measures that provide the QUALITY OF LIFEthat is
acceptable to them. Treatment decisions are
uniquely individual.
About 40 percent of people who have ALS live
5 to 10 years after diagnosis, and 10 percent sur-
vive longer than 10 years. Pulmonary failure and
its complications are usually the cause of death.
Because ALS is a fatal disease, those who have it
should discuss their treatment preferences and END
OF LIFE CONCERNSwith their physicians and family
members, and establish their desires in writing
through advance directives such as medical power
of attorney and living will.
Risk Factors and Preventive Measures
ALS appears to be familial (hereditary) in about
20 percent of people who develop it, occurring in
an autosomal dominant INHERITANCE PATTERN. Neu-
rologists classify the remaining 80 percent as spo-
radic. Family history is the strongest individual
risk factor for developing ALS. Epidemiologists can
identify trends in which pockets of ALS occur,
suggesting there are common risk factors for spo-
radic ALS. As yet no clear evidence has emerged
that identifies these risk factors or that establishes
any explanation for why only a small percentage
of people exposed to the same circumstances
develop ALS. Some research suggests ALS may
have components of autoimmune and mitochon-
drial dysfunction, though the causes and mecha-
nisms of ALS remain unknown. There are no
known measures to prevent ALS.
See also APOPTOSIS; AUTOIMMUNE DISORDERS;
CRAMP; GUILLAIN-BARRÉ SYNDROME; HEAVY-METAL POI-
SONING; MITOCHONDRIAL DISORDERS; MULTIPLE SCLERO-
SIS; MYASTHENIA GRAVIS; SPASM; STROKE.
aphasia Loss of the ability to use language.
Aphasia results from damage to the areas of the
BRAIN responsible for language, often due to
STROKE. Because these areas of the brain are func-
tional rather than structural, doctors cannot pre-
dict the extent to which injury will affect
language. Other causes of aphasia include BRAIN
TUMORand TRAUMATIC BRAIN INJURY(TBI). Aphasia
sometimes occurs in the later stages of neurode-
generative disorders such as ALZHEIMER’S DISEASE
and PARKINSON’S DISEASE. It may involve any indi-
vidual aspect or combination of aspects of the abil-
ities to speak, read, write, and understand lan-
guage.
In most people the left brain contains the func-
tional centers responsible for speech and language,
so stroke or other injury affecting the left brain
may produce aphasia, ranging from limited (cer-
tain kinds of words or expressions) to global (com-
plete inability to communicate through language).
These functional centers conduct all brain activity
related to language concepts, including expression
such as through SIGN LANGUAGE, not only through
speech. Severe damage to these centers appears to
prevent the person also from engaging in pan-
tomime and other methods of communication,
creating significant disability.
People with mild to moderate aphasia typically
have difficulty articulating and understanding the
correct words for objects and activities as well as
in structuring words they do understand into sen-
tences. Speech and language therapy can help
people with mild to moderate aphasia use their
remaining language functions to their best ability
and learn alternate means of expression. Family
and friends can assist by developing mechanisms
for interpreting and understanding the person’s
expressions.
See also APRAXIA; ATAXIA; SPEECH DISORDERS.apraxia The inability to engage in learned pat-
terns of voluntary MUSCLE activity though the
capability (muscle function) is present. Apraxia,
also called dyspraxia, may affect various functions
and tasks that require voluntary muscle activity.
Among them speaking (verbal apraxia, sometimes
called apraxia of speech), clapping hands or brush-
ing the TEETH (limb apraxia), swallowing or
whistling (buccofacial apraxia), using implements
such as eating utensils or hand tools (motor
apraxia), and moving the eyes to follow an object
(occulomotor apraxia). Verbal apraxia is the most
common form of this neurologic disorder.Verbal Apraxia in Children
Developmental verbal apraxia in children results
from injury, often unidentified as to its nature and
cause, to the BRAINregions and neural pathways
that produce speech. Verbal apraxia begins to
show symptoms between the ages of 18 and 30
months, the age in normal development at whichapraxia 225