Causes of Dizziness
DIZZINESS, VERTIGO, DISEQUILIBRIUM
Dizziness, vertigo and disequilibrium are
common symptoms reported by adults during visits to
their doctors. They are all symptoms that can result from a peripheral
vestibular disorder (a dysfunction of the balance organs of the inner ear) or
central vestibular disorder (a dysfunction of one or more parts of the central nervous system
that help process balance and spatial information). Although these three
symptoms can be linked by a common cause, they have different meanings, and
describing them accurately can mean the difference between a successful
diagnosis and one that is missed. Dizziness is a sensation of lightheadedness,
faintness, or unsteadiness. Unlike dizziness, vertigo has a rotational,
spinning component, and is the perception of movement, either of the self or
surrounding objects. Disequilibrium simply means unsteadiness, imbalance, or
loss of equilibrium that is often accompanied by spatial disorientation.
Dizziness: a sensation of lightheadedness, faintness, or
unsteadiness. Dizziness does not involve a rotational component.
Almost everyone
experiences a few seconds of spatial disorientation at some point. For example,
when a person watches a 3-D movie in the theater and momentarily perceives an
illusion of moving or falling as the images rush past. However, frequent
episodes of vertigo—whether lasting only for a few seconds or days on end—are a
primary sign of a vestibular dysfunction, especially when linked to changes in
head position. By contrast, dizziness can be a primary sign of a vestibular
disorder in addition to a broad array of cardiovascular, neurological,
metabolic, vision, and psychological problems. It is also quite possible that a
person may have a combination of problems, such as a degenerative vestibular
disorder along with a visual deficit such as cataracts or a neurological
disorder such as a stroke.
Because of the many
possible causes of dizziness, getting a correct diagnosis can be a long and frustrating
experience.
DIZZINESS CAUSED BY VESTIBULAR DISORDERS
The body maintains
balance with sensory information from three systems:
·
vision
·
proprioception (touch sensors in the feet,
trunk, and spine)
·
vestibular system (inner ear)
Sensory input from
these three systems is integrated and processed by the brainstem. In response,
feedback messages are sent to the eyes to help maintain steady vision and to the
muscles to help maintain posture and balance.
Vertigo: the perception of movement or whirling - either of the
self or surrounding objects.
A healthy vestibular system supplies the most reliable information about
spatial orientation. Mixed signals from vision or proprioception can usually be
tolerated. When sitting in a car at a railroad crossing, seeing a passing train
may cause the sensation of drifting or moving, and feeling a soft, thick carpet
underfoot as opposed to a solid wood floor can
produce a floating sensation. However, compensating for vestibular system
abnormalities is more problematic.
Just as a courtroom
judge must rule between two sides presenting competing evidence, the vestibular
system serves as the tie-breaker between conflicting forms of sensory
information. When the vestibular system malfunctions, it can no longer help
resolve moments of sensory conflict, resulting in symptoms such as dizziness,
vertigo, and disequilibrium.
SPECIFIC VESTIBULAR SYSTEM PROBLEMS
Vestibular
dysfunction is most commonly caused by head injury, aging, and viral infection.
Other illnesses, as well as genetic and environmental factors, may also cause
or contribute to vestibular disorders. Causes of dizziness related to
vestibular system dysfunction are listed below.
Disequilibrium: unsteadiness, imbalance, or loss of equilibrium;
often accompanied by spatial disorientation.
·
An acoustic neuroma is a benign tumor growing on the
vestibulo-cochlear nerve.
·
Autoimmune inner ear
disease occurs
when the defense capabilities of a mal-functioning immune system harm the cells
of the body that affect the ear. Specific diagnoses include Cogan’s syndrome,
Wegener’s granulomatosis, systemic lupus, Sjogren’s syndrome, and rheumatoid
arthritis, among others.
·
Benign paroxysmal positional vertigo
(BPPV) is a
condition resulting from loose debris (otoconia) that collect within a part of
the inner ear. In addition to head injury, BPPV can occur due to the
degeneration of inner-ear hair cells during the natural process of aging.
·
Cervicogenic dizzinessis
a clinical syndrome of disequilibrium and disorientation in patients with neck
problems that include cervical trauma, cervical arthritis, and others.
·
Cholesteatoma is a skin growth that occurs in the
middle ear behind the eardrum.
·
An enlarged vestibular aqueduct houses the fluid-filled endolymphatic
duct, which is connected to the endolymphatic sac. The function of the duct and
the sac are affected when the aqueduct is larger than normal.
·
Labyrinthitis and vestibular
neuritis are
inflammations caused by a viral infection that can result in damage to hearing
and vestibular function (labyrinthitis) or damage to vestibular function only
(vestibular neuritis).
Spatial disorientation: a sensation of not knowing where one's
body is in relation to the vertical and horizontal planes.
·
Mal de débarquement is a sensation of rocking or movement
that persists after a sea cruise or other form of travel.
·
Ménière’s disease,
or primary endolymphatic hydrops, involves abnormalities in quantity,
composition, or pressure of the endolymph (one of the fluids within the inner
ear). It is a progressive condition.
·
Middle ear pressure changes, such as from colds
or allergies, can result from swelling of the Eustachian tube or the presence
of fluid in the middle ear.
·
Migraine associated
vertigo (MAV) is
typically characterized by head pain with symptoms associated with vestibular
impairment such as dizziness, motion intolerance, spontaneous vertigo,
sensitivity to light and sound, TINNITUS
, imbalance, and spatial
disorientation.
, imbalance, and spatial
disorientation.
·
Otitis media is a bacterial infection of the middle ear and
meningitis is a bacterial infection of the brain covering that may spread to
the inner ear.
·
Otosclerosis is an abnormal growth of bone of the
middle ear that prevents structures within the middle and inner ear from
working properly.
·
Ototoxicity is caused by exposure to certain drugs or
chemicals (e.g., intravenous aminoglycoside antibiotics) that damage the
inner-ear nerve hair cells or the vestibulo-cochlear nerve.
·
Perilymph fistula,
caused by injury, is a tear or defect in the oval or round window, which are
small, thin membranes that separate the middle ear from the fluid-filled inner
ear.
·
Superior semicircular
canal dehiscence is
an opening in the bone overlying the uppermost semicircular canal within the
inner ear.
·
Secondary endolymphatic
hydrops involves
abnormalities in quantity, composition, or pressure of the endolymph.
·
Vascular compression of the vestibular nerve is an irritation of the vestibular portion of the
vestibulo-cochlear nerve by a blood vessel.
NON-VESTIBULAR CAUSES OF DIZZINESS
Dizziness can be
linked to a wide array of problems and is commonly linked to blood-flow
irregularities from cardiovascular problems. Non-vestibular causes of dizziness
are listed below.
·
An aneurysm is a weak spot in an artery wall that
balloons out and allows blood to leak into the vessel walls. An aneurysm is a
catastrophic event that can cause severe dizziness and difficulty with walking.
·
An arrhythmia is a irregular or abnormal heartbeat and
can result in low blood flow to the brain, causing one to faint or feel faint.
·
Atherosclerosis is hardening or narrowing of the vertebral arteries. In
older people who have high blood pressure, plaque is sometimes deposited within
the arteries. This narrows the interior of the arteries and impedes blood flow.
Heredity may be a factor in development of this condition.
·
Carotid sinus reflex works rapidly in younger people but sometimes is much
slower in older people, especially those with circulatory problems. The carotid
sinus is very sensitive to decreases in blood pressure in the carotid artery.
With a drop in blood pressure, the reflex constricts blood vessels in the lower
extremities and dilates vessels in the head to maintain a normal blood pressure
in the head and adequate blood flow to the brain.
·
A defective heart valve usually involves the aortic valve,
which when shut down (aortic stenosis) prevents the proper amount of blood from
flowing to the brain.
·
Dehydration can produce lightheadedness through its affect on
multiple systems.
·
People with severe degenerative
arthritis of the
spine can develop bone spurs that may press on the vertebral arteries and
interfere with blood supply to the brain.
·
Embolism can occur when an embolus, or blood clot, forms around a
heart valve that is not working properly, or is released within the arteries to
the brain, causing a stroke. The effects of a stroke may include temporary
dizziness. However, if the embolus travels to the vestibular system, it can
cause severe dizziness.
·
A heart attack rarely causes dizziness;
when it does, lack of blood to the brain is the cause.
·
Hyperventilation is a condition resulting from rapid breathing, when more
carbon dioxide than normal is expelled. When this happens, the level of carbon
dioxide in the blood falls and affects the function of brain cells, causing
temporary dizziness.
·
Certain medications, including some prescription and
over-the-counter drugs, can cause temporary dizziness.
·
Nervous-system disorders such as peripheral neuropathies (diminished nerve
function in the legs or feet) and multiple sclerosis can cause unsteadiness.
·
Orthostatic hypotension is common in older people, especially those with
circulatory problems and diabetes. When a person has low blood pressure and pooling
of blood in the lower part of the body while sitting or laying down, the
process of standing up quickly can cause dizziness and fainting. Normally, body
reflexes accommodate such position changes. However, when circulation problems
impair these compensation mechanisms, faintness occurs.
·
Osteoarthritis is a joint disease that can narrow the openings in the
neck vertebrae (bones) through which blood vessels flow. Blockage of these
vertebral arteries results in an inadequate blood supply to the base of the
brain or brainstem—where the balance information is controlled. This causes
symptoms of dizziness and lightheadedness. The condition is termed vertebral
basilar insufficiency. If this arterial narrowing takes place gradually over
time, other arteries may enlarge and take over some of the function of the
affected vessels. This event, called development of a collateral blood supply,
can’t happen if the arterial narrowing occurs suddenly (for example, if an
embolus completely shuts off the blood supply). In such cases, death by stroke
may result.
·
Stress, tension, or fatigue may cause the brain stem to function less efficiently,
resulting in some loss of automatic reflex control of balance. This leads to
elevated levels of activity for the cerebral cortex as it works to help
maintain balance through the control of voluntary muscle movements.
Lightheadedness and unsteadiness can result.
·
A tumor may affect the brain stem, the cerebellum
(the coordination center of the brain), or the part of the cerebral cortex that
controls voluntary muscle movements.
·
Vasovagal syndrome is a nervous-system response that causes sudden loss of
muscle tone in peripheral blood vessels.
·
Vision disturbances can occur when a person adjusts to bifocals or a new
eyeglass prescription, or must compensate for reduced vision due to cataracts.
DIZZINESS CAUSED BY MULTIPLE SENSORY DEFICITS
Maintaining balance
and equilibrium can be very difficult when more than one health problem exists.
A mild vestibular disorder can be much more problematic when accompanied by a
visual deficit. The ability to compensate for a vestibular disorder is
compounded when there is also a deficit with proprioception due to disease or
an injury and severe dizziness can result. Careful evaluation, including a
complete medical history noting all potential causes of dizziness, is essential
to correct diagnosis and treatment.
Photo courtesy of D.Sharon Pr
- See more at:
http://vestibular.org/node/2#sthash.gzAV0OkM.dpuf
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