Introduction: Reliable anatomical landmarks are essential to avoiding injuries to the optic tract, anterior choroidal artery and the basal ganglia during anterior temporal lobectomy (ATL). We describe a new anatomic landmark, specifically the Anterior Temporal Sulcus (ATS), as a reliable method to define the anterior portion of the endorhinal sulcus and the superior limit of amygdala resection.

Methods: Twenty-five consecutive patients undergoing anterior temporal lobectomies at Rush University Medical Center (RUMC) were identified and their pre-operative brain magnetic resonance imaging (MRI) studies were analyzed.

Results: The ATS was clearly identifiable on coronal MRI in 48 out of 50 temporal lobes (96%). The ATS was present in all 25 left temporal lobes (100%); two of the 25 right temporal lobes had absent ATS (8%). Following the ATS posteriorly on coronal MRI, it lead to the endorhinal sulcus and accurately predicted the superior extent of in all 25 patients (48 temporal lobes). There is zero incidence of injury to the optic tract, anterior choroidal artery, or basal ganglia using ATS as the landmark for superior limit of amygdala resection.

Conclusions: The ATS is a reliable anatomical landmark that accurately delineates the superior border of the amygdala during anterior temporal lobectomy.

Patient Care: The ATS is a reliable anatomical landmark that accurately delineates the superior border of the amygdala during anterior temporal lobectomy to minimize potential surgical complications.

Learning Objectives: 1) Describe the anatomy of the mesial temporal region 2) Identify the anatomical boundaries for amygdala 3) Identify potential neurovascualr structure that could be injuried during temporal lobectomy.

References: 1. Wiebe S, Blume WT, Girvin JP, Eliasziw M, Effectiveness and Efficiency of Surgery for Temporal Lobe Epilepsy Study Group: A randomized, controlled trial of surgery for temporal-lobe epilepsy. N Engl J Med 2001 Aug 2;345:311–318. 2. Hu W-H, Zhang C, Zhang K, Meng F-G, Chen N, Zhang J-G: Selective amygdalohippocampectomy versus anterior temporal lobectomy in the management of mesial temporal lobe epilepsy: a meta-analysis of comparative studies: A systematic review. J Neurosurg 2013 Nov;119:1089–1097. 3. Campero A, Tróccoli G, Martins C, Fernandez-Miranda JC, Yasuda A, Rhoton AL: Microsurgical approaches to the medial temporal region: an anatomical study. Neurosurgery 2006 Oct;59:ONS279–307; discussion ONS307–308. 4. Earle KM, Baldwin M, Penfield W: Temporal lobe seizures; the anatomy and pathology of the probable cause. J Neuropathol Exp Neurol 1953 Jan;12:98–99. 5. Kiernan JA: Anatomy of the Temporal Lobe. Epilepsy Res Treat 2012;2012:1–12. 6. Kucukyuruk B, Richardson RM, Wen HT, Fernandez-Miranda JC, Rhoton AL: Microsurgical Anatomy of the Temporal Lobe and Its Implications on Temporal Lobe Epilepsy Surgery. Epilepsy Res Treat 2012;2012:1–17. 7. Roper SN, Rhoton AL: Surgical anatomy of the temporal lobe. Neurosurg Clin N Am 1993 Apr;4:223–231. 8. Straus D, Byrne RW, Sani S, Serici A, Moftakhar R: Microsurgical anatomy of the transsylvian translimen insula approach to the mediobasal temporal lobe: Technical considerations and case illustration. Surg Neurol Int 2013;4:159. 9. Fernández-Miranda JC, de Oliveira E, Rubino PA, Wen HT, Rhoton AL: Microvascular anatomy of the medial temporal region: part 1: its application to arteriovenous malformation surgery. Neurosurgery 2010 Sep;67:ons237–276; discussion ons276. 10. Wen HT, Rhoton AL, de Oliveira E, Castro LHM, Figueiredo EG, Teixeira MJ: Microsurgical anatomy of the temporal lobe: part 2--sylvian fissure region and its clinical application. Neurosurgery 2009 Dec;65:1–35; discussion 36. 11. Novak K, Czech T, Prayer D, Dietrich W, Serles W, Lehr S, et al.: Individual variations in the sulcal anatomy of the basal temporal lobe and its relevance for epilepsy surgery: an anatomical study performed using magnetic resonance imaging. J Neurosurg 2002 Mar;96:464–473. 12. Wen HT, Rhoton AL, Marino R: Gray matter overlying anterior basal temporal sulci as an intraoperative landmark for locating the temporal horn in amygdalohippocampectomies. Neurosurgery 2006 Oct;59:ONS221–227; discussion ONS227.