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Balance Disorder Pathophysiology

By Dr Ananya Mandal, MD

Balance disorders are caused by several incidents that may be episodes of infection, injury or blood flow problems to the inner ear or to the brain.

Normal functioning of the balance organs within the ear

The ears are divided into three discernible parts – the outer, middle and the inner ear. The outer ear is composed of the pinna that brings in sound waves onto the ear drum.

The middle ear amplifies the sound wave and transmits it into the inner ear. 

The inner ear contains an organ called the labyrinth. There two major organs in the inner ear – the cochlea or the shell shaped hearing organ and the semicircular canals or the balance organs.

The semicircular canals work to co-ordinate with the eyes (what they see) as well as the feeling of the bones and joints to maintain normal balance.

When the inner ear coordinates with the signals from the eyes, it is called the vestibulo-ocular reflex (VOR). The inner ear sends signals to the brain that also receives signals from these peripheral organs to given an idea of the position of the body. This helps in maintenance of balance.

The semicircular canals are three tubes set in three different right angles. They have a bulb at their ends. These are called superior, posterior, and horizontal canals. The canals converge at a point and this is close to the cochlea. These are filled with a fluid. As the body or the head moves, this fluid also moves.

The bulbs at the ends of the canals contain tiny hair like structures. Rotation of the head causes a movement of the fluid leading to movement of the top portion of the hair cells that are embedded in the jelly-like cupula.

There are two other organs called the utricle and saccule that are called otoliths. These detect linear acceleration, or movement in a straight line.  When the hair is displaced, it sends signals to the brain via nerves and the body corrects itself or balances accordingly.

Pathophysiology of balance disorders

An acute loss of balance sensation can be either partial or total. It may be caused by viral infections or due to injury to the vital structures of the brain or inner ear.

In the case of benign paroxysmal positional vertigo (BPPV),  calcium carbonate crystals get dislodged from their usual position and move to one of the semicircular canals of the inner ear when the head is moved. There is an incorrect registration of movements with changes in body position and this may trigger an episode of intense vertigo.

Injuries to the central nervous system may be caused by head injury or by disturbances of the blood circulation. This leads to dizziness, vertigo, and disequilibrium.

With age there is a deterioration of the balance system leading to balance problems. Physical disabilities such as arthritis and joint pain also contribute to the problem.

Reviewed by , BA Hons (Cantab)

Further Reading

Last Updated: May 26, 2013

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