Myoclonic Seizure
This is a myoclonic seizure (Answer C). A sudden, brief, shock-like muscle contraction in a conscious patient is the defining characteristic of myoclonic seizures 1, 2.
Key Distinguishing Features
Myoclonic seizures are characterized by:
- Sudden, brief, involuntary jerks lasting only a fraction of a second 1
- Shock-like muscular contractions that can affect specific body parts 2
- Preserved consciousness during the event 1
- Can be symmetrical/synchronous or asymmetrical/asynchronous 1
Why Not the Other Options
Tonic seizures (Option B) are distinctly different:
- Involve sustained, forceful muscle contractions rather than brief jerks 3
- Cause forceful extension of extremities 3
- Can cause the patient to "keel over like a falling log" 3
- Typically associated with loss of consciousness 3
Clonic seizures (Option A) differ significantly:
- Consist of massive, synchronous, rhythmic jerks of arms and/or legs 3
- Involve repetitive rhythmic contractions at 0.2-5 Hz frequency 4
- Characterized by synchronized tetanic contractions alternating with silent periods 4
- Usually many movements (20-100) rather than single brief jerks 3
- Most commonly associated with loss of consciousness 4
Critical Clinical Distinction
The terminology matters for accurate diagnosis:
- The term "myoclonus" describes individual abrupt involuntary movements 3
- "Clonic" in everyday neurological use is restricted to epilepsy with rhythmic, massive jerks 3
- Myoclonic movements can occur with preserved consciousness, making this the correct answer for a conscious patient 1
Common Pitfall
Do not confuse myoclonic seizures with syncope-related myoclonus:
- Syncopal movements are typically asynchronous, limited in scope, and occur after loss of consciousness 3
- Epileptic myoclonic seizures begin at or shortly after onset of any loss of consciousness, but can occur while fully conscious 1
- In this case, the patient was explicitly conscious, pointing away from syncope 1