Epilepsy is a disorder that is characterized by seizures. The International League Against Epilepsy (ILAE) defined a seizure as “a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain". Not all seizures are due to epilepsy, for example febrile seizures or drug induced seizures are not considered as epilepsy. A seizures should be limited in time. The, usual distinct, period of the seizure is referred to as ictal (during a seizure), between the seizures interictal and postictal after a seizure. EEG recording is potentially very helpful for confirmation, classification and localization. About a half-dozen common EEG patterns are encountered during seizures (Fisher et al 2014). Numerous conditions can imitate seizures, such as syncope, transient ischemic attacks, sleep disorders, migraine, tremor, dystonia, psychological states.

Epilepsy is classified primarily for clinical purposes. The classification of the epilepsies is the mandate of the ILAE Commission for Classification and Terminology. The term “classification” is employed based on clinical features. The level of classification is dependent on diagnostic facilities. In some settings, clinicians may not have the resources to take the diagnosis further than a classification according to seizure type. In other circumstances, clinicians may have too little information available to be able to make a higher‐level diagnosis, such as when a patient has had only a single event. Higher level epilepsy classifications include epilepsy syndromes are determined by a distinctive clinical features and EEG pattern, associated imaging, etiological, genetic, prognostic, and treatment implications (Scheffer et al 2016). Evolving data from modern imaging and genetics need to be incorporated when these are available.

Diagnosis of epilepsy may be difficult when in practice, the diagnostic electrical hallmark of epilepsy is absent in the interictal period and when seizures are infrequent. Also when interictal epileptiform discharges are occasionally present in individuals without seizures.

Seizures can be part of focal or generalized epilepsy. In some cases, such as tuberous sclerosis, genetic and structural causes overlap.

Despite numerous antiepileptic drugs are available, not al individuals with epilepsy become seizure free. A number rare monogenic cases of epilepsy have been evaluated in detail and treatment tailored to the identified pathophysiological mechanism, with varying success (Manford 2017)

The Rare Epilepsy Network (REN) identified individuals with rare epilepsies and caregivers through the Epilepsy Foundation and more than 30 rare epilepsy advocacy organizations (Ho et al 2018).They found that 795 persons with more than 30 different rare epilepsy diagnosis groups, one-half had ≥5 comorbidity classes and 97% were classified as complex chronic disease. The highest number of comorbidity classes reported per person were persons with Aicardi syndrome, Phelan-McDermid syndrome, and tuberous sclerosis complex. The most common comorbidity classes were learning/developmental disability, brain abnormalities, oral issues, bone-joint issues, hyper or hypotonia, and eye-vision disorders. The prevalence of brain abnormalities, hyper or hypotonia, eye, and cardiac disorders was significantly higher in persons first diagnosed with epilepsy at a younger age (<9 months) than in those first diagnosed at an older age.

Comorbidities should be carefully considered in the diagnosis and management of persons with rare epilepsies.

On the other hand a rare disease, as the r(20) chromosome syndrome, should be considered when a child has epilepsy as well as developmental disability.

Panels of genes possibly responsible for conditions that have seizure activity as a clinical presentation can be investigated in persons with complex seizure-related symptoms without a clear aetiology presenting, from neonate to adult.