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

Abstract

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.

Defining the relationship of the optic radiation to the roof and floor of the ventricular atrium: a focused microanatomical study

“…2,11,24,26,35,48 The fiber microdissection technique is still the gold standard for exploring intricate white matter pathways, which is why we chose it to be our basic method of investigation. 11,19,22,24,26,30,35,48 Through these focused white matter dissections, we consistently observed the roof of the atrium to be covered by claustrocortical fibers, parietopontine fibers, and fibers of the parietal thalamic radiation and tapetum and found no evidence of optic radiation fibers arching over this segment of the ventricular trigone. Accordingly, neurosurgical approaches that aim to access the atrium through its roof do not potentially place the visual pathway at risk of injury and therefore do not increase surgery-related morbidity.…”

“…The dissection tools used were fine metallic periosteal elevators, variously sized anatomical forceps, and microsurgical scissors, because they were easier to use and more precise in their handling than wooden spatulas. [20][21][22] During the dissections, numerous photographs were acquired to illustrate the regional cortical and subcortical anatomies of interest vividly. It must be highlighted that no photographs included in this study were edited by any image-correcting software so that they closely resemble the anatomy encountered during standard fiber microdissections in the setting of a microneurosurgical laboratory.…”

“…It must be highlighted that no photographs included in this study were edited by any image-correcting software so that they closely resemble the anatomy encountered during standard fiber microdissections in the setting of a microneurosurgical laboratory. [19][20][21][22]…”

Letter to the Editor: White matter fiber tract architecture and ventricular surgery

“…Firstly, Sir Hugh Cairns who established the Nuffield Department of Surgery at Oxford, where I trained. 15 Secondly, Sir Wylie McKissock who founded neurosurgery at Atkinson Morley Hospital, now part of St. George's Hospital in London, where I work. 1 Finally, F. John Gillingham in Edinburgh, whom I came to know first as my patient and then as a friend and inspiration in his final years.…”

“…8,9 Like Knight's subcaudate tractotomy, Richardson's limbic leukotomy continues to be performed in carefully selected cases refractory to medical treatment. 15 Gildenberg has suggested 4 tenets that characterize the field of functional neurosurgery: 1) the need to be innovative, 2) that functional neurosurgery is a science, 3) that functional neurosurgeons work as a community not in isolation, and 4) that there is also appreciation for the insight and courage of true pioneers. 4 Knight worked not in isolation but within such a neurosurgical community, and the centers that these 3 British giants of neurosurgery founded continue to exemplify such principles.…”