ABSTRACT
Understanding and diagnosing cognitive impairment in epilepsy remains a prominent challenge. New etiological models suggest that cognitive difficulties might not be directly linked to seizure activity, but are rather a manifestation of a broader brain pathology. Consequently, treating seizures is not sufficient to alleviate cognitive symptoms, highlighting the need for novel diagnostic tools. Here, we investigated whether the organization of three intrinsic, resting-state functional connectivity networks was correlated with domain-specific cognitive test performance. Using individualized EEG source reconstruction and graph theory, we examined the association between network small worldness and cognitive test performance in 23 patients with focal epilepsy and 17 healthy controls, who underwent a series of standardized pencil-and-paper and digital cognitive tests. We observed that the specific networks robustly correlated with test performance in distinct cognitive domains. Specifically, correlations were evident between the default mode network and memory in patients, the central-executive network and executive functioning in controls, and the salience network and social cognition in both groups. Interestingly, the correlations were evident in both groups, but in different domains, suggesting an alteration in these functional neurocognitive networks in focal epilepsy. The present findings highlight the potential clinical relevance of functional brain network dysfunction in cognitive impairment.
Subject(s)
Brain/diagnostic imaging , Cognition , Epilepsies, Partial/diagnostic imaging , Magnetic Resonance Imaging/methods , Nerve Net/diagnostic imaging , Neuropsychological Tests , Brain/physiology , Cognition/physiology , Epilepsies, Partial/physiopathology , Female , Humans , Male , Middle Aged , Nerve Net/physiologyABSTRACT
OBJECTIVE: The hypersynchronous neuronal activity associated with epilepsy causes widespread functional network disruptions extending beyond the epileptogenic zone. This altered network topology is considered a mediator for non-seizure symptoms, such as cognitive impairment. The aim of this study was to investigate functional network alterations in focal epilepsy patients with good seizure control and high quality of life. METHODS: We compared twenty-two focal epilepsy patients and sixteen healthy controls on graph metrics derived from functional connectivity of source-level resting-state EEG. Graph metrics were calculated over a range of network densities in five frequency bands. RESULTS: We observed a significantly increased small world index in patients relative to controls. On the local level, two left-hemisphere regions displayed a shift towards greater alpha band "hubness". The findings were not mediated by age, sex or education, nor by age of epilepsy onset, duration or focus lateralisation. CONCLUSIONS: Widespread functional network alterations are evident in focal epilepsy, even in a cohort characterised by successful anti-seizure medication therapy and high quality of life. These findings might support the position that functional network analysis could hold clinical relevance for epilepsy. SIGNIFICANCE: Focal epilepsy is accompanied by global and local functional network aberrancies which might be implied in the sustenance of non-seizure symptoms.
Subject(s)
Brain/physiopathology , Electroencephalography/methods , Epilepsies, Partial/diagnosis , Epilepsies, Partial/physiopathology , Nerve Net/physiopathology , Brain Mapping/methods , Female , Humans , Male , Middle AgedABSTRACT
BACKGROUND: Juvenile myoclonic epilepsy (JME) is a generalised epilepsy with seizure onset in youth. The aim of this review is to present updated knowledge about the etiology, diagnosis and treatment of JME. MATERIAL AND METHOD: The review is based on a judicious selection of original English language articles, meta-analyses, and reviews found in PubMed, and the authors' own experience with the patient group. RESULTS: Seizure onset occurs in adolescence. All have myoclonias, about 90 % have generalized tonic-clonic seizures, and one third have absences. Myoclonic jerks are frequently the debut symptom, while tonic-clonic seizures appear later on. Patients are particularly susceptible to seizures shortly after waking. It is important to ask specifically about myoclonias as most patients do not report jerks spontaneously. The electroencephalograms of 44-81 % of the patients show discharges of 4-6 Hz polyspike waves. Focal EEG abnormalities may be seen in about 30 %. When patients are treated with valproate and seizure-precipitating factors are avoided, especially sleep deprivation, about 80 % become seizure-free. Lamotrigine and levetiracetam are alternative therapies for women of childbearing age. Attempts to taper off the medication after several years of seizure freedom entail a high risk of seizure relapse. INTERPRETATION: As there may be features of focal epilepsy in the seizure semiology and/or the EEGs, it may be difficult to diagnose JME. Thus, many patients are misdiagnosed as having a focal epilepsy and are given antiepileptic drugs that may aggravate the tendency to seizures.
