Page 354 - Color Atlas Of Pathophysiology (S Silbernagl Et Al, Thieme 2000)

Aphasias
Speech and language comprehension are tasks of “spin”) or semantic errors (“mother” instead
that engage a large part of the cerebral cortex. of “woman” [paraphasia]) or create new words
For this reason, lesions in various parts of the (neologisms).
cortex may lead to an impairment of speech In conductive aphasia the connection be-
and of language comprehension. tween sensory and motor speech center (arcu-
Systems ceived in the primary auditory cortex (→ A; ate fasciculus) is interrupted. Speech is fluent
Simply put, spoken language is first per-
(although sometimes paraphasic) and com-
marked in violet) and then in the sensory
prehension is good. However, their repetition
ability is greatly impaired. They are also un-
speech center (Wernicke’s area, marked in
Neuromuscular and Sensory the primary (gray-blue) and secondary (dark stand the text they read.
able to read aloud, even though they under-
light blue). Written words are transmitted via
blue) visual cortex to area 39, where acoustic,
In global aphasia (damage to both the sen-
sory and the motor centers, e.g., by occlusion
optical, and sensory perceptions are integrat-
ed. When writing, the premotor cortex is
of the medial cerebral artery) both sponta-
activated via the arcuate fasciculus of the pre-
neous speech and comprehension are im-
paired.
motor cortex that, in turn, activates the motor
cortex via the basal ganglia and the thalamus.
Anomic aphasia is the result of a lesion in
are predominantly localized in the left hemi-
and inferior gyri. Patients’ speech is largely
normal but it is difficult for them to find the
sphere, and speech disorders (aphasia) are al-
10 In right-handed people the structures involved the temporal lobe in the region of the medial
most always the result of lesions in the left
right word for certain objects. In achromatic
hemisphere. aphasia (lesion at the left inferior temporal
Each of the above-mentioned structures can lobe close to temporal-occipital border) the
cease functioning, for example, due to trau- person cannot name a color (even though it is
matic or ischemic damage. Depending on correctly recognized and objects can normally
which cerebral area is affected, abnormalities be sorted by color).
characteristic for each will develop. Transcortical motor aphasia is caused by a
Broca’s aphasia is caused by a lesion of the lesion in the anterior inferior frontal lobe near
motor speech center in area 44 and the neigh- the Broca speech center. Spontaneous speech
boring areas 9, 46, and 47. Spontaneous speech is markedly impaired, while repetition and
(verbal output) is grammatically incorrect and comprehension are normal.
the patient typically communicates by using Transcortical sensory aphasia occurs after a
single words and is incapable of repeating lesion in the parietal–temporal association
someone else’s words (impaired repitition cortex near the Wernicke speech center or
ability). Language comphrehension is not, or area 39. The patient can speak fluently and
less markedly, impaired. As a rule patients repetition is normal. However, there is a prob-
cannot write normally. However, if the lesion lem understanding words and finding the
is limited to area 44, the ability to write is pre- right word; reading and writing are impossi-
served (a rare disorder, called aphemia). ble.
Wernicke’s aphasia results from a lesion in Subcortical aphasia is due to lesions in the
the sensory speech region, i.e., in the posterior region of the basal ganglia (especially the cau-
portion of the temporal gyrus of the auditory date nucleus) and the thalamus. There are
association cortex (area 22) and/or the supra- transient disorders of comprehension and
marginal gyrus (area 40). Language compre- finding of words.
hension is impaired in these patients. At the
same time they also lose the ability to repeat
words spoken by somebody else. Spontaneous
speech is fluent; sometimes patients speak all
344 the time (logorrhea). However, in doing so they
may make occasional phonetic (“spill” instead
Silbernagl/Lang, Color Atlas of Pathophysiology © 2000 Thieme
All rights reserved. Usage subject to terms and conditions of license.