The onset of idiopathic seizures typically affects patients between ages 5 and 20. 

Therefore, be highly suspicious of a diagnosable etiology in patients who present with new onset seizure prior to age 5 or after age 20.

Common causes of such seizures include:

• Tumors or other structural brain lesions (i.e. intracranial hemorrhage)
• Traumatic brain injury
• Abrupt cessation of alcohol abuse
• Dementia ( i.e. Alzheimer's disease)
• Congenital brain defects
• Intra-partum brain injury
• Hypoglycemia or hyponatremia
• Renal or hepatic insufficiency
• Cocaine or amphetamine illicit drug use
• Abrupt cessation of benzodiazepines, barbiturates, analgesics (i.e. morphine, gabapentin), or sleeping pills
• Infection (i.e. brain abscess, meningitis, encephalitis, neurosyphilis, AIDS)
• Phenylketonuria (PKU) in infants

References