Wernicke's
Aphasia
This is the most
common of the fluent aphasias. It is also known as semantic
aphasia
Site of
Lesion
The
lesion is located in Wernicke's area, which is the posterior
region of the left superior temporal gyrus or the first
gyrus of the temporal
lobe.
Brodmann's areas 21 and 42 correspond to Wernicke's area
(FitzGerald, 1997). The damage often extends into the
parietal lobe, affecting the angular
gyrus
(Brodmann's area 39). Meaning is associated with speech
sounds in Wernicke's area. It is also a center for abilities
like reading and writing which have been learned in
conjunction with auditory comprehension. As Wernicke's area
is adjacent to Heschl's gyrus, it can be considered an
auditory association area. Temporal lobe lesions are responsible for a number of problems other than aphasia.
Characteristics
The
major impairment is semantic. With severe Wernicke's aphasia
there is usually a severe impairment in auditory
comprehension. Speech, while fluent, is semantically
inappropriate and paraphasic. The speech of Wernicke's
patients is sometime called cocktail hour speech.
Comprehension and expression tend to be equally impaired.
Patients with moderate Wernicke's can get the point in
conversations but miss many specifics (Brookshire,
1997).
Articulation is
normal
Melodic Line is
unaffected. If one ignores the content, the form of the
patient's speech may sound normal. They have long,
grammatically well formed utterances that contain almost no
meaning.
According to
Goodglass and Kaplan, 1983, speech is paragrammatical.
Wernicke's patients make grammatical errors but their speech
cannot be considered agrammatical as it does contain complex
syntactical forms.
Wernicke's
aphasics can exhibit disassociation between the sounds or
sights of words and their meanings (Brookshire,
1997).
Although the form
of language may be relatively unimpaired, speech may be
essentially meaningless in the most severe cases, and sound
a little like "Jabberwocky."
Verbal paraphasias
consist of words usually of allied meanings: knife for fork.
Literal or phonemic paraphasias consist of made up but
similar sounding syllables (bife for knife) with fifty
percent or more correct). Neologistic paraphasias are when
less than half of the utterance is correct (bort for fork).
Paraphasias are common (FitzGerald, 1997).
Repetition is
typically poor. Patients may use paraphasias and also
commonly add words, complicating the utterance. This
phenomenon is known as augmentation. Also due to auditory
comprehension deficits, the patient may repeat the
examiner's words without understanding them.
Word finding
problems are very common.
Confrontation
naming is
typically impaired.
Auditory
comprehension is impaired. In severe cases,
patients may not even understand one word utterances.
Both reading and
writing can be seriously impaired if the angular gyrus is
compromised.
Hemiplegia/hemiparesis are rare due to the
posterior nature of the lesion. Patients can usually still
use their right hands to write and the form of their
handwriting may be normal. However, the content of their
written output is very similar to their speech.
A phenomenon
called press of speech also characterizes Wernicke's
aphasics. Patients may speak very rapidly, interrupting
others. It may seem as though the patient is striving for a
sense of closure or a sense that he has actually
communicated what he intended to say (Goodglass and Kaplan,
1983).
Unlike Broca's
aphasics, Wernicke's aphasics tend to have anosognosia (lack
of awareness) of their communication problems (Davis, 1983).
They often seem unaware of their speech problems. Or, at
least, they are not concerned about them. (The occasional
patient will be frustrated.) This lack of concern is
indicative of the more severe cognitive problems that give
Wernicke's patients a worse prognosis than Broca's.
Anomic
Aphasia (also called amnesic)
Site of
Lesion
According to Goodglass and Kaplan
(1983), anomia can be localized with the
least reliability of any of the aphasic syndromes. The
lesion is often temporal parietal area. The angular
gyrus may
also be affected, causing alexia and agraphia. (Some patients with
anomic aphasia can write well, however).
Characteristics
The
boundary between anomic aphasia and Wernicke's aphasia is
fuzzy, but classic cases of each syndrome can be readily
distinguished from one another. A patient may initially be
diagnosed with Wernicke's aphasia, but eventually come to
resemble the profile of anomic aphasia as he/she
recovers.
Naming or word
finding problems are the major feature of the syndrome.
Patients sometimes use elaborate circumlocutions to
compensate for this, and the content of their speech may
come to sound fairly bizarre as a result. For example, a
patient might say that he's "had one of them up there" when
trying to explain that he's had brain surgery.
Grammar is
unaffected.
Paraphasias are
rare.
Repetition is
good.
Auditory
comprehension is relatively intact.
Reading and
writing are variable with abilities ranging from normal to
very poor. Sometimes, a patient will be able to write a word
that he cannot say, suggesting that its written and auditory
representations were stored separately.
Anomia is
typically the first language symptom of a brain tumor, even
if the growth is located far away from the language center.
It is also seen in a variety of dementias.
On the BDAE
(Goodglass and Kaplan, 1983), anomic patients rarely receive
extremely low scores. They typically have a severity rating
of 3 or 4 (1 being very poor and 5 being relatively intact).
Conduction
Aphasia
According to
Bhatnager, and Andy (1995), conduction aphasia occurs in
fewer than 10% of aphasia cases.
Site of
Lesion
According to Geschwind, conduction
aphasia results from damage to the arcuate fasciculus, a
bundle of nerve fibers that lies below the supramarginal
gyrus in
the temporal lobe and connects Broca's and Wernicke's areas.
Both Broca's and Wernicke's areas are left intact.
Lesions are also found in the left perisylvian area of the cortex.
Effected areas may
include superior temporal gyrus, the insula (Island of Reil), the primary auditory
cortex (Brodmann's areas 41 and 42), auditory
association areas (Brodmann's 21 and 22), and the
supramarginal gyrus (Brodmann's area 40).
Characteristics
Spontaneous speech is usually fluent.
There are frequent literal paraphasias and error awareness,
with attempts made by the patient to correct them (Bhatnager
and Andy, 1995). In addition there can be some verbal
paraphasias. Auditory comprehension and reading
comprehension are fairly good.
Poor repetition,
in comparison to problems with comprehension and spontaneous
expression, is the hallmark of this syndrome. Spontaneous
speech is better than repetition. Patients typically produce
many paraphasias when trying to repeat. They may be able to
reproduce short utterances, however, they will be unable to
repeat polysyllabic words or syntactically complex
utterances. Patients with this syndrome have difficulty
repeating even the high probability sentences included in
the repetition subtest of the Boston. Patients' ability to
repeat numbers is typically much better than their ability
to repeat words. Errors in number repetition tend to be verbal
paraphasias while errors made while repeating
words are typically literal (phonological)
paraphasias When testing it's best to use
sentences that contain both words and numbers for repetition
tasks. For example the patient might be asked to repeat the
sentence "There were 25 at the concert last week" (Goodglass
and Kaplan, 1983).
Conduction
aphasics usually perform even more poorly on tasks when
given a model. (A Broca's patient would perform better when
modeling.)
Although this is
classified as a fluent aphasia, fluent speech may be
restricted to brief runs (they don't sound like Wernicke's
patients). In this case, conduction aphasics can be
differentiated from Broca's aphasics by their good
articulation, normal intonation and use of a variety of
syntactic patterns.
The major speech
difficulty in this syndrome is the sequencing of phonemes.
Patients may produce many literal paraphasias. (This is
another attribute that may cause confusion with Broca's
aphasia.) The patient is aware of his paraphasic errors and
will produce repeated approximations of the intended word,
as if he is trying to untangle it. This phenomenon is called
conduit d'approche (Goodglass and Kaplan, 1983).
Patients may
distort words by adding syllables or by adding sounds to a
word which are called intrusive additions.
Anomia is
common.
Auditory
Comprehension is typically nearly normal and may
be completely intact. Conduction aphasics could comprehend
the nouns and verbs in a sentence, but would not be able to
understand grammatical morphemes such as prepositions and
conjunctions because incoming information is not transferred
from Wernicke's area to Broca's area.
A patient could
understand "Do you write with a pen?"
A patient could
not understand "Before you raise your hand, read
this."
Unambiguous cases
of conduction aphasia usually receive a score between 2 and
4 on the severity rating scale of the Boston. In very severe
cases, the patient may receive a rating of 1 or 2 and it
will be extremely difficult to differentiate the disorder
from Broca's
aphasia.
When the patient is very fluent, the prevalence of
paraphasias in his speech may result in a diagnosis of
Wernicke's aphasia (Goodglass and Kaplan, 1983).
Reading abilities
are commensurate with the patient's severity rating, but are
typically good. They have difficulty reading aloud.
Writing typically
contains spelling errors and transpositions of words and
syllables (Brookshire, 1997).
Transcortical Sensory
Aphasia
This is an
extremely rare form of fluent aphasia.
Site of
Lesion
It is
hypothesized that this type of aphasia occurs when Broca's
area, Wernicke's area and the arcuate
fasciculus are undamaged but are cut off from
the rest of the brain by infarcted tissue. A lesion of this
type could occur due to vascular insufficiency because of
problems at the ends of the cerebral arteries distribution
system, the watershed
areas of
the blood supply.
Such lesions would
be found in Brodmann's areas: 37, 22, and 39. Lesions in
area 37 are known to cause anomia. Area 22 is near
Wernicke's
area and
area 39 is the angular
gyrus.
Characteristics
According to Goodglass and Kaplan
(1983) the hallmark of this syndrome is extremely
well-preserved repetition abilities in the context of no
comprehension and no propositional speech. This shows that
the arcuate
fasciculus
is still intact, allowing information to pass from
Wernicke's to Broca's
area.
Patients can repeat very long, complicated utterances. Also,
automatic speech is very good and they can produce lengthy
chunks of memorized material like prayers and song lyrics if
they can be made to understand the task.
In addition,
patients may echo their conversation partners in such a way
that they sound as if they do understand language and are
participating in the conversation. For example, if asked if
he likes his lunch, the patient might say "like lunch."
Within the repeated phrases, phonology and intonation are
intact.
Reading
and Writing
Patients cannot read and also cannot
write, even in the absence of paralysis or limb
apraxia.
Auditory
comprehension is non-existent. In the absence of
other lesions, the patient would still be able to think, but
would not be able to connect language with information about
meaning stored in memory.
My experience with
one patient revealed intact cognition, including his ability
to find his way around the hospital. Prior to being assessed
by me he had been diagnosed as having Wernicke's
aphasia.
Such a patient
would typically receive a score of 1 or 2 on the severity
rating scale of Boston (1 is very low, 5 is relatively
intact). A high repetition score is the only factor that
would differentiate a transcortical sensory aphasia from
Wernicke's and, in fact, patients are often misdiagnosed as
having Wernicke's aphasia.