Home
Overview
|
|
General Principles.
Cognitive impairment can be broken down into deficits in attention, orientation, memory, intelligence, and higher executive functions. The pattern of deficits is affected by whether the pathology is acute or chronic and whether it is diffuse or focal .
In assessing a patient where an organic psychiatric disorder is suspected a standard assessment of mental state should be carried out and in addition greater attention paid cognitive function testing and other specific details.
Acute v's Chronic:
Acute |
Chronic |
|
Example |
Acute confusional state secondary to drug intoxication, cerebral anoxia, liver failure etc. | The dementias e.g. Senile Dementia of the Alzheimer's Type. |
Onset |
Rapid | Insidious |
Course |
Usually short lived, fluctuating picture | Chronic, progressive course |
Consciousness |
Impaired | Clear |
Perception |
Usually altered causing misperception or hallucinations | Hallucinations may occur in the later stages |
Sleep |
Sleep-wake cycle often disturbed | Sleep-wake cycle usually intact |
Memory & Orientation |
Impaired | Impaired |
A brain suffering an acute insult is likely to show signs of impaired consciousness. The degree of impairment varies from slight problems with concentration and attention to coma.
Focal v's Diffuse:
Organic mental states are caused by both focal pathology (e.g. tumour, stroke) and diffuse pathological conditions (e.g. Senile dementia of the Alzheimer's type, generalised cerebral anoxia etc.). However focal lesions may cause general cerebral dysfunction and hence cause global cognitive impairment, as may systemic disease.
There is considerable localisation of brain function. Hence a discrete lesion confined to the posterior part of the inferior frontal gyrus on the dominant lobe (Broca’s area) will cause an expressive dysphasia, and a lesion confined to the posterior part of the superior temporal gyrus (Wernicke's area) causes a receptive dysphasia. When widespread cortical neurodegeneration occurs, as is the case in dementia, these brain areas are frequently affected as well and language functions are often impaired. Language deficits occurring in dementia are quite variable and various combinations of expressive and receptive deficits may occur.
This work is licenced under a Creative Commons Licence.