DIZZINESS
It takes three kinds of sensation to keep a person informed on movements of his body: sensations from the eyes (vision); from the muscles, joints, and tendons; and from his semicircular canals. When a person receives conflicting sensations regarding the movements of his body, as when the semicircular canals register movement and the other sensations indicate no movement, the result is dizziness.
The semicircular canals are easily disturbed by abnormal conditions and may produce misleading nerve impulses. Also when the nerve which carries impulses from the semicircular canals to the brain is irritated or compressed the brain's interpretation of the impulses will be distorted, and dizziness may result.
A common cause of dizziness is an ordinary overstimulation of the semicircular canals, as in motion sickness. Reflex stimulation of the canals causing dizziness may occur in excessive use of the eyes, in indigestion, in epilepsy, or in migraine headaches.
Meniere's syndrome is a distressing illness in which dizziness is a prominent symptom. Dizziness may come from a head injury. There is a brain tumor, known as an eighth nerve neuroma, which may cause dizziness by irritating the nerve which carries sensation from the internal ear and semicircular canals to the brain. This dizziness is usually associated with ringing in the ear. Symptoms may later seem to improve as the tumor completes the destruction of the nerve, but deafness of the involved ear results. This type of tumor can be treated successfully by surgery when recognized early.
Arteriosclerosis may cause dizziness by limiting the blood to one set of semicircular canals more than to the other. Serious hemorrhage and anemia may cause dizziness. Mumps and encephalitis often produce dizziness by damage to the semicircular canals. The toxins of some diseases, drugs taken to excess, and allergy sometimes cause dizziness, as do psychic factors, such as concern over finances, tension between relatives, or personal crises.
