Isolated seizures can be caused by nearly any condition that affects brain function. These conditions include toxic-metabolic disturbances such as:
Most metabolic conditions become more common with aging, as does the use of multiple prescription medications.1 Offending drugs(see Table: Drugs That May Lower Seizure Threshold) include theophylline and neuroleptics, as well as a variety of antidepressants.2 Sedative and alcohol withdrawal are also significant causes.
Although metabolic conditions and medication side effects may be recurrent, they are at least potentially preventable and, therefore, would not lead to a diagnosis of epilepsy.
On the other hand, acute neurologic conditions such as stroke or trauma may produce structural damage to the brain. Even functionally minor damage can permanently alter neuronal excitability and synchronization, resulting in a tendency toward recurrent unprovoked seizures—that is, epilepsy.
Because recovery from central nervous system injury, at least on a cellular level, is usually incomplete, the accumulation of brain insults over time would lead to increased incidence and prevalence of epilepsy with aging.
It is important to recognize, however, that even in patients with structural lesions that could potentially cause epilepsy, seizures can have a toxic-metabolic or other preventable cause. These should be ruled out before assuming that epilepsy has developed.
Nearly every study of epilepsy in the elderly has found vascular disease (either acute or remote) to be responsible for the largest proportion of cases, in general the majority of those for which a cause is known.Table: Etiology of Seizures and Epilepsy
Brain tumor (either metastatic or primary) is the next most common cause of epilepsy, reported in up to 28% of new-onset cases.
Other structural causes of epilepsy include:
Alzheimer’s disease, associated with seizures in perhaps 10% of cases,3,4 will be an increasingly important cause of epilepsy in the future unless effective methods of prevention or treatment are found.
Reviewed and revised June 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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