Pathological brain ageing in epilepsy and dementia: two sides of the same coin?

Neuropsychology of late-onset epilepsies

In an increasingly ageing society, patients ageing with epilepsy and those with late-onset epilepsies (LOE) represent a challenge for epilepsy care and treatment. Senescence itself bears risks of pathologies which in the form of acute focal damage (e.g. stroke) or slowly progressive degenerative damage can cause seizures and substantial cognitive impairment. There is converging evidence from studies in LOE that cognitive impairments are present from epilepsy onset before treatment is initiated and may even precede the emergence of seizures. This suggests that these impairments (like the seizures) are expressions of the underlying disease. Indeed, both seizures and cognitive impairments can be early indicators of disease conditions which lead to mental decline. Cognitive decline over time poses the challenge of disentangling the interrelation between seizures, treatment effects and underlying disease. This issue must be considered as some of the etiologies for causing neuropsychological decline can be addressed. Medication and active epilepsy can contribute to impairments and their impact may be reversible. Dementia is rare if seizures are what has brought the person to attention, and if this is not accompanied by other slowly developing features (such as cognitive of psychiatric changes). From a neuropsychological point of view choosing the right screening tools or assessments, obtaining the history and timeline of impairments in relation to epilepsy, and most importantly longitudinally following the patients regardless of whether epilepsy is ultimately controlled or not appear essential.

Long non-coding RNAs: Potential therapeutic targets for epilepsy

Epilepsy is a common and disastrous neurological disorder characterized by abnormal firing of neurons in the brain, affecting about 70 million people worldwide. Long non-coding RNAs (LncRNAs) are a class of RNAs longer than 200 nucleotides without the capacity of protein coding, but they participate in a wide variety of pathophysiological processes. Alternated abundance and diversity of LncRNAs have been found in epilepsy patients and animal or cell models, suggesting a potential role of LncRNAs in epileptogenesis. This review will introduce the structure and function of LncRNAs, summarize the role of LncRNAs in the pathogenesis of epilepsy, especially its linkage with neuroinflammation, apoptosis, and transmitter balance, which will throw light on the molecular mechanism of epileptogenesis, and accelerate the clinical implementation of LncRNAs as a potential therapeutic target for treatment of epilepsy.

Barbeau E, Pariente J, Dahan L, Valton L. Sleep: The Tip of the Iceberg in the Bidirectional Link Between Alzheimer's Disease and Epilepsy

The observation that a pathophysiological link might exist between Alzheimer's disease (AD) and epilepsy dates back to the identification of the first cases of the pathology itself and is now strongly supported by an ever-increasing mountain of literature. An overwhelming majority of data suggests not only a higher prevalence of epilepsy in Alzheimer's disease compared to healthy aging, but also that AD patients with a comorbid epileptic syndrome, even subclinical, have a steeper cognitive decline. Moreover, clinical and preclinical investigations have revealed a marked sleep-related increase in the frequency of epileptic activities. This characteristic might provide clues to the pathophysiological pathways underlying this comorbidity. Furthermore, the preferential sleep-related occurrence of epileptic events opens up the possibility that they might hasten cognitive decline by interfering with the delicately orchestrated synchrony of oscillatory activities implicated in sleep-related memory consolidation. Therefore, we scrutinized the literature for mechanisms that might promote sleep-related epileptic activity in AD and, possibly dementia onset in epilepsy, and we also aimed to determine to what degree and through which processes such events might alter the progression of AD. Finally, we discuss the implications for patient care and try to identify a common basis for methodological considerations for future research and clinical practice.

Amyloid-β: a potential link between epilepsy and cognitive decline

People with epilepsy - in particular, late-onset epilepsy of unknown aetiology - have an elevated risk of dementia, and seizures have been detected in the early stages of Alzheimer disease (AD), supporting the concept of an epileptic AD prodrome. However, the relationship between epilepsy and cognitive decline remains controversial, with substantial uncertainties about whether epilepsy drives cognitive decline or vice versa, and whether shared pathways underlie both conditions. Here, we review evidence that amyloid-β (Aβ) forms part of a shared pathway between epilepsy and cognitive decline, particularly in the context of AD. People with epilepsy show an increased burden of Aβ pathology in the brain, and Aβ-mediated epileptogenic alterations have been demonstrated in experimental studies, with evidence suggesting that Aβ pathology might already be pro-epileptogenic at the soluble stage, long before plaque deposition. We discuss the hypothesis that Aβ mediates - or is at least a major determinant of - a continuum spanning epilepsy and cognitive decline. Serial cognitive testing and assessment of Aβ levels might be worthwhile to stratify the risk of developing dementia in people with late-onset epilepsy. If seizures are a clinical harbinger of dementia, people with late-onset epilepsy could be an ideal group in which to implement preventive or therapeutic strategies to slow cognitive decline.