What is the likely cause of dizziness in a middle-aged woman with a history of migraines (since her 40s), worsening migraine frequency, and no response to the Epley maneuver, following a normal complete neuro exam and negative Dix-Hallpike maneuver?

Vestibular Migraine is the Most Likely Diagnosis

Given the negative Dix-Hallpike maneuver, lack of response to the Epley maneuver, normal neurological examination, and history of worsening migraines, vestibular migraine is the most probable cause of this patient's dizziness. 1

Why This is Vestibular Migraine

The clinical presentation strongly points to vestibular migraine based on several key features:

• Negative Dix-Hallpike maneuver rules out typical BPPV, which would show characteristic torsional upbeating nystagmus with latency and fatigability 2, 1
• Lack of response to Epley maneuver is a red flag against BPPV, as properly performed canalith repositioning procedures achieve 80% success rates after 1-3 treatments for true BPPV 2, 3
• History of migraines since her 40s with recent worsening is the critical diagnostic clue—vestibular migraine has a lifetime prevalence of 3.2% and accounts for up to 14% of all vertigo cases, being extremely common in women 1
• Dizziness episodes occurring without concurrent migraine headache is typical of vestibular migraine, where vertigo can occur before, during, or after headache, or even independently 1

Critical Distinguishing Features to Confirm

You need to specifically assess these features to solidify the diagnosis:

• Duration of dizziness episodes: Vestibular migraine episodes can be short (<15 minutes) or prolonged (>24 hours), unlike BPPV which lasts <1 minute 1
• Triggers: Ask about motion intolerance, light sensitivity, and visual stimuli as triggers 1
• Associated symptoms during at least 50% of vertigo episodes: Photophobia, phonophobia, or visual aura 1
• Hearing status: Vestibular migraine typically has stable or absent hearing loss, NOT fluctuating hearing loss like Ménière's disease 1

What You Must Rule Out Now

Despite the normal neuro exam, you cannot stop here:

• Perform the supine roll test to evaluate for horizontal canal BPPV, which accounts for 10-15% of BPPV cases and would be missed by Dix-Hallpike alone 2, 1
• Assess for fluctuating hearing loss, tinnitus, and aural fullness to exclude Ménière's disease, which presents with the classic triad of episodic vertigo lasting hours, fluctuating sensorineural hearing loss, and aural fullness 1
• Formal audiometry is mandatory given the abnormal Weber test mentioned in related evidence—this will differentiate conductive from sensorineural hearing loss and help distinguish vestibular migraine from Ménière's disease 1

Red Flags That Would Demand Immediate MRI

Watch for any of these features that would indicate central pathology requiring urgent neuroimaging:

• Severe postural instability with falling 1
• New-onset severe headache with vertigo (could indicate vertebrobasilar stroke) 1
• Downbeating nystagmus without torsional component 1
• Baseline nystagmus present without provocative maneuvers 1
• Any additional neurological symptoms beyond what you've already examined 1

Treatment Approach for Vestibular Migraine

Once you've confirmed the diagnosis:

• Dietary modifications and lifestyle interventions are first-line approaches 1
• Vestibular rehabilitation therapy can be beneficial for residual dizziness and postural instability 1, 3
• Do NOT prescribe vestibular suppressants (meclizine, antihistamines, benzodiazepines) as they are ineffective for vestibular migraine and cause drowsiness, cognitive deficits, and increased fall risk 3

Common Diagnostic Pitfalls to Avoid

• Overlooking vestibular migraine as a diagnosis—it is under-recognized despite being extremely common in patients with both migraine and vertigo 1
• Failing to repeat the Dix-Hallpike test—sometimes being held in head-hanging positions allows canaliths to collect such that the test becomes positive on repeat 4
• Not testing horizontal canals—failure to perform the supine roll test may miss 10-15% of BPPV cases 2, 1
• Assuming all dizziness with migraine history is benign—approximately 10% of cerebellar strokes present similar to peripheral vestibular disorders 1

Next Steps Algorithm

1. Perform supine roll test immediately to rule out horizontal canal BPPV 2, 1
2. Order formal audiometry to assess for fluctuating hearing loss (Ménière's) versus stable/absent hearing loss (vestibular migraine) 1
3. Reassess within 1 month to document symptom pattern and response to any interventions 3
4. If symptoms persist or worsen despite appropriate management, or if any red flags develop, obtain MRI brain without and with contrast 2, 5
5. Consider referral to neurology or otolaryngology if diagnosis remains uncertain or symptoms are refractory 5