The cerebral isthmus: fiber tract anatomy, functional significance, and surgical considerations

OBJECT The cerebral isthmus is the white matter area located between the periinsular sulcus and the lateral ventricle. Studies demonstrating the fiber tract and topographic anatomy of this entity are lacking in current neurosurgical literature. Hence, the authors’ primary aim was to describe the microsurgical white matter anatomy of the cerebral isthmus by using the fiber dissection technique, and they discuss its functional significance. In addition, they sought to investigate its possible surgical utility in approaching lesions located in or adjacent to the lateral ventricle. METHODS This study was divided into 2 parts and included 30 formalin-fixed cerebral hemispheres, 5 of which were injected with colored silicone. In the first part, 15 uncolored specimens underwent the Klinger’s procedure and were dissected in a lateromedial direction at the level of the superior, inferior, and anterior isthmuses, and 10 were used for coronal and axial cuts. In the second part, the injected specimens were used to investigate the surgical significance of the superior isthmus in accessing the frontal horn of the lateral ventricle. RESULTS The microsurgical anatomy of the anterior, superior, and inferior cerebral isthmuses was carefully studied and recorded both in terms of topographic and fiber tract anatomy. In addition, the potential role of the proximal part of the superior isthmus as an alternative safe surgical corridor to the anterior part of the lateral ventricle was investigated. CONCLUSIONS Using the fiber dissection technique along with coronal and axial cuts in cadaveric brain specimens remains a cornerstone in the acquisition of thorough anatomical knowledge of narrow white matter areas such as the cerebral isthmus. The surgical significance of the superior isthmus in approaching the frontal horn of the lateral ventricle is stressed, but further studies must be carried out to elucidate its role in ventricular surgery.

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

Operative Neurosurgery ◽

10.1227/neu.0b013e3182556fde ◽

2012 ◽

Vol 71 (suppl_1) ◽

pp. ons160-ons172 ◽

Cited By ~ 8

Author(s):

Richard Gonzalo Párraga ◽

Guilherme Carvalhal Ribas ◽

Leonardo Christiaan Welling ◽

Raphael Vicente Alves ◽

Evandro de Oliveira

Keyword(s):

White Matter ◽

Temporal Lobe ◽

Lateral Geniculate Body ◽

Microsurgical Anatomy ◽

Optic Radiation ◽

3 Dimensional ◽

Important Relationship ◽

Fiber Dissection ◽

The Mean ◽

Dissection Technique

Abstract BACKGROUND: The fiber dissection technique provides unique 3-dimensional anatomic knowledge of the white matter. OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

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Anatomy of the Anterior Temporal Lobe and the Frontotemporal Region Demonstrated by Fiber Dissection

Neurosurgery ◽

10.1227/01.neu.0000140843.62311.24 ◽

2004 ◽

Vol 55 (5) ◽

pp. 1174-1184 ◽

Cited By ~ 74

Author(s):

Diedrik Peuskens ◽

Johannes van Loon ◽

Frank Van Calenbergh ◽

Raymond van den Bergh ◽

Jan Goffin ◽

...

Keyword(s):

White Matter ◽

Temporal Lobe ◽

Anterior Commissure ◽

Three Dimensional ◽

Dimensional Structure ◽

Surgical Approaches ◽

Anterior Temporal Lobe ◽

White Matter Tracts ◽

Fiber Dissection ◽

Dissection Technique

Abstract OBJECTIVE: The white matter structure of the anterior temporal lobe and the frontotemporal region is complex and not well appreciated from the available neurosurgical literature. The fiber dissection method is an excellent means of attaining a thorough knowledge of the three-dimensional structure of the white matter tracts. This study was performed to demonstrate the usefulness of the dissection technique in understanding the white matter anatomy and the effects of current surgical approaches on the subcortical structure of the region. METHODS: Seventeen brain specimens obtained at routine autopsy were dissected by use of Klingler's fiber dissection technique after preparation by fixation and freezing. The dissections were performed with an operating microscope and followed a stepwise pattern of progressive white matter dissection. RESULTS: The dissection is described in an orderly fashion showing the white matter tracts of the anterior temporal lobe and the frontotemporal region. An insight is gained into the three-dimensional course of the anterior loop of the optic radiation, the temporal stem, the anterior commissure, and the ansa peduncularis. CONCLUSION: The anterior temporal lobe and the frontotemporal region contain several important white matter tracts that can be uniquely understood by performing a white matter dissection of the region. Surgical procedures on the anterior temporal lobe differ substantially as to their repercussions on the subcortical white matter tract anatomy, as shown by the findings in this study.

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Surgical anatomy of supratentorial midline lesions

Neurosurgical FOCUS ◽

10.3171/foc.2005.18.6.14 ◽

2005 ◽

Vol 18 (6) ◽

pp. 1-9 ◽

Cited By ~ 43

Author(s):

M. Gazi Yaşargil ◽

Uğur Türe ◽

Dianne C. H. Yaşargil ¸

Keyword(s):

White Matter ◽

Surgical Approach ◽

Surgical Anatomy ◽

Cerebral Hemispheres ◽

Surgical Exploration ◽

Fiber Dissection ◽

Dissection Technique ◽

Surgical Aspects ◽

The Brain

Object In this paper the authors correlate the surgical aspects of deep median and paramedian supratentorial lesions with the connective fiber systems of the white matter of the brain. Methods The cerebral hemispheres of 10 cadaveric brains were dissected in a mediolateral direction by using the fiber dissection technique, corresponding to the surgical approach. Conclusions This study illuminates the delicacy of the intertwined and stratified fiber laminae of the white matter, and establishes that these structures can be preserved at surgical exploration in patients.

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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

Operative Neurosurgery ◽

10.1227/neu.0000000000000271 ◽

2013 ◽

Vol 10 (2) ◽

pp. 294-304 ◽

Cited By ~ 8

Author(s):

Carlos Alarcon ◽

Matteo de Notaris ◽

Kenneth Palma ◽

Guadalupe Soria ◽

Alessandro Weiss ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

White Matter ◽

Magnetic Resonance ◽

Ex Vivo ◽

Central Core ◽

Resonance Imaging ◽

Anatomic Study ◽

Neuronavigation System ◽

Fiber Dissection ◽

Dissection Technique

Abstract BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

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Posterior Quadrant Disconnection: A Fiber Dissection Study

Operative Neurosurgery ◽

10.1093/ons/opx060 ◽

2017 ◽

Vol 14 (1) ◽

pp. 45-50 ◽

Cited By ~ 7

Author(s):

Alexander Verhaeghe ◽

Thomas Decramer ◽

Wim Naets ◽

Wim Van Paesschen ◽

Johannes van Loon ◽

...

Keyword(s):

White Matter ◽

Corpus Callosum ◽

Anatomic Study ◽

Posterior Cortex ◽

Optimal Outcomes ◽

Posterior Quadrant ◽

Fiber Dissection ◽

Temporal Stem ◽

Dissection Technique ◽

The Brain

AbstractBACKGROUNDPosterior quadrant disconnection can be highly effective in the surgical treatment of selected cases of refractory epilepsy. The technique aims to deafferent extensive areas of epileptogenic posterior cortex from the rest of the brain by isolating the temporoparietooccipital cortex.OBJECTIVETo describe this procedure and relevant white matter tracts with a specific emphasis on the extent of callosotomy in an anatomic study.METHODSTwenty hemispheres were dissected according to Klingler's fiber dissection technique illustrating the peri-insular (temporal stem, superior longitudinal fasciculus, corona radiata) and mesial disconnection (mesiotemporal cortex, cingulum, and corpus callosum).RESULTSExtensive white matter tract disconnection is obtained after posterior quadrant disconnection. Callosal fibers connecting the anterior most part of the parietal cortex invariably ran through the isthmus of the corpus callosum and need to be disconnected, while frontal lobe connections including the corticospinal tract and the anterior two-thirds of the corpus callosum are spared during the procedure.CONCLUSIONOur findings suggest the involvement of both the splenium and the isthmus in interhemispheric propagation in posterior cortex epilepsies. Sectioning the total extent of the posterior one-third of the corpus callosum might therefore be necessary to achieve optimal outcomes in posterior quadrant epilepsy surgery.

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Optic radiations: a microsurgical anatomical study

Journal of Neurosurgery ◽

10.3171/jns.2006.105.2.294 ◽

2006 ◽

Vol 105 (2) ◽

pp. 294-300 ◽

Cited By ~ 49

Author(s):

Johann Peltier ◽

Nadine Travers ◽

Christophe Destrieux ◽

Stéphane Velut

Keyword(s):

Lateral Ventricle ◽

Average Distance ◽

Morphological Characteristics ◽

Anatomical Study ◽

The Body ◽

Surgical Approaches ◽

Optic Radiation ◽

Fiber Dissection ◽

Dissection Technique ◽

Optic Radiations

Object In this study, the authors used a fiber-dissection technique to describe the optic radiation. They focused on the morphological characteristics (length and breadth) of this structure, its course, and its relationships with neighboring fasciculi and the lateral ventricle. Methods The authors dissected 10 previously frozen, formalin-fixed human brains with the aid of an operating microscope by following the fiber dissection technique described by Klingler in 1960. Lateral, inferior, and medial approaches were made. The optic radiation, also known as the Gratiolet radiation, extended from the lateral geniculate body to the calcarine fissure. The average distance from the tip of the anterior Meyer loop to the calcarine sulcus was 105 mm (range 95–114 mm). The breadth of the optic radiations, one on each side of the brain, averaged 17 mm at the level of the inferior horn (range 15–18 mm). This tract could be divided into three main segments: the anterior or Meyer loop, the body, and the end of the optic radiation. Adjacent anatomical structures included: laterally, the inferior longitudinal fasciculi; medially, the tapetum of the corpus callosum; and the ependyma of the inferior horn of the lateral ventricle. Conclusions Various practical surgical approaches are discussed. The knowledge gained by studying this particular anatomy will help prevent injury to the optic radiations during neurosurgery.

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The white matter tracts of the cerebrum in ventricular surgery and hydrocephalus

Journal of Neurosurgery ◽

10.3171/2016.1.jns152082 ◽

2017 ◽

Vol 126 (3) ◽

pp. 945-971 ◽

Cited By ~ 34

Author(s):

Abuzer Güngör ◽

Serhat Baydin ◽

Erik H. Middlebrooks ◽

Necmettin Tanriover ◽

Cihan Isler ◽

...

Keyword(s):

White Matter ◽

Anterior Commissure ◽

Internal Capsule ◽

Surgical Approaches ◽

White Matter Tracts ◽

Lateral Ventricles ◽

Fiber Dissection ◽

Dissection Technique ◽

Relationship Of ◽

The Relationship

OBJECTIVE The relationship of the white matter tracts to the lateral ventricles is important when planning surgical approaches to the ventricles and in understanding the symptoms of hydrocephalus. The authors' aim was to explore the relationship of the white matter tracts of the cerebrum to the lateral ventricles using fiber dissection technique and MR tractography and to discuss these findings in relation to approaches to ventricular lesions. METHODS Forty adult human formalin-fixed cadaveric hemispheres (20 brains) and 3 whole heads were examined using fiber dissection technique. The dissections were performed from lateral to medial, medial to lateral, superior to inferior, and inferior to superior. MR tractography showing the lateral ventricles aided in the understanding of the 3D relationships of the white matter tracts with the lateral ventricles. RESULTS The relationship between the lateral ventricles and the superior longitudinal I, II, and III, arcuate, vertical occipital, middle longitudinal, inferior longitudinal, inferior frontooccipital, uncinate, sledge runner, and lingular amygdaloidal fasciculi; and the anterior commissure fibers, optic radiations, internal capsule, corona radiata, thalamic radiations, cingulum, corpus callosum, fornix, caudate nucleus, thalamus, stria terminalis, and stria medullaris thalami were defined anatomically and radiologically. These fibers and structures have a consistent relationship to the lateral ventricles. CONCLUSIONS Knowledge of the relationship of the white matter tracts of the cerebrum to the lateral ventricles should aid in planning more accurate surgery for lesions within the lateral ventricles.

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Deciphering the frontostriatal circuitry through the fiber dissection technique: direct structural evidence on the morphology and axonal connectivity of the fronto-caudate tract

Journal of Neurosurgery ◽

10.3171/2020.7.jns201287 ◽

2021 ◽

pp. 1-13

Author(s):

Spyridon Komaitis ◽

Christos Koutsarnakis ◽

Evgenia Lani ◽

Theodosis Kalamatianos ◽

Evangelos Drosos ◽

...

Keyword(s):

Diffusion Tensor ◽

Anterior Part ◽

Relevant Literature ◽

The Body ◽

Fiber Tracts ◽

Brodmann Areas ◽

Fiber Dissection ◽

Dissection Technique ◽

Subcortical Pathway ◽

Formalin Fixed

OBJECTIVEThe authors sought to investigate the very existence and map the topography, morphology, and axonal connectivity of a thus far ill-defined subcortical pathway known as the fronto-caudate tract (FCT) since there is a paucity of direct structural evidence regarding this pathway in the relevant literature.METHODSTwenty normal adult cadaveric formalin-fixed cerebral hemispheres (10 left and 10 right) were explored through the fiber microdissection technique. Lateral to medial and medial to lateral dissections were carried out in a tandem manner in all hemispheres. Attention was focused on the prefrontal area and central core since previous diffusion tensor imaging studies have recorded the tract to reside in this territory.RESULTSIn all cases, the authors readily identified the FCT as a fan-shaped pathway lying in the most medial layer of the corona radiata and traveling across the subependymal plane before terminating on the superolateral margin of the head and anterior part of the body of the caudate nucleus. The FCT could be adequately differentiated from adjacent fiber tracts and was consistently recorded to terminate in Brodmann areas 8, 9, 10, and 11 (anterior pre–supplementary motor area and the dorsolateral, frontopolar, and fronto-orbital prefrontal cortices). The authors were also able to divide the tract into a ventral and a dorsal segment according to the respective topography and connectivity observed. Hemispheric asymmetries were not observed, but instead the authors disclosed asymmetry within the FCT, with the ventral segment always being thicker and bulkier than the dorsal one.CONCLUSIONSBy using the fiber microdissection technique, the authors provide sound structural evidence on the topography, morphology, and connectional anatomy of the FCT as a distinct part of a wider frontostriatal circuitry. The findings are in line with the tract’s putative functional implications in high-order motor and behavioral processes and can potentially inform current surgical practice in the fields of neuro-oncology and functional neurosurgery.

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

ARS Medica Tomitana ◽

10.2478/arsm-2014-0021 ◽

2015 ◽

Vol 20 (3) ◽

pp. 115-122 ◽

Cited By ~ 1

Author(s):

Goga Cristina ◽

Brinzaniuc Klara ◽

Florian I.S. ◽

Rodriguez Mena R.

Keyword(s):

White Matter ◽

Three Dimensional ◽

Internal Capsule ◽

Brain Anatomy ◽

Neurosurgical Procedures ◽

Fiber Tracts ◽

Fiber Dissection ◽

White Matter Fiber Tracts ◽

Three Dimensional Configuration ◽

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.

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Central core of the cerebrum

Journal of Neurosurgery ◽

10.3171/2010.9.jns10530 ◽

2011 ◽

Vol 114 (2) ◽

pp. 463-469 ◽

Cited By ~ 14

Author(s):

Chan-Young Choi ◽

Seong-Rok Han ◽

Gi-Taek Yee ◽

Chae-Heuck Lee

Keyword(s):

White Matter ◽

Caudate Nucleus ◽

Anterior Commissure ◽

Central Core ◽

Surgical Approaches ◽

Fasciculus Retroflexus ◽

Complex Anatomy ◽

Fiber Dissection ◽

Mammillothalamic Tract ◽

Dissection Technique

Object The purpose of this study was to understand 3D relationships of white matter fibers and subcortical areas of gray matter in the central core. Methods The lateral and medial aspects of 4 cerebral hemispheres were dissected, applying the fiber dissection technique under the microscope. Results 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. Conclusions 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.

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