The word epilepsy is derived from Greek words meaning “to seize upon” or a “taking hold of.” Our predecessors referred to it as the “falling sickness” or the “falling evil.” Although a useful medical term to denote recurrent seizures, the words epilepsy and epileptic may still have unpleasant connotations and should be used advisedly in dealing with patients. In 1870, Hughlings Jackson, the eminent British neurologist, postulated that seizures were due to “an excessive and disorderly discharge of cerebral nervous tissue on muscles.” The discharge may result in an almost instantaneous loss of consciousness, alteration of perception or impairment of psychic function, convulsive movements, disturbance of sensation, or some combination thereof.
Terminologic difficulty arises from the diversity of the clinical manifestations of seizures. The term convulsion, referring as it does to an intense paroxysm of involuntary repetitive muscular contractions, does not fully capture the range of disorders resulting from abnormal electrical discharges, or seizures, that may consist only of an alteration of sensation or consciousness. Seizure is preferable as a generic term because it embraces all paroxysmal electrical discharges of the brain, and also because it lends itself to qualification. The term motor or convulsive seizure, therefore, is not tautologic, and one may likewise speak of a sensory seizure or psychic seizure. There is also an entity of “nonconvulsive seizure” that may impair consciousness, but not manifest any abnormal convulsive movement. This represents an important and potentially treatable form of an encephalopathy or confusional state.
A first solitary seizure or brief outburst of seizures may occur during the course of many medical illnesses. It indicates that the cerebral cortex has been affected by disease, either primarily or secondarily. If prolonged or repeated every few minutes, the condition termed status epilepticus, it may threaten life. Equally important, a seizure or a series of seizures may be the manifestation of an ongoing neurologic disease that requires special diagnostic and therapeutic measures. Status epilepticus may be of the nonconvulsive type, and continuously impair consciousness and is difficult to detect clinically because of the absence of characteristic movements.
A more common and less-grave circumstance is for a seizure to be but one in an extensive series recurring over a long period of time, with most of the attacks being more or less similar in type. In this instance, they may be the result of an inactive lesion that remains as a scar in the cerebral cortex. The original disease may have passed unnoticed, or perhaps had occurred in utero, at birth, in infancy, or in parts of the brain inaccessible for examination or too immature to manifest signs. The increasingly refined techniques of MRI now also reveal small zones of developmental cortical dysplasia and hippocampal sclerosis, both of which tend to be epileptogenic. Patients with such long-standing but subtle lesions probably make up a large portion of those with recurrent seizures. If there is no underlying lesion, the condition is classified as idiopathic or primary, but in the modern era, this is come to be almost synonymous with a genetic cause. In this category, there are a large number of important types of epilepsy for which no pathologic basis has been established, and for which there is no apparent underlying cause except a genetic disorder of ion channel function. Included here are special hereditary forms such as generalized tonic-clonic (grand mal), and “absence” seizure states as suggested in classifications many years ago by Lennox and Forster. Persistent seizures, regardless of cause, can secondarily damage cortical tissue by several mechanisms that include excitotoxicity and, in the setting of prolonged tonic seizures, systemic hypoxia.