DEFINITIONS AND CAUSES OF SEIZURES AND EPILEPSY
Seizures are caused by abnormal electrical discharges in the brain. Epilepsy is the condition of recurrent unprovoked seizures. The definition of “provoked” here is more precise than in common parlance and refers to acute, reversible provoking factors causing seizures. For example, acute hypoglycemia, alcohol withdrawal, high fever, and medication or drug toxicity are all acute reversible factors that can provoke seizures (Table 18–1). In these scenarios, the brain may be structurally normal, but exposure to the acute provoking factor leads to seizures. When the cause is treated, the seizures typically improve and the patient is not necessarily at risk for future recurrent seizures.
TABLE 18–1Causes of Provoked Seizures and Epilepsy.
Brain tumors, prior stroke, prior head trauma, prior CNS infection, and cortical malformations can all cause seizures, but these entities are neither acute nor reversible, and so recurrent seizures due to any of these causes are considered unprovoked. A patient with a brain tumor (or any of the prior CNS insults listed above) who has a first seizure has had the underlying potential seizure focus for some time. If no acute provoking factor is present (e.g., infection, metabolic derangement), one may ask why the patient seized on that particular day and not the day, week, or month before? Seizures in this context are considered to be unprovoked because they can occur at any time without any provoking factor, just like the unprovoked seizures of idiopathic genetic epilepsy syndromes. Therefore, patients with recurrent seizures due to brain tumors, prior trauma, prior stroke, prior neurosurgery, prior CNS infection, or any other irreversible underlying seizure focus (see Table 18–1) are considered to have epilepsy and should be treated as such.
Some causes of acute symptomatic (provoked) seizures such as acute stroke or hemorrhage, head trauma, or meningitis can increase the risk for development of epilepsy in the future since they can lead to irreversible brain damage, creating an epileptogenic focus.
EVALUATION OF PATIENTS WITH SEIZURES
A patient with seizure(s) will generally present for evaluation in one of three scenarios:
After a first seizure (or other type of ...