What are the causes of near dissociation, ranging from common to rare, in patients with lightheadedness (near syncope)?

From the Guidelines

The most common causes of near dissociation, or lightheadedness, in patients range from orthostatic hypotension (OH) to postural orthostatic tachycardia syndrome (POTS), with the specific cause often depending on the patient's symptoms and medical history, as outlined in the 2018 ESC guidelines for the diagnosis and management of syncope 1.

Causes of Near Dissociation

The causes of near dissociation can be categorized into several types, including:

• Orthostatic Hypotension (OH): a drop in systolic blood pressure of ≥20 mmHg or diastolic blood pressure of ≥10 mmHg within 3 minutes of standing, which can be further divided into initial, classical, and delayed OH, with classical OH being the most common form 1.
• Postural Orthostatic Tachycardia Syndrome (POTS): a sustained increase in heart rate of ≥30 bpm within 10 minutes of standing, often accompanied by symptoms such as lightheadedness, palpitations, and fatigue 1.
• Reflex Syncope: a type of syncope caused by a reflex that leads to vasodilation, bradycardia, or both, often triggered by specific actions or events, such as coughing or standing 1.
• Vasovagal Syncope: a type of reflex syncope mediated by the vasovagal reflex, often characterized by symptoms such as diaphoresis, warmth, nausea, and pallor 1.

Diagnosis and Management

Diagnosing the cause of near dissociation requires a thorough medical history, physical examination, and diagnostic tests such as electrocardiogram (ECG) and blood pressure monitoring 1. Management of near dissociation depends on the underlying cause, but may include lifestyle modifications, such as increasing fluid and salt intake, and medications to control blood pressure and heart rate 1.

Key Takeaways

• Near dissociation, or lightheadedness, can be caused by a range of factors, including OH, POTS, reflex syncope, and vasovagal syncope.
• Diagnosis requires a thorough medical history, physical examination, and diagnostic tests.
• Management depends on the underlying cause, but may include lifestyle modifications and medications to control blood pressure and heart rate.
• It is essential to prioritize the patient's morbidity, mortality, and quality of life when diagnosing and managing near dissociation, and to base treatment decisions on the most recent and highest-quality evidence available 1.

From the Research

Causes of Near Dissociation in Patients with Lightheadedness (Near Syncope)

The causes of near dissociation in patients with lightheadedness (near syncope) can be attributed to various factors, ranging from common to rare. Some of the possible causes include:

• Refractive errors, such as myopia, hyperopia, and astigmatism, which can affect the quality of the focused image on the retina and decrease visual acuity 2
• Convergence insufficiency, a condition that affects near vision and can cause symptoms such as eye strain, headaches, and blurred vision 3, 4
• Esotropia, a type of strabismus that can be associated with hyperopia and can cause problems with near vision 5
• Other eye conditions, such as presbyopia, which can affect near vision in patients older than 40 years 2

Common Causes

The most common causes of near dissociation in patients with lightheadedness (near syncope) are:

• Refractive errors, which can be corrected with glasses, contact lenses, or refractive surgery 2, 6
• Convergence insufficiency, which can be treated with orthoptic/vergence therapy 3, 4

Rare Causes

The rare causes of near dissociation in patients with lightheadedness (near syncope) are:

• Esotropia, which can be treated with glasses, prismatic correction, or surgery 5
• Other eye conditions, such as strabismus, which can be associated with refractive errors and can cause problems with near vision 5, 6