The selective amygdalohippocampectomy for intractable temporal limbic seizures

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The proximal (anterior) transsylvian approach through a pterional craniotomy was developed by the senior author (M.G.Y.) in 1967 for the microsurgical treatment of saccular aneurysms of the circle of Willis, frontoorbital and temporobasal arteriovenous malformations, cavernomas, and extrinsic and intrinsic tumors. The acquired positive surgical experiences on this large series enabled the senior author, in 1973, to apply this approach for the selective amygdalohippocampectomy in patients with intractable mesial temporal lobe epilepsy.


The proximal (anterior) transsylvian-transamygdala approach to the mesial temporal structures permits the selective two-thirds resection of the amygdala and hippocampus-parahippocampus in an anteroinferior to posteroinferior exploration axis along the base of the semicircular temporal horn. This strategy ensures preservation of the overlying neopallial temporal convolutions such as the T1, T2, T3, and T4 gyri as well as the related subcortical connective fiber systems and other essential components of the temporal white matter.

The application of rigid brain self-retaining retractor systems was strictly avoided during the entire procedure. Computer-assisted navigation was never used. On routine postoperative CT scanning and MR imaging studies, infarction was not observed in any patient. The availability of tractography technology has proven that the connective fiber system around the resected mesial temporal area remains intact.


The surgical outcome and results on neoplastic and vascular lesions of the mesiobasal temporal region have been presented in Volumes II, IIIB, and IVB of Microneurosurgery. The surgical outcomes and results in 102 patients with mesial temporal seizures who underwent surgery performed by the senior author in Zürich have been previously published.

In this paper, 73 patients who underwent surgery between 1994 and September 2006 in Little Rock, Arkansas, are presented, and 13 other patients are excluded who underwent surgery after September 2006. Altogether, among 188 patients who underwent surgery, there was no surgical mortality or morbidity, and no neurological deficits, new neurocognitive dysfunction, or impairments of the preoperative incapacities.


The surgical outcome in terms of seizures was rewarding in the majority of patients, particularly in those who exhibited the following irregularities on preoperative investigations: regular local dysfunctions on electroencephalography, dysmorphic changes in the mesiobasal temporal parenchyma on MR imaging studies, and hypometabolism in the anterior third of the temporal lobe on PET studies.

Abbreviations used in this paper: AChA = anterior choroidal artery; EEG = electroencephalography; ICA = internal carotid artery; MCA = middle cerebral artery; MTLE = mesial temporal lobe epilepsy; PCA = posterior cerebral artery; PCoA = posterior communicating artery.

Article Information

Address correspondence to: M. Gazi Yaşargil, M.D., University of Arkansas for Medical Sciences, Department of Neurosurgery, 4301 West Markham, #507, Little Rock, Arkansas 72205.

© AANS, except where prohibited by US copyright law.



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    Illustration showing the position of the patient's head and craniotomy site. Reprinted from Microneurosurgery (Thieme), Vol 4B, Fig. 3a, p 37, with permission of the author.

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    Left: Illustration of the sylvian cistern with its distinct 3 components: fissure, interopercular sulci, and fossa. Right: Illustration showing sections of the sylvian fossa with a variety of interopercular sulci along the fissure. The sylvian fissure comprises the following 3 parts: the proximal (preinsular, 1), middle (insular, 2), and posterior (retroinsular, 3). Inf = inferior pouch of the sylvian fossa. Reprinted with permission from Dr. Yaşargil.

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    Illustrations showing the course variations of the left M1 segment in the horizontal plane: the straight diagonal (A), temporal convex (B), orbital convex (C), and S-shaped (D) courses.

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    Illustrations showing the course variations of the left M1 segment in the vertical plane: the straight diagonal (in 45% of cases [A]), posterior (in ~ 10% [B]), anterior (in ~ 40% [C]), and double anterior loupe (in ~ 5% [D]) courses.

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    Illustrations of the branching variations of the left M1 segment. A: The common trunk of the temporal arteries arising from the proximal or middle part of the M1 segment (temporal early bifurcation; in ~ 10% of cases). B: The common trunk of the orbital and frontal arteries arising from the medial wall of the M1 segment (frontal early bifurcation; ~ 18%). C: Both common trunks arising from the proximal or middle part of the M1 segment (early pseudobifurcation; ~ 2%). D: The accessory MCA can imitate a double M1 segment (~ 0.5%). E: The proximal origin of both trunks and accessory MCA imitating 4 M1 segments (~ 0.1%).

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    Illustrations showing variations of MCA divisions on the left side. A: No bifurcation (~ 2% of cases). B: Typical bifurcation with superior and inferior trunks (50%). C: Pseudo-tetrabifurcation; early divisions of superior and inferior trunks create 4 trunks (~ 8%). D: The middle trunk originates from the inferior (temporal) trunk (~ 10%). E: The middle trunk originates from the superior (frontal) trunk (~ 15%). F: The middle trunk arises from the distal inferior (temporal) trunk (~ 15%).

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    Illustration of the M1–M4 segments, coronal view, left side. H = Heubner artery; Lst = lenticulostriate arteries.

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    Illustrations showing variations in the width of the proximal sylvian cistern and the location of the M1 segment and the MCA (M). Left: The large interopercular sulci (~ 5%). Right: The narrow interpeduncular sulci (~ 30%). Fr. = frontal lobe; Tem. = temporal lobe. Reprinted from Microneurosurgery (Thieme), Vol 1, p 38, Fig. 24A and B, with permission of the author.

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    Illustrations. Left: The lateral orbital gyrus (Fr.) indents the polar planum (Tem.) (~ 60). Right: The proximal part of the superior temporal gyrus indents the lateral orbital gyrus (~ 5%). Reprinted from Microneurosurgery (Thieme), Vol 1, p 38, Fig. 25A and B, with permission of the author.

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    Drawing showing the proximal transsylvian approach. The ICA, PCoA, AChA, M1 segment, MCA bifurcation, and temporal branches are exposed. The arrow and dotted line indicate the place of incision over amygdala. Reprinted from Advances and Technical Standards in Neurosurgery, Vol 12, p 109, Fig. 9, with permission from Springer.

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    Illustration of the surgical exploration of the right mesial temporal region. Incision (dotted line indicated by arrow) through the piriform cortex over the amygdala between the polar and anterior temporal arteries, or just distal to the latter. Reprinted from Advances and Technical Standards in Neurosurgery, Vol 12, p 114, Fig. 11, with permission from Springer.

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    Postresection illustration of the anterior two-thirds of the right hippocampus and parahippocampus. 1 denotes the optic tract; 2, the basilar vein; 3, the AChA; 4, the P2 segment; and 5, the choroidal plexus. Reprinted from Advances and Technical Standards in Neurosurgery, Vol 12, p 117, Fig. 13, with permission from Springer.

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    Left: Drawing showing the vascularization of the right hippocampus and parahippocampus from branches of the AChA and PCA, which may display reciprocal variation in dominance. Right: Illustration showing the variation of vascularization within the right hippocampal and parahippocampal regions. Arrows indicate the prominent origins of feeding vessels from the AChA, PCA, and their branches. a. = artery; aita = anterior inferior temporal artery; ant. = anterior; B = basilar artery; chor. = choroidal; com. = communicating; gen. = geniculate; III = cranial nerve III; inf. = inferior; lat. = lateral; lpcha = lateral posterior choroidal artery; med. = medial; mita = middle inferior temporal artery; occ. = occipital; par. = parietal; parietoocc. = parietoocipital; post. = posterior; post. com. a. = PCoA; sca = superior cerebellar artery; temp. = temporal; trunc = trunk. (Drawn based on the study by Dr. A. Erdem.) Reprinted from Microneurosurgery (Thieme), Vol 4B, p 256, Fig. 17.5a, with permission of the author.

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    Illustration of the right basilar vein, its tributaries, and connections. Reprinted from Microneurosurgery (Thieme), Vol 4B, p 258, Fig. 17.6A, with permission of the author.

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    A: Illustration of right hippocampus and parahippocampus, hippocampal head (1), hippocampal body (2), hippocampal tail (3), fimbria (4), subiculum (5), collateral eminence (6), hippocampal and parahippocampal veins entering the basilar vein (7), red arrows indicate lines of dissection (8), peduncle (crus cerebri; 9), and hippocampal arteries in hippocampal sulcus (10). Reprinted from Microneurosurgery (Thieme), Vol 4B, p 259, Fig. 15.7b, with permission of the author. B: Photographs of a selectively resected right-sided amygdala, hippocampus, and parahippocampus. Parts of the amygdala and hippocampus can be seen through the temporal horn side (left). View from the basal (tentorial) side, showing the parahippocampus (right).

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    A: Coronal MR image obtained after a left-sided selective amygdalohippocampectomy was performed in a 23-year-old man with mesial temporal epilepsy since his childhood. Arrows indicate the anterior commissure. B: Diffusion tensor tractography in the same patient. The yellow area denotes the anterior commissure; green, the uncinate fascicle; and pink, the inferior frontooccipital fascicle. C: Axial postoperative diffusion tensor MR image obtained in the same patient. Blue area denotes posterior thalamic peduncle together with optic radiation. Since surgery 2 years ago, no seizure has occurred.

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    Photograph of a cadaver brain showing the different approaches for selective amygdalohippocampectomy. The proximal transsylvian-transamygdala (1), transgyral (2), transsulcal (3), subtemporal (4), and supracerebellar-transtentorial (5) approaches. Reprinted from Yaşargil et al: J Neurosurg 101:725–738, 2004.



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