Vestibular Causes
The vestibular organs of the inner ear provide the brain with information about changes in head movement. If the vestibular system is not functioning properly, dizziness, vertigo, imbalance, spatial disorientation, and other symptoms can result. Vestibular-system distress can be caused by a variety of influences, including
- Viral infections of the labyrinth or vestibular nerve.
- Bacterial infection of either the middle ear or the brain coverings which may spread to the inner ear.
- Allergies can cause changes in the inner ear fluids or middle ear pressure because of swelling of the Eustachian tube and production of fluid in the middle ear.
- Head trauma is a common cause of inner ear damage in people under age 50. A blow to the head or a "whiplash" injury can result in, for example, perilymph fistula or benign paroxysmal positional vertigo (BPPV).
- Exposure to ototoxins (drugs or chemicals that are harmful to the inner ear or the vestibulo-cochlear nerve).
- Degeneration of the hair cells in the inner ear is also thought to occur with aging and can result in dizziness and vertigo as well as hearing loss.
- A benign tumor known as an acoustic neuroma can grow on the vestibulo-cochlear nerve.
Non-Vestibular Causes
Dizziness has many causes other than inner ear dysfunction, such as:
- Visual disturbances can result in lightheadedness or dizziness. Some people feel dizzy while adjusting to bifocals or a new eyeglass prescription, or from reduced vision due to cataracts
- Hyperventilation can cause temporary dizziness. During rapid breathing, more carbon dioxide than normal is expelled and the level of carbon dioxide in the blood falls, which in turn affects the function of brain cells.
- Decreased blood flow to the brain or brain stem can cause dizziness, because insufficient oxygen is reaching the cells
- Nervous-system disorders such as peripheral neuropathies (diminished nerve function in the legs or feet) can cause unsteadiness.
- Stress, tension, or fatigue may cause dizziness. Under these conditions, the brain stem functions less efficiently, resulting in some loss of automatic reflex control of balance. This leads to elevated levels of activity for the cerebral cortex, as conscious energy is used to help maintain balance by controlling voluntary muscle movements.
