Elsevier

World Neurosurgery

Volume 100, April 2017, Pages 144-158
World Neurosurgery

Original Article
Three-Dimensional Anatomy of the White Matter Fibers of the Temporal Lobe: Surgical Implications

https://doi.org/10.1016/j.wneu.2016.12.120Get rights and content

Background

The aim of this work is to describe in detail the complex 3-dimensional organization of the white matter of the temporal lobe and discuss the surgical implications of the approaches to lesions located into the mesial temporal region and within the temporal horn and the atrium of the lateral ventricles.

Methods

Sixteen human cerebral hemispheres fixed in a 10% formalin solution for at least 40 days were studied. After removal of the arachnoid membrane, the hemispheres were frozen at −15°C for at least 14 days, and the Klingler technique, which consists of the microscopic dissection and progressive identification of white matter fibers, was performed.

Results

The dissection allowed us to appreciate the topographical organization of the white matter of the temporal lobe identifying the most important association, projection, and commissural fasciculi. The dissection from the lateral side allowed the progressive visualization of the superior longitudinal fasciculus and its components, the extreme and external capsule, the uncinate fasciculus, the inferior fronto-occipital fasciculus, the anterior commissure, the internal capsule, and the optic radiations. The dissection was completed from the inferior and medial side for identification of the cingulum and the fornix.

Conclusions

The complex 3-dimensional organization of the white matter substance of the temporal lobe is characterized by 2 main systems of boundaries: the sagittal stratum and the temporal stem. Their knowledge is essential for the appropriate treatment of pathologies localized in this region as demonstrated by the 2 clinical cases presented in this work.

Introduction

The temporal lobe is one of the regions of great neurosurgical interest in regard to its complex anatomical organization and the large number of diseases localized in its context. Cerebral aneurysms, arteriovenous malformations, cavernomas, brain gliomas, and traumatic pathology potentially can occur in the temporal lobe. In addition, its mesial portion, in relation to a complex cytoarchitectonic organization, is the source of origin for drug-resistant epilepsies. A detailed knowledge of the surgical anatomy of the temporal lobe is essential to treat pathologies located in regions of difficult surgical access to limit the risk of damaging functionally important structures.1, 2

The aim of this work is to describe in detail the complex but at the same time magnificent 3-dimensional organization of the white matter of the temporal lobe through the Klingler dissection. This technique is based on the freezing of previously formalin-fixed brains. The aqueous formalin solution penetrates little or not at all into the myelinated fibers but instead remains between the fibers. Consequently, when the brain is frozen, ice forms between the fibers. Because the volume of water increases by about 10% when it solidifies into ice, the fibers thus separate from each other. This loosening up of the brain substance facilitates dissection.3, 4, 5, 6, 7 This technique allows the identification of the countless white matter tracts that underlie in this area by providing a clear overview of the topographical relationships of the individual fiber bundles. After we examine the complex topographical organization of the white matter of the temporal lobe and the clinical consequences of injury of each identified bundle, we discuss the surgical implications of the approaches to lesions located into the mesial temporal region and within the temporal horn and the atrium of the lateral ventricles.

Section snippets

Materials and Methods

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.

Sixteen human cerebral hemispheres were fixed in a 10% formalin solution for at least 40 days (demographics data are summarized in Table 1). The first step was the removal of the arachnoidal and vascular structures under microscopic

Anatomical Dissection

The dissection started with the removal of the cerebral hemispheric cortex with the exception of the frontal, parietal, and temporal operculum. In this first phase of dissection, we began to appreciate the morphology of the superior longitudinal fasciculus. For a better view, it was necessary to extend the removal to the opercular surfaces until the peripheral portion of the Sylvian fissure to visualize the superficial part of the insula. This appeared to be localized between the pars

Illustrative Case 1

A 40-year-old woman came to our attention because of the sudden onset of drug-resistant headache. At the emergency department of our institution, she underwent computed tomography scan of the brain, which documented the presence of hemoventricle involving both the frontal horns, the atrium, and the right temporal horn (Figure 7A). As a consequence, an angio-computed tomography scan also was performed. It showed an arteriovenous malformation (AVM) of the right temporo-mesial region (Figure 7B).

Discussion

There are several features that make the temporal lobe unique. From a cytoarchitectonic point of view, 3 different areas can be identified: the allocortex, composed of 3 layers including the pre-piriform area, the uncal semilunar gyrus, and the hippocampus; the mesocortex, composed of 6 layers represented by the parahippocampal gyrus; and the isocortex, also composed of 6 layers, which is identifiable in the superior, middle, and inferior temporal gyrus. Therefore, there is a gradual transition

Conclusions

The 3-dimensional organization of the white matter fibers localized within the temporal lobe is one of the most fascinating but, at the same time, complex neuroanatomic topics. The Klingler white matter dissection technique still plays a pivotal role in the study of the cerebral white matter substance and through its development it has been possible to deepen the knowledge in the field of the temporal white matter three dimensional organization.

From a surgical point of view, these studies

References (17)

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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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