Myoclonic and atonic seizures vs Tonic-clonic seizures
How to tell Myoclonic and atonic seizures and Tonic-clonic seizures apart when a board question makes them look alike.
Myoclonic and atonic seizures are brief with little postictal state; tonic-clonic seizures have tonic-then-clonic phases and prolonged postictal confusion.
Side by side
Myoclonic seizures are brief shock-like muscle jerks; atonic seizures are sudden loss of tone with drop attacks, often requiring injury prevention.
Tonic-clonic seizures cause loss of consciousness with tonic stiffening followed by rhythmic clonic jerking and postictal confusion.
Generalized or focal network bursts can produce brief jerks or abrupt tone loss depending on seizure type and syndrome.
Bilateral seizure activity recruits motor networks, producing tonic then clonic phases and postictal recovery.
Brief lightning-like jerks support myoclonic seizure; sudden drop from loss of tone supports atonic seizure.
Tonic stiffening, clonic jerking, tongue biting, incontinence, and postictal confusion support tonic-clonic seizure.
The trap
Motor seizures can all look dramatic, so duration, tone change, and postictal state decide.
The repair move
For motor seizures, identify the motor phase before naming the syndrome and choosing the drug: (1) lightning-like jerk without LOC is myoclonic (valproate or levetiracetam; carbamazepine and lamotrigine can worsen); (2) sudden loss of tone with fall is atonic (consider Lennox-Gastaut, especially in pediatric patients); (3) tonic stiffening followed by clonic jerks with postictal confusion, possibly tongue biting and incontinence, is generalized tonic-clonic (valproate, lamotrigine, or levetiracetam). Any seizure lasting over 5 minutes is status epilepticus and needs IV benzodiazepine first, then fosphenytoin or IV valproate.
Try a free question
CoreA teenager has brief shock-like jerks of both arms shortly after waking, causing objects to fly from the hands. Awareness is otherwise quickly regained. Which seizure type is most likely?
Show answer and explanation
Answer: A. Myoclonic seizure. Brief shock-like jerks, especially without sustained tonic-clonic sequence or postictal state, support myoclonic seizure.
Why the other choices are tempting
- B. Atonic seizure causes sudden loss of tone and falls.
- C. Tonic-clonic seizure has tonic stiffening, clonic jerking, and postictal confusion.
- D. Absence seizure causes brief staring with 3-Hz spike-wave.
- E. Focal impaired-awareness seizure has focal onset, impaired awareness, automatisms, or postictal confusion.
Flashcards
Tap a card to flip it.
What movement defines myoclonic seizure?
Brief shock-like muscle jerks define myoclonic seizure.
What movement defines atonic seizure?
Sudden loss of tone with drop attack defines atonic seizure.
Quick answers
What is the fastest way to tell Myoclonic and atonic seizures from Tonic-clonic seizures?
Myoclonic and atonic seizures are brief with little postictal state; tonic-clonic seizures have tonic-then-clonic phases and prolonged postictal confusion.
What is the key clue for Myoclonic and atonic seizures?
Myoclonic seizures are brief shock-like muscle jerks; atonic seizures are sudden loss of tone with drop attacks, often requiring injury prevention.
What is the key clue for Tonic-clonic seizures?
Tonic-clonic seizures cause loss of consciousness with tonic stiffening followed by rhythmic clonic jerking and postictal confusion.
What is the common trap with Myoclonic and atonic seizures vs Tonic-clonic seizures?
Motor seizures can all look dramatic, so duration, tone change, and postictal state decide.