about the claustrum-including studies in animal models and in humans-has evidenced the vast anatomical connections between the claustrum and the entire cerebral cortex and the subcortical structures [1-4, 6-9]. ...
... The claustrum is an irregular and fine sheet of grey matter in the basolateral telencephalon present in almost all mammals. The claustrum is separated from the insular cortex by the extreme capsule and medially from the lentiform nucleus by the external capsule [1][2][3][4][5][6][7][8]. One of the most challenging issues in studying the human claustrum is its intricate anatomical location and its irregular form. ...
... One of the most challenging issues in studying the human claustrum is its intricate anatomical location and its irregular form. Actually, the claustrum dimensions have been reported through a postmortem 3D reconstruction imaging study by Kapakin [5] (right claustrum 35.5710mm x 1.0912mm x 16.00mm and a volume of 828.8346mm 3 and left claustrum 32.9558mm x 0.8321mm x 19.00mm and a volume of 705.8160 mm 3 ) and Milardi et al. [7] have reported similar values for the claustrum mean volume. We propose approaching these challenges by assessing the claustrum's whole brain resting state functional connectivity using the WU-Minn Human Connectome Project (HCP) dataset. ...
The claustrum is an irregular and fine sheet of grey matter in the basolateral telencephalon present in almost all mammals. The claustrum has been the object of several studies using animal models and, more recently, in human beings using neuroimaging. One of the most extended cognitive processes attributed to the claustrum is the salience process, which is also related to the insular cortex. In the same way, studies with human subjects and functional magnetic resonance imaging have reported the coactivation of the claustrum/insular cortex in the integration of sensory signals. This coactivation has been reported in the left claustrum/insular cortex or in the right claustrum/insular cortex. The asymmetry has been reported in task studies and literature related to neurological disorders such as Alzheimer’s disease and schizophrenia, relating the severity of delusions with the reduction in left claustral volume. We present a functional connectivity study of the claustrum. Resting-state functional and anatomical MRI data from 100 healthy subjects were analyzed; taken from the Human Connectome Project (HCP, NIH Blueprint: The Human Connectome Project), with 2x2x2 mm ³ voxel resolution. We hypothesize that 1) the claustrum is a node involved in different brain networks, 2) the functional connectivity pattern of the claustrum is different from the insular cortex’s pattern, and 3) the asymmetry is present in the claustrum’s functional connectivity. Our findings include at least three brain networks related to the claustrum. We found functional connectivity between the claustrum, frontoparietal network, and the default mode network as a distinctive attribute. The functional connectivity between the right claustrum with the frontoparietal network and the dorsal attention network supports the hypothesis of claustral asymmetry. These findings provide functional evidence, suggesting that the claustrum is coupled with the frontoparietal network serving together to instantiate new task states by flexibly modulating and interacting with other control and processing networks.
... As mentioned previously, the ventral most region of the claustrum connects to various limbic brain structures that are implicated in seizure generation and epileptic pathology . These regions include the piriform, medial prefrontal, orbitofrontal, and entorhinal cortices, the amygdala (basolateral, central, and medial nuclei), and the anterior and mediodorsal nuclei of the thalamus (Fernandez-Miranda et al., 2008;Watson et al., 2017;Smith et al., 2019b) (Figure 1B). Despite its anatomical significance, the involvement of this limbic subsector of the claustrum has largely been overlooked in seizure research, potentially due to its obscurity and the ability to selectively modulate it without affecting neighboring white matter (Watson and Kopell, 2022). ...
... We hypothesize that seizures arising from temporal lobe structures can generalize broadly across ipsi-and contralateral neocortices (e.g., generalized tonic-clonic seizures) through ventral claustrum projections. Considering this subcortical generalization network, we further speculate that anterior temporal lobectomy and other temporal lobe resection techniques utilized in epilepsy could, in some cases, resect the ventral portion of the claustrum or transect limbic fibers to this subregion (Feindel et al., 2009;Borger et al., 2021;Dalio et al., 2022). The incidence, benefits, and/or altered outcomes of these surgical possibilities are unknown. ...
... We previously discussed data hinting at the possibility that resecting the ventral claustrum could, theoretically, provide benefit in patients with generalized seizures that arise from temporal lobe structures (Feindel et al., 2009;Borger et al., 2021;Dalio et al., 2022). However, this viewpoint is highly speculative and requires formal investigation to support or refute. ...
The function of the claustrum and its role in neurological disorders remains a subject of interest in the field of neurology. Given the claustrum's susceptibility to seizure-induced damage, there is speculation that it could serve as a node in a dysfunctional epileptic network. This perspective article aims to address a pivotal question: Does the claustrum play a role in epilepsy? Building upon existing literature, we propose the following hypotheses for the involvement of the claustrum in epilepsy: (1) Bilateral T2/FLAIR magnetic resonance imaging (MRI) hyperintensity of the claustrum after status epilepticus represents a radiological phenomenon that signifies inflammation-related epileptogenesis; (2) The ventral claustrum is synonymous with a brain area known as 'area tempestas,' an established epileptogenic center; (3) The ventral subsector of the claustrum facilitates seizure generalization/propagation through its connections with limbic and motor-related brain structures; (4) Disruption of claustrum connections during seizures might contribute to the loss of consciousness observed in impaired awareness seizures; (5) Targeting the claustrum therapeutically could be advantageous in seizures that arise from limbic foci. Together, evidence from both clinical case reports and animal studies identify a significant role for the ventral claustrum in the generation, propagation, and intractable nature of seizures in a subset of epilepsy syndromes.
... (d) Illustration of medial side of cerebrum with white matter pathways by ALF Foville: Traité Complet de l'Anatomie, de la Physiologie et de la Pathologie du Système Nerveux Cérébrospinal. Paris, Fortin, Masson et Cie, 1844 [16] Franz Joseph Gall (1758Gall ( -1828 and JC Spurzheim (1776-1832) distinguished the important aspects of gray and white matter in 1810 [4], while Karl Friedrich Burdach (1776Burdach ( -1847 focused his three-volume study Vom Baue und Leben des Gehirns und Rückenmarks on fiber bundles and identified complicated structures in 1819 [20,21]. In 1827, Bell's student, English anatomist Herbert Mayo, published some of the best-dissected brain illustrations available at the time ( Fig. 1c) [6]. ...
... Extreme capsule: The extreme capsule, located just below the insular cortex, interconnects the adjacent insular and medial opercular gyri with short association fibers [1,16,46,50]. Thus, these fibers provide connections between which consists of fronto-occipital fasciculus, anterior commissur fibers, thalamic radiation and optic radiation fibers. ...
White matter fiber dissection is a technical procedure used in neuroanatomy studies to gain a comprehensive three-dimensional understanding of both gray and white matter anatomy as well as deep nuclei [1]. While difficult and time consuming, this technique is critical for constructing a proper conceptual notion about accurate intrinsic brain anatomy and architecture. This method is the legacy of many early anatomists [2–8].
... (Park et al., 2012). Neuroanatomical studies show that several fiber bundles including the corona radiata, uncinate fasiculi, and inferior occipitofrontal fasiculi project to the claustrum from brain regions including the superior frontal, precentral, postcentral, superior parietal, and parietooccipital regions (Fernández-Miranda et al., 2008a, 2008b. Amyloid plaques have been shown to accumulate in the claustrum of people with AD (Fernández-Miranda et al., 2008a, 2008bMorys et al., 1994), which can disrupt corticoclaustral connectivity, manifesting as memory dysfunction (Sener, 1993). ...
... Neuroanatomical studies show that several fiber bundles including the corona radiata, uncinate fasiculi, and inferior occipitofrontal fasiculi project to the claustrum from brain regions including the superior frontal, precentral, postcentral, superior parietal, and parietooccipital regions (Fernández-Miranda et al., 2008a, 2008b. Amyloid plaques have been shown to accumulate in the claustrum of people with AD (Fernández-Miranda et al., 2008a, 2008bMorys et al., 1994), which can disrupt corticoclaustral connectivity, manifesting as memory dysfunction (Sener, 1993). Interestingly, an fMRI music study in people with mild cognitive impairment and early AD by Fischer et al. (2021) examined the impact of a three-week music listening intervention of autobiographically salient music that was known to participants for at least 20 years and thus, deeply encoded. ...
Accumulating evidence suggests that the neural activations during music listening differs as a function of familiarity with the excerpts. However, the implicated brain areas are unclear. After an extensive literature search, we conducted an Activation Likelihood Estimation analysis on 23 neuroimaging studies (232 foci, 364 participants) to identify consistently activated brain regions when healthy adults listen to familiar music, compared to unfamiliar music or an equivalent condition. The results revealed a left cortical-subcortical co-activation pattern comprising three significant clusters localized to the supplementary motor areas (BA 6), inferior frontal gyrus (IFG, BA 44), and the claustrum/insula. Our results are discussed in a predictive coding framework, whereby temporal expectancies and familiarity may drive motor activations, despite any overt movement. Though conventionally associated with syntactic violation, our observed activation in the IFG may support a recent proposal of its involvement in a network that subserves both violation and prediction. Finally, the claustrum/insula plays an integral role in auditory processing, functioning as a hub that integrates sensory and limbic information to (sub)cortical structures.
... In left-onset PD patients, FA and AD of the left EC were lower than the right EC. Contrarily, FA, MD, AD, and RD of the left EC were all higher than the right EC in rightonset PD patients. EC connects frontal and parietal areas [33], participates in the cortico-striatal pathway [33,55], regulates motor activity, cognition, and behavior [56], which are impaired in PD [50,51]. ...
Background
Parkinson's disease (PD) is characterized by a lateralized onset, but its cause and mechanism are still unclear.
Methods
Obtaining diffusion tensor imaging (DTI) data from the Parkinson’s Progression Markers Initiative (PPMI). Tract-based spatial statistics analysis and region-of-interest-based analysis were performed to evaluate the white matter (WM) asymmetry using original DTI parameters, Z Score normalized parameters, or the asymmetry index (AI). Hierarchical cluster analysis and least absolute shrinkage and selection operator regression were performed to construct predictive models for predicting the PD onset side. DTI data from The Second Affiliated Hospital of Chongqing Medical University were obtained for external validation of the prediction model.
Results
118 PD patients and 69 healthy controls (HC) from PPMI were included. Right-onset PD patients presented more asymmetric areas than left-onset PD patients. The inferior cerebellar peduncle (ICP), superior cerebellar peduncle (SCP), external capsule (EC), cingulate gyrus (CG), superior fronto-occipital fasciculus (SFO), uncinate fasciculus (UNC), and tapetum (TAP) showed significant asymmetry in left-onset and right-onset PD patients. An onset-side-specific pattern of WM alterations exists in PD patients, and a prediction model was constructed. The predicting models based on AI and ΔZ Score presented favorable efficacy in predicting PD onset side by external validation in 26 PD patients and 16 HCs from our hospital.
Conclusions
Right-onset PD patients may have more severe WM damage than left-onset PD patients. WM asymmetry in ICP, SCP, EC, CG, SFO, UNC, and TAP may predict PD onset side. Imbalances in the WM network may underlie the mechanism of lateralized onset in PD.
... Insular cortex area has common connections to anterior inferior parietal cortex, parietal operculum, retro insular parietal region and somatosensory cortex. Insular 26 cortex deep lesions, may result in short association fibers disconnection with subsequent front parietal circuitry disruption 27,28 . ...
... В качестве подтверждения анатомического различия между двумя субрегионами ДМО определены отдельные кластеры нейронов, связанные с различными отделами ГМ [30]. Например, предДМО преимущественно связана с хвостатым ядром, скорлупой, передними ядрами таламуса, с ПФК, НЛИ, ВЛИ, угловой извилиной, передней частью ПИ и островком, тогда как собственно ДМО -с ПМК, вентролатеральным ядром таламуса, премоторной, орбитофронтальной, соматосенсорной корой, средней частью ПИ, а также с НЛИ [31,32]. ...
... As confirmation of the anatomical difference between the two subregions of the SMA, individual clusters of neurons associated with different parts of the brain were identified [30]. For example, the preSMA is predominantly associated with the caudate nucleus, putamen, anterior thalamic nuclei, the PFC, IFG, SFG, the angular gyrus, the anterior part of the CG, and the insula, while the SMA proper is associated with the PMC, the ventrolateral thalamic nucleus, the premotor, orbitofrontal, somatosensory cortex, the middle part of CG, as well as with IFG [31,32]. ...
... Большое количество исследований выявило вклад ДМО в процессах осуществления математических, вычислительных операций [70,71]. [14,30,31] to the angular gyrus [30,31] claustrocortical fibers [32] frontostriate fibers [33,34] to the anterior thalamus [31] to opposite SMA [14,34] SMA proper to the middle part of the cingulate gyrus [30,31] to the primary motor cortex [14,30,31] to the premotor cortex [30,31] to the orbitofrontal cortex [30,31] to the somatosensory cortex [30,31] corticospinal tract [34,39] to the middle parts of the thalamus [31] Both subregions to the convex surface of the superior frontal gyrus [30,31] to the insula [36] superior longitudinal fascicle [29,34,35] cingulate fascicle [34] frontal oblique fascicle [13,45] to the subthalamic nucleus [38] to the cerebellum [27] the nature of the sequence elements themselves, has also been noted [59][60][61]. The role of SMA in cognitive control, response inhibition, or task switching is undoubted [62]. ...
Methods: The supplementary motor area (SMA) is a cortical region, that is located on the medial surface of the frontal lobe entirely within the interhemispheric fissure between the primary motor cortex (PMC) and prefrontal cortex (PFC). This area is a heterogeneous region in its structure, as well as in its connections with other parts of the brain; on the basis of these differences, the pre-SMA and SMA-proper regions are distinguished in it. Numerous neural connections with other parts of the central nervous system (CNS) suggest the involvement of the SMA in many cognitive functions, and not only in higher motor ones, as previously was thought. In particular, in the dominant hemisphere, the SMA performs the speech function through the frontal oblique fascicle (FOF), a bundle of association fibers that connects the SMA with Broca's area. In the event of various pathologies affecting the SMA and after neurosurgical manipulations in this area, a variety of neurological disorders can occur both motor and verbal. With the damage of this cortical region in the dominant hemisphere, SMA syndrome (akinetic mutism) can occur. This paper provides a review of the anatomical, cytoarchitectonic, and functional features of the SMA, as well as a detailed description of the clinical picture of the lesion of this cortical region. Keywords: Brain, supplementary motor area, SMA syndrome.
... In most previous studies of the insula and deep white matter pathways, the opercula region white matter pathways were removed and most of the dissection around the insula started with removing all opercula. [34][35][36] For this reason, there is a gap in understanding the insulo-opercular region. Our study presented the opportunity to better demonstrate the relationship between the cerebral opercula, insula, and other deep white matter tracts. ...
... Thus, the integration of inputs from the limbic cortex, visual cortex, and somatosenorial cortex is provided in the claustrum. 34 The high functionality of these fibers shows that the normal opercular parenchyma is an extremely eloquent cortex and should be preserved as much as possible during any surgery in this region. Many pathological processes, especially gliomas, affect the insular region. ...
Objective:
Radiological, anatomical, and electrophysiological studies have shown the insula and cerebral opercula to have extremely high functionality. Because of this complexity, interventions in this region cause higher morbidity compared to those in other areas of the brain. In most early studies of the insula and white matter pathways, insular dissection was begun after the opercula were removed. In this study, the authors examined the insula and deep white matter pathways to evaluate the insula as a whole with the surrounding opercula.
Methods:
Twenty formalin-fixed adult cerebral hemispheres were studied using fiber microdissection techniques and examination of sectional anatomy. Dissections were performed from lateral to medial, medial to lateral, inferior to superior, and superior to inferior. A silicone brain model was used to show the normal gyral anatomy. Sections and fibers found at every stage of dissection were photographed with a professional camera. MRI tractography studies were used to aid understanding of the dissections.
Results:
The relationships between the insula and cerebral opercula were investigated in detail through multiple dissections and sections. The relationship of the extreme and external capsules with the surrounding opercula and the fronto-occipital fasciculus with the fronto-orbital operculum was demonstrated. These findings were correlated with the tractography studies. Fibers of the extreme capsule connect the medial aspect of the opercula with the insula through the peri-insular sulcus. Medial to lateral dissections were followed with the removal of the central core structures, and in the last step, the medial surface of the cerebral opercula was evaluated in detail.
Conclusions:
This anatomical study clarifies our understanding of the insula and cerebral opercula, which have complex anatomical and functional networks. This study also brings a new perspective to the connection of the insula and cerebral opercula via the extreme and external capsules.
... The anterior commissure (AC) is a paleopallial white matter tract that connects the two temporal lobes of the cerebral hemispheres across the midline and olfactive areas (Johann Peltier 2011). In its compact part, the tract is covered by the wall of Gratiolet's canal, a canal of grey matter with a thin sheet, that was termed by Dejerine with attention to the passage of the anterior commissure through the putamen (Dejerine 1895). However, many aspects of its structure are unknown, and its functions remain elusive. ...
... DSI overcomes this limitation by visualizing crossing fibers and been validated in the normal human brain Wedeen et al. 2005;Schmahmann et al. 2007). Therefore, the combination of classical FD and modern MRI tractography are used as mutually complementary methods in analyses of anatomical structures (Fernandez-Miranda et al. 2008). Primary brain tumors tend to infiltrate preferentially along white matter tracts such as the corpus callosum (Bellail et al. 2004;Bolteus et al. 2001). ...
The anterior commissure, which connects bilateral temporal lobes and olfactive areas, remains elusive in many aspects of its structure and functional role. To comparatively describe anatomical details of the anterior commissure using cadaveric fiber dissection (FD) and diffusion spectrum imaging (DSI) thus refining our knowledge of the tract and exploring its clinical relevance in glioma migration. Twelve normal postmortem hemispheres were treated with Klingler’s method and subjected to FD with medial, inferior, and lateral approaches. The FD findings were correlated with DSI tractography results. To illustrate the clinical relevance, two patients with recurrent temporal high-grade glioma are described. Our FD and DSI tractography of the anterior commissure disclosed a new anatomical paradigm. The FD confirmed that the anterior limb (absent sometimes and variable) and the lateral/temporal extension include the rostral portion and caudal portion, respectively, of the anterior commissure fibers. The shape of the lateral/temporal extension predominantly resembles an ‘H’. The DSI tractography findings corresponded to these FD results. According to the FD, the Virchow-Robin space is continuous with the subarachnoid space and very close to the anterior commissure. The two clinical cases presented severe disturbances of consciousness and behavior despite good local tumor control. Subsequent magnetic resonance images showed new lesions infiltrating the contralateral temporal lobes. FD combined with DSI provided anatomical details facilitating a better understanding of the anterior commissure. Glioma migration routes to the contralateral temporal lobe included the anterior commissure, Virchow-Robin space, and subarachnoid space and were clinically relevant.
... This space is very narrow in nontumoral hemispheres and is approximately 3 mm, whereas in tumoral hemispheres, it can extend up to 21 mm [33]. Identification of the UF/IFOF complex is important from a surgical point of view in terms of the risk of injury to LSAs related to anterior perforating substances [20,29,32,55]. As these small branches provide vascular supply to the basal ganglia and internal capsule, it is reasonable to leave a small amount of the tumor medially to the UF/IFOF complex at the level of the temporal stem to avoid injuring them [9]. ...
The insula is a lobe located deep in each hemisphere of the brain and is surrounded by eloquent cortical, white matter, and basal ganglia structures. The aim of this study was to provide an anatomical description of the insula and white matter tracts related to surgical treatment of gliomas through a transcortical approach. The study also discusses surgical implications in terms of intraoperative brain mapping. Five adult brains were prepared according to the Klingler technique. Cortical anatomy was evaluated with the naked eye, whereas white matter dissection was performed with the use of a microscope. The widest exposure of the insular surface was noted through the temporal operculum, mainly in zones III and IV according to the Berger-Sanai classification. By going through the pars triangularis in all cases, the anterior insular point and most of zone I were exposed. The narrowest and deepest operating field was observed by going through the parietal operculum. This method provided a suitable approach to zone II, where the corticospinal tract is not covered by the basal ganglia and is exposed just under the superior limiting sulcus. At the subcortical level, the identification of the inferior frontoocipital fasciculus at the level of the limen insulae is critical in terms of preserving the lenticulostriate arteries. Detailed knowledge of the anatomy of the insula and subcortical white matter that is exposed through each operculum is essential in preoperative planning as well as in the intraoperative decision-making process in terms of intraoperative brain mapping.
