October 20, 2003
Form
of Memory Loss Confused With Alzheimer’s
CHICAGO
--- Alzheimer’s disease is the single most common
cause of dementia, a chronically progressive brain condition that
impairs intellect and behavior to the point where customary activities
of daily living become compromised. Over 4 million Americans have
Alzheimer’s disease. Its high prevalence may lead people
to believe that dementia is always due to Alzheimer’s disease
and that memory loss is a feature of all dementias.
However,
an article by Alzheimer’s disease expert M.-Marsel
Mesulam, M.D., in the Oct. 16 issue of The New England Journal
of Medicine reports that nearly a quarter of all dementias, especially
those of presenile onset, may be caused by diseases other than
Alzheimer’s disease and that some of these so-called atypical
dementias involve cognitive abnormalities in areas other than memory.
Mesulam
is Ruth and Evelyn Dunbar Professor of Psychiatry and Behavioral
Sciences and professor of neurology at the Feinberg
School of Medicine and director of the Cognitive Neurology and
Alzheimer’s Disease Center at Northwestern University.
Mesulam described, for example, primary progressive aphasia,
an unusual dementia of unknown cause that is characterized by a
relentless loss of language but with memory relatively preserved.
Once considered a rare condition, primary progressive aphasia is
now commonly included among dementia syndromes and has been reported
in several hundred individuals.
Alzheimer’s disease patients have forgetfulness, usually
accompanied by apathy. They misplace personal objects, repeat questions
and forget recent events. However, while these patients may forget
people’s names, word-finding during conversation is not a
major problem.
In contrast, patients with primary progressive aphasia come to
medical attention because of the onset of word-finding difficulties,
abnormal speech patterns and glaring spelling errors. Some patients
cannot find the right words to express their thoughts. Others cannot
understand the meaning of words either heard or seen. Still others
cannot name objects in their environment.
In some patients with primary progressive aphasia, the ability
to write language may be less impaired than the ability to speak
it. Others develop agrammatism, using inappropriate word order
and misusing word endings, prepositions, pronouns, conjunctions
and verb tenses.
Language
is the only area of prominent dysfunction for at least the first
two years of primary progressive aphasia. In these patients,
structural brain imaging studies do not reveal a specific lesion,
other than atrophy, that can account for the language deficit,
Mesulam said. Language difficulties may be the patient’s
only symptoms for 10 to 14 years. Other cognitive impairments may
emerge, but the language deficit remains the primary feature throughout
the illness and progresses more rapidly than deficits in other
areas.
Also
in contrast to many patients with Alzheimer’s disease,
who tend to lose interest in recreational and social activities,
some individuals with primary progressive aphasia maintain and
even intensify their involvement in complex hobbies such as gardening,
carpentry, sculpting and painting. One patient Mesulam described
continued to fly his airplane until aphasia prevented him from
communicating with ground control.
In
patients with suspected primary progressive aphasia, evaluation
by a speech
therapist is useful for exploring alternative communication
strategies, Mesulam said. Unlike patients with Alzheimer’s
disease, who cannot retain new information in memory, patients
with primary progressive aphasia can recall and evaluate recent
events even though they may not be able to express their knowledge
verbally.
Currently, there is no effective pharmacologic treatment for
primary progressive aphasia. However, from the vantage point of
research, the condition provides a rare opportunity for investigating
the molecular mechanisms of focal neurodegeneration and the neuropsychological
organization of language function, Mesulam said. |