What is the differential diagnosis for an 85-year-old male presenting with sudden onset vertigo (dizziness) and unsteadiness, exacerbated by standing, with electrocardiogram (ECG) findings of sinus bradycardia and suspected complete right bundle branch block (RBBB)?

Differential Diagnosis for Sudden Onset Vertigo with Bradycardia and RBBB in an 85-Year-Old Male

This patient requires urgent evaluation for posterior circulation stroke (vertebrobasilar insufficiency) given the prolonged vertigo (5 hours), severe postural instability preventing safe ambulation, and cardiac conduction abnormalities that may indicate underlying vascular disease. 1

Primary Diagnostic Considerations

Central Vertigo (Posterior Circulation Stroke/Vertebrobasilar Insufficiency) - MOST LIKELY

This is the most concerning diagnosis that must be ruled out urgently:

• Prolonged continuous vertigo lasting 5 hours places this in the "acute vestibular syndrome" category (continuous symptoms lasting days to weeks), which includes posterior circulation stroke as a major differential 1, 2
• Severe postural instability with inability to walk safely is a cardinal red flag for central causes, particularly vertebrobasilar insufficiency and cerebellar lesions 1
• The negative Dix-Hallpike maneuver effectively excludes BPPV, which typically causes brief episodes (<1 minute) 1, 2
• Approximately 25% of patients presenting with acute vestibular syndrome have cerebrovascular disease, rising to 75% in high vascular risk cohorts 1
• Critical point: 75-80% of patients with acute vestibular syndrome from posterior circulation infarct have NO focal neurologic deficits on standard examination 2
• The ECG findings (sinus bradycardia at 52 bpm, complete RBBB, suspected ventricular hypertrophy) suggest underlying cardiovascular disease and increased stroke risk 3, 4
• Age 85 years is a significant vascular risk factor 1

Cardiac Arrhythmia with Cerebral Hypoperfusion

The ECG abnormalities warrant serious consideration:

• Sinus bradycardia (HR 52 bpm) can cause vertigo, dizziness, and syncope due to diminished cerebral blood supply 4
• Complete RBBB with suspected ventricular hypertrophy may indicate underlying structural heart disease 3
• However, the standing BP actually increased (152/76 vs 139/69 lying), making orthostatic hypotension unlikely and suggesting adequate cardiac output 3
• The correlation between symptoms and bradyarrhythmia is essential when deciding on cardiac pacing therapy 3
• Prolonged monitoring (Holter or telemetry) may be needed to document symptom-arrhythmia correlation 3

Vestibular Neuritis - LESS LIKELY

While this causes acute vestibular syndrome, several features make it less probable:

• Vestibular neuritis accounts for approximately 41% of peripheral vertigo cases and presents with acute onset severe vertigo lasting days to weeks 1
• However, the severe postural instability preventing ambulation is atypical for peripheral causes, where patients typically maintain some degree of postural control 1
• The negative Dix-Hallpike and normal ENT examination are consistent with vestibular neuritis 1
• Age 85 and cardiovascular risk factors make central causes more likely 1

Critical Red Flags Present in This Case

Multiple red flags demand immediate neuroimaging (MRI brain without contrast preferred): 1, 2

• Severe postural instability with falling/inability to walk safely 1
• Prolonged continuous vertigo (5 hours) in acute vestibular syndrome category 1, 2
• Age 85 with high vascular risk (bradycardia, RBBB, ventricular hypertrophy) 1
• Normal neurologic exam does NOT exclude stroke - this is a critical pitfall 2

Diagnoses Appropriately Excluded

The clinical assessment correctly ruled out:

• BPPV: Negative Dix-Hallpike maneuver and prolonged (5-hour) duration inconsistent with BPPV's brief (<1 minute) episodes 3, 1
• Orthostatic hypotension: No postural BP drop; standing BP actually increased 3
• Meniere's disease: No hearing loss, tinnitus, or aural fullness 1
• Labyrinthitis: No hearing loss 1

Immediate Management Recommendations

The referral to the Emergency Department was absolutely appropriate. The following should occur urgently:

• MRI brain without contrast (NOT CT) is the imaging modality of choice, as CT has only 20-40% sensitivity for posterior circulation infarcts 2
• HINTS examination (Head Impulse, Nystagmus, Test of Skew) by a trained examiner has 100% sensitivity for posterior circulation stroke versus 46% for early MRI 2
• Continuous cardiac monitoring to document any arrhythmias correlating with symptoms 3
• Cardiology consultation for evaluation of bradycardia and complete RBBB in the context of acute neurologic symptoms 3
• Neurology consultation if imaging or HINTS examination suggests central pathology 1

Common Pitfalls to Avoid

• Do not assume normal neurologic exam excludes stroke - most posterior circulation strokes present without focal deficits 2
• Do not rely on CT imaging - it misses the majority of posterior circulation infarcts 2
• Do not attribute all symptoms to bradycardia without documenting symptom-arrhythmia correlation 3
• Do not discharge without imaging in elderly patients with acute vestibular syndrome and vascular risk factors 1, 2