Cerebral DysfunctionsThe 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
The dominant hemisphere (usually left)
Aphasia is loss of or defective language from damage to the speech centers within the left hemisphere
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'.
Broca's aphasia (expressive aphasia, anterior 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 behavior.
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.
Wernicke's aphasia (receptive aphasia, posterior 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
Global aphasia (central aphasia)
Conduction aphasiaPatients 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.
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
The non-dominant hemisphereProgressive loss of ability to learn, retain and process new information
• ACUTE e.g. head trauma, acute confusion ,hypoxia, ischemia,wernick,s encephalopathy and psychogenic amnesia
• Chronic like dementia, brain tumour, post encephalitis amnesia and alcoholic Korsakov syndrome
• Some patients with amnestic syndrome may attempt to fill gaps in memory with false recall
Memory loss (the amnestic syndrome)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
• E.g. gait apraxia; loss of ability to walk [frontal lobe damage]
• Dressing apraxia; failure to put on clothing correctly [non dominant lobe lesion]
• Constructional apraxai; failure to draw simple shape
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,