A breakthrough seizure is an epileptic seizure that occurs despite the use of anticonvulsants that have otherwise successfully prevented seizures in the patient.:456 Breakthrough seizures may be more dangerous than non-breakthrough seizures because they are unexpected by the patient, who may have considered himself or herself free from seizures and therefore, not take any precautions.
Often when a breakthrough seizure occurs in a person whose seizures have always been well controlled, there is a new underlying cause to the seizure.
Causes of a breakthrough seizure include:
- Missed dose of an anticonvulsant
- This is the most common cause, and it may even result in status epilepticus. In some patients, even a single missed dose may be responsible for a breakthrough seizure.:57
- Incorrectly timed dose
- This may occur, for example, if a patient takes a dose a later than the prescribed time. Also, a patient traveling across time zone lines may alter their medicating schedule, resulting in interference with the therapeutic effects of the drug:60
- Incorrect dosage amount
- A patient may be receiving a sub-therapeutic level of the anticonvulsant.
- Switching medicines
- This may include sudden withdrawal of an anticonvulsant without replacing it at all, or to switch abruptly to another anticonvulsant. In some cases, switching from brand to the generic version of the same medicine may induce a breakthrough seizure.
- Sleep deprivation
- Failure to get enough restorative sleep in some patients may result in a seizure.:61 This will often be the patient's only change in routine prior to a seizure.
- Alcohol or drug use:63
- This includes caffeine and over-the-counter drugs in some.:67
- This may be the result of hormonal fluctuation or over-the-counter drugs that are used to treat symptoms of menstruation.
- Acute illness
- Some illnesses caused by viruses or bacteria may lead to a seizure, especially when vomiting or diarrhea occur, as this may reduce the absorption of the anticonvulsant.:67
- May be the result of poor dietary habits, lack of access to proper nourishment, or fasting.:68 In seizures that are controlled by diet in children, a child may break from the diet on their own.
- Drug interactions
- caused by antihistamines and antidepressants lower the effectiveness of anticonvulsants.
Rates of breakthrough seizures vary. Studies have shown the rates of breakthrough seizures ranging from 11–37%.
The treatment for a breakthrough seizure involves measuring the level of the anticonvulsant in the patient's system, and may include increasing the dosage of the existing medication, adding another medication in addition to the existing one, or altogether switching medications.
One who suffers a breakthrough seizure when he or she is not known to have them may require hospitalization for a period of time for observation.:498
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