Fifth Stage
Internal Medicine
Dr. Abbas / Lec . 7
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Cerebral Dysfunctions
The dominant hemisphere (usually left)
The concept of cerebral dominance arose with a simple observation. Right-handed
stroke patients with acquired language disorders had destructive lesions within the left
hemisphere. Almost all right-handed and 70% of left-handed people have language
function in the left hemisphere.
Aphasia
Aphasia is loss of or defective language from damage to the speech centres within
the left hemisphere
Broca's aphasia (expressive aphasia, anterior aphasia
Damage in the left frontal lobe causes reduced speech fluency with
comprehension relatively preserved. The patient makes great efforts to initiate
language, which becomes reduced to a few disjointed words. There is failure to
construct sentences. Patients who recover from this form of aphasia say they knew what
they wanted to say, but 'could not get the words out'.
Wernicke's aphasia (receptive aphasia, posterior aphasia)
Left temporo-parietal damage leaves language that is fluent but the words
themselves are incorrect. This varies from insertion of a few incorrect or nonexistent
words into fluent speech to a profuse outpouring of jargon (that is, rubbish with wholly
nonexistent words). Severe jargon aphasia may be bizarre - and confused with psychotic
behaviour. Patients who have recovered from Wernicke's aphasia say that when aphasic
they found speech, both their own and others', like a wholly unintelligible foreign
language. They could neither stop themselves, nor understand themselves and others.
Global aphasia (central aphasia)
This means the combination of the expressive problems of Broca's aphasia and
the loss of comprehension of Wernicke's. The patient can neither speak nor understand
language. It is due to widespread damage to speech areas and is the commonest
aphasia after a severe left hemisphere infarct. Writing and reading are also affected
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Conduction aphasia
Patients with lesion in arecute fasiculus will have difficulty with repetition,
Nominal aphasia (anomic aphasia or amnestic aphasia)
This means difficulty naming familiar objects. Naming difficulty is an early sign in
all types of aphasia. A left posterior temporal/inferior parietal lesion causes a severe,
isolated form.
The non-dominant hemisphere
Disorders in right-handed patients with right hemisphere lesions are often difficult
to recognize. They comprise abnormalities of perception of internal and external space.
Examples are losing the way in familiar surroundings, failing to put on clothing correctly
(dressing apraxia), or failure to draw simple shapes - constructional apraxia
Memory loss (the amnestic syndrome)
Progressive loss of ability to learn, retain and process new information
Causes
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ACUTE e.g. head trauma, acute confusion,hypoxia,ischemia,wernick,s
encephalopathy and psychogenic amnesia
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Chronic like dementia, brain tumour,post encephalitis amnesia and alcoholic
Korsakov syndrome
Confabulation
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Some patients with amnestic syndrome may attempt to fill gaps in memory with
false recall
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APRAXIA
Is the inability to perform previously learned tasks despite intact motor, sensory and
cerebellar function [ inability to do certain act or movement even though no sensory
defect, weakness or ataxia
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E.g. gait apraxia; loss of ability to walk [frontal lobe damage]
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Dressing apraxia; failure to put on clothing correctly [non dominant lobe lesion]
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Constructional apraxai; failure to draw simple shape
Agnosia
Agnosia is the inability to recognize certain objects, persons or sounds, yet there
are many more specific diagnoses of agnosia. Agnosia is typically caused by damage to
the brain (most commonly in the occipital or parietal lobes) Some examples of specific
types of Agnosia include: Visual Agnosia, Auditory Agnosia,
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