Acute Neurologic Emergencies - USMLE Step 2

1. The patient's acute neurologic decline is most likely a complication of which of the following?
   Answer: Accumulation of dabigatran due to renal failure Dabigatran is a direct thrombin inhibitor that is primarily cleared by the kidneys. In the setting of acute kidney injury, the drug can accumulate to toxic levels, leading to a profound anticoagulant effect and increased risk of bleeding, including intracranial hemorrhage. Even without overt bleeding on CT, supratherapeutic levels can cause encephalopathy. The patient's acute decline in the setting of new renal failure makes dabigatran toxicity the most likely cause. Donepezil overdose is less likely to cause this presentation. While NCSE is possible, the medication toxicity is a more direct explanation given the labs. A rapid two-day decline is too acute for typical dementia progression.
2. In addition to emergent neurosurgical consultation, which of the following is the most important immediate step in her medical management?
   Answer: Administer fresh frozen plasma and intravenous vitamin K This patient has a life-threatening traumatic intracranial hemorrhage (subdural hematoma) complicated by supratherapeutic anticoagulation with warfarin. The most critical step is to urgently reverse the coagulopathy to prevent further bleeding. This is achieved by administering intravenous vitamin K along with a rapid-acting reversal agent. Prothrombin complex concentrate (PCC) is the preferred rapid agent; if unavailable, fresh frozen plasma (FFP) is an alternative. Mannitol is used for increased ICP but does not address the underlying coagulopathy. Protamine sulfate reverses heparin, not warfarin. Seizure prophylaxis may be considered but is not as immediately life-saving as reversing the anticoagulation.
3. Which of the following is the most appropriate management for this patient?
   Answer: Mechanical thrombectomy This patient has a severe ischemic stroke (NIHSS 18) due to a large vessel occlusion (left M1) and presents within the extended window for mechanical thrombectomy (up to 24 hours in selected patients). He is outside the 4.5-hour window for intravenous alteplase. Therefore, the most appropriate management is mechanical thrombectomy, which has been shown to improve functional outcomes in patients with large vessel occlusions. Heparin infusion is not indicated for acute ischemic stroke and may increase the risk of hemorrhagic conversion. Dual antiplatelet therapy is used for secondary prevention but is not the primary acute treatment for a severe stroke of this nature.
4. What is the most appropriate initial diagnostic test to guide immediate management?
   Answer: Non-contrast CT scan of the head In any patient presenting with acute focal neurologic deficits suggestive of a stroke, the most critical initial step is to differentiate between ischemic and hemorrhagic stroke, as their management is drastically different. A non-contrast CT scan of the head is the fastest and most widely available imaging modality to reliably detect acute intracranial hemorrhage. While MRI with DWI is more sensitive for early ischemia, it takes longer to perform and is not the first-line test. The immediate priority is to rule out a bleed before considering therapies like thrombolysis. Carotid ultrasound and lumbar puncture are not indicated for the initial evaluation of acute stroke.
5. This patient's clinical presentation is most concerning for which of the following neurologic emergencies?
   Answer: Nonconvulsive status epilepticus This critically ill patient's presentation of unexplained coma with subtle motor phenomena (myoclonic jerks of the eyelids and fingers) is highly concerning for nonconvulsive status epilepticus (NCSE). NCSE is a state of continuous seizure activity without the overt convulsions seen in generalized tonic-clonic status epilepticus. It is a common cause of altered mental status in ICU patients and requires EEG for diagnosis. While the other conditions are in the differential for altered mental status in a patient with alcohol use disorder, the subtle motor activity strongly points toward NCSE as the most likely acute neurologic emergency.
6. Which of the following is the most likely diagnosis?
   Answer: Ischemic stroke of the cerebellum This patient's constellation of acute-onset vertigo, nystagmus, dysmetria, and gait ataxia points strongly to a cerebellar lesion. These are the classic signs of a posterior circulation stroke affecting the cerebellum. Acute labyrinthitis typically presents with vertigo and nystagmus but not with focal neurologic signs like dysmetria or ataxia. A basal ganglia hemorrhage would cause contralateral hemiparesis. A carotid territory TIA would cause symptoms like transient monocular blindness (amaurosis fugax) or unilateral weakness/numbness, not cerebellar signs.
7. Which of the following is the most appropriate initial pharmacologic treatment?
   Answer: Intravenous lorazepam This patient is in status epilepticus, defined as a continuous seizure lasting more than 5 minutes or recurrent seizures without a return to baseline. The initial management priority is to terminate the seizure. First-line therapy is an intravenous benzodiazepine, such as lorazepam, diazepam, or midazolam. These medications enhance the effect of the neurotransmitter GABA, causing widespread CNS inhibition. If the seizure persists after an adequate dose of a benzodiazepine, a second-line agent such as fosphenytoin, valproic acid, or levetiracetam should be administered. Phenobarbital is typically reserved for refractory status epilepticus.
8. What is the most appropriate immediate action?
   Answer: Stop the alteplase infusion and obtain an emergent non-contrast head CT The patient's clinical deterioration with severe headache, vomiting, hypertension, and worsening neurologic status during or after alteplase administration is highly concerning for symptomatic intracerebral hemorrhage, the most feared complication of thrombolysis. The most appropriate immediate action is to stop the alteplase infusion and obtain an emergent non-contrast head CT to confirm or rule out bleeding. Increasing the infusion would be catastrophic. While mannitol and labetalol might be needed, diagnosing the hemorrhage is the absolute first priority that will guide all subsequent management.
9. Which of the following is the most critical immediate step in this patient's management?
   Answer: Initiate an intravenous nicardipine infusion to lower systolic blood pressure This patient has an acute intracerebral hemorrhage (ICH) associated with severe hypertension. The most critical immediate step is to rapidly but carefully lower his blood pressure to prevent ongoing bleeding and hematoma expansion, which is a major cause of early neurologic deterioration. The current guidelines recommend lowering the systolic blood pressure to a target of 140-160 mm Hg using a titratable intravenous agent like nicardipine or labetalol. While mannitol and neurosurgical consultation may be necessary if there are signs of increased ICP or mass effect, blood pressure control is the first priority. Alteplase is absolutely contraindicated as it would worsen the hemorrhage.
10. What is the most likely diagnosis?
    Answer: Posterior reversible encephalopathy syndrome (PRES) This patient's presentation of headache, visual changes, and seizures in the setting of a hypertensive emergency, along with MRI findings of posterior vasogenic edema, is classic for Posterior Reversible Encephalopathy Syndrome (PRES). PRES is a clinicoradiologic syndrome caused by failed cerebral autoregulation in the setting of severely elevated blood pressure or other triggers (e.g., eclampsia, immunosuppressive drugs). Management involves treating the underlying cause, primarily by carefully lowering the blood pressure. Bilateral PCA strokes would show restricted diffusion, not vasogenic edema. Herpes encephalitis typically affects the temporal lobes. CJD is a rapidly progressive dementia and is not associated with these acute findings.
11. Which of the following is a contraindication to administering alteplase in this patient?
    Answer: Major surgery within the past 3 months The administration of intravenous alteplase (tPA) has strict inclusion and exclusion criteria to minimize the risk of bleeding. A major surgery, such as a total knee replacement, within the preceding 3 months is an absolute contraindication to tPA due to the high risk of severe bleeding at the surgical site. While advanced age was previously a relative contraindication, current guidelines support its use in older adults. The patient's blood pressure is below the 185/110 mm Hg threshold. A history of hypertension is not a contraindication, although uncontrolled hypertension at the time of administration is.
12. Which of the following is the most appropriate next step in management?
    Answer: Administer a dose of oral lamotrigine and arrange for a refill This patient had a single, self-limited breakthrough seizure in the context of a known seizure disorder and medication nonadherence. Since the seizure has terminated and she is returning to baseline, she is not in status epilepticus. The most appropriate management is to address the underlying cause, which is the missed medication. She should be given a dose of her home antiepileptic drug (lamotrigine) and provided with a prescription refill. Administering a loading dose of a different antiepileptic like fosphenytoin is unnecessary as she is not actively seizing and could cause adverse effects. Urgent neuroimaging and continuous EEG are not indicated for a simple breakthrough seizure with a clear precipitant.
13. Which of the following cerebrospinal fluid findings would be most diagnostic of a subarachnoid hemorrhage in this patient?
    Answer: Xanthochromia When a non-contrast head CT is negative in a patient with a high suspicion for subarachnoid hemorrhage (SAH), the next step is a lumbar puncture (LP). The most specific finding for SAH on LP is xanthochromia, which is the yellow discoloration of the CSF due to bilirubin from the breakdown of red blood cells. Xanthochromia takes several hours to develop and distinguishes a true hemorrhage from a traumatic tap (where the RBC count would be high but no xanthochromia would be present). Lymphocytic pleocytosis suggests viral meningitis, low glucose suggests bacterial meningitis, and albuminocytologic dissociation (high protein, normal cells) is seen in Guillain-Barré syndrome.
14. Which of the following is the most appropriate next step in management?
    Answer: Administer intravenous alteplase This patient presents with classic signs of an acute ischemic stroke within the 3-hour window for thrombolysis (and up to 4.5 hours in eligible patients). The non-contrast head CT has appropriately ruled out hemorrhage. Her blood pressure is below the 185/110 mm Hg contraindication threshold for alteplase (tPA). Therefore, the most appropriate next step is to administer intravenous alteplase to attempt reperfusion. CT angiography is useful for identifying large vessel occlusion for potential thrombectomy but should not delay tPA administration. Aggressively lowering blood pressure to <140/90 mm Hg is not indicated and could worsen cerebral perfusion. Aspirin should be administered, but not until 24 hours after tPA administration to reduce the risk of hemorrhagic conversion.
15. Which of the following MRI findings would suggest that this patient might still be a candidate for reperfusion therapy?
    Answer: Hyperintensity on DWI with corresponding hypointensity on FLAIR in the left MCA territory In patients with an unknown time of stroke onset ('wake-up stroke'), MRI can help determine eligibility for thrombolysis or thrombectomy. A diffusion-weighted imaging (DWI) sequence becomes positive within minutes of an ischemic event, while the fluid-attenuated inversion recovery (FLAIR) sequence typically takes 4.5-6 hours to become positive. A 'DWI-FLAIR mismatch' (positive DWI, negative FLAIR) indicates that the stroke likely occurred within the past 4.5 hours, making the patient a potential candidate for intravenous thrombolysis. If both DWI and FLAIR are positive, the stroke is likely older than 4.5-6 hours. Normal signals would not explain the deficit, and periventricular hyperintensities are chronic small vessel ischemic changes.
16. Which of the following is the most appropriate next medication to administer?
    Answer: An intravenous loading dose of fosphenytoin This patient has benzodiazepine-refractory status epilepticus. After initial treatment with adequate doses of a benzodiazepine fails, the next step is to administer a non-benzodiazepine intravenous antiepileptic drug. The three recommended second-line agents are fosphenytoin, valproic acid, and levetiracetam. Fosphenytoin is a common and appropriate choice. Administering more lorazepam is unlikely to be effective and increases the risk of respiratory depression (though the patient is already intubated). A continuous infusion of an anesthetic agent like propofol or midazolam is third-line therapy for refractory status epilepticus. Magnesium sulfate is used for eclamptic seizures.
17. Which of the following interventions should be performed most urgently?
    Answer: Endotracheal intubation and controlled hyperventilation This patient has a severe traumatic brain injury (GCS < 8) with clinical signs of uncal herniation (anisocoria with a fixed, dilated pupil). This is a neurosurgical emergency due to rapidly increasing intracranial pressure (ICP). The most urgent intervention is to secure the airway via endotracheal intubation and initiate controlled hyperventilation. Hyperventilation causes cerebral vasoconstriction by lowering PaCO2, which transiently reduces cerebral blood volume and ICP. This serves as a critical bridge to more definitive treatments like osmotic therapy (hypertonic saline or mannitol) or surgical intervention (e.g., craniotomy, EVD placement). Prophylactic antibiotics are not the most urgent step.
18. Which of the following is the most appropriate initial management for this patient's condition?
    Answer: Initiation of anticoagulation or antiplatelet therapy Carotid artery dissection is an important cause of stroke in young adults, often precipitated by trauma or strenuous activity. The primary goal of treatment is to prevent thromboembolic stroke from the site of the dissection. This is typically achieved with either anticoagulation (e.g., with heparin followed by warfarin) or antiplatelet therapy (e.g., aspirin). The choice between the two is debated, but one must be started. Surgical intervention is reserved for rare cases. tPA is not indicated as there is no evidence of an established ischemic stroke on imaging, and it could worsen the intramural hematoma of the dissection. While blood pressure control is important, it is not the primary treatment, unlike in aortic dissection.
19. Which of the following is the most likely finding on the head CT scan?
    Answer: Hyperdensity in the basilar cisterns and sulci consistent with subarachnoid hemorrhage This patient's presentation with a sudden-onset, severe "thunderclap" headache, vomiting, nuchal rigidity, and decreased level of consciousness is classic for a subarachnoid hemorrhage (SAH). The most common cause of non-traumatic SAH is a ruptured saccular (berry) aneurysm. A non-contrast head CT is the initial diagnostic test of choice and would show hyperdense (bright) blood in the subarachnoid space, including the basilar cisterns and sulci. If the CT is negative but clinical suspicion remains high, a lumbar puncture should be performed to look for xanthochromia.
20. In addition to arranging for urgent neuroimaging and neurosurgical consultation, which of the following is the most appropriate immediate intervention?
    Answer: Administration of intravenous dexamethasone This patient's presentation, including the triad of hypertension, bradycardia, and irregular respirations (Cushing's triad), along with papilledema, is highly suggestive of acutely increased intracranial pressure (ICP). Given her history of brain metastases, this is likely due to vasogenic edema surrounding the tumors. The most appropriate immediate intervention is to administer high-dose intravenous corticosteroids, such as dexamethasone, which rapidly reduces vasogenic edema and can alleviate symptoms of increased ICP. Antibiotics are not indicated. A lumbar puncture is contraindicated due to the risk of uncal herniation. Sodium bicarbonate is not a primary treatment for increased ICP.

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