Intraoperative hippocampal electrocorticography frequently captures electrographic seizures and correlates with hippocampal pathology

Objective

Relationship between electrographic seizures on hippocampal electrocorticography (IH-ECoG) and presence/type of hippocampal pathology remains unclear.

Longitudinal Quantitative Hippocampal Magnetic Resonance Imaging Study of Adults with Newly Diagnosed Partial Seizures: One-Year Follow-Up Results

Summary: Purpose: We wished to establish whether hippocampal changes occur in 1 year in adults with newly diagnosed partial seizures and, if so, to identify possible causes and mechanisms. Methods: Thirty-six adult patients with newly diagnosed partial seizures underwent a magnetic resonance imaging (MRI) scan of the brain including hippocampal volume and T, relaxation time (HCT2) measurement and had a follow-up quantitative MRI scan ～1 year after the baseline MRI scan. Results: At baseline, 4 patients (11%) had hippocampal sclerosis (HS), 4 (11%) had abnormalities other than HS, and 28 had a normal MRI scan (78%). Twenty-three patients (64%) had recurrent seizures in the period between the two MRI scans. One of the 4 patients with HS, who had daily seizures, had significantly increased HCT2 values on follow-up, possibly reflecting progressive hippocampal damage. None of the 32 patients with MRI findings other than HS at baseline progressed to HS on follow-up. However, 2 of the 32 patients had significant hippocampal changes, probably related to resolution of inflammatory swelling or edema after seizures were controlled. Conclusions: Subtle changes in hippocampi can occur in 1 year in adults with newly diagnosed partial seizures, which could be due to resolution of edema after seizure control or to hippocampal changes associated with frequent and daily seizures. Follow-up of the studied cohort for several years will be required to settle the question of whether progressive hippocampal damage occurs in temporal lobe epilepsy (TLE).     

Hippocampal or neocortical lesions on magnetic resonance imaging do not necessarily indicate site of ictal onsets in partial epilepsy

Advances in neuroimaging techniques, particularly high-resolution magnetic resonance imaging (MRI), have proved invaluable in identifying structural brain lesions in patients with epilepsy. The assumption that such focal lesions invariably predict the site of seizure origin may not be correct, however. We report a series of 20 adults with medically intractable partial epilepsy, where high-resolution brain MRI disclosed a unilateral, focal, hippocampal, or neocortical lesion as the only abnormality in each case; nevertheless, based on electroencephalographic (EEG) recordings, ictal onsets arose from a completely different location than that of the MRI lesion. All patients underwent epilepsy surgery, with the operations based on ictal EEG findings, and all were followed at least 2 years after the resection. After the most recent follow-up examination, 50% (10/20) of the patients were completely seizure-free, 35% (7/20) had at least a 75% reduction in the number of seizures, and 15% (3/20) had less than a 75% reduction in the number of seizures. We conclude that the identification of a focal, structural, hippocampal, or neocortical lesion on brain MRI is not always indicative of the site of seizure origin in partial epilepsy. Furthermore, in cases of discordance between MRI and EEG data, a good outcome after epilepsy surgery is possible if EEG ictal onsets are definitive.     

Outcome of surgical treatment in familial mesial temporal lobe epilepsy

PURPOSE: To describe postoperative outcome in patients with familial mesial temporal lobe epilepsy (FMTLE). METHODS: We studied FMTLE patients who underwent surgical treatment for refractory seizures. FMTLE was defined when at least two individuals in a family had a clinical EEG diagnosis of MTLE. Preoperative investigation included magnetic resonance imaging (MRI), interictal/ictal EEGs, and neuropsychological evaluation. We used Engel's classification for postoperative outcome. RESULTS: To date, 20 FMTLE patients have been operated on, with 1.6 to 9.8 years of follow-up (mean, 5.5 years). Hippocampal atrophy (HA) and other signs of mesial temporal sclerosis (MTS) were present in 18 patients (15 unilateral). Seizures were recorded in 19 patients. Seventeen (85%) patients are in class I. Two patients had normal hippocampal volumes (HcV): one (5%) is in class II and the other (5%) in class IV (extratemporal seizures developed after surgery). One (5%) patient had bilateral HA and is in class III. Qualitative histopathology showed MTS with different degrees of severity. CONCLUSIONS: Refractory FMTLE patients have good surgical outcome when unilateral or clearly asymmetric HA is identified. Preoperative investigation should be the same as that in patients with sporadic refractory MTLE.     

Temporal lobe epilepsy due to hippocampal sclerosis in pediatric candidates for epilepsy surgery.

OBJECTIVE: To characterize the clinical, EEG, MRI, and histopathologic features and explore seizure outcome in pediatric candidates for epilepsy surgery who have temporal lobe epilepsy (TLE) caused by hippocampal sclerosis (HS). METHODS: The authors studied 17 children (4 to 12 years of age) and 17 adolescents (13 to 20 years of age) who had anteromesial temporal resection between 1990 and 1998. RESULTS: All patients had seizures characterized by decreased awareness and responsiveness. Automatisms were typically mild to moderate in children and moderate to marked in adolescents. Among adolescents, interictal spikes were almost exclusively unilateral anterior temporal, as opposed to children in whom anterior temporal spikes were associated with mid/posterior temporal, bilateral temporal, extratemporal, or generalized spikes in 60% of cases. MRI showed hippocampal sclerosis on the side of EEG seizure onset in all patients. Fifty-four percent of children and 56% of adolescents had significant asymmetry of total hippocampal volumes, whereas the remaining patients had only focal atrophy of the hippocampal head or body. Subtle MRI abnormalities of ipsilateral temporal neocortex were seen in all children and 60% of adolescents studied with FLAIR images. On histopathology, there was an unexpectedly high frequency of dual pathology with mild to moderate cortical dysplasia as well as HS, seen in 79% of children and adolescents. Seventy-eight percent of patients were free of seizures at follow-up (mean, 2.6 years). A tendency for lower seizure-free outcome was observed in patients with bilateral temporal interictal sharp waves or bilateral HS on MRI. The presence of dual pathology did not portend poor postsurgical outcome. CONCLUSIONS: TLE caused by HS similar to those in adults were seen in children as young as 4 years of age. Focal hippocampal atrophy seen on MRI often was not reflected in total hippocampal volumetry. Children may have an especially high frequency of dual pathology, with mild to moderate cortical dysplasia as well as HS, and MRI usually, but not always, predicts this finding. Postsurgical seizure outcome is similar to that in adult series.     

颞叶癫痫颅内EEG记录定位与海马病理变化的关系

目的探讨颞叶癫痫颅内EEG记录与颞叶海马病变程度的关系。方法视频EEG证实为颞叶癫痫并经MRI检查的病人序贯进入本研究,采用硬膜下电极及深部电极联合纪录,确定领先发作释放(initialictaldischarge,IID)部位。37例病人中,无或轻度海马萎缩(hippocampalatrophy,HA阴性组)27例,中至中度HA(HA阳性组)者10例。海马病理变化依据MRI检查的海马容积测量及术后组织病理学的海马硬化分级。结果本组HA阴性组27例病人中,9例病人IID广泛出现在海马区、内侧旧皮层及外侧新皮层;3例在海马区及内侧古皮层;14例完全出现在海马区以外的颞叶皮层;仅1例局限于海马区。在HA阳性组中,90%的病人IID局限于海马区(P<0.05),在25例低级别海马硬化(HS)中,IID局限于海马区显著低于12例HS高级别病人(P<0.05)。结论颞叶癫痫的抽搐发作放电定位与海马的病理变化存在着密切关系,无HA和低级别HS病人的IID多出现在海马、颞叶内侧皮层、颞叶新皮层的部位,而HA明显者和高级别的HS病人出现的IID往往仅局限于海马(HF)。     

Chronic Intracranial EEG Monitoring for Localizing the Epileptogenic Zone: An Electroclinical Correlation

Summary: Purpose: To evaluate the diagnostic yield and identify predictive factors of the surgical outcome in patients with intractable partial epilepsy undergoing chronic intracranial EEG monitoring (CIEM).
Methods: The clinical, magnetic resonance imaging (MRI) and electrophysiologic data of 108 patients that underwent CIEM were retrospectively reviewed. The discharge pattern and spatial extent of the initial ictal discharge were determined by blinded visual inspection and computerized analysis.
Results: The main predictive indicator for epilepsy surgery outcome in patients that underwent CIEM was the presurgical MRI findings. Most patients with hippocampal atrophy or complete lesionectomy were rendered seizure free after epilepsy surgery (83 and 80%, respectively), whereas only a small minority of patients with partial lesipectomy or no detected MRI lesion had seizure–free operative outcomes (21 and 22%, respectively). Multifocal independent initiation of the initial ictal discharge was associated with a poor surgical outcome. In contrast, the pattern and local spatial extent of the initial ictal discharge observed with CIEM failed to predict the surgical outcome.
Conclusions: The main predictor of the surgical outcome in patients that underwent CIEM was the MRI findings, whereas CIEM had only limited use in localizing the epileptogenic zone in the absence of an MRI lesion. The reported findings indicate a low specificity of CIEM in defining the site of seizure onset, which in turn significantly impairs the reliability of CIEM in delineating the epileptogenic zone for epilepsy surgery. Further studies are required to define the indications and patient sub–populations who can benefit from CIEM before epilepsy surgery.     

海马头部海马趾的丢失对海马硬化的诊断价值

目的探讨海马头部海马趾的丢失对海马硬化的MR诊断价值.方法50例手术病理证实为海马硬化的难治性颞叶癫痫患者和30例健康志愿者为研究对象.采用GE 1.5 T Signa Horizon LX超导型磁共振机,行垂直于海马长轴的倾斜冠状面T1W、T2W成像.回顾性分析MR检查资料,重点评价海马头部海马趾的情况,分为海马趾完全丢失、海马趾部分丢失和海马趾清晰存在三种情况.结果30例健康志愿者的双侧海马趾清晰存在,50例海马硬化患者中22例病侧海马趾完全丢失,22例病侧海马趾部分丢失,1例双侧海马趾完全丢失,另5例海马趾清晰存在.海马趾丢失对诊断海马硬化的敏感性达到90%,特异性为100%.将对海马趾的评价与原海马硬化MRI诊断标准结合起来,诊断敏感性可提高至94%.结论海马头部海马趾的丢失对海马硬化具有重要诊断价值,可作为海马硬化MR诊断的主要征象之一.     

Unilateral hippocampal sclerosis with contralateral temporal scalp ictal onset

PURPOSE: To investigate the clinical characteristics and surgical outcomes in patients with unilateral hippocampal sclerosis whose scalp ictal EEG recordings localize to the opposite temporal lobe. METHODS: We retrospectively reviewed the data of all adult patients who had undergone depth electrode implantation for suspected temporal lobe epilepsy (TLE) at UCLA (1993-2000) or the Montreal Neurological Institute (1991-1998) to identify patients who had (a) unilateral hippocampal atrophy, and (b) surface ictal recordings in which the majority of seizures appeared to initiate in the opposite temporal lobe, with few or none that were concordant with the hippocampal atrophy. RESULTS: Of 109 patients with suspected TLE who underwent depth electrode study at the two centers, five patients met the aforementioned criteria. Four of these five had very severe hippocampal atrophy, whereas the fifth had mild atrophy but extensive signal change on magnetic resonance imaging (MRI). Depth electrode recordings in four of the five patients yielded clear ictal onset in the mesial temporal lobe ipsilateral to the imaging abnormality (contralateral to apparent scalp ictal onset). One patient had an unusual bitemporal onset pattern, which was nonetheless suggestive of onset in the sclerotic hippocampus. No patient had intracranial ictal onset contralateral to the imaging abnormality. All patients underwent resection of the structurally abnormal temporal lobe. After follow-up of > or = 2 years, four (80%) of five patients were seizure free, while the fifth showed lesser improvement (class III). CONCLUSIONS: Some patients with severe hippocampal sclerosis (sometimes called a "burned-out hippocampus") have atypical spread of ictal discharges, resulting in apparent gross discordance between imaging and scalp ictal recordings. These patients nonetheless have excellent surgical outcomes on the whole. Whether such patients may forego intracranial recordings requires further study.     

磁共振波谱分析与液体衰减反转恢复成像在诊断海马硬化中的作用分析

目的通过对23例颞叶癫痫病人的磁共振波谱分析(magnetic resonance spectroscopy，MRS)与液体衰减反转恢复(nuid attenuated inversion recovery，FLAIR)序列成像结果进行分析，探讨其在诊断海马硬化中的作用与意义。方法经手术治疗的23例颞叶癫痫病人，术中皮层电极及深部电极、术后病理检查结果证实为外侧型癫痫6例，海马硬化型17例，分析其术前磁共振T1、T2、FLAIR序列、MRS检查结果。结果6例颞叶外侧型癫痫海马区T1、T2、FLAIR序列、MRS检查均无异常，17例海马硬化型中6例T1、T2显示异常，7例FLAIR序列高信号，16例MRS显示氮-乙酰天冬氨酸(N—acetylaspantate，NAA)峰明显下降，其中1例显示双侧NAA峰下降。结论MRS可在MRI出现改变之前发现海马硬化，其诊断海马硬化灵敏且特异性高，FLAIR序列优于T2加权相，MRS与FLAIR序列是海马硬化术前诊断一个可靠的方法。