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Introduction
The cerebral hemispheres represent the highest and most complex level of
neurological function. There is so much integration of cortical function
that whatever system is used to clinically "examine" the cerebral hemispheres
will be an over simplification and somewhat artificial compartmentalization.
Although a lot of mental status reflects integration of cortical function,
it can still be divided into parts that correspond to the divisions of the
cerebral hemispheres. This anatomy review will be a brief overview of areas
of cortical function that can be examined by components of the mental status
exam.
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Frontal
Lobes
The frontal lobes are important for attention, executive function,
motivation, and behavior. Tests for frontal lobe function include working
memory (digit span, spelling backward), judgment, fund of knowledge, task
organization and set generation such as naming lists of things in a certain
category.
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Temporal
Lobes
The temporal lobes are important for emotional response (amygdala and its
connections to the hypothalamus and frontal lobes) and memory (hippocampus
and limbic connections). Clinically the main tests for temporal lobe function
are those of memory, particularly declarative memory.
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Language-
Temporal and Frontal Lobes
The principle area for receptive language is Wernicke's area, which
is located in the posterior part of the superior temporal gyrus of the dominant
temporal lobe. The major region for expressive language is Broca's area
located in posterior part of the inferior frontal gyrus of the dominant
hemisphere. Homologous regions of the non-dominant hemisphere are important
for the non-verbal contextual and emotional aspects as well as the prosody
(rhythm) of language. Tests for written and spoken receptive and expressive
language are used to "view" these language centers.
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Parietal
Lobes
The parietal lobes are important for perception and interpretation
of sensory information especially somatosensory information. The non-dominant
parietal lobe is particularly important for visual-spatial function. The
dominant parietal lobe is important for praxis, which is the formation
of the idea of a complex purposeful motor act while the frontal lobes are
important for the execution of the act. The Gerstmann syndrome, which
consists of the constellation of acalculia, finger agnosia, right-left confusion
and agraphia, occurs with damage to the dominant inferior parietal lobe.
Clinical tests for parietal lobe function include tests for agnosia
(such as inability to identify objects by tactile exploration), apraxia
(inability to perform purposeful motor acts on command), constructional
apraxia (inability to draw objects which require use of visual spatial
organization) and testing for elements of Gerstmann's syndrome.
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Occipital
Lobes
The occipital lobes are important for perception of visual information.
Areas in the inferior temporal visual association cortex are important for
recognition of color and shape as well as the recognition of faces. Projections
from the occipital lobe to the superior temporal-parietal area are important
for perceiving motion of objects. Tests that are used to examine the occipital
lobes and its connections include visual fields (see Cranial Nerve 2), naming
of objects, naming of colors and recognition of faces.
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Traps
- There is more
variability to the expression of lesions of the cerebral cortex than
of structures more caudal in the neuroaxis.
- Time of day, stress,
fatigue, and pain can affect a patient's performance on the mental status
exam.
- You need to consider
the patient's social and educational background when evaluating the
results of the mental status exam.
Video is sound only.
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Pearls
- The mental status
exam begins with listening and watching the patient during the history
part of the examination.
- The patient must
be awake and alert in order to have a "window" to view the cortex. So
assessment of the level of alertness and the intactness of the reticular
activating system is actually the first step in the mental status assessment.
Video is sound only.
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