Complex sentence: Early PTSs are considered to be provoked seizures, because they result from the direct effects of the head trauma and are thus not considered to be actual epilepsy, while late seizures are thought to indicate permanent changes in the brain's structure and to imply epilepsy.
Split into simpler sentences: Early PTSs are considered to be provoked seizures, because they result from the direct effects of the head trauma and are thus not considered to be actual epilepsy. Late seizures are thought to indicate permanent changes in the brain's structure and to imply epilepsy.