Question
A 67-year-old man is brought to the physician by his daughter because he frequently misplaces his personal belongings and becomes easily confused. His daughter mentions that his symptoms have progressively worsened for the past one year. On mental status examination, he is oriented to person, place, and time. He vividly recalls memories from his childhood but can only recall one of three objects presented to him after 5 minutes. His affect is normal. This patient’s symptoms are most likely caused by damage to which of the following?
| A. |
Amygdala
|
| B. |
Ventral posterolateral nucleus
|
| C. |
Nucleus accumbens
|
| D. |
Hippocampus
|
Show Answer
|
Correct Answer � D
Explanation
|
|
Answer D) HippocampusShort-term memory loss is often the earliest sign of Alzheimer disease, the most common cause of progressive dementia in the United States.
Hippocampus
Amygdala
-
The amygdala is a structure of the limbic system that plays a role in the processing of emotions.
-
Involvement of the amygdala in Alzheimer disease causes emotional lability, depression, and/or anhedonia.
-
Damage to a different structure would more likely explain the short-term memory loss in this patient with a normal affect.
-
Bilateral damage to the amygdala results in Klüver-Bucy syndrome, which is characterized by emotional lability, anxiety, hypersexuality, hyperorality, and hyperphagia.
Ventral posterolateral nucleus
-
The ventral posterolateral nucleus is a structure of the thalamus involved in relaying sensory input from the spinothalamic tract and dorsal column to the primary somatosensory cortex.
-
This nucleus does not play a role in memory formation and is not affected in early Alzheimer disease.
-
The medial dorsal nucleus of the thalamus and the anterior thalamic nucleus are involved in memory formation.
Nucleus accumbens
-
The nucleus accumbens is a basal forebrain structure that has a role in the reward pathway. This structure does not play a major role in semantic (factual) recall.
-
Degeneration of other basal forebrain structures such as the nucleus basalis of Meynert can cause memory loss and cognitive decline in Alzheimer disease.
-
Decreased GABA secretion by the nucleus accumbens is seen in Huntington disease and anxiety disorders.
