title: The cerebral isthmus: fiber tract anatomy, functional significance, and surgical considerations.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Neurosurgery, University of Athens, Evangelismos Hospital;|Microneurosurgery Laboratory, Evangelismos Hospital, Athens, Greece.
authors.forename: Christos
authors.initials: C
authors.lastname: Koutsarnakis
authors.affiliation: Department of Neurosurgery, University of Athens, Evangelismos Hospital;|Microneurosurgery Laboratory, Evangelismos Hospital, Athens, Greece.
authors.forename: Faidon
authors.initials: F
authors.lastname: Liakos
authors.affiliation: Hellenic Center for Neurosurgical Research "Petros Kokkalis;" and.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Liouta
authors.affiliation: Department of Neurosurgery, University of Athens, Evangelismos Hospital;|Microneurosurgery Laboratory, Evangelismos Hospital, Athens, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Themistoklis
authors.affiliation: Department of Neurosurgery, University of Athens, Evangelismos Hospital;|Hellenic Center for Neurosurgical Research "Petros Kokkalis;" and.
authors.forename: Damianos
authors.initials: D
authors.lastname: Sakas
authors.affiliation: Department of Neurosurgery, University of Athens, Evangelismos Hospital;|Hellenic Center for Neurosurgical Research "Petros Kokkalis;" and.|Microneurosurgery Laboratory, Evangelismos Hospital, Athens, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Stranjalis
mesh_terms: D002102:Cadaver; D006801:Humans; D020547:Lateral Ventricles / Q000033:anatomy & histology; D008866:Microsurgery; D009412:Nerve Fibers; D009413:Nerve Fibers, Myelinated; D009434:Neural Pathways / Q000033:anatomy & histology* / Q000601:surgery; D019635:Neurosurgical Procedures / Q000379:methods*; D011712:Pyramidal Tracts / Q000033:anatomy & histology; D016707:Tissue Fixation; D066127:White Matter / Q000033:anatomy & histology* / Q000601:surgery*
keywords: DTI = diffusion tensor imaging; MCA = middle cerebral artery; anatomy; cerebral isthmus; fiber dissection; insula; microsurgical anatomy; periinsular sulcus; ventricular approaches