1.
An 83-year-old man is brought to the emergency department by his daughter, who explains that her father started having "fits." The examination reveaIs 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 patient's symptoms of uncontrollable flailing movements of his left arm suggest a lesion in the subthalamic nucleus. The subthalamic nucleus is part of the basal ganglia circuitry and plays a role in motor control. Lesions in this area can result in hyperkinetic movements, such as the flailing movements seen in this patient. The other structures listed, such as the cerebellar cortex plus nuclei, lenticular nucleus, ventral lateral nucleus, and ventral posterolateral nucleus, are not typically associated with these specific symptoms.
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 correct answer because it is a prominent population of melanin-containing cells located immediately internal to the crus cerebri. It is part of the basal ganglia and is involved in the regulation of movement and reward. The locus ceruleus is located in the pons and is involved in the regulation of arousal and stress responses. The pontine nuclei are also located in the pons and are involved in motor coordination. The red nucleus is located in the midbrain and is involved in motor control. The reticular formation is a network of neurons located throughout the brainstem and is involved in various functions including sleep, arousal, and attention.
3.
A 68~year-old woman is brought to the emergency department by her godson. He explains that she unexpectedIy began to have sudden movements of her left arm. /I 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 a vascular occlusion, MRI would most likely show an infarction in which of the following structures?
Correct Answer
E. Right subthalamic nucleus
Explanation
The patient's symptoms of sudden, uncontrollable movements of her left arm suggest hemiballismus. Hemiballismus is typically caused by a lesion in the contralateral subthalamic nucleus. Since the symptoms are on the left side, the lesion is most likely on the right side. Therefore, MRI would most likely show an infarction in the right subthalamic nucleus.
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 fromdementia. The neighbor believes that the man's father died from a simi lar 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
Huntington's disease is a neurodegenerative disorder characterized by movement abnormalities, cognitive decline, and psychiatric symptoms. It is caused by a genetic mutation that leads to degeneration of the basal ganglia, particularly the caudate nucleus. The absence of the head of the caudate in an MRI would be consistent with the diagnosis of Huntington's disease.
5.
A 59-year-old man, who is a family physician, confides in a neurology colleague that he believes he has early-stage Parkinson 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 most likely location of the degenerative changes at this stage of the physician's disease is the right substantia nigra. This is because Parkinson's disease is characterized by the degeneration of dopaminergic neurons in the substantia nigra, which leads to a decrease in dopamine levels. The symptoms described, such as the resting tremor, slow gait, and lack of facial expression, are consistent with the motor symptoms associated with Parkinson's disease. The fact that the tremor is present in the left hand suggests that the degenerative changes have already affected the contralateral side of the brain, which is why the right substantia nigra is the most likely location.
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. The patient's symptoms of involuntary left-hand twitches, resting hand tremor, and the ability to stop the shaking by looking at his hand and concentrating are characteristic of Parkinson's disease. Additionally, the absence of tremor in the right hand and unaffected lower extremities further support this diagnosis. The presence of bilateral cogwheel rigidity is also consistent with Parkinson's disease, as rigidity is a common symptom of the condition.
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 this patient's condition is levodopa/carbidopa. This patient's symptoms of involuntary left-hand twitches, resting hand tremor, and the ability to stop the shaking by looking at his hand and concentrating are consistent with Parkinson's disease. The bilateral cogwheel rigidity further supports this diagnosis. Levodopa/carbidopa is the mainstay treatment for Parkinson's disease as it helps to replenish dopamine levels in the brain and improve motor symptoms. Alteplase is a thrombolytic agent used for treating acute ischemic stroke, carbamazepine is an antiepileptic drug, glatiramer and interferon beta-l alpha are used for multiple sclerosis, and sertraline is an antidepressant.
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 catechol-O-methyltransferase (COMT) inhibitor. COMT is an enzyme that breaks down dopamine in the brain. By inhibiting COMT, tolcapone increases the levels of dopamine in the brain, which can help improve symptoms of Parkinson's disease. This mechanism of action allows for better uptake of L-dopa into the brain, enhancing its therapeutic effects.
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 (1-methyl-4-phenyl-l,2,3,6-tetrahydropyridine) is the correct answer because it is known to produce a syndrome similar to the one seen in this patient. MPTP is a neurotoxin that selectively damages the substantia nigra, which is the part of the brain that is affected in Parkinson's disease. The symptoms described in the patient, such as involuntary left-hand twitches, resting hand tremors that can be stopped by looking at the hand and concentrating, and bilateral cogwheel rigidity, are characteristic of Parkinson's disease. MPTP is a known toxin that can cause Parkinsonism symptoms, making it the most likely agent responsible for the patient's 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 resting hand tremors, suggest a movement disorder. The presence of bilateral cogwheel rigidity also indicates a dysfunction in the basal ganglia, which is involved in motor control. COMT is an enzyme that metabolizes dopamine, and its degeneration can lead to an accumulation of dopamine in the brain, causing movement disorders like Parkinson's disease. Therefore, the degeneration of neurons containing COMT can explain the patient's disorder.
11.
Group A monkeys were given MPTP (1-methyl-4-phenyl-l,2,3,6-tetrahydropyridine) and developed akinesia, rigidity, and a 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 was given to group B monkeys?
Correct Answer
C. A monoamine oxidase B inhibitor
Explanation
The correct answer is a monoamine oxidase B inhibitor. This drug prevents the breakdown of dopamine by inhibiting the enzyme monoamine oxidase B, which is responsible for breaking down dopamine in the brain. By inhibiting this enzyme, the drug helps to maintain higher levels of dopamine in the brain, preventing the development of Parkinsonian symptoms in the monkeys.
12.
A patient presented with, a severe tremor, bradykinesia and rigidityI 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, along with the pigmented cell loss in the substantia nigra seen on the CT scan, suggest a diagnosis of Parkinson's disease. Parkinson's disease is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the substantia nigra. Dopamine is the primary neurotransmitter involved in this disorder, as its deficiency leads to the motor and cognitive symptoms observed in Parkinson's disease. Treatment with L-dopa/carbidopa aims to increase dopamine levels in the brain and alleviate the dyskinetic symptoms.