Partial-Onset Seizures: What’s in a Name?

When you see the acronym POS, what comes to mind? If you’re a person with epilepsy, “partial-onset seizure” probably tops the list. But that’s just one of the terms used to refer to seizures that begin in one, not both parts of the brain. Do you know them all?

The adjective “partial” has been used to describe this category of seizures because they begin with an electrical discharge in only one part of the brain, as opposed to a generalized seizure, which involves the entire brain. Physicians, however, are increasingly using the term “focal” when referring to partial seizures, to note this area of focus. Whatever you call them these seizures are divided into two categories: simple and complex.

During a simple partial-onset seizure, there is no loss of awareness or consciousness; during a complex partial-onset seizure, there is. Simple partial-onset seizures fall into one of four categories, determined by location in the brain and the symptoms: motor (muscle activity affected), sensory (sense affected), autonomic (automatic functions like blood pressure affected), psychic (may cause feelings of panic or déjà vu). The types of seizures that occur in temporal lobe epilepsy have had many different names including psychomotor seizures and limbic seizures. Today these are referred to as complex partial or simple partial seizures.

With so many terms, no wonder patients and their caregivers are confused. That said, doctors can be confused too, because patients may have their own vocabularies.

Sometimes a person with epilepsy will come up with words to define their experience without even knowing what a partial-onset seizure is. Some terms you may have heard specific to partial seizures are auras, déjà vu, becoming a space cadet, zoning out and daydreaming.