Neurocognitive And Developmental Disorders - USMLE Step 2

1. Which of the following is the most appropriate next step in management?
   Answer: Initiate a low-dose atypical antipsychotic When non-pharmacologic interventions fail to manage severe agitation or aggression in dementia and the patient poses a danger to self or others, a low-dose atypical antipsychotic (e.g., risperidone, olanzapine, quetiapine) may be indicated. Benzodiazepines like lorazepam should generally be avoided due to the risk of falls, paradoxical disinhibition, and worsening confusion. Restraints are a last resort. Changing dementia medications is unlikely to address acute severe agitation.
2. What is the most likely diagnosis?
   Answer: HIV-associated neurocognitive disorder HIV-associated neurocognitive disorder (HAND) is a common complication in patients with advanced HIV/AIDS (typically CD4 < 200). It characteristically presents as a subcortical dementia with symptoms of apathy, executive dysfunction, and psychomotor slowing. Other opportunistic infections like PML, CNS lymphoma, and toxoplasmosis typically present more acutely with focal neurological deficits and show characteristic focal lesions on MRI.
3. To establish a diagnosis of attention-deficit/hyperactivity disorder, it is essential to confirm that the symptoms cause impairment in which of the following settings?
   Answer: At least two settings (e.g., home and school) A key diagnostic criterion for ADHD according to the DSM-5 is that several inattentive or hyperactive-impulsive symptoms must be present and cause impairment in two or more settings (e.g., at home, school, or work; with friends or relatives; in other activities). This requirement helps to distinguish the disorder from situational difficulties or behavior limited to a single context.
4. What is the most likely diagnosis?
   Answer: Dementia with Lewy bodies This patient's presentation includes the core features of dementia with Lewy bodies (LBD): fluctuating cognition, well-formed visual hallucinations, and parkinsonism. The presence of REM sleep behavior disorder (acting out dreams) is also highly suggestive. In LBD, cognitive decline begins before or within one year of the onset of motor symptoms. In Parkinson disease dementia, dementia develops more than one year after the diagnosis of Parkinson disease.
5. What is the most likely diagnosis?
   Answer: Alzheimer disease This patient presents with an insidious onset and gradual progression of cognitive decline, primarily affecting recent memory (amnestic presentation) and executive function. This clinical picture in an elderly individual is classic for Alzheimer disease, the most common cause of dementia. The absence of stepwise decline, parkinsonism, hallucinations, or prominent early personality changes makes other dementia subtypes less likely.
6. In addition to the neuroimaging findings, which of the following procedures is most useful for confirming the diagnosis?
   Answer: High-volume lumbar puncture The clinical triad of gait disturbance ('magnetic' gait), dementia, and urinary incontinence, along with ventriculomegaly on imaging, is classic for Normal Pressure Hydrocephalus (NPH). The most useful diagnostic procedure is a high-volume lumbar puncture (spinal tap), where removal of 30-50 mL of cerebrospinal fluid leads to a temporary improvement in gait, which supports the diagnosis and predicts response to ventriculoperitoneal shunting.
7. This clinical presentation is most characteristic of which of the following neurodegenerative syndromes?
   Answer: Primary progressive aphasia Primary progressive aphasia (PPA) is a clinical dementia syndrome characterized by the gradual and prominent decline in language abilities, while other cognitive domains like memory and executive function are relatively spared early in the disease course. PPA is considered a form of frontotemporal lobar degeneration. This contrasts with typical Alzheimer disease (early memory loss) and behavioral-variant FTD (early personality and behavioral changes).
8. Which of the following is the most appropriate first-line treatment for his ADHD?
   Answer: Atomoxetine In patients with ADHD and a co-occurring substance use disorder, particularly with a history of diversion, non-stimulant medications are preferred. Atomoxetine, a norepinephrine reuptake inhibitor, is an effective and FDA-approved non-stimulant treatment for ADHD and lacks abuse potential. Stimulants like amphetamine-dextroamphetamine would be a poor choice due to the high risk of abuse and diversion.
9. This patient's symptoms are most likely caused by degeneration of which of the following brain regions?
   Answer: Frontal and temporal lobes The clinical picture of early and prominent personality change (disinhibition), apathy, and altered food preferences with relatively preserved memory is characteristic of the behavioral variant of frontotemporal dementia (bvFTD). This condition is caused by focal neurodegeneration in the frontal and temporal lobes.
10. What is the most likely cause of this patient's cognitive complaints?
    Answer: Major depressive disorder This patient's cognitive symptoms are occurring in the context of classic neurovegetative symptoms of depression (anhedonia, low energy, poor sleep, weight loss) following a major life stressor. This presentation is consistent with cognitive impairment secondary to major depression (formerly 'pseudodementia'). The patient's significant distress about her deficits and giving 'I don't know' answers are also characteristic, contrasting with the frequent lack of insight in early Alzheimer disease.
11. What is the most likely diagnosis?
    Answer: Vascular dementia This patient's presentation is classic for vascular dementia. Key features include the presence of significant cardiovascular risk factors, a stepwise or fluctuating decline in cognitive function corresponding to new ischemic events, and the presence of focal neurologic deficits on examination. This is in contrast to the insidious, gradual decline seen in Alzheimer disease.
12. What is the most appropriate management recommendation?
    Answer: Administer the medication with or after a calorie-dense breakfast Decreased appetite and weight loss are common side effects of stimulant medications. Since the medication is effective, the first step is to implement behavioral strategies to mitigate the side effect. Giving the dose with or after a meal, especially a high-calorie breakfast, can help improve overall daily caloric intake. Discontinuing or switching an effective medication is not the first step. Adding another medication to treat a side effect is generally avoided if simpler strategies are available.
13. Which of the following is the most likely diagnosis?
    Answer: Creutzfeldt-Jakob disease The clinical presentation of a rapidly progressive dementia, myoclonus (involuntary jerky movements), and ataxia is highly suggestive of Creutzfeldt-Jakob disease (CJD), a prion disease. The MRI finding of cortical ribboning (hyperintensity in the cerebral cortex on DWI) is also a classic feature. Other dementias typically progress over years, not months.
14. Which of the following clinical features is most indicative of delirium rather than a primary psychotic disorder?
    Answer: Impaired attention The core feature that distinguishes delirium from most other psychiatric disorders, including primary psychosis, is a disturbance of attention and awareness. The inability to perform a task requiring sustained attention, such as reciting the months in reverse, is a classic sign of this deficit. While psychosis and disorientation can occur in both delirium and dementia or primary psychotic disorders, the prominent attentional deficit is a hallmark of delirium.
15. Which of the following is the most appropriate next step in management?
    Answer: Obtain urinalysis, CBC, and chest x-ray This patient has an acute change in mental status superimposed on her chronic dementia, which is highly suggestive of delirium. The most important initial step is to identify and treat the underlying medical cause. In elderly patients, infections such as urinary tract infections or pneumonia are common precipitants. Therefore, an infection workup including urinalysis, CBC, and chest x-ray is the most appropriate next step.
16. Which of the following is the most likely diagnosis?
    Answer: Autism spectrum disorder This child displays the core features of autism spectrum disorder (ASD): 1) persistent deficits in social communication and social interaction (impaired eye contact, lack of response to name, no pretend play), and 2) restricted, repetitive patterns of behavior, interests, or activities (spinning wheels, insistence on sameness). While he has developmental delay, the specific pattern of deficits points to ASD.
17. What is the most likely diagnosis?
    Answer: Language disorder This child's primary difficulty is in the acquisition and use of language. Importantly, she demonstrates intact social-emotional reciprocity (eye contact, shared interest, reciprocal smiling) and symbolic play, which are key domains that are impaired in autism spectrum disorder. Her deficits are confined to language, making a language disorder the most likely diagnosis. Global developmental delay or intellectual disability would involve delays in multiple developmental domains (e.g., motor, cognitive), which are not described.
18. Which of the following is the most appropriate medication to add to his current regimen?
    Answer: Memantine This patient has progressed from mild to moderate/severe Alzheimer disease. Memantine, an NMDA-receptor antagonist, is indicated for the treatment of moderate to severe Alzheimer disease. It is often added to a cholinesterase inhibitor (like donepezil) when the disease progresses. Adding another cholinesterase inhibitor (rivastigmine, galantamine) is not indicated. Sertraline would be used for comorbid depression, which is not described here.
19. Which of the following features most specifically suggests a diagnosis of delirium superimposed on a neurocognitive disorder?
    Answer: Acute onset and fluctuating course While cognitive deficits like memory impairment and executive dysfunction are present in both dementia and delirium, the hallmark features that distinguish delirium are its acute onset (hours to days) and a fluctuating course of symptoms, with variations in attention and arousal level throughout the day. The slow, progressive decline is characteristic of the underlying neurocognitive disorder (dementia), while the recent, rapid change with fluctuations points to delirium.
20. Which of the following laboratory tests is most likely to identify the cause of her cognitive symptoms?
    Answer: Serum TSH and free T4 This patient's constellation of symptoms, including fatigue, cold intolerance, cognitive slowing ('brain fog'), and physical signs of bradycardia and delayed reflexes, is classic for hypothyroidism. Hypothyroidism is a common and reversible cause of cognitive impairment. Therefore, measuring serum TSH and free T4 is the most direct and highest-yield test to confirm the diagnosis.

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