Facts on File Encyclopedia of Health and Medicine

medical care. The diagnostic path begins with a
complete PERSONAL HEALTH HISTORY and family
health history. The neurologist conducts a NEURO-
LOGIC EXAMINATION, and may conduct COMPUTED
TOMOGRAPHY(CT) SCANor MAGNETIC RESONANCE IMAG-
ING(MRI) of the brain to look for changes that sug-
gest other causes for the tremors. The diagnosis
combines the neurologist’s clinical observations
about the characteristics of the tremor with nega-
tive findings for other causes.

Treatment Options and Outlook

Medications to mitigate tremors include beta block-
ers such as propanolol, certain Antiseizure medica-
tions (notably primidone), and MUSCLErelaxants
such as alprazolam. BOTULINUM THERAPY, in which
the neurologist injects botulinum toxin into
affected muscles to paralyze them, can provide
long-term relief for some people. Surgical interven-
tions such as DEEP BRAIN STIMULATIONand THALAMO-
TOMYmay be options for tremors that fail to respond
to less invasive treatments. Most people are able to
find treatments that minimize the extent to which
tremors interfere with their daily activities.

Risk Factors and Preventive Measures

Benign essential tremor appears to run in families.
About half of tremor disorders appear to occur in

people who mutations in one or both of two

genes, etm1and etm2. Researchers suspect as yet

unidentified mutations in other genes are respon-

sible for tremor disorders in people who do not

have etm1or etm2 mutations. Other tremor disor-

ders may have genetic components as well.

Tremor disorders are far more common in people

who are older than age 60 than in those who are

younger. However, there are no known measures

to prevent tremor disorders.

See also DYSKINESIA; GENE; MUTATION; PARESTHESIA.

unconsciousness A state in which a person is

unaware of and does not interact with the exter-

nal environment. The most common experiences

of unconsciousness are sleep, fainting (SYNCOPE),

and general ANESTHESIA. Unconsciousness may also

occur with CONCUSSION, seizures, HYPOTENSION(low

BLOOD PRESSURE), ENCEPHALITIS, ENCEPHALOPATHY, and

INTOXICATION. Most people are easily aroused from

the unconsciousness of sleep though people who

are unconsciousness due to other causes may not

arouse until or if the underlying cause resolves.

See also ARRHYTHMIA; BRAIN DEATH; CONSCIOUS-

NESS; COMA; LONG QT SYNDROME(LQTS); PAROXYSMAL

ATRIAL TACHYCARDIA (PAT); PERSISTENT VEGETATIVE

STATE; SEIZURE DISORDERS; WOLFF-PARKINSON-WHITE

SYNDROME.

unconsciousness 289