###### Created: 2023-05-07 10:56 ###### Areas & Topics: #medicine #neurology ###### Note Type: #permanent ###### Connected to: [[Blackouts]] - Syncope is the medical term for fainting or passing out. - It comes from the Ancient Greek συγκοπή (sunkopē) meaning 'cutting up' or 'sudden loss of strength. - It describes a transient (short-term) loss of consciousness. - Syncope is a symptom of an underlying condition, rather than being a specific condition itself. ### Aetiology - Essentially, the brain needs a constant supply of glucose to function and maintain consciousness. - This is provided via cerebral blood flow and the underlying mechanisms which maintain cerebral perfusion. - Any condition which causes a reduction in cerebral blood flow can thereby lead to syncope The main causes of syncope can be divided into 4 main categories: Cardiovascular Disorders - Arrythmias - Structural and obstuctive disorders Cerebrovascular Causes - Vertebrobasilar insufficiency (where the vertebral arteries cannot supply sufficient blood flow to the posterior portion of the brain) Disorders of Blood Flow or Vascular Tone - Vasovagal (also known as neurocardiogenic or common faint) - Orthostatic hypotension - Situational (where a patient faints due to a specific trigger or situation e.g. coughing, sneezing, micturition, swallowing etc.) - Carotid Sinus Syncope (where hypersensitive receptors in the area where the external and internal carotid arteries bifurcate, known as the carotid sinus, lead to hypotension and bradycardia and thereby syncope) Mimic Conditions - Seizures - Hypoxia - Panic attacks ### Vasovagal Syncope - Vasovagal syncope is the most common reason for patients experiencing syncope. - It is also known as neurocardiogenic syncope and common faint. - The word vasovagal refers to the fact that this type of syncope is caused by a combination of vasodilation and increased parasympathetic activity (i.e. activation of the vagus nerve). - Vasodilation can be caused by increased parasympathetic activity or issues with autonomic blood pressure regulation. - Increased parasympathetic activity can lead to bradycardia and systemic vasodilation. - In combination, these changes can transiently reduce cerebral perfusion and lead to syncope. #### Clinical Features of Vasovagal Syncope - The typical features of vasovagal syncope are prodromal (i.e. come before syncope occurs). - Patients may begin to experience prodrome symptoms when standing or sitting upright for prolonged periods and may find symptoms are lessened when laying down (as cerebral perfusion is better maintained when lying as blood is not flowing against gravity). - They may also found prodrome symptoms are provoked by certain factors (e.g. stress, hot environments, extreme fatigue etc.) - Once syncope has occurred, patients are recommended to be put in a lying position to increase cerebral perfusion, and also because remaining upright can cause prolonged cerebral hypoperfusion with potential serious effects. The main prodrome features of vasovagal syncope are: - Lightheaded/Dizziness - Decreased Pallor (i.e. pale) - Diaphoresis (sweating) - Feeling especially warm or cold - Nausea - Vision Disturbance (e.g. blurring, darkening etc.) - Hearing Disturbance (e.g. reduced hearing, buzzing in ears etc.) N.B. Incontinence and injury can also occur following syncope In vasovagal syncope, LOC typically is brief (under 15 seconds) and patients should recover quickly, but may feel fatigued after regaining consciousness You can differentiate vasovagal syncope from cardiac syncope as cardiac syncope typically will have a sudden onset with no prodrome symptoms and no post-syncope fatigue ### Investigations - When investigating syncope, it is important to rule out non-syncopal causes where possible. - Syncope is typically diagnosed through a thorough clinical history and examination (mainly using cardiovascular and neurological examinations). - A witness account or an observation period can be helpful for confirming diagnosis. - ECG should be used in all cases to rule out any potential cardiac causes of syncope as these can be more dangerous. - Capillary blood glucose can be used to rule out hypoglycemia. - Lying-standing blood pressure can be used to rule out orthostatic hypertension (where a difference of more than 20mmHg systolic or 10mmHg diastolic is observed between lying and standing) ### Management - The essential idea in managing true syncope is to treat the underlying cause where possible. - In vasovagal syncope, patients should be advised to avoid precipitating factors and to lie down when prodromal symptoms occur. - In other types of syncope, management should concern the underlying cause (e.g. treating arrythmias, switching syncopal medications etc.). ### Resources Syncope - Statpearls https://www.ncbi.nlm.nih.gov/books/NBK442006/ Syncope - Pulsenotes https://app.pulsenotes.com/presentations/neurosciences/notes/syncope Vasovagal Syncope Pulsenotes https://app.pulsenotes.com/medicine/neurology/notes/vasovagal-syncope Carotid Sinus Hypersensitivity - Statpearls https://www.ncbi.nlm.nih.gov/books/NBK559059/ Blackouts and Syncope - NICE CKS https://cks.nice.org.uk/topics/blackouts-syncope/