Breakthrough Seizure

A Breakthrough Seizure is one that occurs in a patient with seizure disorder while still on AED (antiepileptic or anti seizure medicine); whose seizures are otherwise assumed to be under control and the blood levels of the AED are within the therapeutic range.

This is not same as a withdrawal seizure, which occurs due to stopping or reducing the dosage of anti seizure medicine or alcohol, benzodiazepines, barbiturates etc (the drugs that suppress the brain activity). Also strictly speaking seizures occurring due to missing the dose, taking inadequate dose or less frequently than recommended, should be preferably called as withdrawal seizures rather than breakthrough-seizures. This is because the decreased anti seizure medicine level in the blood precipitates seizures in these situations, so it is similar to withdrawal conditions.

One scenario is patient’s current blood levels are simply not sufficient to control the seizures because the seizure tendency is high. Sometimes this may be an idiopathic situation means no cause is found why the seizure occurs, or why the seizure focus has become hyperactive all over suddenly.

But if a detailed history is taken then many times we will be able to find out one or other cause for breakthrough-seizures and they may include;

• Infections with fever
• Lack of adequate sleep
• Missing food (hypoglycemia)
• Dehydration
• Electrolyte disturbances
• Menstruation
• Stress
• Intake of alcohol, other toxins and medications that can cause lowering of seizure threshold
• Or it may not be a breakthrough-seizure at all, rather patient had a seizure due to a new reason or pathology e.g. new brain insult etc.

A breakthrough-seizure requires the doctor look at all these possibilities, and if history is not enough to arrive at the cause for the seizure then investigations are necessary as below (not every patient require all these tests);

• Estimation of blood concentration of AED
• Blood electrolyte estimation
• Complete blood count if fever is present
• Urine analysis
• Chest x ray etc

An EEG, CT or MRI of the brain is not always necessary with typical breakthrough seizures. However if the diagnosis is not clear then such tests may be necessary.

Treatment obviously would depend upon what precipitated the breakthrough-seizure.

If the AED level is sub therapeutic (prferably called as withdrawal seizure) then boost up the level with additional AED dose and increasing the maintenance dose. If the dose the level is therapeutic; but still away from the upper normal range or patient is not having a side-effect with the current dose then increase the dose further.

The other causes mentioned above are treated appropriately. With these other causes patient may still require optimization of the AED dose as above. If a precipitating factor is found and it is fully reversible then the AED dosage can be increased just temporarily.

In some situations we may add another AED, switch over the current AED to another AED etc. Of course all these decisions are made on case to case basis. A neurologist is frequently involved in the care of these patients.