A 56-year-old man who is hospitalized for viral encephalitis develops pill-rolling tremors of the hands and cogwheel rigidity. He is thought to have parkinsonian symptoms that developed because of an underlying secondary cause. Which of the following is the most likely etiology of this condition?

Correct Answer: C

Rationale: In this scenario, the most likely etiology of the parkinsonian symptoms in the 56-year-old man with viral encephalitis is option C: Viral encephalitis. Viral encephalitis can lead to the development of parkinsonian symptoms due to the inflammation and damage caused to the basal ganglia by the viral infection. This can result in pill-rolling tremors of the hands and cogwheel rigidity, as seen in Parkinson's disease. Option A, Carotid arterial atherosclerosis, is not typically associated with the development of parkinsonian symptoms. Option B, Large brain aneurysm, would more likely present with symptoms related to increased intracranial pressure rather than parkinsonian features. Option D, Use of cocaine, can cause movement disorders but is less likely to be the cause in this patient with a clear history of viral encephalitis. Understanding the etiology of parkinsonian symptoms in this context is crucial for healthcare providers to make accurate diagnoses and provide appropriate treatment for patients presenting with similar symptoms following viral encephalitis.

Correct Answer: B

Rationale: In this scenario, the most appropriate treatment for the 18-year-old woman with obsessive thoughts and compulsive behaviors is Clomipramine (option B). Clomipramine is a tricyclic antidepressant that is effective in treating obsessive-compulsive disorder (OCD), which is characterized by intrusive thoughts and repetitive behaviors like checking locks excessively. Amitriptyline (option A) is also a tricyclic antidepressant but is not the first-line treatment for OCD. Lithium (option C) is primarily used in mood disorders like bipolar disorder and has limited efficacy in treating OCD. Quetiapine (option D) is an atypical antipsychotic that may be used as an augmenting agent in OCD treatment resistant to other medications, but it is not the initial choice for this condition. Educationally, understanding the rationale behind selecting the appropriate medication for specific mental health conditions is crucial for healthcare professionals. Knowing the mechanisms of action, side effects, and efficacy of different drug classes in treating OCD helps tailor treatment plans to individual patients, improving outcomes and quality of life. It is important to consider patient history, previous treatment responses, and potential side effects when selecting pharmacological interventions for mental health disorders.

Correct Answer: D

Rationale: The correct answer for this question is D) Unknown. Vagal nerve stimulation (VNS) is a treatment option for patients with refractory epilepsy, particularly when other medications have failed. The exact mechanism of action of VNS in treating seizures is not fully understood. Educationally, this question highlights the complexity of pharmacological interventions in the central nervous system (CNS) and the limitations of our current understanding of certain therapies. It emphasizes the importance of exploring alternative treatments in cases of refractory epilepsy and the need for further research to elucidate the mechanisms behind VNS efficacy. Now, let's examine why the other options are incorrect: A) Blockade of potassium channels: While some antiseizure medications work by modulating potassium channels, VNS does not primarily function in this manner. B) Blockade of sodium channels: This is a common mechanism of action for many antiseizure medications, but it is not the main mechanism of VNS. C) Depolarization of neuronal circuits: While VNS may influence neuronal activity, it is not primarily through direct depolarization of circuits. In conclusion, understanding the mechanisms of action of different treatment modalities in CNS disorders like epilepsy is crucial for healthcare professionals to provide optimal care for patients with refractory conditions.

Correct Answer: A

Rationale: Morphine affects the gastrointestinal tract (GIT) via mu-opioid receptors. Decreased gastric motility slows emptying, contributing to nausea and constipation. Decreased biliary, pancreatic, and intestinal secretions result from opioid-induced smooth muscle relaxation and reduced exocrine activity. Increased intrabiliary pressure stems from sphincter of Oddi constriction, potentially causing biliary colic. However, morphine decreases, not increases, propulsive peristaltic waves in the colon (choice A), leading to constipation by enhancing non-propulsive contractions and reducing motility. This mischaracterization makes it the exception. Recognizing these effects is critical for managing opioid side effects, particularly constipation, a common patient complaint requiring adjunctive therapy.

Correct Answer: A

Rationale: Loperamide (choice A), a mu-opioid agonist, acts peripherally on GIT receptors, reducing motility and treating diarrhea without significant CNS effects due to poor blood-brain barrier penetration. Pentazocine (choice B), a mixed agonist-antagonist, and Heroin (choice C), a full agonist, primarily affect the CNS, not selectively the GIT. Neostigmine (choice D), a cholinesterase inhibitor, increases motility, opposing morphine's effect. Loperamide's selective GIT action makes it ideal for diarrhea, distinguishing it from systemic opioids.