KISEP REVIEW ARTICLE J of The Kor Soc of Ster and Func Neurosur 2005;1:127-131 Temporal Lobectomy Dae-Hee Seo, MD1, Seung-Chyul Hong, MD, PhD2 1Department of Neurosurgery, Myongji Hospital, Kwandong University, Goyang, Korea 2Department of Neurosurgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea The temporal lobe is an area of great importance for the surgical treatment of epilepsy. Temporal lobe epilepsy (TLE) is not a single clinicopathologic entity but a number of disease variants with different anatomic, electrophysiologic, and behavioral cha- racteristics. TLE surgery has recently demonstrated a highly significant superiority over optimal medical therapy in recent studies. Technical advances such as high-resolution MRI, microneurosurgical methods, neuronavigation techniques and intraoperative MRI have improved the effectiveness of these procedures. The neurosurgeon perform the task of temporal lobe resection for epilepsy often encounters no apparent anatomic abnormalities and is expected to proceed with resection of seemingly normal brain tis- sue. Therefore, successful surgery within the temporal lobe requires an understanding of both structural and functional relation- ships and demands the three-dimensional grasp of anatomy. Diverse surgical approaches have been proposed to achieve better seizure outcome with fewer complications. Recently there has been a trend to remove less lateral temporal neocortex and excise more mesial structure. But, there are controversies in the matter of seizure, neuropsychological and psychosocial outcomes. Va- rious selective amygdalohippocampectomies have been increasingly used but advantages or disadvantages with respect to pos- toperative cognitive outcome are still a matter of debate. The authors review and compare the diverse surgical approaches of the temporal lobectomy briefly. KEY WORDS: Temporal lobectomy·Surgical approach·Nonlesional temporal lobe epilepsy. INTRODUCTION because often there is neuronal loss in the neighboring entorhinal cortex (Broadman’s area 28 in the anterior part Brain damage resulting to epileptogenesis can be indu- of the parahippocampal gyrus) and amygdala. There is ced by a variety of brain insults. Consequent reorganization vigorous debate about whether hippocampal sclerosis is of neuronal circuitries during epileptogenesis includes neu- a cause or an effect of seizures.2)3) This article focus on ronal loss, axonal and dendritic plasticity of surviving diverse surgical approaches of the temporal lobectomy neurons, neurogenesis, gliosis, and molecular reorgani- for nonlesional TLE. zation in cellular membranes and extracellular matrix (Fig. 1).1) HISTORICAL ASPECTS The growing knowledge about the neurobiology of epi- leptogenesis and progression of epilepsy may affect the In 1928, Penfield systematized temporal lobe resection timing of operation, choice of the tissue to be resected to treat uncontrolled seizure. During the following decade, and consequently improve the seizure outcome after ope- Penfield and Jasper’s conception of temporal lobe resec- ration. tion expanded to include the removal of the amygdala and The most common lesion in surgically resected tissue hippocampus. In 1951, Falconer modernized Penfield’s from patients with mesial TLE is hippocampal sclerosis, operation by designing the en bloc resection of the ante- a well-described entity whose cause remains elusive. The rior temporal lobe.4) dense gliosis that accompanies the loss of neurons causes Recently there has been a trend to remove less lateral shrinkage and hardening of tissue. The term “mesial tem- temporal neocortex and excise more mesial structure. This poral sclerosis (MTS)” has also been used for this lesion, topic will be discussed in other paragraph of this review. Controversies with regard to the removal of mesial struc- Address for correspondence: Seung-Chyul Hong, MD, PhD, Department of Neurosurgery, Samsung Medical Center, Sungkyun- tures persist. According to several studies, the resection kwan University School of Medicine, 50 Ilwon-dong, Kangnam-gu, of the mesial structure is associated with a better seizure Seoul 135-710, Korea outcome. Especially, the extent of hippocampal resection Tel: +82-2-3410-3493, Fax: +82-2-3410-0048 5) E-mail: [email protected] may be associated with better outcome. Wyler et al., re- 127 J of The Kor Soc of Ster and Func Neurosur 2005;1:127-131 be blend into the pes hippocampus without a sharply de- Epileptic process marcated borders. So, the amount removed is difficult to Neuronal damage judge during surgery. Removing the amygdala by this approach is not generally a bloody procedure, but it should Latency period (epileptogenesis) be remembered that on approaching the ventricular wall, especially medially, there are veins returning from the Epilepsy amygdala within the subependymal layer and its injury may result in the torrential bleeding. The vital step in the hippocampal removal is the iden- TLE with good Drug-refractory TLE Secondary epileptogenesis (?) seizure control (mirror focus) tification of the hippocampal sulcus and Ammon’s horn arteries from the anterior and posterior choroidal arteries. Fig. 1. Symptomatic TLE typically develops in three phases：brain The sclerotic hippocampus is carefully separated from the damage → latency phase or epileptogenesis → appearance of intact pial surface. It is crucial to keep the pial boundary spontaneous seizures or epilepsy which can be easy to control or turn out to be drug-refractory over the time. †：TLE：tempo- intact. But, Hippocampal sclerosis make the hippocampus ral lobe epilepsy. hard and rubbery, necessitating a considerable degree of manipulation and the ultrasound aspirator frequently is ported that postoperative seizure control was best with unable to manage this degree of fibrosis and it may injure removal of hippocampus to the level of the superior col- the thin arachnoid layer. Pial bleeding should be carefully liculus (total hippocampectomy group had a 69%, partial controlled by bipolar cautery at a low setting. During the hippocampectomy group had a 38% of seizure-free out- hippocampal resection, care is taken to coagulate and cut come). But, the association between the extent of amy- the numerous small vessels arising from the posterior gdala resection and outcome remains to be proven. Similar communicating and posterior cerebral arteries without outcomes for a variety of anterior temporal lobectomies damaging vessels supplying the peduncle and thalamus. in which the amount of hippocampus varies from entire Usually 4 to 7 perforating arteries supplying the hippo- resection to no removal were also reported.6) Other stu- campus are encountered. The vessel injury may cause the dies have pointed out that sparing of mesial structure may traction hemiplegia or homonymous hemianopsia. It is produce a good outcome when preoperative or intraope- recommended that posterior hippocampus is usually left rative electrographic studies do not implicate mesial struc- beyond the beginning of the P3 segment of the posterior ture in the seizure focus.6)7) cerebral artery to minimize injury to the lateral geniculate body and the geniculocalcarine radiations of Meyer. Va- ANATOMICAL AND INTRAOPERATIVE riations in PHG resection usually correspond to variations CONSIDERATIONS in extent of hippocampal resection. The boundaries of temporal lobe include the sylvian SURGICAL APPROACHES fissure superiorly and the middle fossa inferiorly and an- teriorly. The medial boundaries are formed by the insula, The goal of surgical treatment is the removal of a focal the crural and ambient cisterns. The posterior limit is de- source for intractable seizures. Several variations of tem- fined by the lateral, basal parieto-temporal lines and tem- poral lobectomy are used. These are en bloc anterior poro-occipital line. The mesial temporal structures lie temporal lobectomy, anteromedial temporal lobectomy, medial to the collateral sulcus and inferior to the temporal cortico-amygdalohippocampectomy (AH), cortico-amy- horn of the lateral ventricle and include the parahippo- gdalectomy, selective hippocampectomy, and selective AH. campal gyrus (PHG), the hippocampal formation, the un- Unfortunately, the terminology used is often misleading cus, and the amygdala. and does not describe all the resected structures. The main The amygdala is a large nuclear complex composed of variant in the different anatomic resections for TLE is the several subunits which lies anterosuperior to the pes hip- medial temporal resection and lateral temporal resection. pocampi. The identification of this nucleus, and especially Also, the surgical approach varies depending on how the its borders is not easy because the amygdala appears to hippocampal complex is approached. 128 DaeDae---HeeHee Seo, et al：Temporal Lobectomy Table 1. Recent studies of seizure control outcome of selective amygdalohippocampectomy Authors & year No. of cases Approach† Outcome Follow up duration Renowden et al., 1995 017 sel-AH 47% (best*) 2 yrs (TS：10, TC：7) 88% (best & good*) Mackenzie et al., 1997 028 sel-AH 21% (Engel I) 1yr ILAE report, 199722) 341 60.1% (seizure-free) NA sel-AH 81.5% (>90% reduction) Vajkoczy et al., 1998 016 sel-AH 81% (Engel I) 1-6.8yrs (TS-transcisternal) 97% (Engel I & II) (24.6mos) Wieser et al., 2003 182 sel-AH (TS) 76.4% curative 1-24 (7.2)yrs Lutz et al., 2004 080 sel-AH Seizure-free rate Up to 7mos TS：41 73.2% TC：39 76.9% *：outcome according to the Oxford grading of seizure, best (Engel