MENTAL STATUS EXAM:
ANATOMY
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.
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.
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.
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.
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.
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.
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.
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.