46

46 CASE 46


A 74-year-old woman is brought to her physician’s office by her daughter, who complains that her mother is behaving oddly.


The woman lives in a house in a small town and has lived alone for the 5 years since her husband died. She admits to forgetting about food while its cooking on the stove but says it is because she is so busy. The woman can remember events 20 years ago but has difficulty recalling recent events. She has begun to call her grandchildren by her children’s names. The patient is healthy and is not on any current medications.



PHYSICAL EXAMINATION



VS: T 37°C, P 72/min, R 15/min, BP 118/65 mm Hg, BMI 22

PE: No significant findings


LABORATORY STUDIES



CT: Significant atrophy of the parietal, temporal, and frontal lobes of the cerebral cortex and degeneration of the cingulate gyrus (Fig. 46-1)

image

FIGURE 46–1 Axial (horizontal) CT section through the temporal lobes. A, Normal. B, Alzheimer’s disease.


(Courtesy of James King-Holmes and Science Photo Library.)



DIAGNOSIS


Alzheimer’s disease



PATHOPHYSIOLOGY OF KEY SYMPTOMS


The patient’s presenting symptoms indicate a gradual cognitive decline. Cognition requires interaction of numerous brain structures, and, consequently, cognitive decline is characteristic of a wide variety of diseases. Specific testing helps to identify potential pathologic processes underlying the cognitive decline.


Memory is the ability to retain and recall information. Physiologically, memories are stored in the brain by enhancing specific patterns of synaptic activity. Memories are stored throughout the cerebral cortex by these preferential neuronal activity patterns. At one extreme, short-term memory persists for only a few seconds and is likely due to synaptic facilitation. At the other extreme, long-term memory persists for years and involves remodeling of synapses as well as long-term potentiation and inhibition. The hippocampus of the limbic system is a key structure involved in the conversion of short-term memory to long-term memory.


Long-term memories can be characterized as either declarative or nondeclarative memory. Declarative memory is explicit and includes complex associations including the event, the surroundings, and the significance of the event. Declarative memory is frequently stored in the temporal lobes. In contrast, nondeclarative memory is associated with complex motor abilities, such as being able to eat with a fork, habits, or emotional responses. The components of nondeclarative memories can be stored throughout the brain, including the cerebellum, basal ganglia, or amygdala (Fig. 46-2).


image

FIGURE 46–2 Major categories of memory. Although the locations of all the altered synapses that underlie each is not known with certainty, the indicated anatomic structures are prominently involved in the synaptic alterations.

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Jul 4, 2016 | Posted by in PHYSIOLOGY | Comments Off on 46

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