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Clinical Neuroscience

SEPTEMBER 30, 2020

Neuroscience highlights: Main cell types underlying memory and spatial navigation

KRABOTH Zoltán, KÁLMÁN Bernadette

Interest in the hippocampal formation and its role in navigation and memory arose in the second part of the 20th century, at least in part due to the curious case of Henry G. Molaison, who underwent brain surgery for intractable epilepsy. The temporal association observed between the removal of his entorhinal cortex along with a significant part of hippocampus and the developing severe memory deficit inspired scientists to focus on these regions. The subsequent discovery of the so-called place cells in the hippocampus launched the description of many other functional cell types and neuronal networks throughout the Papez-circuit that has a key role in memory processes and spatial information coding (speed, head direction, border, grid, object-vector etc). Each of these cell types has its own unique characteristics, and together they form the so-called “Brain GPS”. The aim of this short survey is to highlight for practicing neurologists the types of cells and neuronal networks that represent the anatomical substrates and physiological correlates of pathological entities affecting the limbic system, especially in the temporal lobe. For that purpose, we survey early discoveries along with the most relevant neuroscience observations from the recent literature. By this brief survey, we highlight main cell types in the hippocampal formation, and describe their roles in spatial navigation and memory processes. In recent decades, an array of new and functionally unique neuron types has been recognized in the hippocampal formation, but likely more remain to be discovered. For a better understanding of the heterogeneous presentations of neurological disorders affecting this anatomical region, insights into the constantly evolving neuroscience behind may be helpful. The public health consequences of diseases that affect memory and spatial navigation are high, and grow as the population ages, prompting scientist to focus on further exploring this brain region.

Clinical Neuroscience

MARCH 30, 2020

[Intracranial EEG monitoring methods]

TÓTH Márton, JANSZKY József

[Resective surgery is considered to be the best option towards achieving seizure-free state in drug-resistant epilepsy. Intracranial EEG (iEEG) is necessary if the seizure-onset zone is localized near to an eloquent cortical area, or if the results of presurgical examinations are discordant, or if an extratemporal epilepsy patient is MRI-negative. Nowadays, 3 kinds of electrodes are used: (1) foramen ovale (FO) electrodes; (2) subdural strip or grid electrodes (SDG); (3) deep electrodes (stereo-electroencephalographia, SEEG). The usage of FO electrode is limited to bitemporal cases. SDG and SEEG have a distinct philosophical approach, different advantages and disadvantages. SDG is appropriate for localizing seizure-onset zones on hemispherial or interhemispherial surfaces; it is preferable if the seizure-onset zone is near to an eloquent cortical area. SEEG is excellent in exploration of deeper cortical structures (depths of cortical sulci, amygdala, hippocampus), although a very precise planning is required because of the low spatial sampling. The chance for seizure-freedom is relatively high performing both methods (SDG: 55%, SEEG: 64%), beside a tolerable rate of complications.]

Clinical Neuroscience

JANUARY 25, 2013

[Sturge-Weber syndrome: clinical and radiological correlates in 86 patients]

FOGARASI András, LODDENKEMPER Tobias, MELLADO Cecilia, TUXHORN Ingrid, EVERS Georg, SARCO Dean, BURGESS C. Richard, HALÁSZ Péter, BARSI Péter, GYORSOK Zsuzsanna, GYIMESI Csilla, KÓBOR Jenõ, SIEGLER Zsuzsanna, JANSZKY József, JAKUS Rita, RÁSONYI György, EBNER Alois, WOERMANN Friedrich, SAHIN Mustafa

[Backgrounds and purpose - To correlate the extent of the leptomeningeal angiomatosis with clinical features in Sturge- Weber syndrome (SWS). Methods - The study group consisted of 86 consecutive patients aged two months to 56 (mean 7.9±10.3) years with SWS and epilepsy. Clinical and MRI data were analyzed. Results - Based on the extent of leptomeningeal angiomatosis, patients were divided into two subgroups: 43 patients had hemispheric angiomatosis and atrophy, whereas, another 43 had focal involvement. Nine of the 43 hemispherial patients (10%) showed bilateral involvement: all of these bilateral cases demonstrated dominance in a single side with hemispheric leptomeningeal angiomatosis and contralateral focal extension. Hemispheric and focal subgroups were clinically different. Patients with hemispheric SWS were younger at the age of epilepsy onset (p<0.001) and age at MRI examination (p<0.05). Neither gender, lateralization, duration of epilepsy, appearance of secondarily generalized seizures, nor seizure frequency revealed a significant difference between subgroups. Conclusion - Bilateral involvement is frequent and occurs in cases with a hemisperic involvement on one side. The age of epilepsy onset is related to the extent of leptomeningeal angiomatosis. Patients with hemispheric form of SWS presented with earlier age of seizure onset. Focal pial angiomatoses do not tend to progress (a longer duration is not associated with more frequent hemispheric involvement). Other variables including seizure frequency and secondary generalized tonic-clonic seizures are not associated with the extent of angiomatosis.]

Clinical Neuroscience

SEPTEMBER 23, 2011

[The role of neuronavigation in the preoperative invasive evaluation and surgical treatment of drug resistant epilepsies]

ERÕSS Loránd

[For localizing the epileptogenic zone in cases of focal epilepsies detailed clinical investigations, imaging studies and electrophysiological methods are in use. In lesional epilepsies the intrapreoperatíve localization of the lesion and it’s location to the eloquent cortex is essential for the neurosurgeon. The development in image guided neurosurgery lead us to use neuronavigation systems to localize intracerebral lesions or functionally eloquent cortical areas or subcortical pathways during surgery. Neuronavigation brought changes in preoperatíve evaluation and in resective surgery in epilepsy as well. In this article we describe the basics of neuronavigation and enhance the advantages of the technique in epilepsy surgery during the presurgical evaluation with invasive electrodes, in resective surgery and DBS for epilepsy.]

AUGUST 15, 2011

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