What is the most common cause of seizures in an adult?

• A. Subtherapeutic levels of anticonvulsant medications
• B. Fever-related convulsions
• C. Intracranial hemorrhage
• D. Electrolyte imbalance

Answer: (A)

Subtherapeutic anticonvulsant levels are the most common cause of seizures in adults, especially for those with epilepsy on chronic therapy. When a patient misses doses, takes medications irregularly, or encounters drug interactions or changes in absorption or metabolism, the blood concentration of the anticonvulsant can drop below the therapeutic range. With insufficient drug effect, neurons remain hyperexcitable and can fire in a synchronized, abnormal way, producing a seizure. This scenario—breakthrough seizures due to falling drug levels—is more frequent than other causes in adults.

Fever-related convulsions are typical in children and are less common in adults. Intracranial hemorrhage and electrolyte imbalances can provoke seizures, but they are not the most frequent triggers in the adult population; they’re important to consider, especially with head injury, stroke symptoms, or metabolic issues, but they occur less commonly as the primary cause of new seizures in adults on maintenance anticonvulsants.