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Cranial Nerve

cranial nerve n : any of the 12 paired nerves that arise from the lower
surface of the brain with one of each pair on each side and pass through
openings in the skull to the periphery of the body see ABDUCENS NERVE,
NERVE, TROCHLEAR NERVE, VAGUS NERVE Merriam-Webster's Medical Dictionary,
1995 Edition

olfactory nerve
olfactory nerve n : either of the pair of nerves that are the first cranial
nerves, that serve to conduct sensory stimuli from the olfactory organ to the
brain, and that arise from the olfactory cells as discrete bundles of
unmyelinated fibers passing in small groups (in humans, about 20) through the
cribriform plate of the ethmoid bone and terminating in the olfactory bulb -
called also first cranial nerve Merriam-Webster's Medical Dictionary, 1995

abducens nerve
abducens nerve n : either of the sixth pair of cranial nerves which are motor
nerves, arise beneath the floor of the fourth ventricle, and supply the
lateral rectus muscle of each eye - called also abducent nerve, sixth cranial
nerve Merriam-Webster's Medical Dictionary, 1995 Edition

 facial nerve
facial nerve n : either of the seventh pair of cranial nerves that supply
motor fibers esp. to the muscles of the face and jaw and sensory and
parasympathetic fibers to the tongue, palate, and fauces - called also
seventh cranial nerve, seventh nerve Merriam-Webster's Medical Dictionary,
1995 Edition

glossopharyngeal nerve
glossopharyngeal nerve n : a mixed nerve that is either of the ninth pair of
cranial nerves, that has sensory fibers arising from the superior and
petrosal ganglia and motor fibers arising with those of the vagus nerve from
the lateral wall of the medulla, and that supplies chiefly the pharynx,
posterior tongue, and parotid gland with motor and sensory fibers including
gustatory and autonomic secretory and vasodilator fibers - called also
glossopharyngeal, ninth cranial nerve Merriam-Webster's Medical Dictionary,
1995 Edition

hypoglossal nerve
hypoglossal nerve n : either of the 12th and final pair of cranial nerves
which are motor nerves arising from the medulla oblongata and supplying
muscles of the tongue and hyoid apparatus in higher vertebrates - called also
hypoglossal, twelfth cranial nerve Merriam-Webster's Medical Dictionary, 1995

oculomotor nerve
oculomotor nerve n : either nerve of the third pair of cranial nerves that
are motor nerves with some associated autonomic fibers, arise from the
midbrain, supply muscles of the eye except the superior oblique and the
lateral rectus with motor fibers, and supply the ciliary body and iris with
autonomic fibers by way of the ciliary ganglion - called also third cranial
nerve Merriam-Webster's Medical Dictionary, 1995 Edition

auditory nerve
auditory nerve n : either of the eighth pair of cranial nerves connecting the
inner ear with the brain, transmitting impulses concerned with hearing and
balance, and composed of the cochlear nerve and the vestibular nerve - called
also acoustic nerve, auditory, eighth cranial nerve, vestibulocochlear nerve
Merriam-Webster's Medical Dictionary, 1995 Edition

optic nerve
optic nerve n : either of the pair of sensory nerves that comprise the second
pair of cranial nerves, arise from the ventral part of the diencephalon, form
an optic chiasma before passing to the eye and spreading over the anterior
surface of the retina, and conduct visual stimuli to the brain - called also
second cranial nerve Merriam-Webster's Medical Dictionary, 1995 Edition

supraorbital nerve
supraorbital nerve n : a branch of the frontal nerve supplying the forehead,
scalp, cranial periosteum, and adjacent parts Merriam-Webster's Medical
Dictionary, 1995 Edition

esser petrosal nerve
lesser petrosal nerve n : the continuation of the tympanic nerve beyond the
inferior ganglion of the glossopharyngeal nerve that passes into the cranial
cavity through the petrosal bone and out again to terminate in the otic
ganglion which it supplies with preganglionic parasympathetic fibers
Merriam-Webster's Medical Dictionary, 1995 Edition

accessory nerve
accessory nerve n : either of a pair of motor nerves that are the 11th
cranial nerves, arise from the medulla and the upper part of the spinal cord,
and supply chiefly the pharynx and muscles of the upper chest, back, and
shoulders - called also accessorius, accessory, spinal accessory nerve
Merriam-Webster's Medical Dictionary, 1995 Edition

peripheral nervous system
peripheral nervous system n : the part of the nervous system that is outside
the central nervous system and comprises the cranial nerves excepting the
optic nerve, the spinal nerves, and the autonomic nervous system
Merriam-Webster's Medical Dictionary, 1995 Edition

Spinal cord trauma

Alternative names:
compression of spinal cord
Damage to the spinal cord that results from injury.
Causes, incidence, and risk factors:
Damage to the spinal cord affects all nervous function that is controlled at
and below the level of the injury, including muscle control and sensation.
More than 30 bones make up the spine. These bones (vertebrae) and the
cushions between the vertebrae (disks) allow the back to bend while
protecting the spinal cord from injury.

Spinal cord trauma is caused by motor vehicle accidents, falls, sports
injuries (particularly diving into shallow water), industrial accidents,
gunshot wounds, assault, and other injuries. A seemingly minor injury can
cause spinal cord trauma if the spine is weakened (such as from rheumatoid
arthritis or osteoporosis).

Direct injury such as cuts can occur to the spinal cord, particularly if the
bones or the discs are damaged. Fragments of bone (from fractured vertebrae
for example) or fragments of metal (such as from a traffic accident) can cut
or damage the spinal cord. Direct damage can also occur if the spinal cord is
pulled, pressed sideways, or compressed. This may occur if the head, neck, or
back are twisted abnormally during an accident or injury.

Bleeding, or fluid accumulation and swelling, can occur within the spinal
cord or outside the spinal cord but within the spine. The accumulation of
blood or fluid can compress the spinal cord and damage it.

A mild injury (such as "whiplash") may resolve when swelling is reduced.
Severe injury (such as occurs from fractures, dislocations, or cutting of the
spinal cord) usually results in permanent damage to the spinal cord.
Spinal-cord trauma often causes permanent disability such as paralysis
because nerve fibers are slow to heal and if they are destroyed, nerve fibers
do not regenerate. Spinal-cord trauma can cause death in some cases.

Spinal-cord injuries occur in approximately 12,000 to 15,000 people per year
in the U.S. About 10,000 of these people are permanently paralyzed, and many
of the rest die as a result of their injuries. Most spinal-cord trauma occurs
to young, healthy individuals. Males between 15 and 35 years old are most
commonly affected.

Numbness and tingling
Alternative names:
lack of sensation
Paresthesias are abnormal sensations, often described as numbness, prickling,
or tingling, usually felt along the extremities.
Tingling is an indication of damage or irritation to the nerves in that area.
Unlike numbness, tingling suggests the nerve is not completely dead or
severed, just injured or experiencing pressure.

Except in cases where the cause is obvious (for example, when a hand or foot
"falls asleep" because of the position it is in), numbness and tingling
should be discussed with your health care provider.
Common Causes:
· local injury to the nerves under the skin
· lack of blood supply to the area
· pressure on the nerves, caused by a herniated disk, tumors, abscesses or
arthritic bones
· toxic action on nerves (lead, alcohol, tobacco)
· diabetes and other chemical abnormalities
· vitamin B-12 deficiency
· hypothyroidism
· carpal tunnel syndrome
· drugs such as chemotherapeutic agents, chloroquine, D-penicillamine,
isoniazid, nitrofurantoin, parenteral gold therapy and phenytoin
· long-term radiation
· transient ischemic attack (TIA)
· stroke
· multiple sclerosis (a less common cause of numbness)

Note: There may be other causes of numbness and tingling. This list is not
all inclusive, and the causes are not presented in order of likelihood. The
causes of this symptom can include unlikely diseases and medications.
Furthermore, the causes may vary based on age and gender of the affected
person, as well as on the specific characteristics of the symptom such as
location, quality, time course, aggravating factors, relieving factors, and
associated complaints. Use the Symptom Analysis option to explore the
possible explanations for numbness and tingling, occurring alone or in
combination with other problems.
Peripheral neuropathy
Alternative names:
neuritis - peripheral
A general classification of disorders involving damage or destruction of
nerves, not including the nerves of the brain or spinal cord.
Causes, incidence, and risk factors:
Peripheral neuropathy (peripheral neuritis) is fairly common. The incidence
varies with the specific type of neuropathy.

Peripheral neuropathy is not a specific, separate disease. It is a
manifestation of many conditions that can cause damage to the peripheral
nerves. The peripheral nervous system includes all nerves not in the brain or
spinal cord (central nervous system, or CNS). The peripheral nervous system
is the nerve system used by the CNS to communicate with the rest of the body,
including the cranial nerves and the nerves supplying the internal organs,
muscles, skin, and other areas. Damage to the nerves of the peripheral
nervous system impairs communication between the CNS and the rest of the body.

Symptoms depend on whether the disorder affects the sensory nerve fibers (the
fibers that transmit information from the area to the brain and spinal cord)
or motor nerve fibers (the fibers that transmit impulses from the brain and
spinal cord to the area) or both. Damage to sensory fibers results in changes
in sensation ranging from perception of abnormal sensations, to pain, to
decreased sensation or lack of sensation in the area. Sensation changes
usually begin in the feet or hands and progress toward the center of the body
with peripheral neuropathies that include degeneration of the axon portion of
the nerve cell.

Damage to the motor fibers impairs movement or function of the area supplied
by the nerve, because impulses to the area are blocked. Impaired nervous
stimulation to a muscle group results in decreased movement or control of
movement. Loss of nerve function causes structural changes in muscle, bone,
skin, hair, nails, and body organs. Structural changes are caused by lack of
nervous stimulation, not using the affected area, immobility, and lack of
weight bearing. There is muscle weakness and muscle wasting (atrophy, loss of
muscle mass). Recurrent, unnoticed injury to the area may occur and cause
infection or structural damage. Changes include ulcer formation, poor
healing, loss of tissue mass, scarring, and deformity.

The autonomic nervous system is the part of the peripheral nervous system
that controls involuntary or semi-voluntary functions, such as control of
internal organs. Damage to nerves of the autonomic nervous system causes
changes in functioning of these organs, resulting in symptoms such as blurred
vision, decreased ability to sweat (anhidrosis), dizziness or fainting
associated with a fall in blood pressure, decreased ability to regulate body
temperature, disturbances in function of the stomach or intestines,
disturbances of bladder function, and sexual dysfunction.

Peripheral neuropathy may involve damage to a single nerve or nerve group
(mononeuropathy) or may multiple nerves (polyneuropathy). Neuropathy involves
damage to the axon of the nerve cell or the myelin sheath. Causes include
nerve destruction from various disorders and nerve destruction caused by
pressure. Degeneration of the axon slows or blocks conduction at the point of
the degeneration. Demyelination (destruction of the myelin sheath around the
nerve cell) greatly decreases the speed of impulse conduction through the

In some cases, no detectable cause of the neuropathy can be identified.
Pressure injury may be caused by direct injury or compression of the nerve
cell by other nearby body structures. Compression can be caused by peripheral
nerve tumors (rare), tumors that press on nerve tissue (rare), abnormal bone
growth, or cysts or collections of fluid or tissue that press on nerves.
Compression can also be caused by pressure from casts, splints, braces,
crutches, or other appliances. Prolonged periods in cramped positions may
cause nerve injury. Entrapment neuropathy includes compression of a nerve
where it passes through a narrow space. The mechanical factors may be
complicated by ischemia (lack of oxygen that results from decreased blood
flow) in the area. Systemic causes of neuropathy include disorders affecting
the connective tissues of the nerves, disorders affecting the blood supply to
the nerve cells, hereditary conditions, metabolic or chemical disorders, and
other disorders that damage nerve tissue.

Some of the specific conditions associated with neuropathy include:
· hereditary disorders
· Charcot-Marie-Tooth disease (most common in both adults and children)
· Friedreich's ataxia
· systemic or metabolic disorders
· diabetes mellitus (diabetic neuropathy)
· dietary deficiencies (especially vitamin B)
· habitual use of alcohol (alcoholic neuropathy)
· uremia (from kidney failure)
· systemic effects of malignancies
· multiple myeloma
· lung cancer
· lymphoma (any type)
· leukemia (any type)
· infectious or inflammatory conditions
· botulism
· Colorado tick fever
· diphtheria
· Guillain-Barre syndrome
· HIV infection without development of AIDS
· leprosy
· periarteritis nodosa
· polyarteritis
· rheumatoid arthritis
· sarcoidosis
· syphilis
· systemic lupus erythematosus
· exposure to toxic compounds
· sniffing glue or other toxic compounds
· nitrous oxide
· industrial agents--especially solvents
· heavy metals (lead, arsenic, mercury, etc.)
· neuropathy secondary to drugs (many drugs can cause neuropathy)
· miscellaneous causes
·NOTE:  ischemia (decreased oxygen/decreased blood flow)
( comprssion of the spinial cord does this also )
· prolonged exposure to cold temperature

If the cause of the peripheral neuropathy can be identified and successfully
treated and if damage is limited to the axon or myelin sheath (leaving the
cell body intact), there is a possibility of full recovery from peripheral

In some cases, there may be partial or complete loss of movement, function,
or sensation resulting in disability. Nerve pain may be quite uncomfortable
and may persist for a prolonged period of time. In some instances, the
neuropathy may cause severe, life-threatening symptoms.
· partial or complete loss of movement
· partial or complete loss of control of movement
· partial or complete loss of sensation
· disturbances of organ function
· difficulty breathing
· difficulty swallowing
· cardiac arrhythmias (uncommon)
· decreased self esteem
· relationship problems related to impotence
· recurrent or unnoticed injury to any part of the body
· infection
· skin ulcer
· poor healing
· loss of tissue mass
· scarring