Vertigo (cont.)

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What is vertigo?

Vertigo is an abnormal sensation that is described by the person as a feeling they are spinning or  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 children'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 don't move.

What are the causes of vertigo?

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 person'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).

Our orientation in space and, therefore, our balance or equilibrium, is primarily measured by three sensory systems:

  1. The eye (visual) system
  2. The balance (vestibular) system of the inner ear
  3. The general sensory system including motion, pressure, and position (proprioception) sensors in joints, muscles, and skin.

These three systems continuously feed information to the brainstem and brain about our position in space relative to gravity and the world. The brainstem connects the brain to the spinal cord. The brain, in turn, processes these data and uses the information to make adjustments of our head, body, joints, and eyes. When all three sensory systems and the brain are properly functioning, the final result is a healthy balance system.

Visual input shows the brain where it is in space, what direction it is facing, what direction it is moving, and whether it is turning or standing still. Simple tasks like walking and picking up an object are much easier if we can see our surroundings. Feeling seasick is a problem resulting from a miscommunication between a healthy visual system and a healthy inner ear (vestibular) system. In this circumstance, the ears are telling the brain that there is movement, while the eyes may be seeing the fixed surroundings of the cabin. Changes in visual acuity, glaucoma, and cataracts are examples of visual problems that in some individuals may be enough to give them a balance disorder.

Vestibular system

The inner ear, or labyrinth, is located deep to the outer ear and middle ear, and is encased within petrous portion of the temporal bone of the skull.

Picture of the outer and inner structures of the ear
Picture of the outer and inner structures of the ear

Figure 1. Diagram of outer, middle, and inner ear. The outer ear is labeled in the figure and includes the ear canal. The middle ear includes the eardrum (tympanic membrane) and three tiny bones for hearing. The bones are called the hammer (malleus), anvil (incus), and stirrup (stapes) to reflect their shapes. The middle ear connects to the back of the throat by the Eustachian tube. The inner ear (labyrinth) contains the semicircular canals and vestibule for balance, and the cochlea for hearing.

The vestibular structures of the inner ear are the vestibule (which is made up of the utricle and saccule) and the three semicircular canals. These structures work somewhat like a carpenter's level (a tool used to show how "level" a horizontal or vertical surface is) or a gyroscope. Information is sent by way of the vestibulocochlear nerve to the cerebellum of the brain, the part that processes information regarding body balance and position. The rest of the inner ear, the cochlea, is concerned with hearing.

The vestibular system measures linear and rotational movement. A number of disorders can cause this system to stop working or provide inappropriate information. These disorders include Meniere's syndrome, labyrinthitis, benign paroxysmal positional vertigo, ear infections, tumors, or trauma.

Peripheral sensory system

The sensory system consists of motion, position, and pressure sensors in the skin, muscles, and joints. These sensors provide important touch and position information to keep us balanced. For example, if someone pushes you from behind, a slight increase will occur in the activity of the pressure sensors in the ball of the feet. As these sensors note the increased pressure, the brain is notified, and it knows from experience that the body is being pushed forward. The brain then uses this information to tell the body to shift a small amount of weight backward to prevent the body from toppling forward.

Brain

The brain processes the information from the three sensory systems. Any problem that interferes with the proper functioning of the central nervous system (CNS) can lead to a balance disorder. Unlike the problems associated with the three sensory input systems discussed above, however, with CNS problems, it is unusual to have vertigo as the only symptom. The most common causes of vertigo are peripheral and involve the inner ear or labyrinth.

Some of the most common causes of vertigo are listed below:

  • Benign paroxysmal positional vertigo (BPPV) may be caused when the crystals in the inner ear become dislodged and irritate the semicircular canals. Often the cause is not found but there may be an association with unusual positioning or movement of the head. It is most frequently seen in people older than 60.
  • Labyrinthitis may follow a viral infection which causes inflammation within the middle ear.
  • Meniere's disease is a group of symptoms associated with vertigo, hearing loss and tinnitus or ringing in the ears.
  • Acoustic neuroma is a benign tumor of the ear that can present with vertigo.
  • Inner ear trauma may be due to a variety of mechanisms. A basilar skull fracture may damage the labyrinth system directly or a concussion, where that area of the skull is shaken and may dislodge some of the inner ear crystals causing symptoms of vertigo.
  • The inner ear may also be affected by barotrauma, a condition where pressure changes may be the causes of damage and vertigo. This type of injury is seen when an individual dives into water and the air in the external ear canal is compressed and damages the ear drum, middle, and inner ear. Barotrauma may also occur as a consequence of diving where an increase of air pressure within the middle and inner ear can cause structures to rupture. This may cause loss of hearing if the tympanic membrane ruptures or it may cause vertigo if the round and oval windows in the inner ear are damaged.
  • Central causes of vertigo that arise in the brain are much less common. Strokes, tumors, seizures, and multiple sclerosis may be associated with vertigo.
  • Vestibular migraines describe migraine headaches associated with vertigo and are a common cause of balance disorders. Migraine is a blood vessel (vascular) disease characterized by periodic, usually one-sided, headaches. These headaches are often preceded for a variable time by associated neurological symptoms, called the aura. Vertigo may occur in individuals with migraine as part of the migraine aura or separately. In younger patients, the vertigo may predate the onset of headaches entirely. A family history of migraine is very common and may be a clue that a balance disorder may be migraine related.
Medically Reviewed by a Doctor on 1/6/2014

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