title: Pathological Location of Cranial Nerves in Petroclival Lesions: How to Avoid Their Injury during Anterior Petrosal Approach.
abstract: ObjectivesNumerous surgical approaches have been developed to access the petroclival region. The Kawase approach, through the middle fossa, is a well-described option for addressing cranial base lesions of the petroclival region. Our aim was to gather data about the variation of cranial nerve locations in diverse petroclival pathologies and clarify the most common pathologic variations confirmed during the anterior petrosal approach.MethodA retrospective analysis was made of both videos and operative and histologic records of 40 petroclival tumors from January 2009 to September 2013 in which the Kawase approach was used. The anatomical variations of cranial nerves IV-VI related to the tumor were divided into several location categories: superior lateral (SL), inferior lateral (IL), superior medial (SM), inferior medial (IM), and encased (E). These data were then analyzed taking into consideration pathologic subgroups of meningioma, epidermoid, and schwannoma.ResultsIn 41% of meningiomas, the trigeminal nerve is encased by the tumor. In 38% of the meningiomas, the trigeminal nerve is in the SL part of the tumor, and it is in 20% of the IL portion of the tumor. In 38% of the meningiomas, the trochlear nerve is encased by the tumor. The abducens nerve is not always visible (35%). The pathologic nerve pattern differs from that of meningiomas for epidermoid and trigeminal schwannomas.ConclusionThe pattern of cranial nerves IV-VI is linked to the type of petroclival tumor. In a meningioma, tumor origin (cavernous, upper clival, tentorial, and petrous apex) is the most important predictor of the location of cranial nerves IV-VI. Classification of four subtypes of petroclival meningiomas using magnetic resonance imaging is very useful to predict the location of deviated cranial nerves IV-VI intraoperatively.
authors.affiliation: Department of Neurosurgery, Clemens Hospital, Münster, Germany; Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Hamid
authors.initials: H
authors.lastname: Borghei-Razavi
authors.affiliation: Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Tomio
authors.affiliation: Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institute, Stockholm, Sweden.
authors.forename: Seyed-Mohammad
authors.initials: SM
authors.lastname: Fereshtehnejad
authors.affiliation: Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Shibao
authors.affiliation: Department of Neurosurgery, Clemens Hospital, Münster, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Schick
authors.affiliation: Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Toda
authors.affiliation: Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawase
keywords: anatomical variation; anterior petrosal approach; cranial nerves; petroclival lesions