Medial temporal lobe atrophy in patients with refractory temporal lobe epilepsy

University of Nottingham, Nottigham, England, United Kingdom
Journal of Neurology Neurosurgery & Psychiatry (Impact Factor: 6.81). 12/2003; 74(12):1627-30. DOI: 10.1136/jnnp.74.12.1627
Source: PubMed


The objective of this study was to assess the volumes of medial temporal lobe structures using high resolution magnetic resonance images from patients with chronic refractory medial temporal lobe epilepsy (MTLE).
We studied 30 healthy subjects, and 25 patients with drug refractory MTLE and unilateral hippocampal atrophy (HA). We used T1 magnetic resonance images with 1 mm isotropic voxels, and applied a field non-homogeneity correction and a linear stereotaxic transformation into a standard space. The structures of interest are the entorhinal cortex, perirhinal cortex, parahippocampal cortex, temporopolar cortex, hippocampus, and amygdala. Structures were identified by visual examination of the coronal, sagittal, and axial planes. The threshold of statistical significance was set to p<0.05.
Patients with right and left MTLE showed a reduction in volume of the entorhinal (p<0.001) and perirhinal (p<0.01) cortices ipsilateral to the HA, compared with normal controls. Patients with right MTLE exhibited a significant asymmetry of all studied structures; the right hemisphere structures had smaller volume than their left side counterparts. We did not observe linear correlations between the volumes of different structures of the medial temporal lobe in patients with MTLE.
Patients with refractory MTLE have damage in the temporal lobe that extends beyond the hippocampus, and affects the regions with close anatomical and functional connections to the hippocampus.

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    • "de Curtis and Avanzini [7] and McCormick and Contreras [8] reported that the mechanisms of epileptiform discharges mainly depend on intrinsic neuronal properties, recurrent synaptic interconnections, and nonsynaptic interactions among closely located neurons, which lead to excessive neuronal synchronization. In addition to the hippocampus, several clinical cases of mTLE showed significant pathologic changes in other limbic structures, such as the EC and the amygdale [9, 10]. Additionally, observations in animal models indicated that the epileptogenic zone was broad, and the substrate for seizure generation was distributed over several limbic structures [11], including the hippocampus, EC, and amygdala. "
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    ABSTRACT: The hippocampus plays an important role in the genesis of mesial temporal lobe epilepsy, and the entorhinal cortex (EC) may affect the hippocampal network activity because of the heavy interconnection between them. However, the mechanism by which the EC affects the discharge patterns and the transmission mode of epileptiform discharges within the hippocampus needs further study. Here, multielectrode recording techniques were used to study the spatiotemporal characteristics of epileptiform discharges in adult mouse hippocampal slices and combined EC-hippocampal slices and determine whether and how the EC affects the hippocampal neuron discharge patterns. The results showed that low-Mg(2+) artificial cerebrospinal fluid induced interictal discharges in hippocampal slices, whereas, in combined EC-hippocampal slices the discharge pattern was alternated between interictal and ictal discharges, and ictal discharges initiated in the EC and propagated to the hippocampus. The pharmacological effect of the antiepileptic drug valproate (VPA) was tested. VPA reversibly suppressed the frequency of interictal discharges but did not change the initiation site and propagation speed, and it completely blocked ictal discharges. Our results suggested that EC was necessary for the hippocampal ictal discharges, and ictal discharges were more sensitive than interictal discharges in response to VPA.
    Neural Plasticity 03/2014; 2014:205912. DOI:10.1155/2014/205912 · 3.58 Impact Factor
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    • "Although for most patients with MTLE-HS the hippocampus is the primary epileptogenic area, the epileptogenic network may extend beyond the hippocampus. There is extensive evidence supporting this statement, including neuroimaging [3] [4] [5] [6] [7] [8] [9], neuropsychological [10] [11], and clinical data [12] [13]. Surgery is superior to clinical treatment in patients with TLE with drug-resistant seizures [14]. "
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    ABSTRACT: We examined the relationship between presence and frequency of different types of auras and side of lesion and post surgical outcomes in 205 patients with medically intractable mesial temporal lobe epilepsy (MTLE) with unilateral hippocampal sclerosis (HS). With respect to the number of auras, multiple auras were not associated with side of lesion (p=0.551). The side of HS was not associated with the type of auras reported. One hundred fifty-seven patients were operated. The occurrence of multiple auras was not associated with post-surgical outcome (p=0.740). The presence of extratemporal auras was significantly higher in patients with poor outcome. In conclusion, this study suggests that the presence of extratemporal auras in patients with MTLE-HS possibly reflects extratemporal epileptogenicity in these patients, who otherwise showed features suggestive of TLE. Therefore, TLE-HS patients undergoing pre-surgical evaluation and presenting clinical symptoms suggestive of extratemporal involvement should be more extensively evaluated to avoid incomplete resection of the epileptogenic zone.
    Epilepsy & Behavior 04/2012; 24(1):120-5. DOI:10.1016/j.yebeh.2012.03.008 · 2.26 Impact Factor
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    • "In general, the closer the structure is anatomically to the hippocampus, the higher the degree of atrophy. Hence, the entorhinal and the perirhinal cortices tend to display a high degree of atrophy (Bonilha et al., 2003). Postoperative imaging studies have suggested that the extent of the resection of the parahippocampal area, which usually comprises the entorhinal and perirhinal cortex in its most anterior portion (Insausti et al., 1998), leads to better outcomes when associated with complete hippocampal resection (Siegel et al., 1990; Bonilha et al., 2007b). "
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    ABSTRACT: Surgical resection of the hippocampus is the most successful treatment for medication-refractory medial temporal lobe epilepsy (MTLE) due to hippocampal sclerosis. Unfortunately, at least one of four operated patients continue to have disabling seizures after surgery, and there is no existing method to predict individual surgical outcome. Prior to surgery, patients who become seizure free appear identical to those who continue to have seizures after surgery. Interestingly, newly converging presurgical data from magnetic resonance imaging (MRI) and intracranial electroencephalography (EEG) suggest that the entorhinal and perirhinal cortices may play an important role in seizure generation. These areas are not consistently resected with surgery and it is possible that they continue to generate seizures after surgery in some patients. Therefore, subtypes of MTLE patients can be considered according to the degree of extrahippocampal damage and epileptogenicity of the medial temporal cortex. The identification of these subtypes has the potential to drastically improve surgical results via optimized presurgical planning. In this review, we discuss the current data that suggests neural network damage in MTLE, focusing on the medial temporal cortex. We explore how this evidence may be applied to presurgical planning and suggest approaches for future investigation.
    Epilepsia 11/2011; 53(1):1-6. DOI:10.1111/j.1528-1167.2011.03298.x · 4.57 Impact Factor
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