en:dizziness

Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.

Dizziness is a common medical complaint, affecting 20-30% of persons. Dizziness is broken down into 4 main subtypes: vertigo (~25-50%), disequilibrium (less than ~15%), presyncope (less than ~15%), and nonspecific dizziness (~10%).

Vertigo is the sensation of spinning or having one's surroundings spin about them. Many people find vertigo very disturbing and often report associated nausea and vomiting.
Presyncope describes lightheadedness or feeling faint; the name relates to syncope, which is actually fainting.
Disequilibrium is the sensation of being off balance and is most often characterized by frequent falls in a specific direction. This condition is not often associated with nausea or vomiting.
Non-specific dizziness may be psychiatric in origin. It is a diagnosis of exclusion and can sometimes be brought about by hyperventilation

Mechanism and causes

Many conditions cause dizziness because multiple parts of the body are required for maintaining balance including the inner ear, eyes, muscles, skeleton, and the nervous system. Thus dizziness can be caused by a variety of problems and may reflect a focal process (such as one affecting balance or coordination) or a diffuse one (such as a toxic exposure or low perfusion state).

Common causes of dizziness include:

Inadequate blood supply to the brain due to:
A sudden fall in blood pressure
Heart problems or artery blockages
Anaemias, such as Vitamin B12 deficiency anemia, Iron deficiency anemia
Loss or distortion of vision or visual cues
Standing too quickly/prolonged standing
Disorders of the inner ear
Dehydration
Distortion of brain/nervous function by medications such as anticonvulsants and sedatives
Dysfunction of cervical proprioception
Side effects from other prescription drugs, such as proton-pump inhibitors or Coumadin (warfarin)