15.11. Syndromes of Calculating Impairment
Aphasic Acalculia
The patient is not able to utilize numbers as a language entity. The patient cannot comprehend or write numbers correctly or substitute one number for another. Aphasic acalculia is seen in most aphasics and follows damage to the dominant hemisphere.
Visual Spatial Acalculia
The patient can compute, understands numbers and computational signs but is unable to place numbers in the correct position in space. Thus, he cannot align numbers in columns or place decimal points which interferes with complex calculations although he can manipulate individual mathematical functions. The lesion affects the non-dominant hemisphere at the parietoccipital junction.
Anarithmia
These patients are not able to manipulate numbers or compute. They can recognize and reproduce individual numbers, understand their value but cannot compute. This defect is noted from dominant posterior parietal lesions.
Apraxias
Apraxias are the inability to perform an individual or sequential function with intact motor, sensory and coordinative abilities. Different areas of the brain are specific for specific forms of apraxia.
Specific Apraxia by Anatomical Site
- Oral-buccal-lingual apraxia (insular cortex; if bilateral Foix–Chavany–Marie Syndrome)
- Ideomotor: inferior parietal; lobes, SMA, premotor cortex (L>R)
- Limb kinetic (same as ideomotor apraxia)
- Dressing apraxia (right parietal lobe)
- Constructional (right frontal, right parietal lobes)
- Eyelid opening (frontal lobe; 2nd frontal gyrus)
- Ideational (left posterior parietal area 5 and 7)
- Sympathetic apraxia (corpus callosum, left and right prefrontal cortex)
- Gait apraxia (leg fibers around the lateral ventricles, paracentral lobule)
- Conceptual apraxia:
- Associative knowledge (tool action)-frontal lobe
- Mechanical knowledge advantage tools offer (frontal lobe)
Oral Motor Apraxia
- Landau–Kleffner seizure disorder
- Benign rolandic epilepsy
- Anterior perisylvian
- Foix–Chavany–Marie syndrome:
- Bilateral insular cortical lesions
The cardinal features of oral-buccal-lingual apraxias are the loss of the patient's voluntary ability to utilize muscles of mastication, swallowing and speech. Those muscles innervated by the first four branchial arches. The patients have difficulty with speech, swallowing, chewing and pursing of the lips. Patients are not able to touch their upper lip with the tongue on command. Coughing, sneezing and involuntary movements are preserved.
Limb kinetic and ideomotor apraxia refers to the inability of a patient to carry out a single purposeful movement such as a salute or the demonstration of how to turn a key in a lock or how to comb ones' hair on command. The patient may perform the task slightly more competently with the appropriate object. Lesions that cause ideomotor apraxia are primarily seen in BA 6 of the premotor area and BA 6 of the supplementary motor cortex. [An anterior alien hand syndrome may be seen with this lesion (BA 6). Ideomotor apraxia may occur with conductive aphasia.]
Ideational Apraxia
The patient is unable to correctly carry out the correct sequence of a common task although each separate part can be successfully performed. The patient would be unable to demonstrate how he would smoke a cigarette even when given the cigarette. He would be expected to show how the cigarette is removed from the package, inserted into the mouth and lit. Lesions causing ideational apraxia are noted primarily in the left posterior parietal BA 5 and BA 7. Patients may be unable to start the sequence or abandon it in the middle. A posterior alien hand syndrome may be seen with lesions in this area. Patients may have an inability to handle real objects even though they can mimic the use of the object.
Constructional apraxia is impairment in the ability to construct the copy of a visually presented object with blocks or by drawing. Patients must be able to perceive the elements of the object, their spatial relationships and possess the motor ability to perform the task. Both left and right parietal lesions can cause a defect in constructional praxis. Right parietal lesions are more commonly associated with constructional apraxia than left sided lesions. The deficit is more severe and is often associated with a neglect of the left side of the object being copied. Patients with left parietal lesions and constructional apraxia frequently suffer a concomitant fluent aphasia. A deficit in constructional ability is hard evidence of a parietal deficit.
Dressing Apraxia
Patients with dressing apraxia are not able to dress themselves properly even when they are given the specific garment. This apraxia is most often noted in patients with right occipitoparietal or bilateral occipitoparietal lesions. Dressing apraxia is rarely if ever noted in isolation. It may be seen in demented or confused patients as well as those with left sided neglect or Balint's Syndrome.
Callosal Apraxia
Callosal apraxia and sympathetic apraxia are the inability to form a simple command with the left hand although the right hand performs it easily.
Gait Apraxia
Patients that suffer gait apraxia have normal pressure hydrocephalus or various lesions that may interfere with the pedunculopontine nucleus or other locomotor centers. Patients have difficulty in initiating the swing component of gait, walk as if they are on eggs or have a foot grasp of the floor. Basal ganglia disease and severe lacunar strokes that affect the descending corticospinal system should be considered in this differential diagnosis.
Movement and Task Specific Praxis
Conceptual praxis refers to the associative knowledge of tool action while mechanical knowledge refers to the advantage tools offer. Frontal lobe degeneration is associated with this conceptual praxis.
Eyelid opening praxis is seen with superior frontal gyrus deterioration. Patients are unable to open their eyelids to command. This apraxia may be seen in isolation or in conjunction with other neurological features of neurodegenerative diseases.
Prosody refers to the rhythm of speech and the modulation of emotional tone to the content of speech. Timbre is the modulation of tone in accordance with the rhythm and content of speech.
Prosody
Prosodic features of language are a graded phenomenon which adds complexity and richness to language.
Kinesics is the study of limb body and facial movements associated with nonverbal communication. Movements used for semantic or referential purposes are pantomime whereas movements used to modify, emphasize or embellish are gestures. Movements frequently are a blend of referential, emotional and attitudinal content. Disorders of pantomime (referential deficit) are caused by left hemisphere damage associated with aphasia. Gestured kinesics is often spared in aphasic patients.
The right hemisphere is dominant for the affective prosodic components of language and gestural behavior. It is organized similarly to that of propositional language of the left hemisphere (i.e. expression is anterior and decoding of gestures and affect is posterior). The linguistic components of prosody may be altered by either right or left hemisphere lesions but affective or attitudinal components are disrupted primarily by damage to the right hemisphere. Lesions bordering the right Sylvian fissure cause defects of affective language known as aprosodias which may be encoding or decoding in type.
Motor Aprosodia
These patients have a right hemisphere and variable left hemisensory deficit. The responsible lesion is in the right frontal and anterior parietal opercula. Many of these patients have transient anosognosia and dysarthria. It may be observed with subcortical and internal capsular lesions. They have a flat monotone speech, no spontaneous gesturing, poor repetition of emotional state but intact comprehension of affective prosody and emotional gesturing. Under extreme emotional stress, these patients demonstrate emotion.
Sensory Aprosodia
These patients have excellent affective prosody in speech with spontaneous gesturing. They lack auditory comprehension of affective (crying or coughing) prosody, visual comprehension of emotional gesturing and repetition of affective prosody. A left cortical sensory loss and left homonymous hemianopsia may be present. The causative lesion is in the right posterior temporal and posterior parietal opercula. Patients may appear inappropriately euphoric.
Global Aprosodia
These patients have suffered a large right frontal, parietal, temporal lesion or a deep right intracerebral hemorrhage. They demonstrate a dense left hemiparesis, hemisensory deficit and homonymous hemianopsia. They have a severe deficit of comprehension and repetition of affective prosody and visual comprehension of emotional gesturing.
Transcortical motor, sensory, and mixed aprosodies are similar to their left hemisphere phonological aphasic counterparts. Transcortical motor aprosopic patients have aprosopic gestalt monotone speech with preserved repetition and comprehension of affective prosody and emotional gesturing. Transcortical sensory aprosody patients have spontaneous affective prosody, emotional gesturing with normal repetition but are unable to comprehend affective prosody. Patients with mixed transcortical aprosody have lesions that involve the right supra sylvian region and posterior temporal operculum.
The right hemisphere plays a dominant role in decoding and encoding affective expression as well as the interpretation of nonverbal and paralinguistic aspects of communication.
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