retrieve existing memories or to store new memo-
ries, and may be temporary (such as following
CONCUSSION) or permanent. Memory loss is an
imprecise term that usually refers to the perma-
nent inability to retrieve information from long-
term memory.
Symptoms and Diagnostic Path
It is normal for people to forget recent information
such as where they placed the car keys or phone
numbers they use infrequently. Forgetfulness
crosses the line to memory impairment when a
person cannot remember information essential for
daily activities, such as familiar faces and names or
where he or she lives. The diagnostic path
includes a comprehensive medical examination,
neurologic examination, and imaging procedures
such as COMPUTED TOMOGRAPHY(CT) SCANto identify
possible organic causes within the brain. Func-
tional magnetic resonance imaging (fMRI), a
dynamic variation of MAGNETIC RESONANCE IMAGING
(MRI) that shows the functional activity of the
brain, may show areas of diminished activity dur-
ing memory tasks. Memory and cognitive tests
help identify the kinds of memory affected and
define remaining memory functions.
Treatment Options and OutlookTreatment for memory impairment depends on
the underlying cause. Memory functions lost due
to injury or infection such as encephalitis often
return as the brain heals. The return commonly
takes place in fragments, often with older memo-
ries (such as from childhood) emerging first.
Memory impairment due to conditions such as
stroke or Alzheimer’s disease is generally perma-
nent. Medications such as the acetylcholinesterase
inhibitors doctors prescribe to treat Alzheimer’s
disease improve memory and cognition in many
people in the early to middle stages of the condi-
tion though do not appear especially effective in
treating memory impairment resulting from other
causes. Permanent memory impairment may also
be progressive, as occurs with degenerative condi-
tions such as Alzheimer’s disease and PARKINSON’S
DISEASE.
Exercising memory and cognition, such as with
crossword puzzles and other activities that require
storage and recall of information, helps keep these
abilities as functional as possible in healthy aging
as well as when health conditions exist that have
the potential to impair memory. Memory special-
ists can help individuals develop methods and
approaches to maintain optimal memory capabil-
ity as well as to accommodate memory impair-
ment. The herbal products GINKGO BILOBA and
GINSENG may improve circulation to the brain,
resulting in overall improvement of memory and
cognitive functions.Risk Factors and Preventive Measures
Diseases, systemic and neurologic, and injuries to
the brain are the primary risk factors for memory
impairment. To a great extent, injuries to the brain
that might result in impaired memory are pre-
ventable through safety measures, such as wear-
ing appropriate protective headgear and avoiding
activities with a high risk for head injury. Lifestyle
factors influence some conditions that can cause
memory impairment, such as HEART ATTACKand
stroke. Chronic ALCOHOLISMcontributes to episodic
as well as progressive memory loss. Family history
may be a risk factor for neurologic conditions such
as Alzheimer’s disease and dementia, for which
there are no known measures of prevention.
See also ACCIDENTAL INJURIES; AGING, NEUROLOGIC
CHANGES THAT OCCUR WITH; ANTI-AGING APPROACHES;
ARTERIOSCLEROTIC PLAQUE; COGNITIVE FUNCTION AND
DYSFUNCTION; HYPNOSIS; LEARNING DISORDERS; NEURON;
POST-TRAUMATIC STRESS DISORDER(PTSD).meninges The connective tissue membranes that
enclose and protect the BRAINand SPINAL CORD(col-
lectively called the CENTRAL NERVOUS SYSTEM). There
are three meninges:- The dura mater is the tough, outermost
meninx. It has two layers, a fibrous outer layer
that attaches to the inside of the cranium (skull
bones) and a soft inner layer that contains an
extensive network of BLOODvessels. The dura
mater sometimes folds back on itself (dural
reflections) or its layers separate to form pock-
ets (dural sinuses). - The arachnoid mater is the middle meninx.
- The innermost meninx is the pia mater, a tis-
sue-like membrane that covers the surface of
the brain.
262 The Nervous System