Nervous System & Special Senses

Secondary headache red flags and workup

Clinical Overview and When to Suspect Secondary Headache

— ~90% of headache presentations are primary; only ~10% are secondary, but secondary causes account for nearly all life-threatening headache morbidity.

— Outpatient family medicine clinics see 1–4% of all visits for headache; the task is not imaging everyone — it is identifying the red-flag minority.

— Systemic symptoms (fever, weight loss)

— Neoplasm history

— Neurologic deficit/dysfunction

— Onset sudden (thunderclap)

— Older age (>50 at new onset)

— Pattern change/Progressive/Precipitated by Valsalva/Postural/Papilledema/Pregnancy/Painful eye/Post-trauma/Pathology of immune system (HIV)/Painkiller overuse

— Vascular: SAH, ICH, dissection, CVST, RCVS, giant cell arteritis

— Infectious: meningitis, encephalitis, brain abscess, sinusitis

— Neoplastic: primary CNS tumor, metastases

— Pressure: IIH, low-CSF (post-LP, spontaneous intracranial hypotension), hydrocephalus

— Toxic-metabolic: CO poisoning, hypoxia, hypercapnia, medication overuse

Definition: Secondary headaches are symptomatic of an underlying structural, vascular, infectious, metabolic, or systemic process — distinct from primary headache syndromes (migraine, tension-type, cluster) which have no identifiable cause.

Epidemiology in primary care:

Conceptual framework — SNNOOP10 mnemonic (ICHD-3 endorsed red flags):

High-pretest-probability secondary etiologies to anchor on:

Step 3 management: In the ambulatory setting, your first decision point is not "what imaging" but "does this headache have ≥1 red flag?" A negative red-flag screen in a patient with a stable, recurrent headache phenotype matching ICHD-3 criteria for migraine/tension is sufficient — neuroimaging is not indicated and exposes the patient to cost, radiation, and incidentaloma risk (Choosing Wisely, AAN, AHS).

Board pearl: "Worst headache of life" reaching maximum intensity in <1 minute = thunderclap = SAH until proven otherwise, regardless of normal exam.

Presentation Patterns and Key History

— Thunderclap (peak <1 min): SAH (highest priority), RCVS, CVST, pituitary apoplexy, cervical artery dissection, third-ventricle colloid cyst, spontaneous intracranial hypotension.

— Subacute progressive (days–weeks): mass lesion, subdural hematoma, IIH, GCA, chronic meningitis (TB, fungal, neoplastic).

— Chronic daily (>15 d/mo × >3 mo): medication-overuse headache, chronic migraine, cervicogenic, post-traumatic.

— Worse lying down, awakens from sleep, worse with cough/bending: increased ICP (mass, hydrocephalus, CVST).

— Worse upright, relieved supine: low-CSF pressure (post-LP, CSF leak).

— Fever + neck stiffness → meningitis

— Jaw claudication, scalp tenderness, vision change, polymyalgia → giant cell arteritis (age >50)

— Painful Horner syndrome, neck pain after trauma/chiropractic → carotid/vertebral dissection

— Pregnancy/postpartum + headache + seizure or HTN → eclampsia, PRES, CVST

— Recurrent thunderclap over days–weeks in women 20–50 + vasoactive drug/SSRI/cannabis: RCVS

— Anticoagulation, antiplatelet use (subdural)

— Hypercoagulable state, OCP, dehydration, postpartum (CVST)

— Immunocompromise/HIV (toxoplasmosis, cryptococcus, lymphoma)

— Cancer history (metastasis)

— Recent LP, epidural, head/neck trauma

— Carbon monoxide: multiple household members ill, winter, gas heater → check COHb

Tempo of onset — the single most discriminating historical feature:

Positional/Valsalva features:

Associated symptoms screening:

Risk factors to elicit:

Key distinction: A patient with longstanding identical migraines is not at zero risk — ask "is this headache different in quality, location, or severity from your usual?" A change-in-pattern is itself a red flag.

Board pearl: Headache that awakens the patient from sleep or is maximal on awakening suggests elevated ICP — image, do not reassure.

Physical Exam Findings and Vital Sign Assessment

— Fever → infectious workup (meningitis, abscess, sinusitis, systemic)

— Hypertension + headache: consider hypertensive emergency, PRES, pheochromocytoma, eclampsia (if pregnant/postpartum)

— Bradycardia + hypertension + irregular respirations = Cushing triad → impending herniation, emergent imaging

— Hypoxia/tachypnea → consider CO poisoning, hypercapnia

— Scalp/temporal artery: tender, beaded, pulseless temporal artery → GCA

— Sinus tenderness, purulent rhinorrhea → bacterial sinusitis (rare cause of severe headache)

— Neck: meningismus (Kernig, Brudzinski), bruit (dissection), lymphadenopathy

— Skin: petechial/purpuric rash → meningococcemia; café-au-lait → NF

— Mental status, level of arousal (subtle encephalopathy = early herniation, encephalitis, CVST)

— Cranial nerves: CN III palsy with pupil involvement → posterior communicating artery aneurysm; CN VI palsy → nonlocalizing sign of ↑ICP

— Visual fields: bitemporal hemianopia → pituitary lesion (consider apoplexy if acute)

— Motor/sensory/cerebellar/gait: any focal deficit is a red flag

— Papilledema → increased ICP (mass, IIH, CVST, hydrocephalus). Spontaneous venous pulsations, if present, argue against elevated ICP.

— Subhyaloid hemorrhage → SAH

Vital signs — never skip:

General exam:

Neurologic exam priorities:

Fundoscopy — required, not optional:

Head/face inspection: Battle sign, raccoon eyes, hemotympanum → basilar skull fracture in trauma context.

Step 3 management: In the office, document a focused but complete neuro exam including fundoscopy on every "first or worst" headache — this single intervention has the highest yield for catching a missed secondary diagnosis and is heavily weighted in board vignettes.

Board pearl: A new headache with any abnormal neurologic finding (including papilledema) mandates neuroimaging before discharge from your office.

Diagnostic Workup — Initial Labs and Imaging

— Non-contrast head CT is the initial test for acute/thunderclap headache, suspected SAH, ICH, or trauma. Sensitivity for SAH is ~98–100% within 6 hours of onset; drops to ~85% by 24 hours and ~50% by day 7.

— CT with contrast adds value for abscess, tumor, meningeal enhancement.

— CT angiography (CTA) head/neck for suspected aneurysmal SAH, dissection, RCVS.

— CT venography (CTV) or MR venography (MRV) for suspected CVST (postpartum, OCP, hypercoagulable, papilledema with normal CT).

— MRI brain with/without contrast is preferred for subacute/progressive headache, posterior fossa lesions, suspected mass, demyelination, low-pressure headache (diffuse pachymeningeal enhancement).

— Suspected SAH with negative CT beyond 6 hours: LP looking for xanthochromia (yellow supernatant from RBC breakdown, present ~12 h after bleed).

— Suspected meningitis/encephalitis: obtain CT first if immunocompromised, focal deficit, papilledema, seizure, or altered mental status; otherwise LP without delay (do not delay antibiotics).

— Suspected IIH: measure opening pressure with patient in lateral decubitus, legs extended. Normal <25 cm H₂O.

— CBC, BMP, coags (especially on anticoagulation)

— ESR and CRP in any patient ≥50 with new headache → GCA screening (ESR often >50, CRP elevated)

— Pregnancy test in reproductive-age women (changes imaging and differential)

— Carboxyhemoglobin if CO exposure plausible

— HIV, RPR in chronic/atypical headache

Imaging — first-line modality selection:

Lumbar puncture indications and sequence:

Initial labs:

CCS pearl: For suspected bacterial meningitis, the correct CCS order sequence is blood cultures → empiric ceftriaxone + vancomycin (+ dexamethasone, + ampicillin if >50 or immunocompromised) → CT if indicated → LP — never delay antibiotics for imaging.

Board pearl: Negative non-contrast CT within 6 hours of thunderclap onset in a neurologically intact patient effectively rules out SAH; LP is not mandatory in that window.

Diagnostic Workup — Advanced and Confirmatory Studies

— Catheter (digital subtraction) angiography: gold standard for aneurysm detection when CTA/MRA is negative but clinical suspicion remains high; also diagnostic for RCVS (segmental vasoconstriction that resolves in 12 weeks) and CNS vasculitis.

— MRA head/neck: dissection (intramural hematoma, "crescent sign" on fat-sat T1), aneurysm screening in high-risk patients.

— DWI: acute ischemia, abscess (restricted diffusion in pus)

— SWI/GRE: microhemorrhages, cavernous malformations, amyloid

— FLAIR: SAH (if CT equivocal), edema, demyelination

— Post-contrast T1: tumor, meningitis, low-pressure headache (diffuse pachymeningeal enhancement, "sagging brain")

— Bacterial meningitis: ↑opening pressure, neutrophilic pleocytosis (>1000), low glucose (<40 or CSF:serum <0.4), high protein (>200)

— Viral: lymphocytic, normal glucose, mildly elevated protein

— Fungal/TB: lymphocytic, very low glucose, very high protein

— SAH: RBCs that do not clear between tubes 1 and 4; xanthochromia

— IIH: normal composition, opening pressure >25 cm H₂O (>28 in obese adults per updated criteria)

Vascular imaging:

MRI sequence selection:

CSF analysis interpretation:

Temporal artery biopsy: Confirms GCA — do not delay steroids while awaiting biopsy. Yield preserved up to 2 weeks after starting prednisone. Bilateral biopsies or ultrasound (halo sign) increase sensitivity.

EEG: Consider for suspected nonconvulsive status, encephalitis, PRES-related seizures.

Toxicology / metabolic: COHb, ABG, ammonia, TSH, drug screen in selected patients.

Step 3 management: When CTA and LP are both negative in a thunderclap headache but the story is classic, admit for repeat imaging or MRI/MRA at 24–48 hours — the differential shifts toward RCVS and cervical artery dissection, both of which can have evolving imaging findings.

Key distinction: SAH xanthochromia vs. traumatic tap — xanthochromia (centrifuged yellow supernatant) is specific; a falling RBC count across tubes suggests traumatic tap.

Risk Stratification and First-Line Management Logic

— Investigate if any of: age ≥40, neck pain/stiffness, witnessed LOC, onset during exertion, thunderclap (instant peak), limited neck flexion on exam.

— 100% sensitivity, ~15% specificity for SAH — excellent rule-out, modest rule-in.

— Step 1: Identify red flags (SNNOOP10). None + recurrent stereotyped headache → diagnose primary headache, treat, follow-up.

— Step 2: Any red flag → determine acuity. Acute/thunderclap → ED for non-contrast CT ± CTA ± LP. Subacute/progressive → urgent MRI brain ± MRV.

— Step 3: Age ≥50 with new headache → ESR/CRP same day; if elevated or high clinical suspicion → start prednisone 40–60 mg (or 1 mg/kg, up to 1 g IV methylprednisolone if vision threatened) before biopsy.

— Suspected SAH, ICH, meningitis, encephalitis, dissection, CVST, pituitary apoplexy, hypertensive emergency, eclampsia → ED/inpatient.

— Suspected GCA, IIH, brain tumor (stable), medication-overuse headache → urgent outpatient workup with close follow-up.

— Suspected sinusitis, dental, TMJ, cervicogenic → targeted outpatient management.

— Time-stamped neuro exam, fundoscopy result, red-flag screen, shared decision discussion if deferring imaging.

Ottawa SAH Rule (alert patients ≥15, new severe nontraumatic headache peaking within 1 hour):

Decision tree for the ambulatory headache patient:

Triage by suspected etiology:

Documentation requirements (Step 3 favorite):

Step 3 management: A 68-year-old with new bitemporal headache, jaw claudication, and ESR 92 — your next step is immediate high-dose prednisone, then arrange temporal artery biopsy within 1–2 weeks. Do not wait for biopsy; vision loss from GCA is irreversible and bilateral within days.

Board pearl: Treat first, biopsy second in GCA. Treat first, image second in suspected bacterial meningitis. These "act-before-confirm" patterns are heavily tested.

Pharmacotherapy — First-Line Regimens by Etiology

— Ceftriaxone 2 g IV q12h + vancomycin 15–20 mg/kg IV q8–12h

— Add ampicillin 2 g IV q4h if >50, pregnant, immunocompromised, alcohol use (Listeria coverage)

— Dexamethasone 0.15 mg/kg IV q6h × 4 days, started before or with first antibiotic dose — reduces mortality and neurologic sequelae in pneumococcal meningitis

— BP control: target SBP <140–160 mmHg (nicardipine, labetalol)

— Nimodipine 60 mg PO q4h × 21 days to prevent vasospasm-related delayed cerebral ischemia (improves outcomes, does not reverse established vasospasm)

— Seizure prophylaxis: short course (3–7 days) acceptable; routine long-term not recommended

— No vision loss: prednisone 40–60 mg/day PO

— Vision threatened/loss: methylprednisolone 1 g IV × 3 days, then oral taper

— Add tocilizumab as steroid-sparing agent (GiACTA trial)

— Aspirin 81 mg daily reduces ischemic events

— Weight loss (5–10%) is first-line

— Acetazolamide 500 mg BID titrated to 1–2 g/day (carbonic anhydrase inhibitor reduces CSF production)

— Topiramate as alternative (bonus: weight loss)

Bacterial meningitis (empiric, adult immunocompetent 18–50):

Herpes simplex encephalitis: Acyclovir 10 mg/kg IV q8h × 14–21 days; start empirically while awaiting CSF PCR.

Subarachnoid hemorrhage:

Giant cell arteritis:

Idiopathic intracranial hypertension:

CVST: Anticoagulation with LMWH/heparin even in the presence of hemorrhagic infarct, then warfarin or DOAC for 3–12 months.

RCVS: Remove triggers (SSRIs, cannabis, sympathomimetics, ergots); nimodipine often used though evidence is observational; avoid steroids (worse outcomes).

Hypertensive emergency with headache: Lower MAP ~25% in first hour with IV nicardipine, labetalol, or clevidipine.

Step 3 management: For migraine + suspected medication-overuse headache, taper the overused analgesic (NSAIDs, triptans, opioids, butalbital) and initiate preventive therapy (topiramate, propranolol, amitriptyline, or CGRP antagonist).

Board pearl: Nimodipine in SAH is oral, not IV — IV use causes severe hypotension and is contraindicated.

Procedures and Invasive Management

— Securing the aneurysm within 24–72 hours is standard.

— Endovascular coiling preferred over surgical clipping for most anterior circulation and all posterior circulation aneurysms (ISAT trial: better 1-year functional outcomes).

— Surgical clipping preferred for MCA aneurysms, large hematoma requiring evacuation, wide-necked aneurysms unsuitable for coiling.

— External ventricular drain (EVD) for acute obstructive hydrocephalus

— Ventriculoperitoneal shunt if chronic communicating hydrocephalus develops (~20%)

— Surgical evacuation (burr hole or craniotomy) for symptomatic acute SDH, midline shift >5 mm, thickness >10 mm

— Chronic SDH in elderly: burr hole drainage; consider middle meningeal artery embolization for recurrence prevention

— Head of bed 30°, normocapnia, avoid hypotonic fluids

— Hypertonic saline (3%) or mannitol 0.5–1 g/kg for acute herniation

— Decompressive craniectomy for refractory ICP after malignant MCA infarct or trauma

— Optic nerve sheath fenestration (for vision preservation)

— CSF diversion (VP or lumboperitoneal shunt) for headache control

— Venous sinus stenting if transverse sinus stenosis with pressure gradient

— Epidural blood patch (autologous blood injected at suspected leak site) — first-line; may need repeat

— CT myelography or digital subtraction myelography to localize leak; surgical repair if persistent

Aneurysmal SAH — definitive treatment:

Hydrocephalus management in SAH/IVH:

Subdural hematoma:

Intracranial pressure management:

IIH refractory to medical therapy:

Spontaneous intracranial hypotension:

Temporal artery biopsy: 1–2 cm segment, ipsilateral to symptoms, performed within 1–2 weeks of starting steroids.

CCS pearl: In a CCS case of aneurysmal SAH, your order set should include: neuro ICU admission, q1h neuro checks, SBP <140–160, nimodipine PO, fluids for euvolemia (not "triple-H"), seizure precautions, neurosurgery consult for coiling/clipping within 24 h, DVT prophylaxis (mechanical until aneurysm secured, then pharmacologic).

Board pearl: Triple-H therapy (hypertension, hypervolemia, hemodilution) is outdated; current standard is euvolemia with induced hypertension only for symptomatic vasospasm.

Special Populations — Elderly and Renal/Hepatic Impairment

— New headache after age 50 is itself a red flag — always image and check ESR/CRP.

— Higher prevalence of giant cell arteritis (peak 70–80), subdural hematoma (cerebral atrophy + falls + anticoagulation), brain tumor/metastasis, medication side effects (nitrates, CCBs, PDE5 inhibitors).

— Chronic subdural hematoma may present as progressive cognitive decline, gait disturbance, or "TIA mimic" — low threshold for non-contrast CT in elderly with new neurologic symptoms and headache.

— Polypharmacy: review for headache-inducing agents (nitrates, dipyridamole, sildenafil, SSRIs, oral contraceptives in late-perimenopausal women).

— Any headache + anticoagulation + minor trauma → CT head. Subdurals can be delayed by days–weeks.

— Reverse coagulopathy if ICH found: 4-factor PCC for warfarin (with vitamin K 10 mg IV); idarucizumab for dabigatran; andexanet alfa for apixaban/rivaroxaban.

— Avoid NSAIDs for symptomatic relief (AKI, especially with ACE/ARB + diuretic "triple whammy").

— Acetazolamide for IIH: reduce dose with CrCl <50; avoid if CrCl <10.

— Gabapentin/pregabalin: dose-adjust for CrCl.

— Contrast considerations: gadolinium with GFR <30 carries risk of nephrogenic systemic fibrosis (use group II macrocyclic agents if necessary); iodinated contrast risk of CIN.

— LMWH for CVST: anti-Xa monitoring or switch to unfractionated heparin if CrCl <30.

— Avoid valproate (used for migraine prevention) — hepatotoxicity

— Acetaminophen max 2 g/day in cirrhosis

— Triptans contraindicated in severe hepatic impairment

Elderly (>65) considerations:

Anticoagulation in elderly headache:

Renal impairment:

Hepatic impairment:

Step 3 management: A 78-year-old on warfarin with INR 3.2 presents with new headache 2 weeks after a fall — order non-contrast head CT before any other workup. If subdural is found, reverse with 4F-PCC + vitamin K, admit, neurosurgery consult.

Board pearl: Headache + new cognitive change + anticoagulation in elderly = chronic SDH until imaging proves otherwise.

Special Populations — Pregnancy, Postpartum, and Pediatrics

— Hypercoagulable state increases risk of CVST, ischemic stroke, PRES, pituitary apoplexy (Sheehan), and reversible cerebral vasoconstriction syndrome (RCVS).

— Eclampsia/preeclampsia: new-onset headache + HTN ≥140/90 + proteinuria after 20 weeks. Severe features include SBP ≥160, DBP ≥110, visual changes, RUQ pain, thrombocytopenia, elevated LFTs. Treat with magnesium sulfate (seizure prevention) + labetalol/hydralazine/nifedipine + delivery.

— PRES: posterior reversible encephalopathy — headache, visual changes, seizure, altered mental status; MRI shows bilateral parieto-occipital vasogenic edema. Manage BP, remove triggers.

— MRI without gadolinium is preferred (no ionizing radiation, no contrast-fetal risk).

— Non-contrast CT head exposes fetus to minimal dose (<0.001 rad with shielding); acceptable when emergent.

— Gadolinium: avoid in pregnancy (associated with stillbirth, neonatal death in animal/observational data).

— Acute migraine: acetaminophen first-line; metoclopramide adjunct; avoid NSAIDs in 3rd trimester (ductus closure, oligohydramnios) and avoid ergots/triptans in 1st trimester preferentially (sumatriptan has most safety data if needed).

— Preventive: propranolol or amitriptyline if needed; avoid topiramate (cleft palate), valproate (neural tube defects, neurodevelopmental).

— Recurrent morning vomiting, worsening headache, gait change, papilledema → posterior fossa tumor (medulloblastoma, astrocytoma, ependymoma) — image with MRI.

— Headache + fever + meningismus in <2 years may lack classic signs; bulging fontanelle, lethargy, paradoxical irritability are key.

— Brief resolved unexplained event + headache → consider trauma/abuse.

— Children <6 with recurrent headache: image — primary headache is less common.

Pregnancy and postpartum — the "danger window":

Imaging in pregnancy:

Pharmacotherapy in pregnancy:

Pediatric red flags:

Step 3 management: Postpartum day 7, woman presents with thunderclap headache and seizure — order MRI/MRV (CVST) and check BP/proteinuria (late postpartum eclampsia, which can occur up to 6 weeks postpartum). Start magnesium if eclampsia suspected.

Board pearl: New headache in late pregnancy/postpartum with HTN = eclampsia until proven otherwise; magnesium and delivery are the answer.

Complications and Adverse Outcomes

— Rebleeding: highest risk first 24 hours (up to 15%); prevented by early aneurysm securing and BP control

— Vasospasm/delayed cerebral ischemia: peak days 4–14; monitored with transcranial Doppler and clinical exam; treat with induced hypertension and endovascular intervention

— Hydrocephalus: acute obstructive or chronic communicating

— Hyponatremia: cerebral salt wasting (treat with salt and fluid replacement, not fluid restriction) vs. SIADH — distinguished by volume status

— Seizures, cardiac dysfunction (neurogenic stunned myocardium), neurogenic pulmonary edema

— Hearing loss (especially pneumococcal — audiology follow-up at discharge and 6 weeks)

— Cognitive impairment, seizures, hydrocephalus, focal deficits

— Septic shock, DIC, adrenal hemorrhage (Waterhouse-Friderichsen with meningococcus)

— Anterior ischemic optic neuropathy → irreversible monocular blindness; second eye affected within 1–2 weeks if untreated

— Aortic aneurysm/dissection (long-term; screen with imaging every 2–3 years)

— Stroke (vertebrobasilar territory)

— Steroid-related: osteoporosis, diabetes, infection, weight gain

— Progressive visual field loss → blindness (the only outcome that matters long-term)

— Chronic headache, depression

SAH complications:

Bacterial meningitis sequelae:

GCA complications:

IIH complications:

Medication-overuse headache: Paradoxical worsening of headache frequency with chronic acute-medication use (>10 days/month for triptans/opioids/combination analgesics; >15 days for simple analgesics). Cycle reinforces itself.

CVST complications: Venous infarction with or without hemorrhage, seizures, elevated ICP with herniation.

Step 3 management: Every patient discharged after bacterial meningitis needs an audiology evaluation before or shortly after discharge — this is a frequently tested quality measure.

Board pearl: Hyponatremia in SAH is usually cerebral salt wasting (hypovolemic) — treat with hypertonic saline and salt tablets, not fluid restriction. Fluid restriction worsens vasospasm.

When to Escalate Care — ICU, Consults, and Inpatient Triage

— Aneurysmal SAH (all): neurocritical care unit for q1h neuro checks, BP control, vasospasm monitoring

— ICH with GCS <13, midline shift, hydrocephalus, or expanding hematoma

— Bacterial meningitis with septic shock, altered mental status, seizures, or need for airway protection

— Status epilepticus from encephalitis

— Malignant cerebral edema (large MCA infarct, fulminant CVST)

— Hypertensive emergency requiring IV titratable agents

— Eclampsia requiring magnesium infusion and close monitoring

— Stable SAH after aneurysm secured (after ICU stay)

— Bacterial meningitis with stable mental status on antibiotics

— Newly diagnosed brain tumor with edema on dexamethasone

— IIH with severe symptoms requiring inpatient acetazolamide titration or LP series

— First seizure related to mass lesion

— Neurosurgery: SAH, ICH with mass effect, SDH/EDH, hydrocephalus, tumor with mass effect, refractory IIH, SIH requiring surgical repair

— Neurology: stroke, CVST, encephalitis, status epilepticus, RCVS, demyelinating disease

— Interventional neuroradiology: aneurysm coiling, mechanical thrombectomy, venous sinus stenting, blood patch

— Rheumatology: GCA confirmation, steroid-sparing therapy planning

— Ophthalmology: GCA (urgent), IIH (visual field monitoring), papilledema evaluation

— Infectious disease: atypical/complicated meningitis, brain abscess, HIV-related CNS disease

— Maternal-fetal medicine: any pregnancy-related neurologic emergency

— Red flags excluded, exam normal, pain controlled, reliable follow-up, clear return precautions documented

ICU admission criteria:

Floor/stepdown admission:

Consult triggers:

Discharge from ED — must satisfy:

CCS pearl: In an SAH CCS case, the order "transfer to neuro ICU" should appear within the first few minutes, alongside neurosurgery consult, nimodipine PO, BP target, and aneurysm imaging (CTA). Forgetting nimodipine costs points.

Step 3 management: A patient with confirmed GCA and new vision loss requires same-day ophthalmology evaluation and IV methylprednisolone — admit, do not send home on oral prednisone.

Key Differentials — Other Headache Etiologies (Same Category)

— SAH: thunderclap, neck stiffness, photophobia; CT positive early, xanthochromia on LP later

— ICH: focal deficits prominent, often hypertensive history; CT shows parenchymal hyperdensity

— Cervical artery dissection: neck/face pain, partial Horner syndrome, history of trauma/chiropractic/connective tissue disease; MRA/CTA shows crescent sign

— CVST: subacute headache, papilledema, seizures, focal deficits; risk factors are hypercoagulability, OCP, pregnancy, dehydration; MRV/CTV diagnostic

— RCVS: recurrent thunderclap headaches over 1–2 weeks, normal initial imaging, "string of beads" on angiography that resolves by 3 months; vasoactive triggers

— Pituitary apoplexy: sudden headache + bitemporal hemianopia + ophthalmoplegia + adrenal insufficiency; MRI shows hemorrhagic pituitary mass

— Bacterial meningitis: rapid onset, high fever, neck stiffness, altered mental status; CSF neutrophilic with low glucose

— Viral (aseptic) meningitis: milder, self-limited; CSF lymphocytic with normal glucose

— Encephalitis (HSV most common): confusion, seizures, temporal lobe involvement on MRI/EEG

— Brain abscess: subacute, often history of sinusitis/dental infection/endocarditis; ring-enhancing lesion with restricted diffusion (distinguishes from tumor)

— IIH: young obese women, papilledema, normal imaging, ↑opening pressure

— Brain tumor: progressive, positional, morning predominance, focal signs

— Hydrocephalus: triad of gait, urinary, cognitive (NPH) or acute headache (obstructive)

— Post-LP headache: within 5 days of procedure, postural, treated with hydration, caffeine, blood patch

— Spontaneous intracranial hypotension: orthostatic headache, MRI shows diffuse pachymeningeal enhancement and "brain sag"

Within secondary headache, distinguish among vascular causes:

Among infectious causes:

Among elevated-ICP causes:

Among low-pressure causes:

Key distinction: Brain abscess and metastases both produce ring-enhancing lesions on MRI, but abscesses restrict diffusion on DWI (bright) while necrotic tumors typically do not — this single sequence resolves the differential.

Board pearl: Recurrent thunderclap headache + normal initial workup + female on SSRI = think RCVS, not migraine.

Key Differentials — Primary Headaches and Mimics

— Migraine: unilateral, throbbing, 4–72 h, with nausea/photophobia/phonophobia; may have aura. Reassuring features: stereotyped recurrent attacks, normal exam, normal interval.

— Tension-type: bilateral, pressing/tightening, mild-moderate, no nausea, not aggravated by activity

— Cluster: unilateral periorbital, severe, 15–180 min, with ipsilateral autonomic features (lacrimation, conjunctival injection, ptosis, miosis, rhinorrhea, restlessness); circadian/seasonal clustering

— Paroxysmal hemicrania: like cluster but shorter (2–30 min), more frequent (>5/day), absolutely responsive to indomethacin (diagnostic)

— SUNCT/SUNA: very brief (seconds), very frequent

— Hemicrania continua: continuous unilateral pain, indomethacin-responsive

— Cervicogenic headache: unilateral, originating from neck, reproduced by neck movement/palpation; treat with PT, trigger-point injection, occipital nerve block

— Temporomandibular disorder: jaw clicking, bruxism, masseter tenderness

— Acute angle-closure glaucoma: unilateral headache + eye pain + halos + mid-dilated nonreactive pupil + red eye → emergent ophthalmology, IV acetazolamide, pilocarpine, laser iridotomy

— Acute sinusitis: facial pressure, purulent rhinorrhea, lasting >10 days or worsening after initial improvement

— Trigeminal neuralgia: lancinating facial pain in V2/V3 distribution, triggered by light touch/chewing; treat with carbamazepine; image with MRI to exclude MS plaque or vascular compression

— Carbon monoxide poisoning: headache + nausea + multiple affected household members + winter season → check COHb

— Hypoxia/altitude/sleep apnea: morning headache → screen with overnight oximetry/sleep study

Primary headache disorders to differentiate from secondary:

Common mimics often missed:

Key distinction: Cluster headache patients are agitated and pace; migraine patients prefer quiet, dark stillness. This behavioral observation alone often nails the diagnosis in vignettes.

Board pearl: Indomethacin-absolute-response defines paroxysmal hemicrania and hemicrania continua — this is a classic test point. Always confirm with neuroimaging to exclude secondary mimics.

Secondary Prevention and Long-Term Management

— Hypertension control to <130/80 mmHg (target as in stroke secondary prevention)

— Smoking cessation (independent risk factor for aneurysm formation and rupture)

— Screen first-degree relatives with CTA if ≥2 affected relatives or in selected families

— Surveillance imaging of treated and untreated aneurysms (timing per neurosurgery)

— Cognitive rehabilitation; depression screening (PHQ-9) — high incidence post-SAH

— Vaccinations: pneumococcal (PCV20 or PCV15 + PPSV23), meningococcal, Hib for at-risk

— Audiology evaluation

— Close contacts of meningococcal disease: chemoprophylaxis with rifampin, ciprofloxacin, or ceftriaxone

— Splenectomized/asplenic patients: encapsulated organism vaccines and antibiotic stewardship

— Prolonged steroid taper over 12–24 months

— Bone protection: calcium 1200 mg, vitamin D 800–1000 IU, DEXA, bisphosphonate

— PCP prophylaxis (TMP-SMX) if on prednisone ≥20 mg for >4 weeks

— Aspirin 81 mg daily

— Annual screening for thoracic aortic aneurysm (CT or MRI every 2–3 years)

— Tocilizumab to reduce cumulative steroid exposure

— Anticoagulation 3–6 months for provoked; 6–12 months or indefinite for unprovoked or thrombophilia

— Thrombophilia workup after anticoagulation completed (timing affects test interpretation)

— Avoid estrogen-containing contraceptives indefinitely

— Weight loss is disease-modifying (bariatric surgery considered if BMI ≥35 with refractory disease)

— Serial visual fields and OCT (optic nerve fiber layer)

— Continue acetazolamide until sustained remission

Post-SAH long-term care:

Post-meningitis:

GCA long-term:

CVST long-term:

IIH long-term:

Medication-overuse headache: Establish preventive therapy, taper overused agents, limit acute meds to <2 days/week, behavioral therapy.

Step 3 management: A patient discharged on prednisone 60 mg for GCA needs bone protection (Ca/vitD/bisphosphonate), PCP prophylaxis if ≥20 mg ≥4 weeks, glucose monitoring, BP monitoring, and a structured taper plan documented at discharge.

Board pearl: All meningococcal disease cases require public health reporting and contact chemoprophylaxis — this is both a clinical and legal obligation.

Follow-Up, Monitoring, and Counseling

— SAH post-discharge: neurosurgery at 4–6 weeks; vascular imaging at 6 months and 1 year; PCP at 2 weeks for medication reconciliation and depression screening

— Bacterial meningitis: PCP within 1–2 weeks; audiology at 4–6 weeks; ID follow-up if complicated

— GCA: rheumatology every 2–4 weeks during taper with ESR/CRP, CBC, glucose, BP; annual aortic imaging

— CVST: hematology for thrombophilia workup at 3–6 months; repeat MRV at 3–6 months to document recanalization

— IIH: ophthalmology every 1–3 months until stable; PCP for weight management

— Brain tumor (post-op): neuro-oncology every 2–3 months with surveillance MRI

— Migraine/primary headache: headache diary review at 4–6 weeks; preventive therapy trial of 2–3 months before declaring failure

— On acetazolamide: electrolytes (metabolic acidosis, hypokalemia), renal function, paresthesias, weight, visual fields

— On chronic steroids: glucose, BP, lipids, DEXA at baseline and annually, weight

— On topiramate: weight, mood, cognition, electrolytes (mild metabolic acidosis), nephrolithiasis history

— On anticoagulation (CVST): INR for warfarin, no routine monitoring for DOACs but periodic renal/liver function

— Headache diary: date, time, duration, severity, triggers, medications used, response — essential for primary headache management and detecting overuse

— Return precautions: sudden severe headache, new neurologic symptoms, fever, vision change, persistent vomiting → ED

— Lifestyle: regular sleep, hydration, meals, aerobic exercise; identify migraine triggers (alcohol, MSG, sleep deprivation, hormonal)

— Driving: review state-specific seizure-related driving restrictions

— Pregnancy planning: counsel about teratogenic preventives (topiramate, valproate) — switch before conception

Follow-up cadence by diagnosis:

Monitoring parameters:

Patient counseling priorities:

Step 3 management: At 2-week post-meningitis visit, your checklist includes audiology referral status, vaccination update, complete neuro exam, mood screen, and confirmation that close contacts received chemoprophylaxis if indicated.

Board pearl: A "headache diary for 4–6 weeks before next visit" is the single highest-yield outpatient intervention for chronic headache evaluation — tested as the correct "next step" repeatedly.

Ethical, Legal, and Patient Safety Considerations

— For elective neuroimaging of low-risk headache: discuss radiation exposure (~2 mSv for non-contrast CT head), cost, and incidentaloma risk (~1–2% find unrelated lesions requiring further workup). Document the conversation.

— For lumbar puncture: risks of post-LP headache (10–30%), bleeding, infection, herniation if undetected mass effect — informed consent required.

— For thrombolysis or endovascular intervention in stroke mimics: time-pressured consent with surrogate decision-makers when patient is impaired.

— A patient with altered mental status from meningitis or SAH lacks decision-making capacity; obtain surrogate consent per state hierarchy (spouse, adult children, parents, siblings).

— In life-threatening emergencies, implied consent applies — treat first, consent later.

— Meningococcal and Haemophilus meningitis are reportable diseases — notify local health department to enable contact tracing and chemoprophylaxis.

— Suspected non-accidental head trauma in children → mandatory child protective services report.

— Seizure-related driving: state laws vary (most require physician reporting or patient self-reporting); document counseling about driving restrictions.

— Discharge after SAH or meningitis requires explicit handoff including: medication reconciliation, follow-up appointments already scheduled before discharge, return precautions, and accurate problem list for receiving PCP.

— Anticoagulation initiation for CVST: ensure patient understands signs of bleeding, has follow-up INR/labs arranged, and a clear contact for questions.

— Steroid taper for GCA: written taper schedule, bone health prescriptions filled, sick-day rules discussed (stress-dose steroids), medical alert bracelet recommended.

— Missed SAH is one of the most common high-payout malpractice claims. Document red-flag screening, exam, imaging rationale, and shared decisions. "Worst headache of life" with normal CT >6 hours from onset requires LP discussion — document the decision either way.

Informed consent and shared decision-making:

Capacity assessment:

Mandatory reporting and public health:

Transition-of-care safety (Step 3 favorite):

Diagnostic error and missed SAH:

Step 3 management: A patient discharged from the ED with "migraine" who returns with confirmed SAH — root-cause analysis should examine red-flag documentation, time to CT, and whether LP was considered when CT was performed >6 hours after onset. This is a high-yield patient-safety vignette pattern.

Board pearl: Document, document, document — the red-flag screen, exam (including fundoscopy), and the patient's understanding of return precautions.

High-Yield Associations and Rapid-Fire Facts

— Worst headache of life + neck stiffness + photophobia → SAH

— Headache + jaw claudication + age >50 + ESR ↑ → GCA

— Headache + papilledema + obese young woman → IIH

— Headache + postpartum/OCP + seizure → CVST

— Recurrent thunderclap + SSRI/cannabis → RCVS

— Headache + bitemporal hemianopia + sudden → pituitary apoplexy

— Headache + Horner syndrome + neck trauma → carotid dissection

— Morning headache + vomiting + papilledema in child → posterior fossa tumor

— Orthostatic headache after LP → post-dural-puncture headache

— Headache + ring-enhancing lesion + DWI restriction → brain abscess (not tumor)

— Headache + multiple household members ill + winter → CO poisoning

— Unilateral periorbital headache + autonomic features + agitation → cluster

— Indomethacin-responsive headache → paroxysmal hemicrania / hemicrania continua

— Headache + red eye + mid-dilated pupil → acute angle-closure glaucoma

— Non-contrast CT sensitivity for SAH: ~98% <6 h, ~85% at 24 h, ~50% at 1 week

— Opening pressure normal: <25 cm H₂O (>25–28 supports IIH)

— Ottawa SAH rule: 100% sensitivity, ~15% specificity

— Nimodipine: 60 mg PO q4h × 21 days post-SAH

— Dexamethasone in meningitis: 0.15 mg/kg q6h × 4 days

— Acetazolamide in IIH: titrate to 1–2 g/day

— Prednisone in GCA: 40–60 mg/day; IV pulse 1 g × 3 days if vision threatened

— Magnesium in eclampsia: 4–6 g IV load, 1–2 g/h maintenance

— Migraine prevention trial duration: 2–3 months before declaring failure

— ISAT: coiling > clipping for most aneurysms

— GiACTA: tocilizumab steroid-sparing in GCA

— IIHTT: acetazolamide + weight loss in mild IIH improves visual outcomes

Classic associations to memorize:

Numbers worth knowing:

Trial recall:

Step 3 management: Memorize the "image then act" vs "act then image" pairs — GCA (treat before biopsy), meningitis (treat before LP if CT needed), SAH (act on suspicion even if CT negative early), tension-type headache (no imaging needed).

Board pearl: A normal head CT does not rule out CVST, dissection, GCA, IIH, or meningitis — each requires its specific test.

Board Question Stem Patterns

"55-year-old develops sudden severe headache while lifting weights, peaks in 30 seconds. Neuro exam normal." → Next step: non-contrast head CT (within 6 hours has near-100% sensitivity for SAH). If CT negative and presentation >6 h: LP. If CT positive: CTA + neurosurgery + nimodipine + neuro ICU.

"72-year-old with bitemporal headache, jaw claudication, transient monocular vision loss, ESR 98." → Next step: start high-dose prednisone immediately, then schedule temporal artery biopsy within 1–2 weeks. If vision involved: IV methylprednisolone 1 g × 3 days.

"29-year-old, 10 days postpartum, presents with headache and tonic-clonic seizure. BP 162/108." → Could be eclampsia (give magnesium + labetalol) or CVST (MRI/MRV) — initial steps: stabilize airway, magnesium, BP control, urgent MRI with MRV.

"28-year-old woman, BMI 38, daily headache, transient visual obscurations. Papilledema bilaterally. CT normal." → LP with opening pressure (likely >25 cm H₂O) → diagnosis IIH → acetazolamide + weight loss + ophthalmology follow-up.

"82-year-old on warfarin, fell 3 weeks ago, now with headache and confusion." → Non-contrast CT head → likely subdural → reverse with 4F-PCC + vitamin K → neurosurgery consult.

"22-year-old with fever, headache, photophobia, neck stiffness." → Blood cultures → ceftriaxone + vancomycin + dexamethasone → then CT (if indicated) → LP. Don't wait on imaging or LP to start antibiotics.

"32-year-old woman on SSRI with 3 thunderclap headaches in 10 days. Initial CT and LP negative." → MRA/CTA → likely RCVS (segmental vasoconstriction) → discontinue trigger, supportive care, avoid steroids.

"Long-standing migraineur now with headache that is different — more severe, with new visual aura lasting hours." → Image (MRI preferred) — change in pattern is a red flag.

Stem 1 — Thunderclap headache:

Stem 2 — Older patient with new headache and vision symptoms:

Stem 3 — Postpartum headache with seizure:

Stem 4 — Obese young woman with daily headache:

Stem 5 — Anticoagulated elderly with confusion:

Stem 6 — Headache + fever + neck stiffness:

Stem 7 — Recurrent thunderclap:

Stem 8 — Stable migraine, new pattern:

Step 3 management: When the stem gives you ESR/CRP in an older patient with headache, the answer almost always involves GCA — recognize it instantly.

Board pearl: "Next best step" questions usually test the earliest decisive action: imaging vs treatment vs LP. Default rule: treat life-threatening empirically; image when red flags are present and stable.

One-Line Recap

Bottom line: In the evaluation of headache, a structured red-flag screen (SNNOOP10) — combined with focused neurologic and fundoscopic examination — distinguishes the 90% of benign primary headaches from the 10% of life-threatening secondary causes that demand targeted imaging, lumbar puncture, ESR/CRP, or empiric treatment before confirmation.

— Thunderclap = SAH until proven otherwise: non-contrast CT first (most sensitive <6 h), LP if delayed presentation or normal CT with high suspicion, CTA for aneurysm; nimodipine PO × 21 days; neuro ICU.

— New headache age >50 = GCA until proven otherwise: check ESR/CRP same day, start high-dose prednisone immediately (IV pulse if vision threatened), biopsy within 1–2 weeks; add aspirin, bone protection, PCP prophylaxis; screen for aortic aneurysm long-term.

— Postpartum/OCP + headache + seizure or focal deficit = CVST or eclampsia: MRI/MRV vs BP/proteinuria assessment; anticoagulate CVST even with hemorrhagic infarct; magnesium and delivery for eclampsia.

— Obese young woman + daily headache + papilledema = IIH: confirm with LP opening pressure; weight loss + acetazolamide; serial visual fields prevent blindness; surgical CSF diversion or stenting if refractory.

High-yield recap bullets:

Never forget: Treat-before-confirm in GCA, suspected bacterial meningitis, and clinical SAH. Image-before-LP only if focal deficit, papilledema, altered mental status, immunocompromise, or seizure. Document red-flag screen, fundoscopy, exam, return precautions — defensible care is also good care.

Outpatient discipline: Headache diary for 4–6 weeks, identify medication overuse (acute meds >10–15 days/month), initiate preventive therapy after 2–3 month trial, address lifestyle (sleep, hydration, exercise, stress) — the longitudinal Step 3 lens.

Board pearl: When a Step 3 stem asks "next best step" in headache, it is almost always testing whether you recognized a red flag and chose the correct first decisive action — imaging, empiric therapy, or specialty consult.