Medicine (RMH) - Theses

Permanent URI for this collection

Search Results

Now showing 1 - 10 of 12
  • Item
    Thumbnail Image
    Cardiorespiratory and autonomic function in epilepsy: implications for clinical practice
    Sivathamboo, Shobitha ( 2019)
    Epilepsy is one of the most common serious neurological disorders in the world, affecting over 70 million people worldwide. It is associated with an increased risk of premature mortality as a direct or indirect consequence of seizures, epilepsy, comorbidities, and treatments for epilepsy. Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in epilepsy, where proposed mechanisms are thought to be seizure-induced brainstem, arousal, and cardiorespiratory dysfunction. Dysfunction to cardiorespiratory and autonomic function has long been recognized, and growing evidence points to its implication in SUDEP. However, comprehensive studies using multimodal physiological monitoring are limited, and a better understanding may improve outcomes in patients with epilepsy. The overall aim of this thesis was to investigate cardiorespiratory and autonomic function in patients with epilepsy to determine the relevance that this may have for outcomes in patients with epilepsy. Firstly, I examined the prevalence and risk factors for sleep-disordered breathing in patients routinely screened using diagnostic polysomnography who were admitted for video-encephalogram (EEG) monitoring, using current guidelines and recommended polysomnography techniques. This study identified a high prevalence of clinically significant sleep-disordered breathing in this population and risk-factors to help guide selection of patients for referral to laboratory-based polysomnography where concurrent video-EEG monitoring and polysomnography is unavailable. Secondly, I examined mortality in patients who had a diagnosis of epilepsy and/or PNES who were found to have sleep-disordered breathing in the first study. Though a higher proportion of deceased patients with clinically significant sleep-disordered breathing compared to living patients was found, we did not find an association between sleep-disordered breathing and mortality. Larger studies with a greater follow-up duration are warranted. Thirdly, I examined cardiorespiratory and autonomic function in patients with epilepsy before, during, and after convulsive and non-convulsive seizures. This study demonstrates substantial cardiorespiratory and autonomic dysfunction among convulsive seizures which may explain why these seizures carry the greatest risk of SUDEP. Lastly, I examined the incidence and frequency of cardiac arrhythmias in a population with drug-resistant chronic epilepsy using implantable cardiac monitors. This study identified that patients with chronic drug resistant epilepsy have a high incidence of cardiac arrhythmias. Two patients had potentially fatal cardiac arrhythmias requiring further cardiology management including sinus arrest and ventricular asystole requiring permeant pacemaker insertion, and polymorphic wide complex tachycardia associated with febrile tonic-clonic seizures. Overall, the findings of this thesis demonstrate cardiorespiratory and autonomic dysfunction are common in drug-resistant epilepsy and warrants the more widespread application of multimodality physiological monitoring including incorporating continuous respiratory monitoring and polysomnography in epilepsy monitoring units, which is not currently standard practice.
  • Item
    Thumbnail Image
    Antiepileptic drug teratogenicity: a human and laboratory translational study
    Jazayeri, Dana ( 2018)
    Antiepileptic drug (AED) associated teratogenicity has been well documented in the literature. The risk of physical birth defects during the first trimester of pregnancy is increased threefold for most AEDs and over ten-fold for the most teratogenic AED, valproate. Despite this risk, women require long term treatment to stop or reduce the occurrence of seizures and the consequent harm to both mother and foetus, including the possibility of sudden unexpected death in epilepsy. The mechanism resulting in this teratogenicity, and in particular why some women are more susceptible to have children with AED induced birth defects is incompletely elucidated. In recent years there has been emerging evidence that AEDs may be interacting with genomic factors to result in birth defects. These genomic factors may be susceptibility alleles in the mother or father, de novo mutations in the child or epigenetic factors such as alterations in DNA methylation in the mother or child. The studies reported in this thesis aim to a) develop an animal model of valproate induced defects that closely mimics a human clinical setting and can be used to better understand the pathogenesis of AED induced defects, and b) identify genomic markers of AED induced defects using whole genome analysis of human samples and determining if having epilepsy is a contributing factor to the onset of these defects. For aim a) the development of the animal model entailed using an epileptic strain of rats, Genetic Absence Epilepsy Rats from Strasbourg, determining a dose at which dietary valproate is therapeutic, mating the rats and conducting a morphological assessment of both internal and external defects. For aim b) human samples were collected and subjected to whole genome analysis, including whole exome sequencing and DNA methylation scans. Additionally, birth defect rates for non-epileptic women in the Australian Pregnancy Register were also separately quantified. The human samples for investigations were collected from participants and their families enrolled in the Register. Using both human and animal models this study aimed to generate new knowledge, which could ultimately lead to a pharmacogenomic approach to the selection of AEDs for women who wish to become pregnant. This would allow women to make more informed decisions, reduce the risk of having a baby with a birth defect and potentially assist in the formation of new AEDs with lower teratogenic risk.
  • Item
    Thumbnail Image
    Clinical and molecular factors associated with post-operative glioma associated epilepsy
    Neal, Andrew ( 2018)
    Post-operative seizures are common in patients with supratentorial diffuse gliomas. Pharmacoresistant seizures occur in up to one third of patients in the post-operative period and for many patients, particularly those with lower grade tumours, seizures are a major determinant of quality of life. More effective anti-epileptic treatments are needed in this patient group. To help achieve this goal, a better understanding of the clinical and molecular factors associated with post-operative glioma associated seizures is required. The intention of this thesis was to help move the tumour associated epilepsy field closer towards an era of individualised, directed pharmacotherapy for glioma associated epilepsy. This thesis has three components i) retrospective analyses of the clinical and molecular factors associated with post-operative seizures, ii) a prospective study examining glutamate quantification in gliomas with 7T MRI and iii) the design and initiation of two pilot randomized controlled trials examining the role of perampanel, a glutamate receptor antagonist, in the prevention and control of post-operative seizures in grade II-III diffuse gliomas. A retrospective database of 216 patients with supratentorial diffuse gliomas was developed and post-operative seizure outcome were examined in detail. The major findings from the retrospective studies were that: i) distinct patterns of seizure outcome can be defined in the post-operative period, with a fluctuating pattern being the most common amongst those with glioma associated epilepsy. This relapsing-remitting outcome was associated with grade II-III gliomas, pre-operative seizure and histological progression; ii) treatment response to anti-epileptic medications in glioma associated epilepsy is poorer than the historical non-tumour epilepsy population; iii) increased glutamate concentration in peritumoural tissue is associated with post-operative seizures; iv) IDH1-R132H mutations in supratentorial gliomas are associated with poorer post-operative seizure outcome and v) glutamate concentration is not associated with IDH1 or IDH2 mutated gliomas. Twelve patients with a radiological or histological diagnosis of supratentorial glioma were imaged with a novel 7 Tesla magnetic resonance glutamate imaging protocol, encompassing GluCEST and magnetic resonance spectroscopy (MRS) sequences. Increased tumour GluCEST signal was associated with features of more aggressive diffuse gliomas, increased peritumoural GluCEST correlated with tumour associated seizures and three unique GluCEST contrast patterns, with distinct clinical and radiological features were defined. Finally, two concurrent phase II multi-centre randomised controlled trials which will examine the role of perampanel in the prevention and control of glioma associated seizures were designed and initiated. All participants will receive pre-operative 7T GluCEST and MRS imaging in addition to tissue analysis for glutamate concentrations. These trials build on findings from the retrospective and prospective studies of this thesis and aim to interrogate a core hypothesis generated from this thesis: Can tissue and imaging glutamate biomarkers select patients for individualised anti-epileptic, anti-epileptogenic and even anti-tumour therapies that target the glutamate pathway.
  • Item
    Thumbnail Image
    Predisposition towards epileptogenesis and its associated behavioural comorbidities: investigations in FAST and SLOW rats
    Sharma, Pragati ( 2017)
    Objective: Nearly half of all epilepsies are acquired following a neurological insult to the brain. However, only a minority of patients develop epilepsy after any particular brain insult suggesting some individuals have a ‘predisposition’ towards developing epilepsy after a brain insult. There is an increased incidence of a family history of epilepsy in those who develop epilepsy following a brain insult, suggesting a genetic predisposing. However, the neurobiological factors that predispose to developing epilepsy following a brain insult are poorly understood. As a tool to investigate this, epileptogenesis ‘prone’ FAST and ‘resistant’ SLOW rats were developed via a selective breeding procedure based on individual differential susceptibility to electrical amygdala kindling. In addition to enhanced vulnerability towards epileptogenesis, FAST rats also exhibit behavioral traits that are reminiscent of those observed in neurodevelopmental disorders that often comorbid with epilepsy, such as Autism Spectrum Disorder (ASD) and Attention-Deficit Hyperactivity Disorder (ADHD). The aim of this thesis was to identify neuroanatomical and neurodevelopmental differences between these two strains that may contribute to predisposition towards epileptogenesis and its associated behavioural comorbidities. Methods: Firstly, brain morphology of adult male FAST and SLOW rats was examined using ex-vivo high resolution T2-weighted Magnetic Resonance Imaging (MRI). Based on brain regions known to be altered in patients with epilepsy and neurodevelopmental disorders, volumetric analysis of selected structures was performed. Secondly, motivated by MRI detected altered morphology of white matter regions between the two strains, white matter integrity in adult FAST and SLOW male rats was investigated using ex-vivo high resolution Diffusion Tensor Imaging (DTI). DTI derived indices namely Fraction Anisotropy (FA), Mean Diffusivity (MD), Axial Diffusivity (AD) and Radial Diffusivity (RD) were compared between the two strains using whole brain Tract-Based Spatial Analysis (TBSS) and specific white matter tracts analysis. Further, characterisation of white matter integrity using electron microscopy was undertaken to identify microstructural abnormalities in the body of corpus callosum of adult FAST and SLOW rats. Thirdly, the rate of neurodevelopment and myelination was compared between FAST and SLOW rats. Neurodevelopment from Postnatal Day (PND) 5-21 was studied using tests including physical growth landmarks, righting reflex, cliff avoidance, negative geotaxis, wire hanging and locomotor activity. Myelination was assessed by measuring mRNA expression level profiles of myelin proteins including Myelin Basic Protein (MBP), Proteolipid Protein (PLP), Myelin Associated Glycoprotein (MAG) and Myelin Oligodendrocyte Glycoprotein (MOG) in brainstem, cerebellum and cerebral hemisphere at PND 5, 11, 17, 23 and 3 months old male rats. Results: Volumetric MRI analysis revealed decreased volume of the anterior cerebellar vermis and increased volume of the posterior inferior cerebellum, the cerebrum, the third ventricle and major cerebral white matter region namely the corpus callosum in adult FAST versus SLOW rats. Further, DTI analysis revealed aberrant white matter integrity within corpus callosum region demonstrated by decreased FA in body of the corpus callosum of adult FAST rats. Corresponding to aberrant white matter integrity, histological examination of body of corpus callosum revealed increased axon diameter and reduced g-ratio of myelinated axons in adult FAST rats. Neurodevelopmental studies revealed developmental delay in FAST rats with only 9% of pups compared to 81% of SLOW rats having opened their eyes by PND 13, with less locomotor activity at PND 12-16 and delayed response to reflexes at PND 5-10. Compared to SLOW rats, FAST rats had reduced mRNA expression of all myelin proteins at PND 5 and 11 in brainstem, cerebellum and cerebral hemisphere indicating global slower rate of myelination. Conclusions: The neuroanatomical and neurodevelopmental studies in this thesis have identified morphological alterations in FAST versus SLOW rats, including aberrant white matter integrity in adulthood with delayed myelination during neurodevelopment. Early disruption in neurodevelopment corresponded to delayed myelination in FAST relative to SLOW rats, which could be the basis of the abnormalities in structural connectivity that were during adulthood in these rats. Thus, structural brain abnormalities and delayed myelination observed in the FAST relative to SLOW rats may potentially be neurobiological factors that predispose towards both epilepsy vulnerability and comorbid neurodevelopmental disorders, such as ASD and ADHD.
  • Item
    Thumbnail Image
    Personalised medicine for epilepsy: long-term outcome of antiepileptic drug therapy and pharmacogenetics testing
    Chen, Zhibin ( 2016)
    Epilepsy is a common neurological disorder that generally requires long-term antiepileptic drug (AED) therapy and poses a substantial public health burden. This thesis reports the studies carried out in three main themes. The first theme quantifies the burden of mortality and morbidity in people living with epilepsy. Screening for HLA-B*15:02 is recommended prior to commencing carbamazepine in Han Chinese and South-East Asians because the allele is strongly predictive of carbamazepine (CBZ)-induced Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN). The second theme sheds light on cost-effectiveness of pharmacogenetics in real-world clinical practice. The last theme aims to provide information on long-term response to AED therapy by analysing newly diagnosed and treated patients followed for up to three decades and to assess potential factors associated with treatment outcomes. By using population-based data from Hong Kong’s public hospitals in the six-year study period (16 September 2005 to 15 September 2011), the first theme demonstrated that newly treated epilepsy patients bear excess mortality and hospitalization risks. The standardized mortality ratio was 5.09 (95% confidence interval [CI]: 4.88-5.31) Patients treated with cytochrome P450 enzyme inducing AEDs (EIAEDs) bore a higher risk of being subsequently recorded with new physical comorbidities than those with non-EIAEDs (relative risk [RR]=1.48; 95% CI: 1.19-1.85), especially for cerebrovascular disease (RR=1.78; 95% CI: 1.14-2.77). In Theme 2, the three sub-studies used the same Hong Kong data as in Theme 1. The first sub-study evaluated the cost and efficiency of routine HLA-B*15:02 screening to prevent CBZ-SJS/TEN. It showed that up to 8,840 persons are need to be screened for HLA-B*15:02 to prevent one death from CBZ-SJS/TEN. The HLA-B*15:02 screening policy is as efficient as other broadly practiced and recommended screening programs, such as mammography and Pap smears for breast and cervical cancer, respectively. The second sub-study evaluated the impact of the HLA-B*15:02 screening policy using data from observed practice in Hong Kong. It reported the CBZ prescription declined from 16.2% (10,077/62,056) in the pre-policy period to 2.6% (1,910/74,606) in the post-policy period (p<0.001). CBZ-SJS/TEN was prevented in the post-policy period, but SJS/TEN induced by phenytoin increased (0.15% [18/11,839] vs. 0.26% [33/12,618], p=0.058) and the overall incidence of AED-induced SJS/TEN remained unchanged (0.09% [42/45,832] vs. 0.07% [39/55,326], p=0.238). Test-prescription practice was adherent to the policy in only 26.4% (1,302/4,929) of relevant patients. By incorporating the findings from the first two sub-studies, the last sub-study estimated the cost-effectiveness of the HLA-B*15:02 screening policy. The current screening policy was associated with an incremental cost-effectiveness ratio (ICER) of US$85,697 per quality adjusted life year (QALY) saved and hence it was not cost-effective. Its cost-effectiveness may be improved by enhancing policy adherence and by low cost point-of-care genotyping. By extending and expanding the newly diagnosed and treated epilepsy patient cohort recruited by the Epilepsy Unit at Western Infirmary in Glasgow since 1982, Theme 3 assessed the long-term outcome of AED therapy. It estimated the probability of achieving seizure freedom for various AED schedules. Despite available of new AEDs with differing mechanisms of action over the last decade, outcomes in newly diagnosed epilepsy have not improved substantially (63.7%) compared to 16 years ago (64.0%). The probability of achieving seizure-free diminishes for each unsuccessful AED schedule.
  • Item
    Thumbnail Image
    Genetic and molecular determinants of acquired and genetic epilepsy
    Casillas Espinosa, Pablo Miguel ( 2016)
    Introduction: Despite the differences in the pathophysiological mechanisms and clinical features of both genetic and acquired epilepsies, dysfunction of both voltage- and ligand-gated ion channels have been highlighted as major contributors of the epileptic phenotype. In this thesis, the molecular mechanism by which T-type Ca2+ channels, AMPAR and TARPs lead to the development of epilepsy was evaluated. In addition, whole genome sequencing was utilised to identify novel candidate genes that could play a role in the epilepsy phenotype. Results: Anti-epileptogenic effects of selective blocking of T-type calcium channels in models of acquired epilepsy. The anti-epileptogenic effects of Z944, a novel, potent and highly selective T-type Ca2+ was used in the amygdala kindling and post-status epilepticus (SE) model. In the amygdala kindling model, Z944 a novel, potent and highly selective T-type Ca2+, did not suppress seizures in fully kindled rats. However, treatment with Z944 delayed de progression of kindling. In the post-SE model, treatment with Z944 after SE massively reduced the number of spontaneous seizures in comparison to vehicle and levetiracetam treated animals. Moreover, treatment with Z944 showed a strong comorbidity modifier effect in depressive like behaviour and may improve cognition after SE. Effects of the T-type calcium channel CaV3.2 R1584P mutation on seizure susceptibility in congenic rats. The CaV3.2 R1584P mutation was not enough to cause absence seizures in a seizure resistant background in the congenic animals but may be associated with the anxiety phenotype. However, the genetic background of the NEC congenic might contain genes that may suppress the pro-epileptic effect of the R1584P mutation. Role of AMPAR and TARPs in the pathogenesis of genetic generalised epilepsy and acquired epilepsy. The results of this chapter indicate a temporal association between the increased TARPs, Stargazin, γ3, γ4, γ5 and γ8, mRNA expression and the development of absence seizures in GAERS. In the post-SE epilepticus model, there was a significant reduction in mRNA expression in the TARPs γ3 and γ8 in the hippocampus 13 weeks after SE. Whole genome sequencing the GAERS and NEC rat strains. TThrough the proposed screen construct variants were identified in high-seizing F2 rats in the following genes; Cacna1h which codes for the CaV3.2 T-type Ca2+ channel, and F1LVI7_RAT and LOC300024. Similarly, non-seizing F2 rats are heterozygous for the mutations in RGD1308133, D3ZPQ1_RAT, Mkl and BiK. In the NEC and F2 non-seizing variants found in Abat, Cyp11b3 and Cyp11b2. Moreover, the flexibility of this method means that it can be applicable with other models of genetic and acquired epilepsies. Conclusions: Here is shown that blocking T-type Ca2+ channels with Z944 has encouraging positive preclinical evidence for disease-modifying in epileptogenesis and in epilepsy behavioural comorbidities that may be possible to translate to a clinical trial. Moreover, the analysis of T-type Ca2+ channels, AMPAR, TARPs and the discovery of novel potential molecular targets using whole genome sequencing uncovers overlap among genetic and acquired epilepsy. Importantly, the findings in this thesis could lead to discoveries that expand our knowledge of epileptogenesis, opening the door for the development of novel therapies.
  • Item
    Thumbnail Image
    Functional analysis of sodium channel gene variation in epilepsy
    Oliva, Megan Kate ( 2013)
    A genetic etiology of epilepsy is widely accepted in 50-70% of all epilepsy syndromes. With genome sequencing now increasingly efficient and affordable, more and more novel genes and mutations are being discovered that are associated with epilepsy. However, most of the mutations have been discovered in genes that code for ion channels which has led to the theory that the genetic epilepsies are a family of channelopathies. The voltage-gated sodium channel family have been particularly implicated with over 800 variants discovered in this gene family. Given their critical role in regulating neuronal excitability it is not surprising that genetic variations in sodium channels can have functional and potentially devastating consequences. With a focus on the voltage-gated sodium channels, the three chapters in this thesis used high-throughput automated planar patch-clamp technology to try and develop a deeper understanding of genetic risk in epilepsy. Chapter two examines a novel cause in a mouse model of absence epilepsy that harbours a mutation in the Scn8a gene. The phenotype of this mouse is enhanced on the C3H background, as opposed to C57, where the C3H animal also has a mutation in the Scn2a gene. The individual biophysical profiles of these two mutations were examined on the Nanion patchliner, and their potential genetic interaction was investigated in a computer model of a layer 5 pyramidal neuron, to see if this could be explained by a biological interaction at the axon initial segment. The results revealed an overall loss of function of the NaV1.6V752F mutant, and an overall gain of function in the NaV1.2V929F mutant. When these changes were implemented in the computer model, it revealed that the output was dominated by the NaV1.2V929F mutant, which suggests there is not a biological interaction of these two genes at the axon initial segment. Alternative scenarios where there may be an alternative site for biological epistasis will be revealed with future studies using immunohistochemistry and brain slice patch clamp recording in the mice. It may also be the case that the NaV1.2V929F mutant is not a modifier of the NaV1.6V752F mutant, which will be revealed by genetic studies to identify the modifier genes. The third chapter examined the modulation of NaV1.2 and NaV1.1 by the β1 auxiliary subunit. As mutations in the β1-subunit have been detected in patients with epilepsy, understanding their impact on subunits from excitatory and inhibitory neurons is critical for understanding how this variation impacts on risk for epilepsy. There was a differential modulation revealed where β1 had a greater functional effect on the NaV1.2 channel but a greater effect on current density on the NaV1.1 channel. Therefore if a variant in β1 experiences a functional change this suggests differentially altered levels of excitation and inhibition in the brain, which could feasibly result in an epileptic phenotype. The fourth chapter looked at exploiting the high-throughput capabilities of the Nanion patchliner, and examined eight mutations in the β1-subunit co-expressed with NaV1.1 and NaV1.2 that have been associated with epilepsy. With this influx of data we needed to devise a new way to represent this data, and converted all raw measurements to effect size values, and represented them on tornado diagrams. With this measurement we could then more easily directly compare parameters from the individual protocols and calculate averages both across mutations, and across parameters. From this data set it is quite apparent that the β1 mutants modulate the α-subunits quite differently, both comparing α-subunits, and comparing mutations. More importantly however this chapter highlighted a new way of thinking about analysis of high-throughput electrophysiology data. As people continue to look into the genetics of epilepsy and reveal novel genes and novel mutations implicated in the disease, we need to look for new ways to tame the genetic complexity, and look for points of convergence. High-throughput technology allows us to decrease the time lapse between the discovery of the genetic variants and the corresponding functional analysis. And the type of analysis as suggested in chapter four, enables us to start to look for points of convergence in the functional data. This data can then be used to train clustering algorithms to group the variants based on their ‘channelomic’ profile. To do this we need a large volume of functional data obtained from variants that have strong corresponding phenotypic data, and future studies should endeavour to accomplish this.
  • Item
    Thumbnail Image
    Antidepressant pharmacotherapy in epilepsy: the effects of chronic fluoxetine and citalopram treatments in a rat model of epileptogenesis
    CARDAMONE, LISA ( 2012)
    Introduction: In patients with epilepsy there is a high incidence of comorbid psychiatric illnesses, especially mood and anxiety disorders, which have been associated with lower quality of life, impaired function and an elevated risk of suicide. In fact, the occurrence of these illnesses in patients with epilepsy has been reported to be a stronger predictor of quality of life than epilepsy variables such as illness duration or seizure frequency. In addition, there is evidence that the depressed state itself may predispose to seizures and epilepsy. For these reasons, effective management of depressive and anxiety symptoms and syndromes in epilepsy is essential. Selective serotonin reuptake inhibitors (SSRIs) are commonly used to treat depression in epilepsy, therefore it is important to consider their impact on epilepsy. To date, many studies have suggested that SSRI are safe for use in epilepsy, but the majority of these studies administered SSRIs only acutely or for short periods, and investigated effects only on acute seizure endpoints. There is no indication of the effect that chronic SSRI treatment may have on epileptogenesis and the associated neurobiological changes that continue after seizures emerge. This thesis aimed to investigate the effects of chronic SSRI treatment in a rat model of epileptogenesis, as well as investigating common neurobiological substrates of SSRI treatment and epileptogenesis that may also influence the disorder. It was hypothesised that chronic SSRI treatment would slow the rate of kindling epileptogenesis, as well as mitigate effects on common neurobiological substrates. Methods: The amygdala kindling model was used to assess the effects of chronic SSRI treatment (with fluoxetine or citalopram) on epileptogenesis. 9-11 week old male Wistar rats were surgical implanted with a bipolar electrode into the left amygdala for electrical kindling and a subcutaneously implanted osmotic pump filled with fluoxetine (10mg/kg/day, n=19) or vehicle (50% DMSO, n=22) or citalopram (10mg/kg/day, n=26) or vehicle (50% DMSO, n=22), comprising two separate cohorts. All rats were given 30 stimulations and then kindling rate, seizure duration and seizure threshold before and after kindling were monitored. Effects on anxiety- and depressive-like behaviours were also investigated after kindling using two well-validated tests, the elevated plus maze and forced swim test respectively, as well as assessing the corticosterone response to stress and dentate gyrus neurogenesis. Results: The key finding of this study was that rats chronically treated with SSRIs, either fluoxetine or citalopram, demonstrated accelerated rates of kindling epileptogenesis, showing a more rapid progression through the different stages of kindling compared to vehicle treated rats. The increase in seizure duration was also accelerated in the early stages of kindling in both cohorts of SSRI treated rats, however seizure threshold was not significantly different between vehicle and fluoxetine or vehicle and citalopram treated rats, either before or after kindling. This indicates that while epileptogenesis itself progressed at a faster rate during chronic SSRI treatment, accelerating the increase in seizure severity and duration, the local excitability and the threshold at which a seizure occurred was not affected by SSRI treatment. In order to investigate potential mechanisms underlying this, neurobiological alterations common to epileptogenesis and SSRI treatment were also investigated. Behavioural analyses found that both fluoxetine and citalopram treatments did not affect anxiety- or depressive-like behaviours, while kindling increased anxiety-like behaviour, but only in the fluoxetine treated cohort. Dentate gyrus neurogenesis was not significantly affected by kindling or drug treatment while stress-induced corticosterone levels were significantly reduced only by fluoxetine treatment. These investigations do not suggest that these alterations are associated with accelerating kindling rate during chronic SSRI treatment, however how these are affected during or immediately after kindling was not investigated. Conclusions: Chronic treatment with fluoxetine and citalopram, at clinically relevant doses, accelerated kindling epileptogenesis in rodents. This highlights the need to investigate the effects of SSRI treatment on epileptogenesis over time in both animal models and people with epilepsy, rather than focusing solely on acute seizure time points. While the investigations in this study do not suggest that alterations in behaviour, neurogenesis or neuroendocrine responses are associated with accelerating kindling rate during chronic SSRI treatment, how these are affected during or immediately after kindling was not investigated. Therefore, future studies should further investigate the mechanisms underlying the effects of SSRIs on epileptogenesis at appropriate time points, such as during kindling epileptogenesis and also in complementary animal models of epilepsy, such as post-status epilepticus and post-traumatic models. It is essential to treat the depressive symptoms that manifest in people with epilepsy; however whether these medications affect the course of epilepsy and how they may do so should become priority areas for future research.
  • Item
    Thumbnail Image
    Identification of predictors of epilepsy outcomes
    Hakami, Tahir M. ( 2013)
    BACKGROUND: Epilepsy is a group of complex conditions characterized by the occurrence of recurrent spontaneous seizures, associated with high risk of brain abnormalities, co-morbid disorders and premature mortality. These issues in patients with new onset-seizures have not been well characterized. Furthermore, the first anti-epileptic drug (AED) treatment will fail in more than 50% of patients because of inadequate seizure control or intolerable adverse effects. Substitution to a newer AED may result in better outcomes. AIMS: (1) To determine the frequency and type of potentially epileptogenic abnormalities identified on MRI, in patients presenting with a possible new-onset seizure disorder, and their association with abnormal electrical activity on electroencephalogram (EEG), the frequency of co-morbidities and injuries, and the incidence of mortality (2) To examine whether patients who fail their first AED will have better neuropsychiatric, neurocognitive, quality of life (QOL), bone density and content, body composition and metabolism outcomes if substituted to monotherapy treatment with a newer-generation AED, levetiracetam, compared with another older-generation AED, valproate or carbamazepine. METHODS: (1) A consecutive series of 993 patients (597 males [61%], mean (SD) age: 42.2 (18.8) years, range: 14.3-94.3 years) who presented to an adult First Seizure Clinic over a ten year period were studied. The MRI scans were acquired using a dedicated epilepsy protocol or other specific protocols depending on clinical indication on either a 1.5T or 3.0T scanners. The co-morbidities and injuries were obtained from two state-wide administrative datasets, the Victorian Admitted Episodes Dataset (VAED) and the Victorian Emergency Minimum Dataset (VEMD), for the period from June 18, 1999 to June 30, 2010. Mortality data were collated from the National Death Index (NDI) developed by the Australian Institute of Health and Welfare (AIHW). (2) A randomized comparative trial was undertaken. Participants with focal epilepsy who had failed monotherapy with phenytoin sodium, carbamazepine, or valproate sodium were randomized to substitution monotherapy with levetiracetam (n= 51) or a different older AED (n= 48). Assessments were performed at baseline, 3 months, and 12 months using questionnaires measuring neuropsychiatric, QOL, seizure control, AED adverse effects, and neurocognitive outcomes. Assessments of bone density and content, body composition and metabolism were performed at 3- and 15 months after randomization. The assessments included: areal bone mineral density (aBMD) at lumbar spine, total hip, forearm, and femoral neck and total body bone mineral content [dual energy x-ray absorptiometry (DXA); Hologic QDR® 4500A densitometer], body composition [Hologic Software Version 5.73], peripheral quantitative computed tomography at non-dominant radius and tibia [pQCT; Stratec XCT 3000], serum markers of bone turnover, sex and metabolism hormones, questionnaires for bone health and lifestyle, blood pressure and anthropometry. RESULTS: (1) Potentially-epileptogenic lesions were detected in 177 (23%) of the patients in the First Seizure Clinic Cohort. Their frequency was higher in patients who had focal-onset seizures (53%). MRI and EEG were concordant in terms of the presence or absence of epilepsy associated abnormality in 62%, with 18% having an abnormality on both utilities. Almost 65% of patients with epilepsy had, at least, one co-morbid disorder as defined by an epilepsy-specific co-morbidity index, and 32% presented to Emergency Departments after sustaining an injury. Those patients were more likely to be males, have lesional focal epilepsy, frequent seizures and be diagnosed with epilepsy at 65+ years of age. The overall case mortality was 8.3% (82 cases) in the cohort. Standardized mortality ratio (SMR) for patients with new-onset seizures was 2.2 (95% CI 1.73-2.80); p< 0.001. The highest excess mortality was seen in younger patients (< 60 years). Proportionate mortality ratio (PMR) was highest for deaths from cerebrovascular diseases (16%) and malignant neoplasms (16%). Epilepsy was listed as the leading cause of death in 10%. (2) In the RCT, there were no differences in depression scores at 3 months between the treatment groups (improvement in 39.5% of the levetiracetam group vs. 34.1% of the older AED group; p= 0.60), but a greater proportion of the older AED group improved on the 89-item Quality of Life in Epilepsy Inventory (QOLIE-89) compared with the levetiracetam group (71.1% vs. 48.8% respectively; p= 0.04). The QOL, anxiety, and AED adverse effects scores were improved in both groups at 3 and 12 months after randomization. There were significant decreases in both treatment groups in aBMD at the lumbar spine (-9.0%; p< 0.001 in the levetiracetam group and -9.8%; p <0.001 in the older AED group), forearm (-1.46%; p< 0.001 and -0.96%; p< 0.001 respectively) and femoral neck (-0.47%; p= 0.026 and -1.45%; p< 0.001 respectively) on DXA scanning. The total hip aBMD significantly decreased in the older AED group (-0.84%; p< 0.001). The treatment groups did differ only in the change in femoral neck aBMD (p= 0.005). The serum levels of C-terminal telopeptides of type I collagen (βCTX), a marker of bone resorption, decreased in both groups (-16.1%; p= 0.021and -15.2%; p= 0.028 respectively) while procollagen 1 N-terminal peptide (P1NP), a marker of bone formation, significantly decreased in the older AED group (-27.3%; p= 0.008). There was no significant change in percentage abdominal fat in either treatment group. CONCLUSIONS: (1) MRI reveals potentially-epileptogenic lesions in a minority of patients who present following a newly-diagnosed seizure disorder. Lesions are most common in patients who have experienced focal seizures. The presence of a potentially-epileptogenic MRI lesion did not influence the likelihood of having an abnormal EEG. The majority of patients with new-onset seizures who consult a specialized First Seizure Clinic suffer from somatic or psychiatric co-morbid disorders. This finding should provide useful implications in the diagnosis and management of epilepsy and co-existing conditions, as well as in health care provision. Patients with new-onset seizures have a two-fold increased mortality compared with the general population. Cerebrovascular disease, and neoplasms, but not epilepsy, were the leading causes of death in epilepsy. (2) Substitution monotherapy in a patient who is experiencing ongoing seizures or tolerability issues is associated with sustained improvements in measures of QOL, psychiatric and adverse events outcomes. The significant bone loss at the lumbar spine, forearm, and femoral neck seen in both treatment groups and the modest reduction in bone turnover indicates that the adverse effects on bone health of chronic AEDs is likely occur with the newer-generation AEDs as well the older-generation AEDs.
  • Item
    Thumbnail Image
    Radiological and molecular factors associated with seizures in patients with supratentorial gliomas
    Liubinas, Simon Vincent ( 2013)
    Tumour associated epilepsy (TAE) is a common and disabling symptom experienced by patients with supratentorial gliomas. The pathogenesis of TAE is likely to involve a complex interplay between macroscopic anatomical factors, molecular factors and individual patient factors. The overarching hypothesis of this thesis is that patients with TAE have tumours with different radiological, molecular and genetic features compared to those without TAE. Furthermore, identification of these features may allow the identification of patients who are at increased risk of the development of TAE, and provide tailored, individualized treatment of these patients. An improved understanding of the genetic and molecular features associated with TAE may also inform the development of novel therapeutic strategies for these patients. There is an increasing body of evidence implicating glutamate, the most abundant neurotransmitter in the mammalian central nervous system, in the pathogenesis of TAE. Magnetic resonance spectroscopy (MRS) provides a non-invasive method to quantify brain metabolites in-vivo, but has not yet been validated for glutamate. In this thesis we firstly demonstrate that MRS quantification of glutamate has a modest, but statistically significant, correlation with concentrations of glutamate measured from tumour biopsy specimens. We then demonstrate that these MRS measurements of glutamate are useful in predicting not only glioma grade, but also the incidence of TAE. We also demonstrate that patients with low-grade gliomas and TAE are more likely to have larger tumours than patients without TAE. The opposite is found in patients with high-grade gliomas and TAE. There is also evidence that common pathological processes, including glutamate excitotoxicity, may be involved in TAE and neurodegenerative conditions such as Alzheimer’s disease, the sequelae of traumatic head injury and idiopathic epilepsy. A number of molecular factors associated with neurodegeneration and excitotoxicity are therefore investigated for their association with TAE. Phosphorylation of tau was found to be lower in patients with TAE compared to those without TAE. Over-expression of glycogen synthase kinase (GSK3β) was found to correlate with TAE, as was loss of glutamic acid decarboxylase 67 (GAD67), potentially reflecting a selective loss of inhibitory interneurons. Finally, the expression of the IDH1-R132H mutation, the most common mutation in low-grade gliomas, is shown to correlate with TAE. In conclusion, TAE results from a complex interaction of patient, environmental and tumour factors, including glutamate excitotoxicity, selective loss of inhibitory interneurons and IDH1-R132H expression. Not only do the results presented in this thesis suggest that TAE differs from other epileptic syndromes, but also that the mechanisms may differ between low and high-grade gliomas. Collaboration between neurosurgeons, neurologists, radiologists, pathologists and basic scientists will be essential for further investigation of this debilitating disease.