Balance is defined as a state of equilibrium. It takes significant amount of work for this to occur in the body. The brain uses inputs from many sources to understand where the body is located in relationship to the world and to allow it to function. Sensory information from the eyes, ears, and position receptors in the rest of the body help keep the body upright and allow it to move in a coordinated fashion.
Information comes to cerebellar lobes located in the base of the brain from the vestibular system in the inner ear, vision from the eyes, and proprioception (position) receptors located throughout the body that send signals through the spinal cord. The cerebellum uses that information to maintain posture, coordinate body motions like walking and also coordinate fine motor skills like using a pen to write.
Vertigo, a feeling of spinning movement and sometimes accompanied by nausea and vomiting, occurs when any part of the system breaks down. However, people tend not to use that word to describe their symptoms but instead use the word dizziness or lightheadedness. It is up to the health care practitioner to understand the personâ€™s symptoms and define vertigo as the cause of the their situation.
Dizziness is a difficult word to understand and needs to be divided into two categories, either lightheadedness or vertigo. Lightheadedness is the feeling that a person might faint while vertigo is most often described as a spinning sensation with loss of balance. The direction of care is markedly different since lightheadedness may suggest to the health care practitioner to investigate decreased oxygen or nutrient supply to the brain due a variety of causes including heart rhythm disturbances or dehydration, while vertigo sends the health care practitioner looking for a neurologic or inner ear cause.
The most important initial step in helping a person with vertigo is to take a history and understand that the person is complaining of spinning symptoms that may be associated with nausea and vomiting and loss of balance among other symptoms.
Vertigo is an abnormal sensation that is described by the person as a feeling they are spinning or that the world is spinning around them. It is most often associated with an inner ear problem.
The inner ear has two parts, the semicircular canals and the vestibule, that helps the body know where it is in relationship to gravity. There are three semicircular canals that are aligned at right angles to each other and act as the gyroscope for the body. The canals are filled with fluid and are lined with a nerve filled, crystal encrusted membrane that transmits information to the cerebellum, the part of the brain that deals with balance and coordination.
The cerebellum adds information from sight and from nerve endings in muscles that deal with proprioception, the perception of movement, to help the brain know where it is in relationship to gravity and the world.
Normally, when the head moves, fluid in the semicircular canals shifts and that information is relayed to the brain. When the head stops moving, the fluid stops as well. There may be a slight delay and is the basis for the vertigo experienced after people participate in many childrenâ€™s games and carnival rides. When a person goes on a merry-go-round or spins quickly around in circles, the fluid in the canals develops momentum and even though the head stops spinning, the fluid may continue to move. This causes vertigo or a spinning sensation and may cause the person to fall or stumble in a crooked line. It also may be associated with vomiting.
In patients with vertigo, inflammation of the fluid or irritation of the crystals on the nerve membrane that lines the walls of the semicircular canals may cause the spinning sensation even without much head movement. Often, only one canal is involved and the person may be symptom free if they donâ€™t move.
While there are many causes of vertigo, the major distinction is between central causes of vertigo and peripheral causes. Central causes occur because of an abnormality in the cerebellum of the brain.
Distinguishing between central and peripheral causes for disease is an important concept in evaluating neurologic problems. The brain and spinal cord make up the central nervous system while the peripheral nervous system describes the nerves outside the central area. Sometimes it is easy to make the distinction, other times it is more difficult to distinguish between central and peripheral causes. For example, if a person hits their funny bone (elbow) and develops pain and numbness in their hand, it is mainly due to a direct blow to the ulnar nerve at the elbow. This is a peripheral nerve problem and most people would not seek medical care. If however, a personâ€™s leg became numb and weak, the cause may be central (perhaps a stroke in the brain) or there may be a peripheral cause (sciatica or nerve impingement).