Modes of onset of epilepsy and differential diagnosis

Epilepsy has protean manifestations and may be diagnosed when two unprovoked seizures have occurred. This determination is nearly always based on the available history because most seizures have stopped long before patients arrive at medical care. Great care must be taken, even by experts, to correctly interpret the history and there is strong evidence that incorrect diagnoses are frequent. An abnormal EEG cannot rule epilepsy in or out unless an actual seizure is recorded. When the diagnosis of epilepsy is based only on two seizures, the seizures are usually generalized tonic-clonic. Less "severe" seizure types usually occur multiple times before prompting a medical visit. Some patients present with what seems to be a first generalized tonic-clonic seizure but have a history of less severe attacks that have not brought them to medical attention - epilepsy can then be diagnosed. Others present with staring spells, episodes of confusion, body jerks, spasms, drops, loss of speech and social interactions and/or cognitive function, paroxysmal events during sleep, and febrile seizures. This chapter examines and considers the differential diagnoses for each of these modes of presentation. The consequences of a missed alternate diagnosis, such as cardiac arrhythmia, may be profound.