Syncope is an entity in which loss of consciousness due to cerebral hypoperfusion presents.  There are several pathways to explain its pathophysiology, depending on if it is either reflex syncope, orthostatic intolerance, or cardiovascular syncope.
Syncope pathophysiology
Neurocardiogenic syncope pathophysiology
Transient ischemic attack risk factors
Transient ischemic attack pathophysiology
Neurocardiogenic syncope symptoms
Brugada syndrome pathophysiology
Insomnia etiology
Cluster headache diagnostic criteria