A transient occurrence of signs and/or symptoms (e.g. sensory, motor, speech, consciousness) due to abnormal excessive or synchronous neuronal activity in the brain

• Excitation: NMDA R (Glutamate)
• Inhibitory: GABA

Definition

• Provoked seizure: occur with an identifiable proximate cause (metabolic, toxic, structural, infectious, inflammatory) and are not expected to recur in the absence of that particular cause/trigger (e.g., hypoglycemia, alcohol withdrawal, etc.)
• Unprovoked seizure: occur without an identifiable cause or in the context of a remote symptomatic cause (i.e., pre-existing brain lesions, such as a remote stroke). Recurrent unprovoked seizures are more likely to be associated epilepsy
• Focal onset (“partial”) seizure: abnormal synchronous neuronal activity originating from one location (within limited to one hemisphere) of the brain, more concerning to be associated with elevated future recurrence risk
• Generalized onset seizure: abnormal synchronous neuronal activity arising within and rapidly engaging bilaterally distributed networks

Source: ILAE operational classification of seizure types: Fisher et al. Instruction manual for the ILAE 2017 operational classification of seizure types. Epilepsia

Differential Diagnosis

• Stroke/TIA
• Syncope: cardiac arrhythmia, orthostatic syncope, vasovagal syncope
• Migraine
• Encephalopathy: drug-induced, metabolic disturbance
• Psychiatric: anxiety/panic attack, PNES