Encyclopedia of Health and Medicine

A
acoustic neuroma A noncancerous tumor of the
eighth cranial (vestibulocochlear) NERVE. Acoustic
neuromas typically grow over years to decades
and in some people cause no symptoms; doctors
detect them incidentally. An acoustic neuroma
does not invade the surrounding tissues, though it
can become life-threatening if it becomes large
enough to put pressure on the structures of the
brainstem. Most often doctors do not know why
acoustic neuromas develop and classify them as
idiopathic (of unknown cause). Acoustic neuromas
sometimes occur with neurofibromatosis type
2, a rare hereditary disorder in which fibrous
growths develop in the CRANIAL NERVES and SPINAL
NERVES.
Early symptoms of acoustic neuroma are vague
and often perceived as normal consequences of
aging because the tumor is so slow growing it typically
appears in the later decades of life. Early
symptoms include
• gradual loss of hearing, especially difficulty
understanding speech, in one EAR
• TINNITUS (rushing or roaring sound) in one ear
• balance disturbances such as dizziness or loss of
balance with motion
Advanced symptoms occur when the tumor’s
size begins to encroach on nearby structures such
as the seventh cranial (facial) nerve. Such symptoms
might include facial PAIN and disturbances of
facial expression. An AUDIOLOGIC ASSESSMENT helps
determine the level of HEARING LOSS and whether it
affects one or both ears. Hearing loss in both ears
suggests causes other than acoustic neuroma; it is
very rare that a person would have two tumors,
one affecting each vestibulocochlear nerve. MAG-
7
NETIC RESONANCE IMAGING (MRI) can usually determine
the presence of an acoustic neuroma.
Treatment depends on the extent of symptoms
and the person’s overall health status. For many
people, especially those who have no symptoms,
the preferred treatment is watchful waiting
(observation and regular tests to monitor the
tumor’s growth). Surgery to remove the tumor or
RADIATION THERAPY to shrink the tumor is an option
when symptoms interfere with QUALITY OF LIFE or
affect vital brainstem functions such as regulation
of BREATHING and HEART RATE or motor control.
Each method has risks and benefits; individual
health circumstances also influence the decision.
When it exists with no symptoms, acoustic
neuroma does not interfere with the regular activities
of living or present any threat to health. For
most people who experience symptoms and
undergo treatment, recovery is complete. Idiopathic
acoustic neuromas do not return, though
acoustic neuromas associated with neurofibromatosis
type 2 often recur. Other than neurofibromatosis
type 2, there are no known risk factors or
preventive measures for acoustic neuroma.
See also AGING, OTOLARYNGOLOGIC CHANGES THAT
OCCUR WITH; CENTRAL NERVOUS SYSTEM; MÉNIÈRE’S DIS-
EASE; SURGERY BENEFIT AND RISK ASSESSMENT; VESTIBU-
LAR NEURONITIS.
adenoid hypertrophy Enlargement of the ADE-
NOIDS, structures of LYMPHOID TISSUE at the back of
the NOSE. The purpose of the adenoids is to trap and
destroy pathogens (disease-causing agents) in children;
by ADOLESCENCE the adenoids atrophy (shrink)
and in adults are not distinguishable. When the
adenoids swell, they can block the nasal passage.
This disrupts BREATHING and can affect the speech.
The eustachian tubes open near the adenoids;