50

CASE 50


A 68-year-old woman accompanied by her 40-year-old daughter appeared in your office. The daughter was concerned about her mother’s mental condition. She said her mother was experiencing difficulty learning new information and was forgetting recent events. The daughter also said her mother had recently gotten lost driving to her house. When the physician asked if anyone else in the family ever had these symptoms, the mother responded with verbal hesitancy that her father had Alzheimer’s disease. An MRI study of the brain supported the diagnosis of Alzheimer’s disease. The patient was treated with the acetylcholinesterase inhibitor, donepezil.



ALZHEIMER’S DISEASE IS ASSOCIATED WITH A DECREASE IN CHOLINERGIC INPUT TO THE CEREBRAL CORTEX. WHAT NUCLEUS OF THE BRAIN CONTAINS THESE CEREBRAL CORTEX-PROTECTING, CHOLINERGIC NEURONS THAT DEGENERATE IN ALZHEIMER’S?


The large, basophilic cell bodies of these cholinergic neurons reside in the basal nucleus (of Meynert) located in the substantia innominata (substance with no name). The substantia innominata occupies the basal forebrain under the anterior commissure. The therapeutic purpose of an acetylcholinesterase inhibitor is to prolong the action of a limited number of acetylcholine molecules by hindering their enzymatic degradation.



ALZHEIMER’S DISEASE IS ALSO ASSOCIATED WITH A LOSS OF NEURONS IN TWO REGIONS OF THE BRAIN INVOLVED IN THE FORMATION OF NEW MEMORIES AND LEARNING. WHAT ARE THESE REGIONS AND WHAT ARE THE CLASSIC MICROSCOPIC ABNORMALITIES THAT ARE OBSERVED IN THESE AREAS?


Neuronal loss is evident in two regions of the temporal lobe of the cerebral cortex involved in the formation of new memories and learning:


• Hippocampal formation

• Parahippocampal gyrus

As the disease progresses, neuronal loss becomes evident in other areas of the cerebral cortex. Cortical atrophy is pronounced in the:


• Frontal lobes

• Temporal lobe

• Parietal lobes.

This global decrease in neurons results in gross pathologic changes, such as cerebral atrophy, widening of the sulci, and dilatation of the ventricles (Fig. 7-1).


image

FIGURE 7-1 Alzheimer brain demonstrating cortical atrophy with widening of the sulci. This is best seen on the right where the meninges have been removed.


(Kumar V, Abbas A and Fausto N: Robbins & Cotran Pathologic Basis of Disease, 7e. WB Saunders, 2004. Fig. 28-34. Courtesy of Dr. E.P. Richardson, Jr., Massachusetts General Hospital, Boston, MA.)


Several derangements in microscopic structure are observed in Alzheimer brains:


• Neuritic plaques

• Neurofibrillary tangles

• Amyloid angiopathy

• Granulovacuolar degeneration.

The two pathologically classic abnormalities are neuritic plaques and neurofibrillary tangles. Neuritic plaques are focal aggregations of argyrophilic (silver-loving) dystrophic neurites (dystrophic neurites are thickened or irregular processes of neurons) surrounding a central core of amyloid (Fig. 7-2A, B

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Jun 16, 2016 | Posted by in ANATOMY | Comments Off on 50

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