Tonic-Clonic Seizure
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Tonic-Clonic
- The most prominent generalized, motor seizure: tonic-clonic seizure.
Overview
Semiology
- Tonic phase = stiffening
- Clonic phase = rhythmic jerking
Mimicker
- A key mimicker of tonic-clonic seizure is convulsive syncope, which are convulsions brought on by syncope, a loss of adequate cerebral perfusion, rather than by abnormal electrical activity in the brain.
- Bear in mind that one of the most common mimickers of generalized seizures, and most seizure types, is actually non-epileptic spells (aka psychogenic seizures).
Syndromes
- Generalized tonic-clonic seizures can occur in a wide-variety of epilepsy syndromes.
Detailed Semiology
Pre-ictal
- There is often a pre-ictal sensory prodrome that can last minutes to hours.
- The ictal phase refers to the seizure, itself: the event.
Tonic Phase
- There is tonic stiffening: show that the back and neck are arched. The patient is lying down because there is a loss of consciousness.
Clonic Phase
- Characterized by rhythmic jerking (convulsions) of the face, arms, and legs.
Apnea
- During the ictal phase, there is often apnea with frothing at the mouth, choking sounds, and cyanosis (a blue appearance to the skin), which can mimic a cardiac arrest.
Post-ictal Relaxation
- Ahen, show that after the event, post-ictal, there is post-ictal relaxation, which involves a stupor with possible bladder or bowel incontinence and deep, slow respirations.
EEG Correlation
- See: Tonic-Clonic Seizure
- For reference, the region between the vertical lines is one second.
- The number of wave cycles within that one second is the frequency, which is measured in Hertz (Hz).
- A single wave cycle in one second would be 1 Hz.
Tonic Phase
- At the initiation of the seizure, during the tonic phase, the EEG rhythm is a 10 Hz tonic (fast frequency), low amplitude waveform.
Clonic Phase
- During the clonic phase, the corresponding EEG rhythm is 4 Hz (slower frequency) spike-and-wave activity.
Post-ictal Slowing
- After the event, there is post-ictal slowing, with only a few wave cycles per second.