From the Guidelines
Neurogenic syncope is primarily caused by dysfunction of the autonomic nervous system, leading to a sudden loss of consciousness due to cerebral hypoperfusion.
Causes of Neurogenic Syncope
The following are some of the key causes of neurogenic syncope:
- Neurogenic Orthostatic Hypotension (OH): a subtype of OH caused by lesions involving the central or peripheral autonomic nerves, leading to a drop in systolic blood pressure of ≥20 mm Hg or diastolic blood pressure of ≥10 mm Hg with assumption of an upright posture 1.
- Reflex (Neurally Mediated) Syncope: syncope due to a reflex that causes vasodilation, bradycardia, or both, often triggered by specific actions or situations such as coughing, laughing, or emotional stress 1.
- Vasovagal Syncope (VVS): the most common form of reflex syncope, mediated by the vasovagal reflex, characterized by diaphoresis, warmth, nausea, and pallor, often preceded by identifiable triggers or a characteristic prodrome 1.
- Carotid Sinus Syndrome: reflex syncope associated with carotid sinus hypersensitivity, which can be triggered by stimulation of the carotid sinus, often occurring in older patients 1.
- Situational Syncope: reflex syncope associated with specific actions or situations, such as micturition, defecation, or coughing 1.
- Autonomic nervous system dysfunction: conditions such as multiple system atrophy, Shy-Drager syndrome, and familial dysautonomia can cause neurogenic syncope due to impaired autonomic function 1. It is essential to note that these causes can be complex and may involve multiple factors, and a thorough evaluation by a healthcare provider is necessary to determine the underlying cause of neurogenic syncope 1.
From the Research
Causes of Neurogenic Syncope
The causes of neurogenic syncope are complex and multifaceted. Some of the key factors that contribute to this condition include:
- Impaired arterial baroreflex adaptation to orthostatic stress 2
- Cessation of vasoconstrictive sympathetic traffic 2
- Modest reduction in central blood volume, which is aggravated by upright posture 3
- Sympathetic blocking agents and vasodilator drugs for hypertension 3
- Tranquilizers in elderly patients 3
- Anemia 3
- Transient reductions in blood volume, such as those that occur after a brisk diuresis or blood donation 3
Pathophysiology of Neurogenic Syncope
The pathophysiology of neurogenic syncope involves a sudden failure of autonomic regulatory mechanisms to maintain adequate blood pressure and, occasionally, heart rate, to sustain cerebral perfusion and consciousness 4. This can lead to a range of symptoms, including:
- Nausea
- Headache
- Diaphoresis
- Dizziness
- Chest pain
- Palpitations
- Dyspnea
- Paresthesia 3
Types of Neurogenic Syncope
Neurogenic syncope encompasses a wide range of reflexogenic syncope, including:
- Vasovagal type
- Micturition syncope
- Carotid sinus hypersensitivity
- Post-prandial syncope 2