Microdialysis of the lateral and medial temporal lobe during temporal lobe epilepsy surgery

BACKGROUND: This study was undertaken to establish whether, in temporal lobe epilepsy (TLE), there are relative differences between the lateral and ipsilateral medial temporal lobe in the extracellular levels of 3 of the human brain's major neuroactive amino acids. METHODS: Seven generally anesthetized patients with TLE undergoing anatomically standardized resective surgery had at operation microdialysis catheters inserted within the middle temporal gyrus (ie, lateral temporal lobe) and anterior hippocampus (ie, medial temporal lobe). Surface electrocorticography (ECoG) recordings were also obtained. Samples of 10-minute dialysate were quantified for glutamate, aspartate, and gamma-aminobutyric acid (GABA) using high-performance liquid chromatography; corresponding ECoG data were assessed for epileptiform activity. Where available, resection tissue was subjected to histopathological analysis. RESULTS: The ratio of mean "sample 3" dialysate levels of glutamate, aspartate, and GABA was approximately 20:2:1, respectively, in both the minimally epileptiform lateral (n = 7) and medial (n = 5) temporal lobe; between the 2 sets of samples, these levels were not significantly different (P > 0.05 for each amino acid studied). From the vigorously epileptiform medial temporal lobe of 2 patients, sample 3 dialysate levels of the excitatory amino acids glutamate and aspartate were found in considerably greater concentrations (between 15- and 37-fold) with correspondingly less dramatic increases of the inhibitory amino acid GABA (more than 11- and 13-fold). Laterally resected tissue (obtained in 3 cases) did not demonstrate significant cortical or subcortical abnormalities; medial resection tissue from all patients demonstrated, in varying degrees, hippocampal sclerosis. CONCLUSIONS: In the absence of significant tissue hyperexcitability, despite known differences in local cellular and/or histopathological architecture, the extracellular relationship among glutamate, aspartate, and GABA is not dissimilar in both the lateral and ipsilateral medial temporal lobe of TLE patients. Considerable disparity in dialysate levels recovered (eg, from the vigorously epileptiform medial temporal lobe) may be related to the functional (ie, hyperexcitable) status of the sampled tissue.     

Access to the posterior medial temporal lobe structures in the surgical treatment of temporal lobe epilepsy

The authors describe a surgical technique that allows access to the posterior temporal horn of the lateral ventricle with preservation of the most functional lateral temporal cortex. Development of the technique was stimulated by the need to resect posteromedial temporal lobe structures in patients with intractable complex partial epilepsy and well-identified unilateral posterior hippocampal foci. This technique has also been of value in the resection of some lateral ventricular and posteromedial temporal lobe masses. The operation consists of three steps. No more than 4.5 cm of the anterolateral temporal lobe is removed en bloc such that the most anterior aspect of the temporal horn is entered. An incision is carried from the floor of the temporal horn through the inferior longitudinal fasciculus to the middle fossa dura mater and posteriorally into the lateral ventricular atrium. The lateral temporal cortex and white matter are then elevated with a self-retaining retractor. This exposes the posteromedial temporal horn or intraaxial mass for excision or allows en bloc resection of the entire hippocampus and medial temporal lobe structures while preserving the functional association areas of the lateral temporal cortex, including speech and visual spatial function.     

Normal magnetic resonance imaging and medial temporal lobe epilepsy: the clinical syndrome of paradoxical temporal lobe epilepsy

OBJECT: The syndrome of medial temporal lobe epilepsy (MTLE) may occur in patients in whom magnetic resonance (MR) images demonstrate normal findings. In these patients, there is no evidence of hippocampal sclerosis on neuroimaging, and histopathological examination of the resected hippocampus does not reveal significant neuron loss. In this paper the authors describe the distinct clinical features of this MTLE subtype, referred to as paradoxical temporal lobe epilepsy (PTLE). METHODS: The authors selected 12 consecutive patients with preoperative findings consistent with MTLE in whom MR imaging did not demonstrate any hippocampal abnormality. Onset of hippocampal seizure was confirmed by long-term intracranial monitoring. There were six female and six male patients with a mean age of 32 +/- 11 years, (mean +/- standard deviation [SD]) at presentation. These patients' seizure histories, available hippocampal volumetric measurements, and hippocampal cell densities in different subfields were reviewed. Sharp electrode recordings from dentate granule cells that had been maintained in hippocampal slices provided a measure of excitation and inhibition in the tissue. We compared these data with those of a cohort of 50 randomly selected patients who underwent anteromedial temporal resection for medial temporal sclerosis (MTS) during the same time period (1987-1999). The durations of follow up (means +/- SDs) for the PTLE and MTS groups were 51 +/- 59 months and 88 +/- 44 months, respectively. A history of febrile seizure was present less frequently in the PTLE group (8%) than in the MTS group (34%). Other risk factors for epilepsy such as trauma, meningoencephalitis, or perinatal injuries were present more frequently in the PTLE group (50%) than in the MTS cohort (36%). In patients in the PTLE group the first seizure occurred later in life (mean age at seizure onset 14 years in the PTLE group compared with 9 years in the MTS group, p = 0.09). Ten patients (83%) in the PTLE cohort and 23 patients (46%) in the MTLE cohort had secondary generalization of their seizures. Among patients with PTLE, volumetric measurements (five patients) and randomized blinded visual inspection (seven patients) of the bilateral hippocampi revealed no atrophy and no increased T2 signal change on preoperative MR images. All patients with PTLE underwent anteromedial temporal resection (amygdalohippocampectomy, in five patients on the left side and in seven on the right side). Electrophysiological studies of hippocampal slices demonstrated that dentate granule cells from patients with PTLE were significantly less excitable than those from patients with MTS. The mean pyramidal cell loss in the CAI subfield in patients in the PTLE group was 20% (range 0-59%) and that in patients in the MTS group was 75% (range 41-90%) (p < 0.001). Maximal neuron loss (mean loss 38%) occurred in the CA4 region in six patients with PTLE (end folium sclerosis). At the last follow-up examination, six patients (50%) in the PTLE group were seizure free compared with 38 patients (76%) in the MTS group. CONCLUSIONS: Clinical PTLE is a distinct syndrome with clinical features and surgical outcomes different from-those of MTS.     

立体定向杏仁核与海马联合毁损治疗颞叶内侧型癫痫

目的 探讨立体定向杏仁核、海马联合毁损治疗颞叶内侧型癫痫(MTLE)的方法。方法患者头部安装Leksell立体定向框架,使其平行于颞角长轴。针对23例一侧MTLE患者,应用核磁共振(MRI)扫描定位、深部电极杏仁核及海马脑电监测和射频毁损技术,局部麻醉下分别经旁正中额、枕入路完成立体定向杏仁核和海马毁损术。结果射频毁损前23例患者深部电极均记录到杏仁核和海马区域棘波或多棘波,术后痫样放电消失。术后1～2周复查MRI显示与毁损部位相一致的广泛凝固性坏死,周围有水肿带。术后随访8～32个月,癫痫发作完全控制者43．48％(10／23例),总有效率(发作减少≥50％)91．30％(21／23)。结论立体定向杏仁核、海马联合毁损治疗MTLE是一种安全有效的微创治疗方法,值得临床推广和应用。     

Magnetic resonance imaging in temporal lobe epilepsy: usefulness for the etiological diagnosis of temporal lobe epilepsy

With improvement in magnetic resonance (MR) imaging techniques, the ability to identify lesions responsible for temporal lobe epilepsy has increased. MR imaging has also enabled the in vivo diagnosis of hippocampal sclerosis. Brain tumors are responsible for 2-4% of epilepsies in adult population and 10-20% of medically intractable epilepsy. The sensitivity of MR imaging in the diagnosis of tumors and other lesions of the temporal lobe (vascular malformations, etc.) is around 90%. Both hippocampal sclerosis and other temporal lobe lesions are amenable to surgical therapy with excellent postsurgical seizure outcome. In this article, we characterize and underline distinguishing features of the different pathological entities. We also suggest an approach to reviewing the MR images of an epileptic patient.     

Surgery for temporal lobe epilepsy in older patients.

OBJECT: The goal of this study was to evaluate the efficacy of surgery for temporal lobe epilepsy (TLE) in older (> or = 50 years of age) patients. METHODS: The authors conducted a review of all patients 50 years of age or older with TLE surgically treated at the Montreal Neurological Institute and Hospital since 1981 by one surgeon (A.O.). Only patients without a mass lesion were included. Outcome parameters were compared with those of younger individuals with TLE, who were stratified by age at operation. In patients aged 50 years and older, the onset of complex partial seizures occurred 5 to 53 years (mean 35 years) prior to the time of surgery. Postoperatively, over a mean follow-up period of 64 months, 15 patients (83%) obtained a meaningful improvement, becoming either free from seizures or only experiencing a rare seizure. Most surgery outcomes were similar in both older and younger individuals, except for a trend to more freedom from seizures and increased likelihood of returning to work or usual activities in the younger patients. Note that a patient's long-standing seizure disorder did not negatively affect their ability to achieve freedom from seizures following surgery. CONCLUSIONS: Surgery for TLE appears to be effective for older individuals, comparing favorably with results in younger age groups, and carries a small risk of postoperative complications.     

Clinical relevance of amygdala sclerosis in temporal lobe epilepsy.

OBJECT: The goal of this study was to define the incidence and clinical significance of amygdala sclerosis (AS) in patients with temporal lobe epilepsy (TLE). METHODS: Surgical specimens of the lateral amygdaloid nucleus and the hippocampus excised from 71 patients who were treated for medically intractable TLE were quantitatively evaluated using a computer-assisted image-analysis system and compared with 10 normal autopsy specimens. Densities of neurons and reactive astrocytes in the patients with TLE were correlated with clinical, neuropsychological, and depth-electroencephalography data. The neuron counts of the lateral amygdaloid nucleus did not correlate with various presumed etiological factors of TLE including hereditary seizures, birth complications, febrile convulsions, traumatic brain injury, infections, seizure semiology, and epileptological outcome. However, patient age at surgery was significantly higher (mean difference 10 years) when AS was present, as compared with patients without AS (p < 0.01). Seizure origin, as determined by using amygdalohippocampal depth electrodes, did not correlate with the presence or absence of AS. Neuropsychologically, there was a significant correlation between the neuronal densities of the lateral amygdaloid nucleus and both preoperative visual recognition and postoperative deterioration of short-term verbal memory performance (p < 0.05). CONCLUSIONS: Except for the relatively long history of epilepsy, the presence of AS is not associated with specific clinical or electrocorticographic features of mesial TLE. However, patients without AS are particularly at risk for deterioration of short-term verbal memory following amygdalohippocampectomy.     

MRI-guided stereotactic placement of depth electrodes in temporal lobe epilepsy.

Electrodes placed stereotactically in mesial temporal lobe structures may be useful for determining laterality, and extent of the epileptogenic zone in temporal lobe epilepsy. We present and compare our experience with the use of two stereotactic arcs, the Brown-Roberts-Wells (BRW) and Cosman-Roberts-Wells (CRW) for magnetic resonance imaging guided placement of multicontact electrodes in the amygdala, anterior and posterior hippocampus. Out of 101 electrodes, 28 were placed in 6 and 17 patients using the BRW and CRW arcs, respectively. The target-centered design of the CRW arc eliminated the need for trajectory calculations, used uniform 'depth' measurements, and allowed greater operative flexibility and a shortened operating time. The use of depth electrode recording allowed 14 of the 23 patients to be selected for temporal lobectomy.     

Failure of low-dose radiosurgery to control temporal lobe epilepsy.

Radiosurgical treatment of intractable epilepsy has emerged as a noninvasive alternative to resection. Although gamma knife surgery (GKS) reportedly is effective when the radiation dose is sufficient to cause a destructive reaction in the targeted medial temporal lobe, the optimal target area and dose distribution are largely unknown. Some investigators have suggested that focused irradiation from a nondestructive dose is also effective. In this article the authors report two cases of medial temporal lobe epilepsy in which the patients underwent GKS performed using a 50% marginal dose of 18 Gy covering the amygdala. hippocampal head and body, and parahippocampal gyrus. In both cases this procedure failed to control seizures. Both patients became seizure free after undergoing anterior temporal lobectomy 30 and 16 months, respectively, after radiosurgery.     

Psychiatric symptom changes after corticoamygdalohippocampectomy in patients with medial temporal lobe epilepsy through Symptom Checklist 90 Revised

Background

Corticoamygdalohippocampectomy (anterior temporal lobe resection plus amygdalohippocampectomy) is common in epilepsy surgery. Pre- and postoperative psychiatric disorders occurred sometimes in patients with refractory medial TLE. We want to know if CAH has an affirmative effect on the psychiatric symptom of patients with medial TLE through a quantitative method.

Methods

Sixty-two patients with medial TLE who had CAH accomplished SCL-90-R questionnaires thrice (presurgical and postsurgical 1 and 2 years). Average GSI scores in SCL-90-R were calculated and statistically analyzed.

Results

There was no statistical difference in the presurgical average GSI scores between Engel I and Engel II to IV subgroup. Postoperative 1 and 2 years' average GSI scores of Engel II to IV subgroup were both statistically higher than those of Engel I subgroup. There were no statistical differences between other subgroups in different time. Postsurgical 1 and 2 years' average GSI scores of the whole group and Engel I subgroup were statistically lower than those of presurgery. Postoperative 2 years' average GSI scores of the whole group and Engel I subgroup were statistically lower than those of postsurgical 1 year. For Engel II to IV subgroup, there were no statistical differences among the average GSI scores in different time.

Conclusion

Corticoamygdalohippocampectomy could improve the psychiatric symptoms of patients with TLE as assessed by the SCL-90-R. This improvement was related to the therapeutic effect and was not related to sex, lateralization, and MRI abnormality.     

Technical note: Anterior cruciate ligament reconstruction in the presence of an intramedullary femoral nail using anteromedial drilling

AIM To describe an approach to anterior cruciate ligament(ACL) reconstruction using autologous hamstring by drilling via the anteromedial portal in the presence of an intramedullary(IM) femoral nail.METHODS Once preoperative imagining has characterized the proposed location of the femoral tunnel preparations are made to remove all of the hardware(locking bolts and IM nail). A diagnostic arthroscopy is performed in the usual fashion addressing all intra-articular pathology. The ACL remnant and lateral wall soft tissues are removed from the intercondylar, to provide adequate visualization of the ACL footprint. Femoral tunnel placement is performed using a transportal ACL guide with desired offset and the knee flexed to 2.09 rad. The Beath pin is placed through the guide starting at the ACL's anatomic footprint using arthroscopic visualization and/or fluoroscopic guidance. If resistance is met while placing the Beath pin, the arthroscopy should be discontinued and the obstructing hardware should be removed under fluoroscopic guidance. When the Beath pin is successfully placed through the lateral femur, it is overdrilled with a 4.5 mm Endobutton drill. If the Endobutton drill is obstructed, the obstructing hardware should be removed under fluoroscopic guidance. In this case, the obstruction is more likely during Endobutton drilling due to its larger diameter and increased rigidity compared to the Beath pin. The femoral tunnel is then drilled using a best approximation of the graft's outer diameter. We recommend at least 7 mm diameter to minimize the risk of graft failure. Autologous hamstring grafts are generally between 6.8 and 8.6 mm in diameter. After reaming, the knee is flexed to 1.57 rad, the arthroscope placed through the anteromedial portal to confirm the femoral tunnel position, referencing the posterior wall and lateral cortex. For a quadrupled hamstring graft, the gracilis and semitendinosus tendons are then harvested in the standard fashion. The tendons are whip stitched, quadrupled and shaped to match the diameter of the prepared femoral tunnel. If the diameter of the patient's autologous hamstring graft is insufficient to fill the prepared femoral tunnel, the autograft may be supplemented with an allograft. The remainder of the reconstruction is performed according to surgeon preference. RESULTS The presence of retained hardware presents a challenge for surgeons treating patients with knee instability. In cruciate ligament reconstruction, distal femoral and proximal tibial implants hardware may confound tunnel placement, making removal of hardware necessary, unless techniques are adopted to allow for anatomic placement of the graft. CONCLUSION This report demonstrates how the femoral tunnel can be created using the anteromedial portal instead of a transtibial approach for reconstruction of the ACL.     

Surgical alternatives for the treatment of temporal lobe epilepsy

Surgical operations for the treatment of intractable temporal lobe epilepsy have been used for well over 40 years and yet there is still controversy about both the clinical situation in which these operations are indicated and their theoretical basis. This brief essay is an attempt to explain and resolve some of these difficulties.     

MR评估颞叶癫痫治疗效果研究进展

颞叶癫痫（TLE）是临床最常见的癫痫类型,一般可予以药物治疗;当发展为难治性癫痫时,需考虑手术治疗。目前主要通过观察治疗后一定时期内癫痫发作的频率来评估治疗效果,无法实现实时、客观评价。随着MRI技术及图像分析方法的不断进步,多模态MRI已广泛应用于评估TLE治疗效果。本文就多模态MRI及其技术评估TLE患者癫痫缓解情况及认知功能的研究进展进行综述。     

多模态磁共振评估颞叶癫痫手术疗效

目前对颞叶癫痫(TLE)大多采取手术治疗,需要在术前、术后进行全面评估。目前多模态磁共振技术已用于评估术后癫痫疗效及术前、术后的语言、记忆功能。本文就多模态MR技术在TLE手术癫痫缓解评估以及认知功能评估中的研究进展进行综述。