From the Guidelines
Loss of consciousness can occur due to various medical conditions, including syncope, seizures, head trauma, metabolic disturbances, stroke, drug overdose, cardiac causes, infections, and psychiatric conditions, with syncope being the most common cause, often triggered by dehydration, emotional stress, or standing up too quickly 1. The causes of loss of consciousness can be categorized into several groups, including:
- Cardiovascular disorders, such as syncope, which is the most common cause of transient loss of consciousness 1
- Neurologic conditions, such as epilepsy, which can cause seizures leading to loss of consciousness 1
- Psychological factors, such as conversion disorder, which can present with apparent loss of consciousness 1
- Metabolic disturbances, such as hypoglycemia, hypoxia, or electrolyte imbalances, which can disrupt brain function 1
- Head trauma, which can lead to concussion or more severe traumatic brain injury resulting in loss of consciousness 1
- Infections affecting the brain, such as meningitis or encephalitis, which can lead to altered consciousness 1
- Drug overdose, particularly with opioids, sedatives, or alcohol, which can depress brain function to the point of unconsciousness 1
- Cardiac causes, such as arrhythmias and cardiac arrest, which can reduce blood flow to the brain 1 When someone loses consciousness, they should be placed in the recovery position if breathing normally, and emergency medical services should be contacted immediately, as prompt identification of the underlying cause is crucial for appropriate treatment 1.
From the Research
Causes of Loss of Consciousness
The causes of loss of consciousness can be classified into several categories, including:
- Neurologic causes, such as epileptic seizures, which occur due to a primary dysfunction of the neuronal circuitry that maintains awareness 2
- Systemic conditions, which affect consciousness through global cerebral dysfunction or hypoperfusion, including mechanisms such as hypoxia, hypoglycemia, and neurocardiogenic syncope 2
- Functional neurologic disorders, also known as conversion disorders or psychogenic spells, which refer to clinical conditions in which clinical presentation can mimic but does not completely fit with any specific neurologic or systemic disorder 2
- Syncope, which is defined as transient loss of consciousness due to cerebral hypoperfusion, and can be further divided into reflex syncope, syncope due to orthostatic hypotension, and cardiac syncope 3
- Generalized epileptic seizures, which are a major group of transient loss of consciousness 3
- Functional TLOC, which is a psychogenic condition that mimics either epilepsy or syncope 3
- Miscellaneous disorders, which include other less common causes of transient loss of consciousness 3
Classification and Diagnosis
The diagnosis of transient loss of consciousness requires a thorough medical history, physical examination, and targeted diagnostic tests 4, 5. A classification scheme for transient loss of consciousness can be based on ongoing multidisciplinary efforts, including those of the Task Force on Syncope of the European Society of Cardiology 3. The importance of accurate diagnosis and the impact of misdiagnosis are also highlighted in the literature 6.
Approach to Diagnosis
The approach to diagnosing the most common etiologies of transient loss of consciousness involves focusing on the importance of the history and physical examination, as well as targeted diagnostic tests 4. The establishment of specialist clinics can also help with diagnosis and management 6.