What is the most likely diagnosis for a patient with a severe throbbing unilateral headache, nausea, photophobia, and transient visual aura, with normal complete blood count (CBC), basic metabolic panel (BMP), and serum C-reactive protein (CRP)?

Migraine with Aura

This patient has migraine with aura (Option C), characterized by the classic presentation of transient visual disturbances ("shimmering lights") followed within 30 minutes by severe unilateral throbbing headache with nausea and photophobia. 1, 2

Why This is Migraine with Aura

The clinical presentation fulfills the diagnostic criteria for migraine with aura:

• Visual aura symptoms: The "shimmering lights" in peripheral vision represent fully reversible visual aura symptoms that developed and then resolved before the headache onset 1
• Temporal relationship: The aura resolved approximately 30 minutes before headache onset, consistent with the criterion that aura is accompanied or followed within 60 minutes by headache 1
• Headache characteristics: Severe, throbbing, unilateral (left-sided) pain lasting hours meets migraine criteria 2, 3
• Associated symptoms: Nausea and photophobia are classic accompanying migraine symptoms 2, 3
• Prior episodes: The patient reports previous episodes of visual flashing, suggesting recurrent attacks 1

The POUND mnemonic helps confirm migraine diagnosis: Pulsating (throbbing), 4-72 hOurs duration, Unilateral, Nausea, Disabling—this patient meets 4 of 5 criteria, yielding a likelihood ratio of 24 for migraine 4

Why Not the Other Diagnoses

Acute angle-closure glaucoma (Option A) is excluded because:

• The neurologic examination including cranial nerves and eyes is completely normal 4
• Acute glaucoma presents with a red, painful eye, fixed mid-dilated pupil, and elevated intraocular pressure—none of which are present 4
• Visual symptoms in glaucoma are persistent (blurred vision, halos), not transient and fully reversible 4

Giant cell arteritis (Option B) is ruled out by:

• Normal serum C-reactive protein (CRP is typically markedly elevated in giant cell arteritis) 4
• No tenderness to palpation over the face or scalp (temporal artery tenderness would be expected) 4
• Patient age and presentation are not typical for giant cell arteritis, which predominantly affects patients over 50 years 4

Intracranial hypertension (Option D) is unlikely because:

• Headaches from intracranial hypertension typically worsen with position changes and Valsalva maneuvers 4
• Visual symptoms in intracranial hypertension are persistent (papilledema, visual field defects), not transient scintillations 4
• The normal neurologic examination, including normal cranial nerve and eye examination, argues strongly against increased intracranial pressure 4
• While BMI of 31 is a risk factor for idiopathic intracranial hypertension, the clinical presentation does not fit 4

Clinical Pearls

• Visual aura characteristics: Scintillations (shimmering lights) and zigzag lines are positive aura symptoms that typically expand over 5-20 minutes and last less than 60 minutes 1
• Normal laboratory studies: The normal CBC, BMP, and CRP effectively exclude inflammatory, infectious, and metabolic causes of secondary headache 2, 4
• Aura without prior migraine headache: Patients can experience visual aura episodes without subsequent headache before developing their first migraine with aura attack 1, 5
• No neuroimaging needed: This patient has no red flags requiring neuroimaging (no abnormal neurologic examination, no cluster-type features, no undefined headache pattern, no exertional component) 4