Clinical Diagnosis and Differentiation of Syncope

Definition: Syncope is characterized as an abrupt, transient loss of consciousness (TLOC) resulting specifically from a decrease in cerebral perfusion.
Brief Motor Manifestations: The majority of individuals experiencing syncope will exhibit brief, transient motor manifestations shortly after the loss of consciousness occurs.
Primary Motor Manifestation (MCQ High Yield): The most common motor manifestation associated with syncope is myoclonus. Chronologically, this myoclonus is multifocal and arrhythmic.
Additional Motor Manifestations: While myoclonus is most frequent, other motor signs can occur, though they are considered less common. these include:
- Posturing.
- Head turning.
- Upward eye movement.
- Oral automatisms.
- Righting movements.
Misdiagnosis as "Convulsive Syncope":
- The presence of motor manifestations, particularly myoclonus, frequently leads to the misdiagnosis of syncope as a seizure.
- This phenomenon is often referred to as "convulsive syncope."
- Distinguishing Feature: Unlike true epileptic seizures, convulsive syncope is not associated with an EEG (electroencephalogram) discharge.
- Neuroanatomical Origin: The origin of the motor movements in syncope is thought to reside in the brainstem rather than the cortex.

Neurally Mediated Syncope: This is the most common form of syncope in younger individuals.
Common Triggers:
- Intense pain.
- Strong emotions.
- Standing for prolonged periods of time, especially in hot or crowded environments.
Situational Triggers: In certain individuals, syncope can be precipitated by specific physiological acts, such as:
- Micturition (urination).
- Defecation.
- Coughing.
Other Pathological Causes:
- Orthostatic Hypotension: A drop in blood pressure upon standing.
- Cardiac Arrhythmias: Syncope caused by arrhythmia is typically more abrupt and frequently occurs without any preceding symptoms or prodrome.
- Structural Cardiopulmonary Disease: Physical abnormalities of the heart or lungs affecting circulation.

The Neurally Mediated Prodrome: Individuals experiencing neurally mediated syncope often report a specific set of warning symptoms (prodrome) before losing consciousness:
- Lightheadedness.
- Nausea.
- Pallor (paleness of the skin).
- Cold sweating (diaphoresis).
- Visual changes, such as "graying of vision."
- Auditory changes, such as hearing becoming distant.
- Visual or auditory hallucinations (less common).

Features that Favor a Diagnosis of Syncope:
1. A history of known heart disease.
2. Prior confirmed episodes of syncope.
3. Precipitation of the event by prolonged standing or rising to an upright position.
4. The presence of dehydration.
5. The occurrence of the typical neurocardiogenic syncope prodrome (lightheadedness, nausea, etc.).
6. Witness reports describing pronounced pallor during the event.
7. The absence of tonic or clonic activity (rhythmic jerking/stiffening).
8. Witness description of multifocal myoclonus that lasts for less than $15\,seconds$ .
9. The patient's recollection of the actual loss of consciousness.
Features that Favor a Diagnosis of Seizures:
1. A history of previous seizures.
2. A known cortical brain lesion.
3. Physical signs such as tongue biting, urinary or fecal incontinence, and cyanosis (bluish skin color).
4. Postictal symptoms, including confusion and headache.
5. A lack of recollection of the actual loss of consciousness.

Anoxic-Epileptic Seizures: While rare, syncope can occasionally trigger a true epileptic seizure. These are referred to as "anoxic-epileptic seizures."
Clinical Distinction: It is critical to distinguish these rare anoxic-epileptic seizures from the much more common nonepileptic "convulsive syncope."