Contribution of seizure semiology to diagnosis and anatomo-electrical localisation of epilepsy

McGonigal, Aileen (2015) Contribution of seizure semiology to diagnosis and anatomo-electrical localisation of epilepsy. PhD thesis, University of Glasgow.

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Epileptic seizures, characterised by paroxysmal disturbance of brain electrical activity, are recognisable by temporary change in clinical state (for example motor signs, behavioural modification or altered conscious level), temporally associated with the cerebral discharge. While analysis of such clinical seizure signs (“semiology”) formed the main basis of epilepsy study from the late 19th century onwards, understanding of the neural basis of semiological expression has advanced relatively little, in comparison to other aspects of epilepsy research. Analysis of ictal clinical signs is today considered essential for diagnosis of epilepsy, offering clues to underlying anatomical localisation and pathophysiology; however, paradoxically, the cerebral substrate of semiological signs remains incompletely understood in many cases and its localising value is therefore debated. Characterising the anatomo-pathophysiological basis of seizure semiology is especially important in the context of epilepsy pre-surgical evaluation, even more so when no radiologically visible lesion is present, since semiological analysis, if validated for a given seizure type, offers crucial localising information. For pharmacoresistant focal epilepsies in which surgical treatment might be possible, a number of cases require intracranial EEG recording. The method of stereoelectroencephalography (SEEG) is particularly useful as this allows simultaneous exploration of multiple, distant brain structures using stereotaxically placed multi-lead electrodes with concurrent video recording. The data thus acquired help form a three dimensional view of spatio-temporal seizure dynamics. Using SEEG it is therefore possible to undertake detailed analysis of semiological patterns and to study their temporal relation to the abnormal electrical cerebral activity occurring in brain networks during seizures. Epileptic seizures characterised clinically by transient cognitive dysfunction, behavioral change and complex motor signs are particularly challenging to analyse and categorise semiologically; indeed any paroxysmal behavioral disturbance must also be analysed with regards to whether it is actually caused by an epileptic discharge or not, since other forms of pathology, particularly psychogenic nonepileptic seizures (PNES), may be difficult to distinguish from epileptic seizures on a purely clinical basis, and require video-EEG recording for confirmation. This issue is particularly pertinent for prefrontal and parietal lobe seizures, which pose specific challenges for electroclinical analysis. PNES have a different and as yet poorly defined neurobiological basis compared to epileptic seizures. However growing understanding of the brain networks underlying emotional dysfunction, complex motor behaviour and altered consciousness, in particular data derived from intracranial studies of epileptic seizures, can help to further knowledge of how altered activity within these neural networks might interact with psychological and other factors in the pathophysiology of PNES.
Through detailed observation of multiple epileptic seizures across a large population of patients, it can be appreciated that similarities exist in both clinical pattern and anatomical organisation of seizures. The existence of semiological patterns is in favour of the hypothesis that specific neural circuits underlie some forms of behavioural expression, and thus reinforces the validity of pursuing this line of investigation in epileptic seizures.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Ph. D. thesis awarded by published work.
Keywords: Epilepsy, seizure, semiology, electroencephalography, EEG, stereoelectroencephalography, SEEG, video-EEG, psychogenic non-epileptic seizures, PNES, frontal lobe, parietal lobe, gamma knife, radiosurgery, MRI-negative, Bancaud, Talairach, brain networks, rostro-caudal gradient, motor stereotypies, consciousness, ictal fear, anatomo-electrical-clinical correlation
Subjects: R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
Supervisor's Name: Duncan, Professor Roderick and Chauvel, Professor Patrick
Date of Award: 2015
Depositing User: Dr Aileen McGonigal
Unique ID: glathesis:2015-6658
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Oct 2015 15:14
Last Modified: 18 May 2022 11:06

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