What clinical feature differentiates a complex febrile seizure from a simple one?

A complex febrile seizure is differentiated from a simple febrile seizure primarily by certain clinical features. One key aspect of complex febrile seizures is their sustained duration, which is typically longer than 15 minutes—a characteristic not seen in simple febrile seizures, which typically last less than 15 minutes.

Additionally, complex febrile seizures often present with focal features, meaning that the seizure is localized to one part of the body rather than being generalized. This is an important distinction, as simple febrile seizures are usually generalized tonic-clonic in nature.

Moreover, complex febrile seizures may occur in multiple episodes within a 24-hour period, unlike simple febrile seizures, which are usually isolated events.

Combining these factors—sustained duration, focal features, and the occurrence of multiple episodes—provides a clear distinction that defines a seizure as complex rather than simple. Therefore, all of these features together are what categorize a seizure as complex, highlighting the multifaceted nature of the clinical presentation.