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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 neuro-
mas sometimes occur with neurofibromatosis type
2, a rare hereditary disorder in which fibrous
growths develop in the CRANIAL NERVESand 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 typ-
ically 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 symp-
toms might include facial PAINand disturbances of
facial expression. An AUDIOLOGIC ASSESSMENThelps
determine the level of HEARING LOSSand 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-

NETIC RESONANCE IMAGING(MRI) can usually deter-

mine 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 THERAPYto shrink the tumor is an option

when symptoms interfere with QUALITY OF LIFEor

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 activ-

ities of living or present any threat to health. For

most people who experience symptoms and

undergo treatment, recovery is complete. Idio-

pathic acoustic neuromas do not return, though

acoustic neuromas associated with neurofibro-

matosis type 2 often recur. Other than neurofibro-

matosis 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 TISSUEat the back of

the NOSE. The purpose of the adenoids is to trap and

destroy pathogens (disease-causing agents) in chil-

dren; by ADOLESCENCEthe adenoids atrophy (shrink)

and in adults are not distinguishable. When the

adenoids swell, they can block the nasal passage.

This disrupts BREATHINGand can affect the speech.

The eustachian tubes open near the adenoids;

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