Dizziness

Dizziness refers to an impairment in spatial perception and stability. It is considered imprecise. It can be used to mean vertigo, presyncope, disequilibrium, or a non-specific feeling such as giddiness or foolishness.

One can induce dizziness by engaging in disorientating activities such as spinning.


 * Vertigo is a specific medical term used to describe 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. It represents about 25% of cases of occurrences of dizziness.
 * 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.
 * Presyncope is lightheadedness, muscular weakness and feeling faint as opposed to a syncope, which is actually fainting.
 * Non-specific dizziness is often psychiatric in origin. It is a diagnosis of exclusion and can sometimes be brought about by hyperventilation.

A stroke is the cause of isolated dizziness in 0.7% of people who present to the emergency room.

Classification
Dizziness is broken down into 4 main subtypes: vertigo (~50%), disequilibrium (less than ~15%), presyncope (less than ~15%) and lightheadedness (~10%).

Differential diagnosis
Many conditions are associated with dizziness. However, the most common subcategories can be broken down as follows: 40% peripheral vestibular dysfunction, 10% central nervous system lesion, 15% psychiatric disorder, 25% presyncope/dysequilibrium, and 10% nonspecific dizziness. The medical conditions that often have dizziness as a symptom include:
 * Benign paroxysmal positional vertigo
 * Meniere's disease
 * Vestibular neuronitis
 * Labyrinthitis
 * Otitis media
 * Acoustic neuroma
 * Chronic motion sickness
 * Ramsay Hunt syndrome
 * Migraine
 * Multiple sclerosis
 * pregnancy
 * low blood pressure (hypotension)
 * low blood oxygen content (hypoxemia)
 * iron deficiency (anemia)
 * low blood sugar (hypoglycemia)
 * hormonal changes (e.g., thyroid disease, menstruation, pregnancy)
 * panic disorder
 * hyperventilation
 * anxiety
 * depression
 * age-diminished visual, balance, and perception of spatial orientation abilities

Mechanism
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.

Common physiological causes of dizziness include:
 * inadequate blood supply to the brain due to:
 * a sudden fall in blood pressure
 * heart problems or artery blockages
 * loss or distortion of vision or visual cues
 * disorders of the inner ear
 * distortion of brain/nervous function by medications such as anticonvulsants and sedatives

Epidemiology
About 20–30% of the population report to have experienced dizziness at some point in the previous year.