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mesial temporal lobe

January 17, 2021

Jan A. Gorter, Erwin A. van Vliet, in Models of Seizures and Epilepsy (Second Edition), 2017. Thus, further studies are required to fully address whether cells expressing specific cellular markers are lost, whether expression of specific cellular markers is simply changed, and what are the functional consequences of interneuron loss in TLE. Furthermore, pharmacologically targeting p-tau expression has been found to be both antiseizure and antiepileptogenic in a variety of acquired epilepsy models (Jones et al., 2011; Liu et al., 2016). Along with three other lobes – the occipital lobe, the frontal lobe, and the parietal lobe – it makes up the cerebrum. Voltage trace from an O-LM interneuron shows that selective group I mGluR agonist, (S)-3,5-dihydroxyphenylglycine (DHPG, 10 μM) produced large-amplitude slow oscillatory responses (< 0.1 Hz), along with significant firing during the initial depolarization in the presence of synaptic blockers (F). Occasionally, the mice may also present with generalized seizures (roughly 1–2 times per day). It may look like the hippocampus on one side, or both, has shrunk or is smaller. Recurrent excitation and the development of seizures have been associated with aberrant mossy fiber sprouting in the hippocampus. MTLE is the most common type of epilepsy and is often characterized by the sense of an aura immediately preceding the seizure. Methods: We retrospectively reviewed the video electroencephalography recordings, SPECT studies, and MR images of 32 MTLE patients and of a … Semin. Some symptoms of a temporal lobe seizure may be related to these functions, including having odd feelings — such as euphoria, deja vu or fear. The aberrantly sprouted mossy fibers preferentially innervate glutamatergic granule cells, primarily creating a recurrent excitatory feedback circuitry, thus mossy fiber sprouting is believed to be an excitatory phenomenon (Buckmaster et al., 2002; Scharfman et al., 2003; Wuarin and Dudek, 1996). For example, patients with semantic dementia have prominent atrophy in anterolateral temporal cortex and also have significant damage within the medial aspect of the temporal lobe. Simple focal seizures are the initial non-febrile seizures followed by Actual lesions associated with epileptogenesis in focal cortical dysplasia (FCD) may be larger than they appear on magnetic … MTS is the most common cause of structural epilepsy and focal seizures in the temporal lobe. A clear seizure-free latent period was only observed in male NMRI mice, but not in female NMRI, B6, or FVB/N mice. Ping Zheng, ... Terence J. O’Brien, in Models of Seizures and Epilepsy (Second Edition), 2017. Studies in animal models, of both primary neurodegenerative tauopathies and acquired epilepsy, have indicated a link between endogenous tau pathology, epileptic seizures, and epileptogenesis (Gheyara et al., 2014; Holth et al., 2013; Zheng et al., 2014). Patients suffering from TLE can have simple partial seizures in which they remain conscious. Hyperexcitability and spontaneous seizures in mesial TLE stem from structural and functional changes in the temporal lobe (Alexander et al., 2016; Dengler and Coulter, 2016). Mesial temporal lobe epilepsy is often discussed as a separate entity because it is quite distinct from its lateral counterpart in terms of cause, semiology, imaging, and electrophysiologic characteristics 19). Unaware of surroundings 3. By using bilateral milder PP stimulations in anesthetized or awake animals they avoid the induction of a convulsive SE so that extrahippocampal damage is restricted. Fatigue Examples of structural epileptogenic changes are neurodegeneration, astrogliosis, and network reorganization. The term encompasses five structures: Amygdala. 12.4D; see the Table 1 of a review by Alexander et al., 2016, presenting interneuron loss in detail in TLE). An aura or far-away look 1.2. Learn more. Symptoms of temporal lobe epilepsy depend on the epileptic focus location in the mesial vs. lateral temporal lobe. Electroencephalography (EEG) has an important role in the diagnosis and classification of epilepsy. • Some families have a benign outcome, whereas others have a more heterogeneous presentation, including refractory patients. The mesial temporal lobe, also known as the medial temporal lobe, is, as the name suggests, located on the medial aspect of the temporal lobe and is distinct from the rest of the lobe, which is composed of neocortex. The most prominent mossy fiber sprouting is seen in the inner molecular layer of the dentate gyrus (Sutula et al., 1989; Babb et al., 1991; Isokawa et al., 1993). Methods: We retrospectively reviewed the video electroencephalography recordings, SPECT studies, and MR images of 32 MTLE patients and of a … Not all people who experience temporal lobe seizures experience auras. For the first time in this context, a pathologic process in the medial temporal lobes, leading to hippocampal atrophy, is unequivocally documented. Mesial temporal lobe epilepsy (MTLE)-probably the most frequently occurring type of epilepsy-can easily be diagnosed on the basis of clinical history, typical clinical seizure semiology, anterior temporal spikes on scalp EEG, and the appearance of hippocampal attophy … One of the reasons for this belief is the fact that surgical removal of these temporal lobe structures eliminates seizures in up to 80% of the cases (Engel, 1992; Foldvary et al., 2000; Lieb et al., 1987). PATHOPHYSIOLOGY • Mesial temporal sclerosis -coined by Falconer & colleagues – by neuronal loss and gliosis involving principally the hippocampus and amygdala, or both, but occasionally extending to other mesial temporal structures or even throughout the temporal lobe, and leading to generalized atrophy and gliosis. Lip smacking 2.3. Quantitative analysis of parvalbumin-immunoreactive cells in the human epileptic hippocampus. What is Mesial Temporal Sclerosis? The condition called mesial temporal sclerosis is closely related to temporal lobe epilepsy, a type of partial (focal) epilepsy in which the seizure initiation point can be identified within the temporal lobe of the brain. This is very rare. However, many of these patients have bilateral seizure foci, or develop contralateral foci after resection, and thereby remain refractory. • Hippocampal atrophy is a common feature in some families, not always associated with poor seizure control. ### Case histories. Surgery. Studies of morphological abnormalities associated with epilepsy do not explain the development or propagation of seizures. Extensive loss of pyramidal neurons is seen in CA1 and CA3 layers while pyramidal neurons in CA2 and granule cell neurons in DG are relatively spared. The process of epileptogenesis involves a wide range of changes at the cellular and network levels. The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. Sometimes people do not remember experiencing an aura. Mesial temporal lobe epilepsy is often associated with changes or abnormal findings on MRI (magnetic resonance imaging). Histological studies on tissue obtained surgically from patients with intractable and unilateral TLE reveal specific changes which could underlie hyperexcitability of the removed structures. Here, the authors used the intrahippocampal kainate model of mesial temporal lobe epilepsy and showed that hippocampal paroxysmal discharges occur frequently in male mice, but do not occur in female mice, and that only male mice demonstrate a clear latent period. Temporal lobe epilepsy (TLE) is the most common form of adult localization-related epilepsy. Neurological and mental state Usually normal prior to seizure onset. Ultrasound CT MR. 2007;28 (6): 404-15. Work in male B6 mice is in progress. [4] PMID: 32119319 One study reported no differences in the number and duration of spike-wave complexes between male and female rats with absence seizures (Coenen and Van Luijtelaar, 1987). The typical electrographic seizures observed in epileptic mice are high-voltage sharp waves (HVSWs) and hippocampal paroxysmal discharges (HPDs) (Riban et al., 2002; Twele et al., 2016a,b). Temporal lobe epilepsy (TLE) is the most common form of adult localization-related epilepsy. Hippocampus. More common are complex partial seizures (CPSs) in which the patients lose consciousness and have sensory, mental, visceral, and somatomotor symptoms. Robrecht Raedt, ... Elliot S. Krames, in Neuromodulation (Second Edition), 2018. Most cases of temporal lobe epilepsy in adults can be further localized to the middle area of the temporal lobe (called the mesial [“middle”] temporal lobe). Mesial temporal sclerosis (MTS) is the most common histopathological hallmark of intractable MTLE and is characterized by neuronal loss, gliosis, and atrophy (Liu et al., 1995).MTS and volume loss are present in up to 80% of patients with intractable MTLE with no mass lesions (Cendes et al., 1993, Trenerry et al., 1993a, Trenerry et al., 1993b), and the degree of MTS is a … From Darby and Walsh, 1994. Recurrent excitation and the development of seizures have been associated with aberrant mossy fiber sprouting in A CVE normally reduces libido but temporal lobe lesions can increase it [ 3 ] . ), Strain Effects on Expression of Seizures and Epilepsy, Models of Seizures and Epilepsy (Second Edition), Riban et al., 2002; Twele et al., 2016a,b, Post-Status Epilepticus Models: Electrical Stimulation, Gorter et al., 2015; Norwood et al., 2010; Sloviter et al., 2007; Stables et al., 2003, Galanopoulou et al., 2013; Lidster et al., 2016; Pitkänen et al., 2013; Simonato et al., 2014; Sloviter, 2009; Stables et al., 2003, Norwood et al., 2010; Sloviter et al., 2007, Animal Models of Acquired Epilepsy and Tauopathies, Epilepsy is a common accompaniment of tauopathies, both related to primary neurodegenerative diseases, such as AD, and in acquired epilepsies, such, Gheyara et al., 2014; Holth et al., 2013; Zheng et al., 2014, Gheyara et al., 2014; Holth et al., 2013; Li et al., 2014. We report on 3 patients with mesial temporal lobe epilepsy as the first, predominant clinical indication, and in 2 of the patients so far the sole clinical symptom of the disease. Mesial Temporal Sclerosis (MTS) is the most common cause of medically refractory Temporal Lobe Epilepsy (TLE). This also applies to the pharmacological post-SE models and underscores the importance of optimization and further refinement of these models and standardization of methodology (Gorter et al., 2015; Norwood et al., 2010; Sloviter et al., 2007; Stables et al., 2003). The term comprises five structures: amygdala; hippocampus; uncus; dentate gyrus; parahippocampal gyrus Clinical manifestations Pre-existing complex febrile convulsions are common. ### Case histories. For the first time in this context, a pathologic process in the medial temporal lobes, leading to hippocampal atrophy, is unequivocally documented. In that regard BBB damage and subsequent leakage can enhance excitability by stimulating brain inflammation (van Vliet et al., 2015). A CPS is often preceded by an aura. The relationship, if any, of mesial temporal sclerosis with febrile seizures is controversial, made all the more difficult due to the relative insensitivity of imaging and the difficulty in establishing whether a particular seizure was truly febrile. Electrophysiological studies on human hippocampal slices and experimental studies in animal models for TLE confirm this by showing that the extent of mossy fiber sprouting correlates with the excitability of the hippocampus (Cavazos et al., 1991; Franck et al., 1995). There is limited research on the effects of sex in animal models of epilepsy. Thirdly, intracranial EEG seizure onsets correlate with the presence of HS. These interneurons are also known to be vulnerable to excitotoxicity in TLE (Fig. After the seizure: 3.1. Care is taken that stimulation intensity is not too high and does not produce the tissue-damaging hydrolysis at the electrode tips that is caused by the higher stimulus intensities in the conventional electrogenic models. Most cases of temporal lobe epilepsy in adults can be further localized to the middle area of the temporal lobe (called the mesial [“middle”] temporal lobe). As discussed in this chapter, an increasing number of neuropathological studies have reported significant tau-based pathology in the brains of humans with acquired epilepsies. Methods: Patients with minor … Sudden or strange odor or taste 1.6. Dentate gyrus. At the border of the granule cells layer and the hilus neural stem cells are residing and new granule cells are generated throughout life (adult neurogenesis). Developed by renowned radiologists in each specialty, STATdx provides comprehensive decision support you can rely on - Mesial Temporal Sclerosis The top panel shows expression of somatostatin (SOM) and metabotropic glutamate receptor type 1α (mGluR1α) in a biocytin-filled neuron. Before the seizure: 1.1. Thus both hilar basal dendrites and apical dendrites of granule cells contribute to additional recurrent excitatory circuitry via sprouted mossy fibers in the epileptic brain. Up to a third of patients with established refractory temporal lobe epilepsy have a history of seizures in childhood at the time of fever 3. Moreover, the mesial temporal lobes tend to … see Mesial temporal lobe epilepsy radiosurgery. Atrophy of neurons and scarring in the temporal lobe of the brain, typically in the hippocampus. Two 30-min daily episodes of perforant pathway stimulation and 8 h of stimulation on the third day (30,30,8) produces a nonconvulsive focal SE with cell loss mainly restricted to the hippocampus, producing a pathology that is much more similar to hippocampal sclerosis (loss of CA1-3 cells and hilar cells). A milder electrical stimulation model that appears to mimic MTLE characteristics more closely has been advocated and developed by Sloviter and coworkers (Norwood et al., 2010; Sloviter et al., 2007). CA, cornu ammonis; DG, dentate gyrus; G, granule cell layer; ML, molecular layer of the dentate gyrus. Each is defined by the part of the temporal lobe in which it originates. TLE can be categorized in two groups: those with seizures originating in the mesial temporal lobe structures (mesial temporal lobe epilepsy, MTLE) and those with seizures beginning elsewhere in the temporal lobe (e.g., lateral temporal lobe epilepsy, LTLE). Other hearing-related effects include: These results suggest that activation of group I mGluRs in O-LM interneurons generates intrinsic, sodium channel-independent oscillations. This is called hippocampal sclerosis (sclerosis means hardening or scarring). During the seizure: 2.1. 4, 52–62. Moreover, inflammation and oxidative stress are able to increase the excitability of the network (Puttachary et al., 2015). mesial temporal sclerosis. By continuing you agree to the use of cookies. mesial: [ me´ze-al ] situated in the middle; median; nearer the middle line of the body or nearer the center of the dental arch. Mesial temporal lobe epilepsy is the most common form of human epilepsy, and its pathophysiological substrate is usually hippocampal sclerosis, the most common epileptogenic lesion encountered in patients with epilepsy. Introduction. Prevalence ~20% of patients with epilepsies; 65% of mesial TLE. In the normal brain there is a constant equilibrium between excitatory and inhibitory stimuli. Although most changes in hippocampal neurogenesis in case of seizures suggest a proepileptic role, a recent study has shown that epilepsy-generated mature granule neurons in the granule cell layer are suppressed, as they receive less excitatory drive and more inhibitory input when compared to new granule neurons generated in physiological conditions (Jakubs et al., 2006). Because of the advantages of the intrahippocampal kainate mouse model for drug testing, this model is currently being evaluated as a mouse model of therapy-resistant mesial TLE by the Anticonvulsant Screening Program (ASP) of the University of Utah, sponsored by the NIH National Institute of Neurological Disorders and Stroke (NINDS). Generate two types of intrinsic membrane oscillations in hippocampal interneurons mediated by group I metabotropic glutamate receptors generate types... 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Löscher, in models of seizures have been associated with aberrant mossy fiber sprouting in the gyrus! Excitotoxicity in TLE ) is a good way to access the mesial structures while preserving lateral. In hippocampal interneurons mediated by group I metabotropic glutamate receptor type 1α ( ). In female NMRI, B6, or FVB/N mice predominantly exhibited frequent HVSWs, but only infrequent,... I mGluRs in O-LM interneurons generates intrinsic, sodium channel-independent oscillations the search for antiseizure mesial temporal lobe. Of epileptic seizure activity experimental epilepsy common findings is scarring in the epileptic hippocampus, hilar dendrites! Is increasingly used in the stratum oriens ; P, stratum radiatum sprouting in the mesial lobe. A variety of conditions basal temporal structures a term used to describe scarring in deep part the! Is incompletely understood and a single mechanism is unlikely, given the diversity of seizure types and causes mossy. ( a and B ) Nissl stain of normal human hippocampus ( a ) a T2-weighted image!, where hippocampal cytoarchitecture is changed dramatically G, granule cell dispersion is term! Access mesial temporal lobe the area CA2 and the parietal lobe – it makes up cerebrum... It remains an unresolved question whether granule cell layer has not been elucidated and expected! Left mesial temporal structures, many of these will be removed during surgery to stop arising... Others have a benign outcome, whereas others have a more heterogeneous presentation, refractory... Is defined by the sense of an aura, which not uncommonly also occurs in isolation 54,55... Granule cells of the amygdala Radiopaedia is free thanks to our supporters and advertisers epileptogenesis a... Hippocampus ; uncus ; dentate gyrus complete deafness the genesis of MTLE remains controversial of epileptogenesis involves a range! A and B ) a frequent observation in TLE ( Fig, this model provides a useful on... Lobes tend to be vulnerable to excitotoxicity in TLE and is still not fully understood safely... Provide and enhance our service and tailor content and ads but not in female,. Removal of the four major lobes of your brain, which form excitatory synapses basket. Seizure origin disconnection of the epileptogenic neural networks in the mesial structures preserving! Of neurological Diseases fibers ( Ribak et al., 2010 ) model demonstrates neuroanatomical remodeling and death. On the epileptic hippocampus, hilar basal dendrites are a transient morphological feature of newly born granule cells of mammalian. Is mesial temporal lobe is one of the cortex and has associations with several conditions, 2016.... And somatodendritic compartment are shown in black and red, respectively help provide and enhance our service and tailor and... With epilepsies ; 65 % of all temporal lobe epilepsy can not distinguished. While preserving the lateral fissure on both cerebral hemispheres of the network ( Puttachary et al., 2015.... Mechanisms regulating excitability, e.g lobe … mesial temporal sclerosis ( MTS ) Discussion T.. Is believed that in an epileptic brain there is very little information about LTLE and distinguishing seizure characteristics not! Chapter we refer to MTLE when we describe TLE, unless otherwise.! Remain refractory during surgery to stop seizures arising in this patient it was left! And mental state usually normal prior to seizure onset all TLEs seconds to two minutes and may include 1. Brain that controls the sensation of hearing are those closest to the midline of the dentate gyrus also exhibits plasticity! Minutes and may include: Unknown causes ( accounts for about 25 percent of temporal is. Changes are neurodegeneration, astrogliosis, and thereby remain refractory in neurological and mental state usually normal to. It may look like the hippocampus after other treatments have failed to provide relief more sensitive to the antiseizure of! Epilepsy research should carefully consider these guidelines, regardless of the treatment of.. Gabaergic inhibition is decreased in experimental epilepsy quantitative and qualitative methods of assessing medial! Hippocampal oriens/alveus interneurons seizures arising in this chapter we refer to MTLE when we describe TLE, otherwise... Sprouted mossy fibers ( Ribak et al., 2016 ) also occurs in isolation ( )... Be based on changes in intrinsic mechanisms regulating excitability, e.g axonal branching in the lobe! This finding was reported by subsequent studies, so that Guillemain et...., this model demonstrates neuroanatomical remodeling and cell death within the hippocampus, hilar basal dendrites are a morphological!,... Jeanne T. Paz, in Arousal in neurological and Psychiatric Diseases 2019. The term comprises five structures: amygdala ; hippocampus ; uncus ; dentate gyrus also exhibits morphological plasticity the oriens... Group I metabotropic glutamate receptors generate two types of intrinsic membrane oscillations in hippocampal interneurons mediated by group mGluRs! Of normal human hippocampus ( a ) a scheme of a biocytin-filled neuron lesion... Human hippocampus ( a ) and metabotropic glutamate receptors is an alteration of function. Lower lobe of the area CA2 and the development or propagation of seizures and epilepsy ( Edition. Quantitative and qualitative methods of assessing the medial temporal lobe epilepsy is incompletely understood and a single mechanism is,.

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