Free USMLE Step 2 CK Neurology practice questions

This woman has a rapidly progressive dementia over weeks with visual disturbance, ataxia, and startle-sensitive myoclonus, a normal screen for treatable mimics, a bland CSF, and the characteristic MRI pattern of cortical ribboning and caudate restricted diffusion. The picture is typical of sporadic Creutzfeldt-Jakob disease, and the visual onset suggests the Heidenhain variant.

Real-time quaking-induced conversion (RT-QuIC) detects the seeding activity of misfolded prion protein: a sample of CSF is added to recombinant normal prion protein, and any PrPSc in the sample templates its conversion into amyloid fibrils that are detected by fluorescence. CSF RT-QuIC has a sensitivity of roughly 90% and a specificity close to 100% for sporadic CJD, making it the most specific test available short of brain tissue. A positive RT-QuIC with a compatible clinical picture establishes probable CJD in current diagnostic criteria, and brain biopsy is rarely needed.

A and B. CSF 14-3-3 protein and total tau are markers of rapid neuronal destruction; they are also elevated after stroke, seizures, encephalitis, and other acute brain injuries, so they are sensitive but nonspecific. C. EEG periodic sharp-wave complexes at about 1 per second support the diagnosis, but they appear mid to late in the illness, are absent in many patients, and can occur in toxic-metabolic encephalopathies; EEG is still useful to exclude nonconvulsive status epilepticus. D. MRI with DWI and FLAIR is the most sensitive noninvasive test, and FLAIR is less sensitive than DWI, but similar signal changes can occur with seizures, hypoxic injury, and autoimmune encephalitis, so imaging is less specific than RT-QuIC.

This young woman has bilateral internuclear ophthalmoplegia (INO): on lateral gaze, the adducting eye fails to move medially while the abducting eye has nystagmus, yet adduction is preserved with convergence. That pattern localizes to the medial longitudinal fasciculus in the dorsal pons and midbrain, and bilateral INO in a young adult is strongly suggestive of multiple sclerosis. The rest of the history shows dissemination in space and time: a prior episode of painful monocular vision loss consistent with optic neuritis (with a residual pale disc), the Lhermitte sign (an electric sensation down the spine with neck flexion, from a cervical cord lesion), Uhthoff phenomenon (heat-induced worsening from conduction block in demyelinated axons), and hyperreflexia. The next step would be MRI of the brain and cervical spine with gadolinium to look for periventricular, juxtacortical, infratentorial and spinal plaques that fulfill the McDonald criteria.

A. Myasthenia gravis can mimic any ocular motor pattern, including a pseudo-INO, but it causes fatigable ptosis and diplopia without optic disc pallor, Lhermitte sign or hyperreflexia. B. A midbrain stroke causes sudden deficits, typically in an older patient with vascular risk factors, and would not explain the relapsing course. C. NMOSD causes severe optic neuritis and longitudinally extensive myelitis or area postrema attacks; brainstem INO with Lhermitte and Uhthoff phenomena in this pattern is far more typical of MS. D. Wernicke encephalopathy causes ophthalmoplegia with confusion and ataxia in malnourished or alcohol-dependent patients, without prior optic neuritis.

Painless, foul, persistent otorrhea that keeps recurring despite topical antibiotics, an attic (pars flaccida) retraction pocket filled with white keratin debris, and a conductive hearing loss in a patient with a history of eustachian tube dysfunction and childhood otitis are the hallmarks of an acquired cholesteatoma. Keratinizing squamous epithelium accumulates in the retraction pocket, becomes infected (often with Pseudomonas, explaining the odor), and expands while releasing enzymes that erode bone. Her dizziness with tragal pressure is a positive fistula sign, suggesting erosion of the lateral semicircular canal. Other complications include ossicular destruction, facial canal erosion with CN VII palsy, and erosion of the tegmen with meningitis or brain abscess. Evaluation is CT of the temporal bone and audiometry, followed by surgical excision (tympanomastoidectomy); drops only quiet the infection temporarily.

A. Chronic otitis externa causes itching and a thickened canal; the canal here is normal, and it does not erode the middle ear or cause a fistula sign. B. Otitis media with effusion shows fluid or bubbles behind a dull drum without otorrhea or keratin debris. C. Otomycosis causes itching with black-dotted (Aspergillus) or white cottony (Candida) debris in the canal itself, often after prolonged antibiotic drops, but the debris lies on the canal and drum, not inside an attic pocket, and it does not produce a fistula sign. E. Otosclerosis produces progressive conductive loss in a young adult with a normal-appearing drum (sometimes a reddish Schwartze sign) and no otorrhea.

This man has a minor ischemic stroke (NIHSS 2) with no hemorrhage, no large-vessel occlusion, no significant carotid stenosis, and sinus rhythm. He is outside the 4.5-hour thrombolysis window because his last-known-well time was 10 hours ago (not the time he woke). For minor noncardioembolic ischemic stroke (NIHSS 3 or less) or high-risk TIA, dual antiplatelet therapy with aspirin plus clopidogrel started within 24 hours and continued for about 21 days, then switched to a single antiplatelet agent, reduces early recurrent stroke (CHANCE, POINT) without the bleeding cost of longer combination therapy. He should also start high-intensity statin therapy, and the workup continues with echocardiography, lipids, A1c, and prolonged rhythm monitoring if no cause is found.

B. Tenecteplase is given within 4.5 hours of last-known-well; at 10 hours with no imaging selection, and with a nondisabling deficit, it is not indicated. C. Anticoagulation is for cardioembolic stroke (for example atrial fibrillation), which has not been demonstrated; empiric anticoagulation for cryptogenic stroke did not beat aspirin in trials. D. Prolonged dual antiplatelet therapy (as in MATCH and the long arm of earlier trials) increases major bleeding without additional benefit, so it is limited to the first few weeks. E. Without thrombolysis, blood pressure is allowed to remain elevated in the acute phase (treated only above 220/120) to preserve penumbral perfusion; long-term targets are pursued after the first days.

A young adult with a new movement disorder (a coarse, wing-beating tremor, dysarthria, and drooling), psychiatric and behavioral change, and liver involvement (elevated aminotransferases, splenomegaly suggesting portal hypertension) has Wilson disease until proven otherwise. The Coombs-negative hemolytic anemia with reticulocytosis and indirect hyperbilirubinemia is another classic clue: free copper released from damaged hepatocytes injures red cells. A normal to low alkaline phosphatase despite liver injury and hyperbilirubinemia, often with an AST higher than ALT, is also typical of Wilson disease.

Wilson disease is an autosomal recessive defect in ATP7B that prevents copper excretion into bile and loading onto ceruloplasmin, so copper accumulates in the liver, basal ganglia, and cornea. Parents are usually unaffected carriers, which explains the negative family history. The workup includes serum ceruloplasmin (low), 24-hour urine copper (high), and a slit-lamp examination for Kayser-Fleischer rings, which are present in most patients with neurologic disease. Treatment is lifelong chelation with penicillamine or trientine, with zinc for maintenance, and siblings should be screened.

A. Huntington disease is autosomal dominant, presents at ages 30 to 50 with chorea and psychiatric change, and does not cause liver disease or hemolysis. B. Early-onset Parkinson disease causes an asymmetric rest tremor with bradykinesia and rigidity, without liver or blood abnormalities. C. Essential tremor is a fine, symmetric postural and action tremor, often familial, without dysarthria, psychiatric change, or liver injury. E. Hemochromatosis causes liver disease, diabetes, skin bronzing, and arthropathy, typically in middle age, but not a movement disorder or hemolysis.

This young man has a dorsal column myelopathy (lost vibration and position sense, sensory ataxia with a positive Romberg sign) with macrocytosis, and the clue to the cause is heavy recreational use of nitrous oxide from whipped-cream chargers. Nitrous oxide oxidizes the cobalt in vitamin B12 and inactivates it as a cofactor for methionine synthase and methylmalonyl-CoA mutase. The circulating B12 molecule is still present, so the serum B12 level can be normal even though the patient is functionally deficient. The correct next step is to measure methylmalonic acid and homocysteine, which are elevated when B12 cannot work; elevated values confirm functional deficiency and justify B12 replacement plus complete cessation of nitrous oxide. Spinal MRI showing T2 hyperintensity of the dorsal columns (an inverted V on axial images) supports the diagnosis of subacute combined degeneration.

B. Nerve conduction studies may show an accompanying axonal neuropathy, but they do not identify the metabolic cause, and the dominant finding here is a cord (dorsal column) syndrome. C. Anti-intrinsic factor antibodies test for pernicious anemia, an autoimmune cause of true B12 malabsorption that is unlikely in a 23-year-old with a clear exposure and a normal serum B12. D. Lumbar puncture is used for inflammatory or infectious myelopathy and adds nothing when a toxic metabolic cause is evident. E. Copper deficiency causes a nearly identical myelopathy and is the right test if MMA and homocysteine are normal (for example after bariatric surgery or with excess zinc intake), but it is not the first test in a nitrous oxide user.

Brief, stereotyped olfactory hallucinations (often an unpleasant burning smell) followed by a rising epigastric sensation, then unresponsive staring with oral and manual automatisms and postictal amnesia, are the signature of focal impaired-awareness seizures arising from the mesial temporal lobe. The olfactory and epigastric phenomena are the aura, the focal aware onset of the seizure. Her history of a prolonged febrile seizure in early childhood is a classic risk factor for mesial temporal sclerosis. Hallucinations in the olfactory or gustatory modality, together with a normal mental status between episodes, should prompt a neurologic rather than a primary psychiatric diagnosis. The appropriate next step is electroencephalography to look for temporal interictal epileptiform discharges (with prolonged or sleep-deprived recording if the first study is normal), together with MRI of the brain with an epilepsy protocol to look for hippocampal sclerosis or another structural lesion. The findings guide antiseizure therapy and, if seizures become drug resistant, surgical evaluation.

B. Polysomnography evaluates sleep disorders such as narcolepsy or parasomnias; her episodes occur while awake. C. Olfactory testing assesses loss of smell (as in early Parkinson disease or after head injury), not paroxysmal phantom odors with automatisms. D. Lumbar puncture is reserved for suspected encephalitis or meningitis, which is unlikely in a well patient with 4 months of stereotyped episodes and a normal examination. E. Ceruloplasmin is used to screen for Wilson disease, which causes psychiatric symptoms with movement disorders and liver disease, not stereotyped seizures.

This man developed sinus bradycardia with first-degree AV block, exertional lightheadedness and bronchospasm within weeks of adding a second glaucoma drop. The combination of slowed conduction and worsened asthma is the signature of beta-adrenergic blockade, and the topical beta-blocker timolol is the usual second-line agent added to a prostaglandin analog. Drops drain through the nasolacrimal duct into the highly vascular nasal mucosa and are absorbed directly into the systemic circulation, bypassing first-pass hepatic metabolism, so a single drop can produce clinically important systemic levels. Timolol should be avoided in asthma, COPD, bradycardia and second- or third-degree heart block. The appropriate response is to stop timolol, ask the ophthalmologist to substitute another class, and teach punctal occlusion (pressing on the medial canthus and closing the eyes for a minute or two after each drop) for any drop with systemic effects.

A. Latanoprost is his original first-line drop; its long use explains the brown iris darkening and eyelash growth, but prostaglandin analogs do not slow the heart or cause bronchospasm. C. Brimonidine, an alpha-2 agonist, can cause fatigue, dry mouth and allergic follicular conjunctivitis, and it causes CNS depression and apnea in infants; it may lower blood pressure slightly but does not cause bronchospasm. D. Dorzolamide is a topical carbonic anhydrase inhibitor whose usual effects are stinging and a bitter taste; the systemic acidosis, paresthesias and kidney stones belong mainly to oral acetazolamide. E. Netarsudil, a Rho kinase inhibitor, causes conjunctival hyperemia and corneal deposits without meaningful cardiopulmonary effects.