Fiber Dissection Technique Research Articles

Three-dimensional topographic fiber tract anatomy of the cerebrum.

The fiber tracts of the cerebrum may be a more important determinant of resection limits than the cortex. Better knowledge of the 3-dimensional (3-D) anatomic organization of the fiber pathways is important in planning safe and accurate surgery for lesions within the cerebrum. To examine the topographic anatomy of fiber tracts and subcortical gray matter of the human cerebrum and their relationships with consistent cortical, ventricular, and nuclear landmarks. Twenty-five formalin-fixed human brains and 4 whole cadaveric heads were examined by fiber dissection technique and ×6 to ×40 magnification. The fiber tracts and central core structures, including the insula and basal ganglia, were examined and their relationships captured in 3-D photography. The depth between the surface of the cortical gyri and selected fiber tracts was measured. The topographic relationships of the important association, projection, and commissural fasciculi within the cerebrum and superficial cortical landmarks were identified. Important landmarks with consistent relationships to the fiber tracts were the cortical gyri and sulci, limiting sulci of the insula, nuclear masses in the central core, and lateral ventricles. The fiber tracts were also organized in a consistent pattern in relation to each other. The anatomic findings are briefly compared with functional data from clinicoradiological analysis and intraoperative stimulation of fiber tracts. An understanding of the 3-D anatomic organization of the fiber tracts of the brain is essential in planning safe and accurate cerebral surgery.

The Three-Dimensional Architecture of the Internal Capsule of the Human Brain Demonstrated by Fiber Dissection Technique

Abstract The fiber dissection technique involves peeling away white matter fiber tracts of the brain to display its three-dimensional anatomic arrangement. The intricate three-dimensional configuration and structure of the internal capsule (IC) is not well defined. By using the fiber dissection technique, our aim was to expose and study the IC to achieve a clearer conception of its configuration and relationships with neighboring white matter fibers and central nuclei. The lateral and medial aspects of the temporal lobes of twenty, previously frozen, formalin-fixed human brains were dissected under the operating microscope using the fiber dissection technique. The details of the three-dimensional arrangement of the fibers within the IC were studied and a comprehensive understanding of their relations was achieved. The white matter fiber dissection provides an enhanced perspective of the intricate architecture of the internal structure of brain. This enhanced understanding of intrinsic brain anatomy, particularly of functional highly relevant fiber systems such as the internal capsule, is essential for performing modern neurosurgical procedures.

The anatomy of Meyer's loop revisited: changing the anatomical paradigm of the temporal loop based on evidence from fiber microdissection.

The goal in this study was to explore and further refine comprehension of the anatomical features of the temporal loop, known as Meyer's loop. The lateral and inferior aspects of 20 previously frozen, formalin-fixed human brains were dissected under the operating microscope by using fiber microdissection. A loop of the fibers in the anterior temporal region was clearly demonstrated in all dissections. This temporal loop, or Meyer's loop, is commonly known as the anterior portion of the optic radiation. Fiber microdissection in this study, however, revealed that various projection fibers that emerge from the sublentiform portion of the internal capsule (IC-SL), which are the temporopontine fibers, occipitopontine fibers, and the posterior thalamic peduncle (which includes the optic radiation), participate in this temporal loop and become a part of the sagittal stratum. No individual optic radiation fibers could be differentiated in the temporal loop. The dissections also disclosed that the anterior extension and angulation of the temporal loop vary significantly. The fiber microdissection technique provides clear evidence that a loop in the anterior temporal region exists, but that this temporal loop is not formed exclusively by the optic radiation. Various projection fibers of the IC-SL, of which the optic radiation is only one of the several components, display this common course. The inherent limitations of the fiber dissection technique preclude accurate differentiation among individual fibers of the temporal loop, such as the optic radiation fibers.

Three dimensional anatomical microdissection of rat brain using fiber dissection technique

IntroductionUsing Klingler's fiber dissection technique, we aimed to demonstrate microdissections of the specific regions in the brain of rat which is undoubtly one of the mostly used animal in neuroscience researches. MethodsFormalin fixed cerebral hemispheres of rat brains were dissected under operating microscope. Klingler's technique of fiber dissection was applied. Cortex, intrinsic anatomy and cranial nerves were studied. During and after dissection, photographs were taken and three dimensional pictures were obtained using a special software (Anamaker 3D©; available free from www.stereoeye.com, Tokyo, Japan). ResultsThe anatomical relation of structures, seen in histological sections, was determined in our study. Hippocampus, thalamus and internal capsule, which are frequently studied, are explained with three dimensional fiber dissection technique. In rats, trigeminal nerve, olfactory nerve, hippocampus lying to the fornix and olfactory bulb lying to the frontal horn are more distinct when compared to humans. DiscussionThe microdissection of rat brain, to obtain needed structures accurately for experimental purposes, is an extremely important model. On this basis, our study serves the microsurgical anatomy of the rat brain for neuroscientists knowledge.

Diffusion tensor imaging for brain malformations: does it help?

In this article, the basics of diffusion-weighted imaging/diffusion tensor imaging (DTI) are discussed, including a short historical perspective on the fiber dissection technique, followed by a review of selected brain malformations in which DTI and tractography have contributed to a better understanding of the malformations, and by a clinical case in which DTI showed a disorder of the internal neuroarchitecture that could not be correctly appreciated by conventional anatomic magnetic resonance imaging.

Three-dimensional microsurgical anatomy and the safe entry zones of the brainstem.

There have been no studies of the structure and safe surgical entry zones of the brainstem based on fiber dissection studies combined with 3-dimensional (3-D) photography. To examine the 3-D internal architecture and relationships of the proposed safe entry zones into the midbrain, pons, and medulla. Fifteen formalin and alcohol-fixed human brainstems were dissected by using fiber dissection techniques, ×6 to ×40 magnification, and 3-D photography to define the anatomy and the safe entry zones. The entry zones evaluated were the perioculomotor, lateral mesencephalic sulcus, and supra- and infracollicular areas in the midbrain; the peritrigeminal zone, supra- and infrafacial approaches, acoustic area, and median sulcus above the facial colliculus in the pons; and the anterolateral, postolivary, and dorsal medullary sulci in the medulla. The safest approach for lesions located below the surface is usually the shortest and most direct route. Previous studies have often focused on surface structures. In this study, the deeper structures that may be at risk in each of the proposed safe entry zones plus the borders of each entry zone were defined. This study includes an examination of the relationships of the cerebellar peduncles, long tracts, intra-axial segments of the cranial nerves, and important nuclei of the brainstem to the proposed safe entry zones. Fiber dissection technique in combination with the 3-D photography is a useful addition to the goal of making entry into the brainstem more accurate and safe.

The Dentate Nucleus and Its Projection System in the Human Cerebellum

Neurosurgical management of cerebellar lesions remains challenging. Thus, it is important to have sound knowledge of the microsurgical anatomy of the cerebellum and dentate nucleus (DN) and to define different types of exposure in a variety of surgical interventions. To examine the anatomy of the DN from a neurosurgical viewpoint using fiber tracking techniques. Ten formalin-fixed human hemispheres were dissected with the Ludwig and Klingler fiber dissection technique under × 6 to × 40 magnification. Anatomic images were created with 3-dimensional diffusion tensor imaging. The relationships of the DN to tentorium and suboccipital and lateral surfaces of the cerebellum and its spatial positioning relative to different surgical approaches in the cerebellum and fourth ventricle were examined. The fiber tracts terminating at and surrounding the DN were defined. The DN is at greater risk of being injured in the transvermian and supratonsillar approaches to the cerebellum and fourth ventricle, with lesser risk in the telovelar and subtonsillar approaches. Superior approaches are safer compared with other approaches. The DN represents an important anatomic structure in surgical interventions involving the posterior fossa, particularly in the elderly because of the common occurrence of atrophy-related problems in this age group. Functionally and anatomically, the DN is closely related to the superior and middle cerebellar peduncles. The inferior cerebellar peduncle poses positional risks because it follows an anterior and superior course relative to the DN. The telovelar approach is a safer procedure for interventions involving the pathological lesions of the fourth ventricle floor.

Anatomic Study of the Central Core of the Cerebrum Correlating 7-T Magnetic Resonance Imaging and Fiber Dissection With the Aid of a Neuronavigation System

Different strategies have been used to study the fiber tract anatomy of the human brain in vivo and ex vivo. Nevertheless, the ideal method to study white matter anatomy has yet to be determined because it should integrate information obtained from multiple sources. We developed an anatomic method in cadaveric specimens to study the central core of the cerebrum combining traditional white matter dissection with high-resolution 7-T magnetic resonance imaging (MRI) of the same specimen coregistered using a neuronavigation system. Ten cerebral hemispheres were prepared using the traditional Klingler technique. Before dissection, a structural ultrahigh magnetic field 7-T MRI study was performed on each hemisphere specifically prepared with surface fiducials for neuronavigation. The dissection was then performed from the medial hemispheric surface using the classic white fiber dissection technique. During each step of the dissection, the correlation between the anatomic findings and the 7-T MRI was evaluated with the neuronavigation system. The anatomic study was divided in 2 stages: diencephalic and limbic. The diencephalic stage included epithalamic, thalamic, hypothalamic, and subthalamic components. The limbic stage consisted of extending the dissection to complete the Papez circuit. The detailed information given by the combination of both methods allowed us to identify and validate the position of fibers that may be difficult to appreciate and dissect (ie, the medial forebrain bundle). The correlation of high-definition 7-T MRI and the white matter dissection technique with neuronavigation significantly improves the understanding of the structural connections in complex areas of the human cerebrum.

Reproducibility of quantitative fiber tracking measurements in diffusion tensor imaging of frontal lobe tracts: A protocol based on the fiber dissection technique

Background:Diffusion tensor imaging (DTI)-based tractography is a noninvasive in vivo method for tracing white matter bundles. This raises possibilities for qualitative and quantitative assessment of the structural organization of tracts. Nevertheless, questions remain about neuroanatomical accuracy, reproducibility for clinical purposes, and accessibility of the best method for broader application. The aim of this study was to combine the fiber dissection technique and tractography to provide more pertinent insight into brain anatomy and, as a result, to test a protocol for reconstruction of six major frontal lobe tracts.Methods:A combination of fiber dissection of formalin-fixed brain tissue after freezing (Klingler's technique) and virtual dissection (tractography) was used to develop a protocol to reconstruct major frontal tracts. Apparent diffusion coefficient (ADC), fractional anisotropy (FA), number of voxels (NVO), volume (VOL), number (NTR), and length (LEN) of tracts were evaluated to assess intra- and interobserver reproducibility. Statistical reliability was evaluated using intraclass correlation coefficients (ICCs) and the Pearson association coefficient (r).Results:The virtual dissection obtained by tractography seemed to reproduce the anatomic knowledge of the white matter tracts obtained through the classic method. In reliability study, most ICC and r values corresponded at least to large correlation. The magnitude of correlation was very high (ICC 0.7-0.9) or almost perfect (ICC 0.9-1.0) for the FA and ADC measures of every tract studied.Conclusion:The DTI protocol proposed herein provided a reliable method for analysis of reconstructed frontal lobe tracts, especially for the FA and ADC variables.

Microsurgical Anatomy of the Optic Radiation and Related Fibers in 3-Dimensional Images

The fiber dissection technique provides unique 3-dimensional anatomic knowledge of the white matter. To examine the optic radiation anatomy and its important relationship with the temporal stem and to discuss its findings in relation to the approaches to temporal lobe lesions. We studied 40 cerebral hemispheres of 20 brains that had been fixed in formalin solution for 40 days. After removal of the arachnoid membrane, the hemispheres were frozen, and the Klingler technique was used for dissection under magnification. Stereoscopic 3-dimensional images of the dissection were obtained for illustration. The optic radiations are located deep within the superior and middle temporal gyri, always above the inferior temporal sulcus. The mean distance between the cortical surface and the lateral edge of the optic radiation was 21 mm. Its fibers are divided into 3 bundles after their origin. The mean distance between the anterior tip of the temporal horn and the Meyer loop was 4.5 mm, between the temporal pole and the anterior border of the Meyer loop was 28.4 mm, and between the limen insulae and the Meyer loop was 10.7 mm. The mean distance between the lateral geniculate body and the lateral margin of the central bundle of the optic radiation was 17.4 mm. The white matter fiber dissection reveals the tridimensional intrinsic architecture of the brain, and its knowledge regarding the temporal lobe is particularly important for the neurosurgeon, mostly because of the complexity of the optic radiation and related fibers.

Analysis of the anatomy of the Papez circuit and adjoining limbic system by fiber dissection techniques

Fiber dissection techniques were used to study the limbic system, in particular the Papez circuit. The course, length and anatomical relations of the structures that make up the Papez circuit were delineated. Ten previously frozen and formalin-fixed cadaveric human brains were used, and dissected according to the fiber dissection techniques of Klingler et al. ( Schweiz Arch Neurol Psychiatry 1935; 36:247–56). The primary dissection tools were thin and curved wooden and metallic spatulas with tips of varying sizes. We found that the Papez circuit (mean length: 350 mm) begins in the hippocampus and continues into the fornix to reach the mamillary body. From there, the mamillothalamic tract continues to the anterior nucleus of the thalamus, which in turn connects to the cingulum by means of anterior thalamic radiations (mean length: 30 mm). The cingulum courses around the corpus callosum to end in the entorhinal cortex, which then projects to the hippocampus, thus completing the circuit. The average length and breadth of the mamillothalamic tract was 18 mm and 1.73 mm respectively. The average length of the cingulum was 19.6 cm and that of the fornix was 71 mm. The entire circuit was anatomically dissected first in situ in the hemisphere and was then reconstructed outside after removing its various components using fine fiber dissection under a surgical microscope. We found that fiber dissection elegantly delineates the anatomical subtleties of the Papez circuit and provides a three-dimensional perspective of the limbic system. Intricate knowledge of the anatomy of this part of the brain aids the neurosurgeon while performing epilepsy surgery and while approaching intrinsic brain parenchymal, ventricular and paraventricular lesions.

Dorsal Fronto‐Parietal Connections of the Human Brain: A Fiber Dissection Study of Their Composition and Anatomical Relationships

The goal of this study was to detail the composition of dorsal fronto-parietal connections in the human brain, focusing on the dorsal component of superior longitudinal fasciculus (SLF), short association fibers, their three-dimensional organization, and relationships with adjacent projection and commissural fibers. Ten human cerebral hemispheres (five left and five right) were obtained from necropsy specimens. The technique for specimen preparation was adapted from that previously described by Ludwig and Klingler for spreading groups of white matter fibers, rendering tracts visible and dissectible. Near the superior border of the hemisphere, we observed an overall organization consisting of a succession of "U" fibers in both sides of a narrow and irregular intermediary layer of white matter. Dissection of the core fibers leads to the corona radiata (intermingled with the callosal radiations) on the lateral aspect and to the callosal radiations at the medial aspect of the hemisphere. Based on our findings, the fiber dissection technique does not provide evidence of the presence of long horizontal association fibers in such location, as suggested by brain imaging techniques. The results of this study lead us to hypothesize that dorsal regions of the frontal and parietal lobes superior to the level of the cingulate sulcus are connected by a succession of short association pathways. Dissectible long association fibers are only encountered in a zone restricted to a lower and deeper portion of the superior parietal lobule. These fibers are clearly integrated in the lower portions of the SLF/arcuate fasciculus complex.

Microsurgical and tractographic anatomical study of insular and transsylvian transinsular approach

This study is to define the operative anatomy of the insula with emphasis on the transsylvian transinsular approach. The anatomy was studied in 15 brain specimens, among five were dissected by use of fiber dissection technique; diffusion tensor imaging of 10 healthy volunteers was obtained with a 1.5-T MR system. The temporal stem consists mainly of the uncinate fasciculus, inferior occipitofrontal fasciculus, Meyer’s loop of the optic radiation and anterior commissure. The transinsular approach requires an incision of the inferior limiting sulcus. In this procedure, the fibers of the temporal stem can be interrupted to various degrees. The fiber dissection technique is a very relevant and reliable method for neurosurgeons to study the details of brain anatomic features. The DTI fiber tracking technique can identify the fiber tracts of the temporal stem. Moreover, it will also help further functional study of human insula.

Microsurgical Anatomy of the Anterior Commissure

Detailed anatomy of the anterior commissure is unknown in the literature. To describe the anterior commissure with the use of a fiber dissection technique by focusing on the morphology (length and breadth of the 2 portions), the course, and the relations with neighboring fasciculi, particularly in the temporal stem. We dissected 8 previously frozen, formalin-fixed human brains under the operating microscope using the fiber dissection described by Klingler. Lateral, inferior, and medial approaches were made. The anterior olfactive limb of the anterior commissure was sometimes absent during dissection. The cross-sectional 3-dimensional magnetic resonance rendering images showed that fibers of the anterior commissure curved laterally within the basal forebrain. The tip of the temporal limb of the anterior commissure was intermingled with other fasciculi in various directions to form a dense 3-dimensional network. Functional anatomy and comparative anatomy are described. The anterior commissure can be involved in various pathologies such as diffuse axonal injury, schizophrenia, and cerebral tumoral dissemination.

The Accumbofrontal Fasciculus in the Human Brain: A Microsurgical Anatomical Study

The fiber-dissection technique provides unique 3-dimensional anatomic knowledge of the white matter. To better identify the frontostriatal pathways in the human brain, we used a fiber-dissection technique to reconstruct neural connections between the frontal cortex and the nucleus accumbens (NAcc), which is the most ventral extent of the striatum. Thirty previously frozen, formalin-fixed human brains were dissected under the operating microscope using a modified fiber-dissection technique, primarily reported by Klingler. Our serial dissections of 30 human brain specimens clearly demonstrated that projection fibers form a connection between the NAcc and the frontal lobe. We evidenced this newly described subcortical tract as an accumbofrontal fasciculus. This focal projection was concentrated at the level of the ventromedial part of the NAcc and characterized by an elective and specific projection from the orbitomedial prefrontal cortex, particularly the gyrus rectus and the medial orbital gyrus situated between the H-shaped and the medial orbital sulcus. The accumbofrontal fasciculus is an elective and specific projection from the orbitoprefrontal cortex. This fasciculus is part of a corticostriatothalamocortical loop and a putative target for deep-brain stimulation in the treatment of obsessive-compulsive disorder and major depression. The analysis of in vivo diffusion tractography, used today as a standard in the investigation of many brain disorders, could potentially take advantage of complementary anatomic correlations and functional extrapolations, as described in this study.

Central core of the cerebrum

The purpose of this study was to understand 3D relationships of white matter fibers and subcortical areas of gray matter in the central core. The lateral and medial aspects of 4 cerebral hemispheres were dissected, applying the fiber dissection technique under the microscope. The central core between the insula and midline includes the extreme, external, and internal capsules; claustrum; putamen; globus pallidus; caudate nucleus; amygdala; diencephalon; substantia innominata; fornix; anterior commissure; mammillothalamic tract; fasciculus retroflexus; thalamic peduncles, including optic and auditory radiations; ansa peduncularis; thalamic fasciculus; and lenticular fasciculus. It is attached to the remainder of the cerebral hemisphere by the cerebral isthmus, which is composed of white matter fibers located between the dorsolateral margin of the caudate nucleus and the full circumference of the circular sulcus of insula. The rostral fibers of the corpus callosum are included in the frontal portion of the cerebral isthmus. It is very useful for neurosurgeons to facilitate the understanding of spatial relationships and pertinent surgical approaches in and around the central core with a highly complex anatomy by using fiber dissection.

Microsurgical anatomy of the temporal stem: clinical relevance and correlations with diffusion tensor imaging fiber tracking

The authors used a fiber dissection technique to describe the temporal stem and explain the tendency of malignant tumors to spread within both the frontal and temporal lobes. The authors focused on the morphological characteristics and course of various fasciculi of the temporal stem, including the uncinate fascicle, occipitofrontal fascicle, anterior commissure, loop of the optic radiations (Meyer loop), and the ansa peduncularis. Eight previously frozen, formalin-fixed human brains were dissected under an operating microscope using the fiber dissection technique described by Klingler. Lateral, inferior, and medial approaches were made. Cross-sectional 3D MR images obtained in 10 patients without brain lesions demonstrated that fibers of the temporal stem, which were intermingled together in various ways, curved laterally within the basal forebrain. Various pathological entities affecting the temporal stem are described and discussed. The uncinate fascicle has 3 portions: a ventral extension, an intermediary segment called the isthmus, and a dorsal segment. The inferior occipitofrontal fasciculus is a layer of more superficial white matter that appeared to be superior to the uncinate fasciculus. A short ventral portion of the radiations of the corpus callosum was sometimes noted to run ventrally to enter the temporal stem and to reach both temporal lobes. To the authors' knowledge, a detailed anatomy of the temporal stem has not been previously described in the literature. The unique anatomy of the temporal stem provides a route for tumor spread between the frontal and temporal lobes.

Microsurgical anatomy of the ventral callosal radiations: new destination, correlations with diffusion tensor imaging fiber-tracking, and clinical relevance

In the current literature, there is a lack of a detailed map of the origin, course, and connections of the ventral callosal radiations of the human brain. The authors used an older dissection technique based on a freezing process as well as diffusion tensor imaging to investigate this area of the human brain. The authors demonstrated interconnections between areas 11, 12, and 25 for the callosal radiations of the trunk and rostrum of the corpus callosum; between areas 9, 10, and 32 for the genu; and between areas 6, 8, and 9 for the ventral third of the body. The authors identified new ventral callosal connections crossing the rostrum between both temporal poles and coursing within the temporal stem, and they named these connections the "callosal radiations of Peltier." They found that the breadth of the callosal radiations slightly increases along their course from the rostrum to the first third of the body of the corpus callosum. The fiber dissection and diffusion tensor imaging techniques are complementary not only in their application to the study of the commissural system in the human brain, but also in their practical use for diagnosis and surgical planning. Further investigations, neurocognitive tests, and other contributions will permit elucidation of the functional relevance of the newly identified callosal radiations in patients with disease involving the ventral corpus callosum.

New Insights Into the Anatomic Dissection of the Temporal Stem With Special Emphasis on the Inferior Fronto-occipital Fasciculus

To analyze the 3-dimensional relationships of the inferior fronto-occipital fasciculus (IFOF) within the temporal stem using anatomic dissection and to study the surgical application. Ten postmortem human hemispheres (5 right, 5 left) were dissected using the Klingler fiber dissection technique. The 3-dimensional relationships of the IFOF with different landmarks of the temporal stem, insula, and temporal lobe were analyzed and measured. An average distance of 10.9 mm (range, 8-15 mm) was observed between the limen insulae and the anterior edge of the IFOF under the inferior limiting sulcus of the insula. This anterior one-third of the temporal stem is crossed by the uncinate fasciculus. The IFOF crosses the posterior two-thirds of the temporal stem, in the space between the posterior limit of the uncinate fasciculus and the lateral geniculate body. The average superoinferior distance between the IFOF and the inferior limiting sulcus was 3.8 mm. The auditory radiations and the claustro-opercular and insulo-opercular fibers of the external and extreme capsules pass through the temporal stem above the IFOF, whereas the optic radiations pass below. In the transsylvian approach to the mesiotemporal structures in the left dominant hemisphere, an incision within the posterior 8 mm from the limen insulae is less likely to damage the IFOF than more posterior incisions along the inferior limiting sulcus. In the temporal transopercular approach to left temporo-insular gliomas, the IFOF constitutes the deep functional limit of the resection within the temporal stem.

A Understanding of the Temporal Stem

There has been inconsistency about definition of the temporal stem despite of several descriptions demonstrating its microanatomy using fiber dissection and/or diffusion tensor tractography. This study was designed to clarify three dimensional configurations of the temporal stem. The fronto-temporal regions of several formalin-fixed human cerebral hemispheres were dissected under an operating microscope using the fiber dissection technique. The consecutive coronal cuts of the dissected specimens were made to define the relationships of white matter tracts comprising the temporal stem and the subcortical gray matters (thalamus, caudate nucleus, amygdala) with inferior limiting (circular) sulcus of insula. The inferior limiting sulcus of insula, limen insulae, medial sylvian groove, and caudate nucleus/amygdala were more appropriate anatomical structures than the roof/dorso-lateral wall of the temporal horn and lateral geniculate body which were used to describe previously for delineating the temporal stem. The particular space located inside the line connecting the inferior limiting sulcus of insula, limen insulae, medial sylvian groove/amygdala, and tail of caudate nucleus could be documented. This space included the extreme capsule, uncinate fasciculus, inferior occipito-frontal fasciculus, anterior commissure, ansa peduncularis, and inferior thalamic peduncle including optic radiations, whereas the stria terminalis, cingulum, fimbria, and inferior longitudinal fiber of the temporal lobe were not passing through this space. Also, this continued posteriorly along the caudate nucleus and limiting sulcus of the insula. The temporal stem is white matter fibers passing through a particular space of the temporal lobe located inside the line connecting the inferior limiting sulcus of insula, limen insulae, medial sylvian groove/amygdala, and tail of caudate nucleus. The three dimensional configurations of the temporal stem are expected to give the very useful anatomical and surgical insights in the temporal lobe.