Vertigo (cont.)
Vertebral basilar insufficiency
Vertebral basilar insufficiency occurs when there is narrowing of the
arteries that supply the posterior brain (subclavian, vertebral, or basilar
arteries). It is usually the result of hardening of the arteries
(atherosclerosis), and occurs among patients older than 50 years of age. The
narrowed arteries decrease the blood flow and, therefore, the oxygen to the
vestibular center in the brain. Since the vestibular system is very sensitive to
a lack of oxygen, balance problems are often one of the first symptoms of
vertebral basilar insufficiency.
Other signs of decreased oxygen to the brain are also usually present. These
signs include visual changes, weakness, and fainting. Patients tend to describe
their imbalance as lightheadedness that frequently occurs when they stand up
quickly. In fact, patients rarely get lightheaded or dizzy when laying flat or
resting in a chair. Measuring a drop in blood pressure and an increase in pulse
rate when a patient stands upright can confirm the vertebral basilar
insufficiency. Other causes of this type of dizziness include heart problems and
medication side effects.
Labyrinthitis
Labyrinthitis is an inflammation of the bony or membranous inner ear
(labyrinth). Recall that the inner ear is made up of balance (vestibular) and
hearing (auditory) components. The bony labyrinth encloses and protects the
delicate membranous labyrinth. In general, bacterial infections affect the bony
labyrinth and viral infections affect the membranous labyrinth.
Bacterial labyrinthitis: There are three types of bacterial infections that
can lead to labyrinthitis: toxic labyrinthitis, acute suppurative
(pus-containing) labyrinthitis, and syphilitic labyrinthitis.
In toxic labyrinthitis, bacterial toxins from the middle ear invade the inner
ear by passing (diffusing) through the round window of the inner ear. (See the figure.) Both hearing loss and imbalance can occur. Treatment includes
antibiotics directed at the bacteria, incision of the eardrum, and drainage of
the middle ear space.
Suppurative labyrinthitis is relatively uncommon. It is a bacterial infection
characterized by the abrupt (acute) onset of vertigo associated with hearing
loss. It is frequently the result of chronic middle ear infections that create a
hardened mass of debris and cholesterol (cholesteatoma). The hard mass wears
away (erodes) the dense surrounding bone of the inner ear, thereby exposing the
inner ear to the infection. The other source of suppurative labyrinthitis is
from inflammation of the covering (meninges) of the brain (meningitis).
Syphilitic labyrinthitis is also a bacterial infection of the inner ear. It
can be either present at birth (congenital) or acquired. The symptoms are
usually fluctuating and slow to develop. But there is a relentless progression
to profound or total loss of hearing and balance. A sudden (acute) episode of
deafness or dizziness, however, may occur.
The congenital form of syphilitic labyrinthitis may have its onset of
symptoms anywhere from birth to age 70. The peak occurrence is between age 30
and 50. Other signs of congenital syphilis are often also present, such as
chronic (long duration) eye inflammation (interstitial keratitis) in 90% of
patients, Hutchinson's notched teeth, saddle-shaped nose, and swelling of the
forehead (frontal bossing).
Syphilitic labyrinthitis is often confused with Meniere disease. The
diagnosis of syphilis is established by finding a positive serum fluorescent
treponemal antibody absorption test in a patient with the typical clinical
history of fluctuating, progressive hearing loss and vertigo. A serum Venereal
Disease Research Laboratory (VDRL) test result is positive in only 75% of cases,
making it an unreliable test for syphilitic labyrinthitis. Examination of the
cerebrospinal fluid (the fluid that surrounds the brain and spinal cord),
however, may show a positive VDRL test or the presence of a particular type of
white blood cell (lymphocytes) in the fluid. Treatment is with high dose
penicillin and cortisone-type drugs.
Viral labyrinthitis (vestibular neuronitis): Labyrinthitis caused by a viral
infection is a common condition. It is usually referred to as vestibular
neuronitis, viral labyrinthitis, or viral neurolabyrinthitis. Although a viral
cause for this disease has not been proven unequivocally, many well conducted
population (epidemiological) and tissue microscoscopy (histopathological)
studies support a viral cause. Typically, a gradual onset of vertigo, nausea,
and vomiting occurs over several hours. Symptoms reach a peak within 24 hours
and then gradually improve over several days. Most patients have complete
recovery within 6 weeks. Treatment is directed at suppression of symptoms. This
includes vestibular suppressants like diazepam (Valium), vestibular exercises,
and hydration. Some evidence suggests that high-dose cortisone-type drugs given
early in the disease with or without antiviral agents may be helpful.
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