Encyclopedia of Health and Medicine

252 The Nervous System
easily remedied causes for the symptoms. Among
such causes might be undiagnosed conditions such
as HYPOTHYROIDISM, DIABETES, vitamin B 12 deficiency,
neurosyphilis, and medication reactions or
interactions. The doctor will also take a careful
medical history, looking for evidence of recent
injury or trauma or of family history of conditions
such as Parkinson’s disease and Alzheimer disease.
The doctor may conduct diagnostic imaging procedures
such as MAGNETIC RESONANCE IMAGING (MRI)
and COMPUTED TOMOGRAPHY (CT) SCAN to rule out
BRAIN TUMOR, brain hemorrhage, or stroke.
Dementia is generally a clinical diagnosis based on
symptoms and on ruling out treatable causes of
the symptoms.
Treatment Options and Outlook
Treatment and outlook vary with the cause of the
dementia. Metabolic dementia is often transient,
with normal brain function returning when treatment
restores the body’s metabolic balance.
Dementia that results from injury to the brain or
neurodegenerative conditions such as Alzheimer’s
disease is generally permanent. Treatment aims to
improve remaining cognitive abilities through
activities that use and exercise the brain, such as
reading and crossword puzzles. Adaptive measures
may also help, such as writing out instructions or
drawing maps or pictures. Persistent, and particularly
progressive, dementia may result in loss of
independent function.
Risk Factors and Preventive Measures
Age is the primary risk factor for dementia. About
half of people over age 85 have Alzheimer’s disease,
the leading cause of dementia. Lewy body
dementia and vascular dementia also become significantly
more common with advanced age.
Appropriate medical and lifestyle management of
conditions such as HYPERTENSION (high BLOOD PRES-
SURE), atherosclerosis, LIVER disease, and diabetes
helps mitigate their health consequences.
See also COGNITIVE FUNCTION AND DYSFUNCTION;
CREUTZFELDT-JAKOB DISEASE; DELIRIUM; MEMORY AND
MEMORY IMPAIRMENT.
dermatome A region of the body a specific, single
spinal NERVE root serves. The SPINAL NERVES convey
motor signals to and sensory signals from the
body. The body’s dermatome pattern is fairly consistent
among individuals though each person has
subtle unique characteristics. Identifying the
involved dermatome for chronic PAIN, MUSCLE
weakness, or PARALYSIS helps the neurologist determine
the region of the spine where the damage
originates. This is particularly useful for therapies
such as NEURAL BLOCKADE (NERVE BLOCK) and RHIZO-
TOMY, which are treatments for intractable pain or
spasticity. The body’s dermatome has the appearance
of a topographic map when rendered as a
visual representation.
A dermatome is also a bladed surgical instrument
used to remove very thin layers of SKIN such
as for skin transplantation.
See also CEREBRAL PALSY; COMPLEX REGIONAL PAIN
SYNDROME; SPINAL CORD INJURY.
dyskinesia Abnormal, involuntary movements.
Dyskinesia results from damage to the structures
within the BRAIN responsible for motor movement
and coordination, notably the basal ganglia.
ATHETOSIS, CHOREA, DYSTONIA, MYOCLONUS, tics, and
tremors are all forms of dyskinesia that may
appear in neurologic disorders such as PARKINSON’S
DISEASE, HUNTINGTON’S DISEASE, TOURETTE’S SYN-
DROME, RESTLESS LEGS SYNDROME, CEREBRAL PALSY, and
essential benign tremor. Abnormally slow movements
are bradykinetic (bradykinesia) and abnormally
rapid movements are hyperkinetic
(hyperkinesis). It is common for people who have
neuromotor disorders to have more than one form
of dyskinesia. Medications such as anticholinergics
and MUSCLE relaxants can sometimes improve
dyskinesia.
Tardive dyskinesia is a form of dyskinesia that
develops with long-term use of DOPAMINE antagonist
medications, which block dopamine from
reaching dopamine receptors in the brain.
Dopamine antagonists are the convention of treatment
for Parkinson’s disease. Many ANTIPSYCHOTIC
MEDICATIONS to treat SCHIZOPHRENIA and other serious
psychiatric illnesses also are dopamine antagonists.
Tardive dyskinesia is often irreversible.
See also TREMOR DISORDERS.
dyslexia
See LEARNING DISORDERS.