STUDY - Technical - New Dacian's Medicine
Aphasia
and other Focal Disorders (1)
Translation Draft
The cerebral cortex is divided into five functional zones: 1. primary sensorimotor zone, 2. unimodal association area, 3. heteromodal association area, 4. paralimbic zone and
5. limbic area. The primary sensory area, intended for elementary motor and sensory functions, occupies less than 10% of the cerebral cortex.
The other four areas, known as the association cortex, comprise most of the cerebral cortex and support complex behavioral and cognitive functions. Conventional neurological examination places more emphasis on sensory and motor function testing than cognitive ones.
Thus, the detection of lesions in the sensoriomotor cortex is much more accurate than the detection of disorders in the association cortex. In the clinic, a patient with extensive frontal, parietal or temporal lesions may have a "normal" neurological examination.
Systematic testing of cognitive functions is necessary so that the clinical evaluation of the association cortex can be approached as rationally as the evaluation of the other components of the nervous system.
The interpretation of the traditional neurological examination tends to be based on the relatively invariable relationships existing between the anatomical structure and its function. Damage to the optic tract or striated cortex, for example, always leads to hemianopsic controlled homonymous visual field defects.
Sciatic nerve damage always causes loss of ankle flexibility. The evaluation of more specialized cortical functions was initially based on the assumption that similar relationships would be discovered in the association cortex, which could allow the identification of the center of "heard words", "perceived space" or "long-term memory" and, consequently, the creation of tests at the patient's bed for the exact location of cortical lesions.
Today, this approach needs to be modified to include the latest localization patterns, based on an understanding of large neural networks and selectively distributed processing.
Consistent with what is known today, behavioral and cognitive functions (domains) are coordinated by intersecting neural networks containing interconnected cortical and subcortical elements. This approach to specialized cortical functions has at least four relevant clinical implications: 1. a single area, such as language or memory, can be affected by damage to any of several areas, as long as these areas belong to the same neural network, 2. damage to a single area can cause multiple deficits, involving the functions of intersecting networks in that region , 3. damage to an element of the network results in a transitional or minimum deficit in an important area if the other elements of the network go through a compensatory reorganisation process and 4. individual anatomical centers within a network exhibit a relative (not absolute) specialization for different behavioural aspects of an important function.
Thus, damage to each of the anatomical components of the network can cause disturbances in the same field, but with different clinical presentations. Five anatomically different networks are the most important in the clinic: the perrisylvian language network, the perifrontal network for spatial orientation, the temporooccipital network for the recognition of limbic network objects for long-term memory and the prefrontal network for attention and behavior.
The left perisylvaan network of language is decisive in terms of aphasia and other associated disorders. Let's see some definitions now! Language allows communication and reshaping of thoughts and experience by associating them with arbitrary symbols that are words. the neural substrate of the language consists of a network centered in the sylvian region of the left hemisphere.
The posterior area of this network is known as the Wernicke area and comprises the posterior third of the upper temporal gyrus and the areas surrounding the lower parietal lobe. An essential function of the Wernicke area is to turn sensory stimuli into neural interpretations in the form of words, so that they allow associations that lead to understanding the meaning.
The anterior area of the language network, known as the Broca area, comprises the posterior part of the lower frontal gyrus and the areas surrounding the heteromodal prefrontal cortex. The essential function of this area is to transform neural representations in the form of words into articulated sequences so that they can be expressed in spoken language.
Also, this function of the Broca area seems to achieve the ordering of words in sentences, so that the resulting phrases have a syntax (grammatic) corresponding to the meaning. The Wernicke and Broca areas are connected to each other and with posterior parietal, prefrontal and near perisylvian regions, creating a neural network that serves the different aspects of language function.
Damage to any of these components or their connections causes a language disorder (aphasia). Aphasia should only be diagnosed when there are deficits in the formal aspects of language, such as object naming, word choice, understanding meaning, spelling and syntax. Dizartria and mutism do not, by themselves, support the diagnosis of aphasia.
The language network demonstrates a dominance of the left hemisphere in most of the population. In about 90% of right-handed and 60% left-handed, aphasia occurs only after injuries in the left hemisphere. In some individuals no hemispheric dominance for language can be distinguished, and in others (including a small part of the right-handed) there is a dominance of the right hemisphere for language. The language disorder that occurs in an injury in the right hemisphere in a right-handed is called cross-aphasia.
Clinical language evaluation should include appointment, spontaneous speech, understanding of meaning, repetition, reading and writing. A deficiency of appointment (anomaly) is the only most common manifestation in aphasic patients. When asked to name common objects (pencil or wristwatch) or parts thereof (wipe, tip, dial, belt), patients cannot indicate the right word and use a location to describe that object ("what is used for writing") or a wrong word (paraphasia).
If patients use an incorrect but close word as meaning ("pen" for "pencil"), naming disorder is known as semantic paraphasia, if the answer approximates the correct answer, but is phonetically inappropriate ("cleion" for "pencil"), then the disorder is known as phonetic paraphrase.
By asking the patient to name the body parts, geometric shape and components of objects (the lapel of the garment, the tip of the pencil) a slight form of anomie can be determined in patients who might otherwise call the common objects.
In most cases of anomie, the patient cannot find the right word when an object is indicated to him, but may show the right object when the examiner pronounces his name. This form of anomie is called a unisens appointment deficit.
The double-sense appointment deficiency occurs in patients who cannot find either the name or indicate the subject matter, this deficiency is always associated with language comprehension disorders. Spontaneous speech is described as "fluent" if the length of the phrases and the appropriate tonality, or "nonfluency", if it is stumbling, dizartric and the average length of the phrase is less than four words.
The examiner should also observe whether speech is paraphrazine or locution, whether there is a relative lack of nouns or action verbs, versus functional words (prepositions, conjunctions) and whether the order of words, times, suffixes, prefixes, plural and possessives are used correctly.
Understanding can be tested by assessing the patient's ability to track the conversation, through questions to which he can answer "yes" or "no" (for example, "Can the dog fly?", "Summer snows?") or by asking the patient to indicate the right object ("Where is the source of light in this room?").
Phrases that contain secondary sentences or constructions in passive diathesis ("If a tiger is eaten by the lion, which animal remains alive?") help to assess the ability to understand complex syntactic structures. Commands to close or open your eyes, stand up or sit or roll should not be used in the assessment of comprehension in general, as these axial movements are supported by neural systems outside the language network and can be correctly performed by patients who otherwise have profound impairments of comprehension.
Repeated speech is evaluated by asking the patient to repeat words, short sentences or groups of words, such as "without," "if," "and" or "but." Repeated speech testing using words that are difficult to pronounce, such as "hypopotamus" or "alien" provides a better assessment of dysarthria than aphasia.
Aphasic patients may have little difficulty repeating words that are difficult to pronounce, but it is most difficult for them to repeat a functional group of words. It is important to ensure that these words do not exceed the patient's ability to concentrate. Thus, the failure of repetition reflects the narrowing of the ability to concentrate and not an aphasic deficit.
Reading should be evaluated for the deficit of reading aloud and for understanding. Writing evaluates spelling errors, word order, and grammar. Alexia refers to the inability to read aloud or to understand separate words or simple sentences, the spelling (or disgraphy) is the term that describes a deficiency acquired in spelling or grammar written language.
Each sector of the language network participates in several language functions, but also presents localized specializations. For example, the Wernicke area occupies the lexical-semantic pole of the language network, while the Broca area occupies the syntactic pole. This type of organization allows the classification of aphasia into specific clinical syndromes and helps to determine the most likely anatomical localization of the underlying neurological disease. It also has implications in etiology and prognosis.
Note that pure syndromes occur very rarely, the most common forms being those combined. The correspondence between the individual deficits of the language function and the location of the lesion does not consist of a rigid relationship and should be viewed in the context of the network model.
Taking these considerations into account, aphasic syndromes can be classified as "central", caused by lesions in the two centers of the language network (Wernicke and Broca areas) and "disconnection", which occur through lesions that interrupt the connections of these centers between them and the other components of the network.
We'll continue tomorrow!
The cerebral cortex is divided into five functional zones: 1. primary sensorimotor zone, 2. unimodal association area, 3. heteromodal association area, 4. paralimbic zone and
5. limbic area. The primary sensory area, intended for elementary motor and sensory functions, occupies less than 10% of the cerebral cortex.
The other four areas, known as the association cortex, comprise most of the cerebral cortex and support complex behavioral and cognitive functions. Conventional neurological examination places more emphasis on sensory and motor function testing than cognitive ones.
Thus, the detection of lesions in the sensoriomotor cortex is much more accurate than the detection of disorders in the association cortex. In the clinic, a patient with extensive frontal, parietal or temporal lesions may have a "normal" neurological examination.
Systematic testing of cognitive functions is necessary so that the clinical evaluation of the association cortex can be approached as rationally as the evaluation of the other components of the nervous system.
The interpretation of the traditional neurological examination tends to be based on the relatively invariable relationships existing between the anatomical structure and its function. Damage to the optic tract or striated cortex, for example, always leads to hemianopsic controlled homonymous visual field defects.
Sciatic nerve damage always causes loss of ankle flexibility. The evaluation of more specialized cortical functions was initially based on the assumption that similar relationships would be discovered in the association cortex, which could allow the identification of the center of "heard words", "perceived space" or "long-term memory" and, consequently, the creation of tests at the patient's bed for the exact location of cortical lesions.
Today, this approach needs to be modified to include the latest localization patterns, based on an understanding of large neural networks and selectively distributed processing.
Consistent with what is known today, behavioral and cognitive functions (domains) are coordinated by intersecting neural networks containing interconnected cortical and subcortical elements. This approach to specialized cortical functions has at least four relevant clinical implications: 1. a single area, such as language or memory, can be affected by damage to any of several areas, as long as these areas belong to the same neural network, 2. damage to a single area can cause multiple deficits, involving the functions of intersecting networks in that region , 3. damage to an element of the network results in a transitional or minimum deficit in an important area if the other elements of the network go through a compensatory reorganisation process and 4. individual anatomical centers within a network exhibit a relative (not absolute) specialization for different behavioural aspects of an important function.
Thus, damage to each of the anatomical components of the network can cause disturbances in the same field, but with different clinical presentations. Five anatomically different networks are the most important in the clinic: the perrisylvian language network, the perifrontal network for spatial orientation, the temporooccipital network for the recognition of limbic network objects for long-term memory and the prefrontal network for attention and behavior.
The left perisylvaan network of language is decisive in terms of aphasia and other associated disorders. Let's see some definitions now! Language allows communication and reshaping of thoughts and experience by associating them with arbitrary symbols that are words. the neural substrate of the language consists of a network centered in the sylvian region of the left hemisphere.
The posterior area of this network is known as the Wernicke area and comprises the posterior third of the upper temporal gyrus and the areas surrounding the lower parietal lobe. An essential function of the Wernicke area is to turn sensory stimuli into neural interpretations in the form of words, so that they allow associations that lead to understanding the meaning.
The anterior area of the language network, known as the Broca area, comprises the posterior part of the lower frontal gyrus and the areas surrounding the heteromodal prefrontal cortex. The essential function of this area is to transform neural representations in the form of words into articulated sequences so that they can be expressed in spoken language.
Also, this function of the Broca area seems to achieve the ordering of words in sentences, so that the resulting phrases have a syntax (grammatic) corresponding to the meaning. The Wernicke and Broca areas are connected to each other and with posterior parietal, prefrontal and near perisylvian regions, creating a neural network that serves the different aspects of language function.
Damage to any of these components or their connections causes a language disorder (aphasia). Aphasia should only be diagnosed when there are deficits in the formal aspects of language, such as object naming, word choice, understanding meaning, spelling and syntax. Dizartria and mutism do not, by themselves, support the diagnosis of aphasia.
The language network demonstrates a dominance of the left hemisphere in most of the population. In about 90% of right-handed and 60% left-handed, aphasia occurs only after injuries in the left hemisphere. In some individuals no hemispheric dominance for language can be distinguished, and in others (including a small part of the right-handed) there is a dominance of the right hemisphere for language. The language disorder that occurs in an injury in the right hemisphere in a right-handed is called cross-aphasia.
Clinical language evaluation should include appointment, spontaneous speech, understanding of meaning, repetition, reading and writing. A deficiency of appointment (anomaly) is the only most common manifestation in aphasic patients. When asked to name common objects (pencil or wristwatch) or parts thereof (wipe, tip, dial, belt), patients cannot indicate the right word and use a location to describe that object ("what is used for writing") or a wrong word (paraphasia).
If patients use an incorrect but close word as meaning ("pen" for "pencil"), naming disorder is known as semantic paraphasia, if the answer approximates the correct answer, but is phonetically inappropriate ("cleion" for "pencil"), then the disorder is known as phonetic paraphrase.
By asking the patient to name the body parts, geometric shape and components of objects (the lapel of the garment, the tip of the pencil) a slight form of anomie can be determined in patients who might otherwise call the common objects.
In most cases of anomie, the patient cannot find the right word when an object is indicated to him, but may show the right object when the examiner pronounces his name. This form of anomie is called a unisens appointment deficit.
The double-sense appointment deficiency occurs in patients who cannot find either the name or indicate the subject matter, this deficiency is always associated with language comprehension disorders. Spontaneous speech is described as "fluent" if the length of the phrases and the appropriate tonality, or "nonfluency", if it is stumbling, dizartric and the average length of the phrase is less than four words.
The examiner should also observe whether speech is paraphrazine or locution, whether there is a relative lack of nouns or action verbs, versus functional words (prepositions, conjunctions) and whether the order of words, times, suffixes, prefixes, plural and possessives are used correctly.
Understanding can be tested by assessing the patient's ability to track the conversation, through questions to which he can answer "yes" or "no" (for example, "Can the dog fly?", "Summer snows?") or by asking the patient to indicate the right object ("Where is the source of light in this room?").
Phrases that contain secondary sentences or constructions in passive diathesis ("If a tiger is eaten by the lion, which animal remains alive?") help to assess the ability to understand complex syntactic structures. Commands to close or open your eyes, stand up or sit or roll should not be used in the assessment of comprehension in general, as these axial movements are supported by neural systems outside the language network and can be correctly performed by patients who otherwise have profound impairments of comprehension.
Repeated speech is evaluated by asking the patient to repeat words, short sentences or groups of words, such as "without," "if," "and" or "but." Repeated speech testing using words that are difficult to pronounce, such as "hypopotamus" or "alien" provides a better assessment of dysarthria than aphasia.
Aphasic patients may have little difficulty repeating words that are difficult to pronounce, but it is most difficult for them to repeat a functional group of words. It is important to ensure that these words do not exceed the patient's ability to concentrate. Thus, the failure of repetition reflects the narrowing of the ability to concentrate and not an aphasic deficit.
Reading should be evaluated for the deficit of reading aloud and for understanding. Writing evaluates spelling errors, word order, and grammar. Alexia refers to the inability to read aloud or to understand separate words or simple sentences, the spelling (or disgraphy) is the term that describes a deficiency acquired in spelling or grammar written language.
Each sector of the language network participates in several language functions, but also presents localized specializations. For example, the Wernicke area occupies the lexical-semantic pole of the language network, while the Broca area occupies the syntactic pole. This type of organization allows the classification of aphasia into specific clinical syndromes and helps to determine the most likely anatomical localization of the underlying neurological disease. It also has implications in etiology and prognosis.
Note that pure syndromes occur very rarely, the most common forms being those combined. The correspondence between the individual deficits of the language function and the location of the lesion does not consist of a rigid relationship and should be viewed in the context of the network model.
Taking these considerations into account, aphasic syndromes can be classified as "central", caused by lesions in the two centers of the language network (Wernicke and Broca areas) and "disconnection", which occur through lesions that interrupt the connections of these centers between them and the other components of the network.
We'll continue tomorrow!
A day of the best!
Dorin, Merticaru