Up-to-date critical review of the classification of epilepsies and epileptic seizures.
Main issues regarding the classifications proposal are as follows:
1. Concepts of epileptic seizure/epilepsy/syndrome
2. Focal & generalized epilepsy concept
a. Idiopathic, genetic, cryptogenic, and symptomatic (structural/metabolic) concepts
Main Differences Between Epileptic Seizure/Epilepsy/Syndrome Classification
Epileptic seizure is a transient occurrence of signs and/or symptoms because of abnormal, excessive, and synchronous discharges of brain neurons. The clinical signs depend not only on the origin of the electrical activity but also on the amplitude, speed, and spreading pathways of the discharges. The diagnosis of the seizure relies on observing the event or watching a video recording of the event or noting down the history of an eye witness.
Epilepsy is a disorder of the brain, characterized by an enduring predisposition to generate epileptic seizures and by the neurobiologic, cognitive, psychological, and social consequences of this condition. The underlying etiology (such as genetic, tumoral, and vascular diseases; immune mechanisms trauma; environmental toxins; infections; neurodegenerative disease) is highly heterogeneous and multifactorial, and the prognosis highly depends on the underlying etiology
Syndrome is a collection of signs and symptoms that occur together These include items such as seizure type, etiology anatomy precipitating factors, age of onset, severity chronicity, diurnal and circadian cycling, and sometimes prognosis. In contrast to a disease, there is no single etiology and/or pathology Therefore, contrary to epileptic seizure, the diagnosis of epilepsy or syndrome is not possible by only observing and/or watching the video but requires information on the age of onset, family history predisposing factors, frequency of the attack, electroencephalography (EEG) and neuroimaging data, etc.
Why Syndromic Diagnosis is Important?
Syndromic diagnosis is necessary for prognostication. For example, while evaluating a patient who has right-sided hemiparesis, a neurologist should spend all his/her effort to determine the underlying etiology For instance, the right-sided hemiparesis could be due to a brain infarction, hemorrhage, or a tumor. The treatment should not be targeted to hemiparesis but to the underlying etiology and in this case it is obviously quite different than each other Thus, by adopting this practice, the doctor can provide the necessary intervention and determine the prognosis of the situation.
Why Seizure Diagnosis is Important?
I. Drug Choice
As an example of routine daily practice, consider the case of a patient presenting with a generalized tonic clonic seizure (GTCS) and/ or dialeptic seizure, in which the only manifestation is a loss of awareness and unresponsiveness. This particular patient could have been suffering from three completely different epileptic syndromes, such as juvenile myoclonic epilepsy (JME), frontal lobe epilepsy (FLE), or mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE). Obviously each of them has its own peculiar EEC findings or concomitant other seizure type or types, genetic tendency, and finally a prognosis. The drug of first choice could also be completely different. All patients with focal epilepsy are treated with more or less the same type of antiepileptic drugs. Patients with generalized epilepsy however; respond differently to different antiepileptic drugs, mainly because of the type of the seizures (for example, patients with generalized myoclonic seizures respond differently to different antiepileptic drugs than patients with absence seizures). A brief summary of drug choice is given in Table I.
2. Presurgical Evaluation
One of the important steps of presurgical evaluation is video-EEG monitoring, by which lateralizing and/or localizing features of epileptic seizures could be recorded; thus, it helps in defining the "symptomatogenic zone."
Focal and Generalized Epilepsy Concepts
Idiopathic, Genetic, Cryptogenic, and Symptomatic (Structural/Metabolic)
Pitfalls of Electroclinical Diagnosis
Recent advances in neuroimaging techniques, widespread use of video-EEG monitoring, and micro-neurosurgical interventions have led to dramatic changes to our understanding on electroclinical syndromes. For example, the seizure type of the West syndrome, which was considered a generalized epilepsy syndrome, was infantile spasms and EEGs showed generalized spike and wave discharges; however; many infants had a causative focal lesion and their epilepsy had been cured by focal resections. Similarly patients with generalized epilepsies such as JME exhibited bilateral asymmetric tonic seizures or those with JAE exhibited automotor seizures and vice versa.
Pitfalls of Genotype-Phenotype Heterogeneity
Recently characterized genetic disorders challenge the distinction between the "pure" genetic epilepsies and structural/metabolic disorders. As a typical example, ARX phenotypes can be responsible either in the West syndrome or in lissencephaly In contrast, we do not have any particular causative gene or genes in well known, classic electroclinical syndromes such as JAE or JME.
Therefore, abandoning the term of idiopathic and refer to that group in unknown or structural/metabolic frame is not compensate our lack of information.
Modern epileptology has stated that epileptic seizures are the consequences of a basic epileptogenic tendency (genes), various more or less obvious triggering factors, and major causative factors. For any given patient, it is essential that we clearly identify these factors. Unfortunately, today we are far more than that to understand completely to the whole pathogenetic mechanisms for all epilepsies.
In general, classification proposals describe seizures as an epilepsy, in line with our current understanding. By its very nature, epilepsy classification will always be subject to revision as our understanding grows. Interested readers can refer to the relevant literature (1,2).
(1.) Bargn E, Aktekin B. State of the Art Approach to the Classification of Epileptic Seizures and Epilepsies. Arch Neuropsychiatr 2014; 51:1 89-194. [CrossRef]
(2.) Baykan B, Ertas NK, Ertas M, Aktekin B, Saygi S, Gokyigit A; EpibaseGroup. Comparison of classifications of seizures: a preliminary study with 28 participants and 48 seizures. Epilepsy Behav 2005; 6:607-612. [CrossRef]
Department of Neurology, Yeditepe University Faculty of Medicine, Istanbul, Turkey
Correspondence Address: Dr Benin Aktekin, Department of Neurology Yeditepe University Faculty of Medicine, istanbul, Turkey Phone: +90 21 6 578 42 74 E-mail: firstname.lastname@example.org
Table I. Seizure/syndrome/drug choice Seizure-aggravated drugs Seizure-specific drugs 1. "Dialeptic" seizure in absence 1. Epileptic spasm [right epilepsy [right arrow] CBZ, arrow] VGB, ACTH OXC, PTH, VGB, GBR PGB 2. "Myoclonic" seizure in 2. "Dialeptic" seizure in generalized epilepsy syndromes absence epilepsy [right [right arrow] CBZ, PTH arrow] ESM, VPA, LTG 3. Lennox-Gastaut Syndrome; 3. Myoclonic" seizure in "Tonic" seizures [right arrow] generalized epilepsy BZD, PB syndromes [right arrow] "Atypical absence" [right arrow] VPA, LEV BZD, ZNS CBZ, GBR PB 4. Lennox-Gastaut syndrome "Atonic" seizures [right arrow] vagal nerve stimulation, RFN CBZ: carbarnazepine; OXC: oxcarbazepine; PTH: phenytoin; VGB: vigabatrin; GBP: gabapentin; PGB: pregabalin; BZD: benzodiazepine; PB: phenobarbital; ESM: ethosuxirnide; ZNS: zonisarnide; LEV: levetiracetarn; RFN: rufinarnide
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|Publication:||Archives of Neuropsychiatry|
|Date:||Jun 1, 2015|
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