Tonic seizure

What it means

A tonic seizure is a type of motor seizure characterized by unilateral or bilateral limb stiffening or elevation, often with neck stiffening.

This term describes the initial semiology of the seizure without specifying whether the onset is focal or generalized. Thus it can be used for coding tonic seizures when the onset is not known. The tonic contraction of muscles can result in a tremor, not to be confused with a clonic phase. This term does not apply to seizures with a tonic phase followed a clonic phase, see bilateral tonic-clonic seizure.

Rare diseases that can present with this1

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category