1.
A 68~year-old woman is brought to the emergency department by her godson. He explains that she unexpectedly began to have sudden movements of her left arm. The examination reveals a slender woman with hypertension and periodic, uncontrollable flailing movements of her left upper extremity suggestive of hemiballismus. Assuming this resulted from vascular occlusion, MRI would most likely show an infarction in which of the following structures?
Correct Answer
E. Right subthalamic nucleus
Explanation
The correct answer is Right subthalamic nucleus. Hemiballismus is a movement disorder characterized by sudden, involuntary, and violent flinging movements of one side of the body. It is commonly caused by a lesion in the contralateral subthalamic nucleus. In this case, the patient's left upper extremity is affected, indicating that the lesion is likely on the right side. Therefore, an MRI would most likely show an infarction in the Right subthalamic nucleus.
2.
Which of the following is the prominent population of melanin-containing cells located immediately internal to the crus cerebri?
Correct Answer
E. Substantia nigra
Explanation
The substantia nigra is the prominent population of melanin-containing cells located immediately internal to the crus cerebri. It is a region of the midbrain that is involved in the production of dopamine, a neurotransmitter that plays a crucial role in movement control. The melanin-containing cells in the substantia nigra give it a dark color, hence the name "substantia nigra," which means "black substance" in Latin.
3.
An 83-year-old man is brought to the emergency department by his daughter, who explains that her father started having "fits." The examination reveals an alert, otherwise healthy, man, who frequently has uncontrollable flailing movements of his left arm. Which of the following structures is most likely involved in this lesion?
Correct Answer
C. Subthalamic nucleus
Explanation
The given correct answer is the Subthalamic nucleus. The patient's symptoms of uncontrollable flailing movements of his left arm suggest a lesion in the Subthalamic nucleus. The Subthalamic nucleus is involved in the regulation of movement and lesions in this area can lead to abnormal movements such as hemiballismus, which is characterized by involuntary flailing movements of one side of the body. The other options listed do not play a significant role in movement regulation or are not associated with the specific symptoms described.
4.
A 64-year-old man is brought to a rural health clinic by a neighbor. The history reveals that the man is a recluse, lives by himself, and does not regularly visit a physician. The examination reveals that the man has difficulty walking, chorea, and dystonia, and is suffering from dementia. The neighbor believes that the man's father died from a similar disease. A tentative diagnosis of Huntington's disease is made. Absence of which of the following structures in an MRI of this man would be consistent with this diagnosis?
Correct Answer
B. Head of the caudate
Explanation
The absence of the head of the caudate in an MRI of this man would be consistent with a diagnosis of Huntington's disease. Huntington's disease is a neurodegenerative disorder characterized by movement abnormalities, cognitive decline, and psychiatric symptoms. The head of the caudate is one of the areas of the brain that is most affected by the disease, leading to the motor and cognitive symptoms observed in this patient.
5.
A 59-year-old man, who is a family physician, confides in a neurology colleague that he believes he has early-stage Parkinson's disease. The neurological examination reveals a slight resting tremor of the left hand, slow gait, and lack of the normal range of facial expression. Which of the following is the most likely location of the degenerative changes at this stage of the physician's disease?
Correct Answer
E. Right substantia nigra
Explanation
The correct answer is Right substantia nigra. Parkinson's disease is characterized by degenerative changes in the substantia nigra, a region of the brain that produces dopamine. The symptoms described in the question, such as resting tremor and slow gait, are consistent with Parkinson's disease. The fact that the symptoms are predominantly on the left side of the body suggests that the degenerative changes are more advanced on the right side of the brain, affecting the right substantia nigra.
6.
A 58-year-old left-handed man is referred to a neurologist for "involuntary left-hand twitches". Between six months and a year ago he noticed that when his left hand was resting it would shake. He can stop the shaking by looking at his hand and concentrating. There is no tremor in his right hand and his lower extremities are not affected. He has had no trouble walking. There is no behavioral or language change. He has bilateral cogwheel rigidity.
(i) What is the most likely diagnosis for this patient?
Correct Answer
D. Parkinson's disease
Explanation
The most likely diagnosis for this patient is Parkinson's disease. This is indicated by the presence of involuntary left-hand twitches, which are a common symptom of Parkinson's. The fact that the shaking can be stopped by looking at the hand and concentrating is also characteristic of Parkinson's disease. Additionally, the absence of tremor in the right hand and unaffected lower extremities further supports this diagnosis. The presence of bilateral cogwheel rigidity is another common feature of Parkinson's disease.
7.
A 58-year-old left-handed man is referred to a neurologist for "involuntary left-hand twitches". Between six months and a year ago he noticed that when his left hand was resting it would shake. He can stop the shaking by looking at his hand and concentrating. There is no tremor in his right hand and his lower extremities are not affected. He has had no trouble walking. There is no behavioral or language change. He has bilateral cogwheel rigidity.
(ii) What is the most appropriate pharmacotherapy for his condition?
Correct Answer
C. Levodopa/carbidopa
Explanation
The most appropriate pharmacotherapy for the patient's condition is levodopa/carbidopa. This is because the patient is presenting with involuntary left-hand twitches, which could be indicative of Parkinson's disease. Levodopa is a precursor to dopamine and helps to replenish dopamine levels in the brain, while carbidopa helps to prevent the breakdown of levodopa before it reaches the brain. This combination is commonly used to manage the symptoms of Parkinson's disease, including tremors and rigidity.
8.
A 58-year-old left handed man is referred to a neurologist for "involuntary left-hand twitches". Between six months and a year ago he noticed that when his left hand was resting it would shake. He can stop the shaking by looking at his hand and concentrating. There is no tremor in his right hand and his lower extremities are not affected. He has had no trouble walking. There is no behavioral or language change. He has bilateral cogwheel rigidity.
(iii) The patient is also given tolcapone to supplement L-dopa/carbidopa therapy. What is the mechanism of action of tolcapone?
Correct Answer
E. It is a COMT inhibitor, it maximizes the uptake of L-dopa into the brain
Explanation
Tolcapone is a COMT inhibitor, which means it inhibits the enzyme catechol-O-methyltransferase (COMT). This enzyme is responsible for breaking down dopamine in the brain. By inhibiting COMT, tolcapone increases the levels of dopamine in the brain, specifically in the caudate/putamen region. This helps to maximize the uptake of L-dopa (a precursor to dopamine) into the brain, leading to better control of symptoms such as tremors. Therefore, tolcapone is used as a supplement to L-dopa/carbidopa therapy in order to enhance its effectiveness in treating Parkinson's disease symptoms.
9.
A 58-year-old left handed man is referred to a neurologist for "involuntary left-hand twitches". Between six months and a year ago he noticed that when his left hand was resting it would shake. He can stop the shaking by looking at his hand and concentrating. There is no tremor in his right hand and his lower extremities are not affected. He has had no trouble walking. There is no behavioral or language change. He has bilateral cogwheel rigidity.
(iv) Which agent has produced a syndrome similar to the one seen in this patient?
Correct Answer
D. MPTP (1-methyl-4-pHenyl-l,2,3,6-tetrahydropyridine)
Explanation
MPTP is the correct answer because it is known to produce a syndrome similar to the one seen in this patient. MPTP is a compound that can cause parkinsonism in humans and animals. It is selectively toxic to the substantia nigra, which is the area of the brain that is affected in Parkinson's disease. Symptoms of MPTP-induced parkinsonism include resting tremor, rigidity, and a lack of involvement of the lower extremities. This matches the symptoms described in the patient, making MPTP the most likely agent responsible for his condition.
10.
A 58-year-old left-handed man is referred to a neurologist for "involuntary left-hand twitches". Between six months and a year ago he noticed that when his left hand was resting it would shake. He can stop the shaking by looking at his hand and concentrating. There is no tremor in his right hand and his lower extremities are not affected. He has had no trouble walking. There is no behavioral or language change. He has bilateral cogwheel rigidity.
(v) Which enzyme is normally present in the neurons whose degeneration leads to the patient's disorder?
Correct Answer
A. COMT (Catechol-O-methyltransfe rase)
Explanation
The correct answer is COMT (Catechol-O-methyltransferase). This is because the patient's symptoms, such as involuntary left-hand twitches and cogwheel rigidity, are consistent with Parkinson's disease. In Parkinson's disease, there is degeneration of dopaminergic neurons in the substantia nigra, which leads to a decrease in dopamine levels. COMT is an enzyme that metabolizes dopamine, and its activity is increased in Parkinson's disease. Therefore, the degeneration of dopaminergic neurons in this patient's disorder is likely due to the activity of COMT.
11.
Group A monkeys were given MPTP (1-methyl-4-phenyl-l,2,3,6-tetrahydropyridine) and developed akinesia, rigidity, and tremor which were irreversible. Group B monkeys were treated with a drug prior to being given the neurotoxin and the second group failed to develop Parkinsonian symptoms. Which one of the following drugs were given to group B monkeys?
Correct Answer
C. A monoamine oxidase B inhibitor
Explanation
Group B monkeys were treated with a monoamine oxidase B (MAO-B) inhibitor prior to being given the neurotoxin. This drug prevented the development of Parkinsonian symptoms in this group. MAO-B inhibitors work by blocking the enzyme monoamine oxidase B, which is responsible for breaking down dopamine in the brain. By inhibiting this enzyme, the MAO-B inhibitor increases dopamine levels in the brain, which helps to protect against the neurotoxic effects of MPTP and prevents the development of Parkinsonian symptoms.
12.
A patient presented with, a severe tremor, bradykinesia and rigidity, and progressive cognitive decline. He was diagnosed with a neurodegenerative disorder and his dyskinetic symptoms were treated with L-dopa/carbidopa. A CT scan showed pigmented cell loss in the substantia nigra. Which neurotransmitter is primarily involved in this disorder?
Correct Answer
E. Dopamine
Explanation
The patient's symptoms of severe tremor, bradykinesia, rigidity, and cognitive decline are consistent with Parkinson's disease, a neurodegenerative disorder. Parkinson's disease is characterized by the loss of dopamine-producing cells in the substantia nigra of the brain. Dopamine is the primary neurotransmitter involved in this disorder, as its deficiency leads to the motor and cognitive symptoms observed in the patient. The treatment with L-dopa/carbidopa aims to replenish dopamine levels in the brain and alleviate the dyskinetic symptoms.