High-Yield Neurology for USMLE Step 3: Stroke, Seizures, and Headache

A 62-year-old right-handed man stops speaking mid-sentence at a dinner party. His wife calls 911 at 7:14 PM. EMS arrives at 7:28. The ED attending orders a stat CT head. It's 7:52 PM and the scan is clean — no hemorrhage. Clock's ticking. What happens in the next 8 minutes determines whether this man ever speaks fluently again.

That's the energy Step 3 brings to neurology. The exam doesn't care whether you memorized the Circle of Willis — it wants to know if you can act under a countdown. Stroke, status epilepticus, and herniation syndromes are where the board loves to park its hardest management questions. But even the "chronic" neuro topics — Parkinson's, dementia subtypes, headache prophylaxis — have testable decision points that trip up residents who studied passively.

I've spent the last eight years tutoring Step 3 candidates, and neurology is consistently where strong test-takers separate from average ones. Not because the content is harder than cardiology or GI — but because the timing details are ruthlessly specific, and the exam exploits that.

Ischemic Stroke

The CT Comes First. Always.

When Step 3 hands you a stroke presentation, your reflex should be CT head without contrast before anything else. Not MRI. Not CTA. A non-contrast CT.

Here's why this trips people up: CT is actually terrible at showing early ischemia. In the first 6-12 hours, the scan often looks completely normal. That's not the point. You're not ordering it to find the infarct — you're ordering it to rule out hemorrhage so you can give tPA. I've seen residents overthink this and jump to MRI because "it's more sensitive." On the real exam, that delay kills the patient.

After you've confirmed no bleed:

• MRI with diffusion-weighted imaging (DWI) lights up ischemic tissue within minutes of onset — it's your confirmatory study
• CT angiography when you suspect large vessel occlusion (internal carotid or proximal MCA) because that changes the interventional plan

tPA Windows: The Numbers They'll Test You On

IV alteplase within 3 hours of last known well — that's the standard window and the one you cannot get wrong.

The 4.5-hour extended window exists but comes with exclusions that the exam loves to test as distractors:

• Patient must be under 80
• Can't have both prior stroke AND diabetes (either alone is okay — the combination kicks them out)
• No anticoagulant use
• NIHSS under 25

Absolute contraindications to tPA — commit these to reflex-level recall:

• Any hemorrhage on CT
• Ischemic stroke or significant head trauma within the past 3 months
• BP above 185/110 that you can't bring down (if you can get it below threshold with IV labetalol or nicardipine, they still qualify)
• Coagulopathy: INR > 1.7, recent heparin with elevated PTT
• Glucose below 50 or above 400

That BP detail is a favorite trap. I've watched residents pick "tPA is contraindicated" when the stem says BP is 192/114, not realizing the next correct move is to treat the BP first and reassess. The exam wants you to fight for reperfusion when it's safe.

What most people miss about thrombectomy: Mechanical thrombectomy for large vessel occlusion (ICA, M1 segment of MCA) can be performed up to 24 hours out if perfusion imaging shows salvageable penumbra. And here's the critical part — it's done in addition to IV tPA, not instead of it. If the patient qualifies for both, they get both. Step 3 has started testing this distinction directly.

Secondary Prevention — The Question After the Emergency

Once you've managed the acute event, Step 3 shifts to "what do you send them home on?"

• Atrial fibrillation identified? Anticoagulation with a DOAC (apixaban, rivaroxaban). Not warfarin as first-line anymore — that's a dated answer choice they use as a distractor.
• No cardioembolic source? Dual antiplatelet with aspirin 81 mg + clopidogrel 75 mg for 21 days, then drop to a single agent. The 21-day dual therapy window comes from the CHANCE and POINT trials, and it's been showing up more frequently.
• High-intensity statin (atorvastatin 80 mg or rosuvastatin 20 mg) regardless of LDL — yes, even if their lipid panel looks fine
• BP target below 130/80 after the acute phase stabilizes (don't aggressively drop pressure in the first 24-48 hours of an acute stroke — you'll extend the infarct)

Seizures and Status Epilepticus

Status Epilepticus: A Protocol You Need Cold

Status epilepticus — continuous seizure activity lasting more than 5 minutes, or two or more seizures without return to baseline — kills neurons every minute it continues. The management algorithm is the single most tested seizure topic on Step 3, and it follows a strict time-based protocol.

Minutes 0-5 — Stabilize: Check glucose immediately (hypoglycemia is the most reversible cause and the most embarrassing to miss). Protect the airway, establish IV access, supplemental O2. Don't shove anything in the patient's mouth — that's a myth that still shows up as wrong answer choices.

Minutes 5-10 — Benzodiazepines:

• IV lorazepam 0.1 mg/kg is preferred if you have IV access
• IM midazolam 10 mg if you don't — and here's a contrarian point that the RAMPART trial proved: IM midazolam given immediately actually beats IV lorazepam when you factor in the time spent establishing IV access. On the exam, if the stem says "no IV access," reach for IM midazolam without hesitation.

Minutes 10-30 — Second-Line Agents (if seizures persist after 2 benzo doses):

• IV fosphenytoin 20 PE/kg
• IV valproate 40 mg/kg
• IV levetiracetam 60 mg/kg

The ESETT trial showed all three are essentially equivalent in efficacy. Step 3 usually won't make you choose between them — but they will test whether you know to move to this step after benzodiazepines fail rather than just giving more lorazepam.

Beyond 30-60 minutes — Refractory Status: ICU transfer, intubation, continuous EEG monitoring, and an anesthetic infusion — propofol or midazolam drip. If a question stem describes a patient still seizing after appropriate benzos and a second-line agent, the answer is always escalation to ICU-level care, never "give another dose of fosphenytoin."

The thiamine-before-glucose rule: In any adult with status epilepticus, give thiamine 100 mg IV before glucose. Glucose loading in a thiamine-depleted patient (chronic alcoholism, malnutrition) can precipitate or worsen Wernicke encephalopathy — acute confusion, ophthalmoplegia, and ataxia that may become irreversible. This is a two-for-one board question: they test seizure management AND Wernicke's in a single stem.

First Unprovoked Seizure — When to Treat

This is a genuinely tricky clinical decision that Step 3 tests well. A single unprovoked seizure in an adult does NOT automatically require antiepileptic drugs.

Work-up first:

• Brain imaging (MRI preferred, CT if emergent)
• EEG
• Basic metabolic panel — sodium, glucose, calcium specifically
• LP only if you suspect CNS infection (fever, meningismus, immunocompromised)

Start an antiepileptic after:

• A second unprovoked seizure (at that point, it's epilepsy by definition), OR
• A first seizure with high recurrence risk: structural lesion on imaging, epileptiform discharges on EEG, or known prior brain injury

In my experience, the most common wrong answer here is starting levetiracetam after a single provoked seizure (alcohol withdrawal, acute hyponatremia) — provoked seizures are treated by fixing the underlying cause, not by chronic AED therapy.

Headache Syndromes

Migraine — The Details That Actually Get Tested

Migraine diagnosis requires at least 2 of 4 features: unilateral location, pulsating quality, moderate-to-severe intensity, worsened by routine physical activity. Plus either nausea/vomiting or photophobia/phonophobia. The "2 of 4 plus associated symptoms" structure is how the exam builds its stems — they'll give you three features and make you decide if it qualifies.

Acute treatment — know the hierarchy:

1. NSAIDs first for mild-moderate attacks: ibuprofen 600 mg or naproxen 500 mg. Simple, effective, and the answer when the stem describes an infrequent migraine without red flags.
2. Triptans (sumatriptan 50-100 mg PO, 6 mg SC; rizatriptan 10 mg) for moderate-severe migraines or when NSAIDs have failed. These are 5-HT1B/1D receptor agonists — they cause vasoconstriction, which means they're contraindicated in hemiplegic migraine, basilar migraine, coronary artery disease, and uncontrolled hypertension. That contraindication list is a guaranteed test point.
3. CGRP receptor antagonists (ubrogepant 50-100 mg, rimegepant 75 mg) — the newer option. The exam uses these when the stem builds a patient who can't take triptans (history of MI, prior stroke). If you see "failed triptans" or "cardiovascular disease" in a migraine stem, think gepants.

Prophylaxis — indicated when migraine frequency hits ≥4 attacks/month or ≥8 headache days/month:

• Old guard (and still first-line on boards): propranolol 40-160 mg, topiramate 50-100 mg, valproate 500-1000 mg, amitriptyline 10-75 mg
• CGRP monoclonal antibodies (erenumab 70-140 mg SC monthly, fremanezumab) for refractory cases — these are showing up more on recent exams but usually as a later step after traditional agents fail

Cluster Headaches — Don't Confuse These With Migraine

Cluster headache is the one that makes grown adults bang their head against a wall. Strictly unilateral periorbital/temporal pain, excruciating intensity, lasting 15-180 minutes, occurring 1-8 times daily in clusters spanning weeks to months.

The distinguishing feature: ipsilateral autonomic symptoms — ptosis, miosis (partial Horner syndrome), lacrimation, conjunctival injection, nasal congestion or rhinorrhea. If a question stem describes severe unilateral headache with a red, teary eye on the same side, that's cluster. Every time.

Acute treatment — this duo is non-negotiable:

• High-flow 100% O2 via non-rebreather mask, 12-15 L/min for 15 minutes
• Subcutaneous sumatriptan 6 mg (faster onset than oral)

Prophylaxis: Verapamil is the drug of choice — that's the testable answer. Lithium and a short prednisone taper are alternatives they might list as options.

Here's a subtle point I always emphasize: cluster headache patients are restless and agitated during attacks. Migraine patients prefer to lie still in a dark room. That behavioral difference is how the exam distinguishes them when the pain description overlaps.

Thunderclap Headache = SAH Until You've Proven It's Not

"Worst headache of my life" with sudden onset reaching maximum intensity within seconds — that's a subarachnoid hemorrhage until imaging and LP say otherwise. No exceptions, no matter how well the patient looks sitting in front of you.

CT head without contrast catches over 95% of SAH when performed within 6 hours of symptom onset. Sensitivity drops after that. If CT is negative but your clinical suspicion is high: lumbar puncture looking for xanthochromia (yellowish discoloration of CSF from bilirubin) and RBCs that don't clear between tubes 1 and 4. A traumatic tap shows decreasing RBCs across sequential tubes; true SAH does not.

Sentinel headaches are real and dangerous. About 30-50% of patients with aneurysmal SAH report a sudden severe headache days to weeks before the catastrophic bleed. If someone describes a thunderclap headache that resolved on its own, you still work it up. The question stem that presents a "resolved thunderclap headache" and offers "reassurance and follow-up" as an answer choice is testing whether you'll fall for that trap.

Movement Disorders

Parkinson Disease — Treatment Logic for Step 3

The classic tetrad — resting "pill-rolling" tremor, cogwheel rigidity, bradykinesia, and postural instability — is straightforward to recognize. Step 3 cares more about your treatment decisions.

Levodopa/carbidopa remains the most effective drug for motor symptoms. Carbidopa blocks peripheral DOPA decarboxylase so levodopa reaches the brain instead of being converted to dopamine in the gut (which just causes nausea). The exam tests this mechanism.

Dopamine agonists (pramipexole, ropinirole) — here's where it gets nuanced. In younger patients (under 65ish), there's a deliberate strategy of starting with a dopamine agonist to delay initiating levodopa, because long-term levodopa use leads to motor fluctuations and dyskinesia. If the stem gives you a 52-year-old with early Parkinson's and mild symptoms, think dopamine agonist first. If it's a 74-year-old with significant functional impairment, go straight to levodopa — quality of life now outweighs long-term dyskinesia risk at that age.

Side note that boards love: dopamine agonists can cause impulse control disorders — pathological gambling, hypersexuality, compulsive shopping. If a Parkinson's patient on pramipexole suddenly develops a gambling problem, the drug is the cause.

MAO-B inhibitors (selegiline, rasagiline) offer mild symptomatic benefit as monotherapy in very early disease or as adjuncts. The "neuroprotective" claim has never been convincingly proven despite years of hope.

COMT inhibitors (entacapone) — used specifically to extend levodopa's duration and reduce "off" time in patients already on levodopa/carbidopa who are experiencing wearing-off between doses.

Dementia Subtypes — The Table You Need in Your Head

Step 3 loves the "which dementia is this?" question. The differentiating features are surprisingly clean once you organize them:

Feature	Alzheimer	Lewy Body	Vascular	Frontotemporal
Earliest symptom	Short-term memory loss	Visual hallucinations, vivid and detailed	Stepwise cognitive decline tied to vascular events	Personality change, disinhibition, or language loss
Motor findings	Late in disease	Parkinsonism early — this is the giveaway	Focal neurological deficits	Generally late
Hallucinations	Occur late if at all	Early, recurrent, well-formed (seeing people, animals)	Uncommon	Uncommon
Key danger	Gradual decline	Severe neuroleptic sensitivity — avoid antipsychotics	Recurrent strokes	Misdiagnosed as psychiatric illness

The Lewy body dementia–antipsychotic interaction deserves special emphasis. Giving haloperidol or even low-dose risperidone to a patient with Lewy body dementia can trigger catastrophic rigidity, obtundation, and death. If a question describes a demented patient with early parkinsonism and visual hallucinations who then gets dramatically worse after an antipsychotic, that's Lewy body. It's one of the most consistently tested safety points in all of neurology.

One thing I tell every resident I tutor: frontotemporal dementia (FTD) gets misdiagnosed as a psychiatric disorder constantly, both in real life and on the exam. A patient in their 50s or 60s with progressive personality change, social disinhibition, or apathy — and a relatively preserved memory early on — that's FTD, not late-onset bipolar or depression. The young age and behavioral-first presentation are your clues.

Frequently Asked Questions

What's the single most tested neurology topic on Step 3?

Ischemic stroke management — specifically the tPA time windows and contraindications. In my experience reviewing practice exams and student score reports, this appears more reliably than any other neuro topic. Know the 3-hour and 4.5-hour windows, the exclusion criteria for the extended window, and the absolute contraindications cold.

Should I memorize every antiepileptic drug for Step 3?

No. The exam cares about the status epilepticus protocol (benzos → fosphenytoin/valproate/levetiracetam → ICU), when to start chronic AED therapy, and a few specific side effect profiles (valproate teratogenicity, carbamazepine hyponatremia and Stevens-Johnson, topiramate kidney stones and word-finding difficulty). You don't need to know dosing for every maintenance AED.

How do I distinguish migraine from cluster headache when they both present as severe unilateral headache?

Three features clinch it: duration (migraine lasts 4-72 hours, cluster 15-180 minutes), behavior (migraine patients lie still in the dark, cluster patients pace and rock), and autonomic signs (cluster headaches have prominent ipsilateral tearing, eye redness, nasal congestion, and partial Horner syndrome). If the stem describes a short severe headache with a red watery eye, that's cluster regardless of what other features they throw in.

Can tPA still be given if the patient is on aspirin?

Yes. Aspirin use alone is NOT a contraindication to IV alteplase. Anticoagulants (warfarin with INR > 1.7, DOACs taken within 48 hours, heparin with elevated PTT) are contraindications, but antiplatelets are not. This is a common point of confusion and a favorite wrong-answer trap.

When should I suspect Lewy body dementia vs. Alzheimer's with behavioral symptoms?

Timing and hallucinations. In Lewy body dementia, visual hallucinations and/or parkinsonian features appear early — often before or concurrent with cognitive decline. In Alzheimer's, hallucinations and motor symptoms are late-stage phenomena. If you see a question about a patient with cognitive decline plus early detailed visual hallucinations plus fluctuating attention, that's Lewy body. And the highest-yield association: extreme sensitivity to antipsychotics.

Practice Neurology Questions

Ready to put this to work? Step3Sim offers free USMLE Step 3 practice questions covering stroke protocols, seizure management, headache classification, and dementia differentiation across neurology and every other organ system. The best way to lock in these timing details is to get them wrong in a low-stakes environment before exam day.