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The clustering of
particular symptoms or language disturbances into syndromes
is in part a function of the anatomic organization of the
substrate for language in the brain. It is also that cerebral vascular accidents frequently affect
certain vulnerable areas of the brain.These syndromes have
been recognized for years, although there is some confusion
about the classification scheme because terminology has been
used inconsistently. Not all cases of aphasia fit the
pattern of one of these syndromes. These syndromes simply
represent the most frequently occurring clusters of language
deficits. Depending on the rigor with which classification
systems are applied, 30% to 80% of cases match up with a
recognized sub-type of aphasia. Syndromes are representative
of the most regularly recurring response patterns of
language behavior to lesions in particular sites within the
language zone. Differences in language performance may be
due to the fact that lesions vary in exact location and
extent, and because individuals may respond differently to
the same lesion types and locations. Goodglass, Kaplan, and
Barresi, 2001,
Mismatches occur
because:
Exact site and
extent of lesion vary.
Response to
the same injury may differ from one individual to
another.
Variations in the lateralization of language
lead to corresponding differences in the anatomical
organization of the components of language. Some adults
develop aphasia from right hemisphere lesions, though
they usually do not display paraphasic speech or have
difficulties with auditory comprehension. The
localization of language is the product of brain
maturation and language use. Focal
lesions
in children may not cause the same clear-cut pattern of
symptoms that would be seen in an adult. (Goodglass,
Kaplan and Barresi, 2001)
Localizationists vs.
Antilocalizationists
Pure
localizationists believe that every type of linguistic
behavior can be localized in a particular part of the brain.
Pure antilocalizationists view the brain as an integrated
unit like a hologram and believe that damage to one area of
the brain will affect the functioning of the brain as a
whole.
Some tests of
aphasia are based on one of these perspectives. Boston
Diagnostic Aphasia Examination is based in part on the principle of
localization, assuming that identification of a particular
syndrome of aphasia provides information about site of
lesion. According to Kearns,1990, the use of CT and PET
scans support the schema for localization.
Fluency vs.
Nonfluency (Use Rating Scale of Speech Characteristics in
the Boston)
This
major subdivision of the aphasic syndromes is based on the
characteristics of speech output (Goodglass and Kaplan,
1983). Fluent aphasia has normal articulation and rhythm of
speech, but is deficient in meaning. McCaffrey, 2000.
Nonfluent aphasic speech is slow and labored with short
utterance length.
Nonfluent
Aphasias
(Lesions are usually anterior to the fissure
of Rolando)
Characteristics
The
flow of speech is more or less impaired at the levels of
speech initiation, the finding and sequencing of
articulatory movements, and the production of grammatical
sequences. Speech is choppy, interrupted, and awkwardly
articulated. According to Goodglass et al, 2001 the speech
of the nonfluent aphasic is laborious and there is usually
less than three or four words in a breath group.
Comprehension appears to be better than production and in a
sense it is. The linguistic competence underlying both
comprehension and production of language is the same, so
both comprehension and production are affected by a
nonfluent aphasia, McCaffrey, 2000. However, just as it is
easier to understand a second language than to produce it,
it is easier for the patient to understand what is said than
to say it. One can often get by with only comprehending the
key words and using non-verbal cues.
Site of
Lesion
Nonfluent aphasias are the result of
damage to the area of the brain anterior to the
central
fissure (Broca's area).
Fluent
Aphasias
Characteristics
Phoneme selection and sequencing as
well as syntax are preserved in fluent
aphasia. Speech is characterized by a
facility of articulation and many long runs of words
combined using a variety of grammatical constructions.
However, fluent speech is not equivalent to meaningful
speech. Often the speech of fluent aphasics sounds like
"jabberwocky." Typically, there are word-finding problems
that most affect nouns and picturable action words. Comprehension
is typically poor with fluent/posterior lesion aphasias.
(Conduction aphasia would be the exception to this). The
amount and type of paraphasias, the presence of auditory
receptive impairments and of impaired repetition are
variable in fluent aphasias, depending upon the exact site
of lesion. According to Goodglass, Kaplan and Barresi, 2001,
p. 7, "fluent aphasia is associated with easy articulation,
facility with the patterns of sentence structure, but with
difficulty in word finding and errors of word and sound
substitution."
Site of
Lesion
Fluent
aphasias are the result of lesions affecting the
post
Rolandic area. Problems with meaning are associated with
posterior lesions.
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