What is the medical term for clonic shaking with syncope (loss of consciousness)?

Myoclonic Syncope: The Correct Term for Clonic Shaking During Syncope

The correct medical term for clonic shaking that occurs during syncope (loss of consciousness) is "myoclonic jerks" or "myoclonic movements," not "convulsive syncope." 1

Understanding Syncope with Movement

Syncope with associated movements is frequently misdiagnosed as epilepsy by both healthcare providers and witnesses. This distinction is crucial for proper treatment and management:

Terminology Clarification

• The term "clonic" in everyday medical use is typically restricted to epilepsy 1
• "Myoclonus" is the preferred term for movements occurring during syncope 1
• "Convulsive syncope" should be avoided as it incorrectly associates these movements with epilepsy 1

Characteristics of Myoclonic Movements in Syncope

• Typically asynchronous and limited in scope 1
• Begin after loss of consciousness (usually some seconds later) 1
• Usually involve few movements (approximately 10) 1
• Often asymmetrical and asynchronous 1
• Occur after the patient has already fallen/collapsed 1
• Brief duration (less than 15 seconds) 1

Differentiating from Epileptic Seizures

• Epileptic movements:
  • Often begin before or at onset of unconsciousness 1
  • Are typically symmetrical and synchronous 1
  • May involve many movements ("100" or "uncountable") 1
  • Include tonic posturing (forceful extension of extremities) 1
  • May include clonic movements that are massive, synchronous jerks 1
  • Often cause the patient to "keel over like a falling log" 1

Pathophysiology

The myoclonic movements in syncope occur as a result of cerebral hypoperfusion and brain ischemia 1. This is fundamentally different from the neuronal hyperexcitability that causes epileptic seizures.

Clinical Significance

Misdiagnosis of syncope with myoclonic movements as epilepsy is common and can lead to:

• Inappropriate antiepileptic medication 2, 3
• Missed diagnosis of potentially serious cardiac causes 4
• Unnecessary restrictions on activities like driving 1
• Psychological impact of an incorrect epilepsy diagnosis

Diagnostic Approach

When evaluating a patient with transient loss of consciousness and movements:

1. Obtain detailed eyewitness accounts focusing on:

   • Timing of movements relative to loss of consciousness
   • Nature and duration of movements
   • Duration of unconsciousness (syncope typically <30 seconds) 1

2. Consider provocative testing in unclear cases:

   • Head-upright tilt testing can reproduce syncopal symptoms 3
   • EEG monitoring during events can help differentiate 5

3. Look for associated features:

   • Sweating, nausea, pallor (suggest neurally-mediated syncope) 1
   • Prolonged confusion after the event (suggests seizure) 1
   • Brief recovery (suggests syncope) 1

Common Pitfalls

• Assuming all movements during loss of consciousness represent epilepsy
• Using the term "convulsive syncope" which can lead to diagnostic confusion
• Failing to consider cardiac causes of syncope with movements
• Over-interpreting EEG findings in patients with syncope 3

Remember that myoclonic movements during syncope are a normal physiological response to cerebral hypoperfusion and do not indicate epilepsy. Proper terminology and understanding of these phenomena are essential for accurate diagnosis and appropriate management.