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. HS in temporal lobe epilepsy. This variability can be reduced when the duration of the SE is restricted by discontinuation of the SE by an anesthetic drug(s) within the first 4 h of SE. Similarly, the blood–brain barrier (BBB) is pivotal for neuronal functioning by maintaining brain homeostasis. Not all people who experience temporal lobe seizures experience auras. mesial temporal sclerosis. Causes of temporal lobe epilepsy include: Unknown causes (accounts for about 25 percent of temporal lobe … The intracranial study of our current patient demonstrates that ictal onset started in the right mesial temporal lobe, including the right hippocampus, without the manifestation of ictal singing. A number of those changes contribute to spontaneous seizures, whereas others prevent hippocampal circuits from seizures. A CPS is often preceded by an aura. Some people remain aware of what's happening, but during more-intense s… Clinical manifestations Pre-existing complex febrile convulsions are common. Mesial temporal lobe seizures are by far the most common seizures originating within the temporal structures and are the single most common seizure type seen in the adult population. Wolfgang Löscher, in Models of Seizures and Epilepsy (Second Edition), 2017. An additional major change in the dentate gyrus is the recurrent sprouting of granule cells’ axon fibers, called mossy fibers (Buckmaster, 2012). Quantitative analysis of parvalbumin-immunoreactive cells in the human epileptic hippocampus. The granule cell layer (G) of the dentate gyrus (DG) sends projections, called mossy fibers, toward the CA3 layer. • Hippocampal atrophy is a common feature in some families, not always associated with poor seizure control. However, a recent study discovered marked sex-related differences in the latent period following brain injury in a rodent model of acquired epilepsy (Twele et al., 2016). 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). 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). mesial: [ me´ze-al ] situated in the middle; median; nearer the middle line of the body or nearer the center of the dental arch. Frances S. Cho, ... Jeanne T. Paz, in Models of Seizures and Epilepsy (Second Edition), 2017. Rising sensation in the abdomen 1.5. Sang-Hun Lee, ... Young-Jin Kang, in Arousal in Neurological and Psychiatric Diseases, 2019. These interneurons are also known to be vulnerable to excitotoxicity in TLE (Fig. There are several indications that HS plays an important contributing role in TLE. The temporal lobe is the main region of the brain that controls the sensation of hearing. Sudden or strange odor or taste 1.6. There is limited research on the effects of sex in animal models of epilepsy. Due to the loss of mossy cells, which form excitatory synapses on basket cells in the dentate gyrus (see Fig. Unlike patients with MTLE, there are no reported large series of patients with well-documented lateral temporal lobe seizure origin. A 6-year-old boy with a 5-year history of intractable complexpartial seizure was referred by his neurologist for a presurgicalevaluation of a brain locus that may have triggered the seizures.The seizures were described as starting with vocalizations thatwould quickly convert to convulsions of all four extremities.Afterward, the patient would become aphasic or dysarthric forapproximately 1 minute; then the patient would become sleepy. Thus, the investigator must evaluate potential sex differences in their animal models of epilepsy. This process is called mossy fiber sprouting, and is most probably the result of the loss of appropriate targets of the mossy fibers, e.g., hilar polymorphic neurons and CA3 neurons, during the epileptogenic process (Cavazos and Cross, 2006). Symptoms of temporal lobe epilepsy depend on the epileptic focus location in the mesial vs. lateral temporal lobe. Cell death in both the anterior and posterior hippocampal segments has been associated with regional mesial temporal onsets (Babb et al., 1984). Mesial temporal lobe epilepsy (MTLE) is often discussed as a separate entity because it is quite distinct from its lateral counterpart in terms of etiology, semiology, imaging, and electrophysiologic characteristics. The complete disconnection of the epileptogenic neural networks in the mesial temporal lobe determines the success of resective surgery. [4] PMID: 32119319 Initial steps to investigate the mechanism of epilepsy were based on the study of pathological and surgical specimens, particularly with regard to seizures with a temporal lobe onset, which are often accompanied by hippocampal sclerosis (HS). Experimental SE leads to extensive brain damage and behavioral disturbances, including cognitive deficits that might be much more severe than observed in MTLE patients. (E and F) Reconstruction of a biocytin-filled CA1 O-LM interneuron. An aura or far-away look 1.2. The temporal lobe functions as one of the four main regions of the brain found within the cerebral cortex, and it is responsible for things like speech, memory, and facial recognition. In both human TLE patients (von Campe et al., 1997) and experimental animal models for TLE (Dashtipour et al., 2003) the presence of persistent basal dendrites in the hilus is reported. 12.3C for an example of PVBC in the dentate gyrus), surviving basket cells in TLE remain hypoactive, resulting in hyperexcitability in the dentate gyrus (also known as “the dormant basket cell hypothesis”), along with interneuron loss. Temporal lobe seizures begin in the temporal lobes of your brain, which process emotions and are important for short-term memory. Mesial temporal sclerosis is the loss of neurons and scarring of the deepest portion of the temporal lobe and is associated with certain brain injuries. 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. This may be based on changes in intrinsic mechanisms regulating excitability, e.g. Growing evidence of altered functional connectivity suggests that mesial temporal lobe epilepsy (mTLE) alters not only hippocampal networks, but also a number of resting state networks. But when both temporal lobes are affected the result might be complete deafness. Temporal lobe seizures begin in the temporal lobes of your brain, which process emotions and are important for short-term memory. 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). All … see Temporal lobe epilepsy surgery. 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 a term used to describe scarring in deep part of the temporal lobe of the brain. In a study by the Pitkänen group, using continuous (24/7) video/EEG monitoring after SE in male B6 mice and defining a seizure by an electrographic event of at least 10 s, the latent period to the first spontaneous seizure ranged from 1–6 days, with a median of 2 days, so that the authors concluded that the mice developed epilepsy without any remarkable latency period (Ndode-Ekane and Pitkänen, 2013). MTS is the most common cause of structural epilepsy and focal seizures in the temporal lobe. Neuropharmacology 139, 150–162. 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). For this model, both inbred (B6, FVB/N) and outbred (Swiss, NMRI) mouse strains have been used without any obvious interstrain differences. 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). Wolfgang Löscher, ... T.N. ### Case histories. In addition, models that have less inter animal variability and a more closely resemblance to human MTLE should be refined further (Pitkänen et al., 2013). In various preclinical models a profound impact of TLE on hippocampal neurogenesis has been demonstrated. (A and B) Nissl stain of normal human hippocampus (A) and damaged hippocampus due to hippocampal sclerosis (B). [4] PMID: 32119319 These data suggest that the seizure disorders affecting patients with tauopathies may be secondary to the damage caused by the accumulation of p-tau, and that this is a potential target to treat or prevent human epilepsy. 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. In a subsequent study, we found that the mouse strain also affected the occurrence of different types of spontaneous electrographic seizures and their pharmacological sensitivity in this model (Twele et al., 2016b). Many or all of these will be removed during surgery to stop seizures arising in this area. Mesial temporal lobe epilepsy (mTLE) is the most common form of epilepsy, believed to arise in part from compromised GABAergic inhibition. Surgical resection is the gold standard treatment for drug-resistant focal epilepsy, including mesial temporal lobe epilepsy (MTLE) and other focal cortical lesions with correlated electrophysiological features. The intrahippocampal kainate mouse model of mesial TLE is increasingly used in the search for antiseizure and antiepileptogenic drugs (Löscher, 2016). Mesial temporal sclerosis is the loss of neurons and scarring of the deepest portion of the temporal lobe and is associated with certain brain injuries. When there is a single identifiable electrographic focus, these patients do well with removal of that focus (i.e., temporal lobectomy), achieving up to 66% long-term seizure freedom (Tellez-Zenteno et al., 2007). In the dentate hilus, there is also significant loss of excitatory mossy cells and interneurons. Unaware of surroundings 3. NMRI mice were more sensitive to the antiseizure effect of carbamazepine than FVB/N mice (Twele et al., 2016b). Severe neuron loss in the anterior hippocampus has been associated with anterior focal EEG ictal onsets. Each is defined by the part of the temporal lobe in which it originates. Some symptoms of a temporal lobe seizure may be related to these functions, including having odd feelings — such as euphoria, deja vu or fear.Temporal lobe seizures are sometimes called focal seizures with impaired awareness. Some symptoms of a temporal lobe seizure may be related to these functions, including having odd feelings — such as euphoria, deja vu or fear. In addition, 17β-estradiol can acutely suppress GABAergic inhibition of the hippocampus of female rats through a sex-specific molecular signaling pathway involving the estrogen receptor ERα (Tabatadze et al., 2015). posterior inferior cerebellar artery (PICA), anterior inferior cerebellar artery (AICA), persistent carotid-vertebrobasilar artery anastomoses, persistent proatlantal intersegmental artery, internal carotid artery venous plexus of Rektorzik, 1. The transsylvian-transcisternal approach is a good way to access the mesial structures while preserving the lateral and basal temporal structures. During the seizure: 2.1. Semin. Along with three other lobes – the occipital lobe, the frontal lobe, and the parietal lobe – it makes up the cerebrum. ), 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. Mesial temporal lobe. What is Mesial Temporal Sclerosis? Space-occupying lesions may be primary brain tumours - benign (such as meningioma) or malignant. Typical alterations that are described in temporal lobe regions involve neuronal loss (Lewis, 2005), gliosis, synaptic plasticity (Cavazos and Cross, 2006), neurogenesis (Parent and Lowenstein, 2002), inflammation (Vezzani et al., 2002), and molecular reorganization in cellular membranes and the extracellular matrix (Avanzini and Franceschetti, 2003; Perosa et al., 2002). It remains an unresolved question whether granule cell dispersion is a developmental defect or the result of epileptic seizure activity. Several working groups on preclinical epilepsy have recommended that the commonly used post-SE models need to be refined in order to reproduce the various aspects of MTLE more closely (Galanopoulou et al., 2013; Lidster et al., 2016; Pitkänen et al., 2013; Simonato et al., 2014; Sloviter, 2009; Stables et al., 2003). 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