A 52-year-old man presents with sudden onset severe vertigo, nausea, and vomiting that began 6 hours ago while he was lying in bed. On examination, he has spontaneous nystagmus with the fast phase beating to the right, and positive Dix–Hallpike maneuver reproducing his symptoms. Romberg test is normal, and gait is not ataxic. Hearing is intact bilaterally. What is the most likely diagnosis?

Explanation

## Diagnosis: Benign Paroxysmal Positional Vertigo (BPPV) ### Clinical Features Supporting BPPV **Key Point:** BPPV is the most common peripheral vestibular disorder, accounting for 20–30% of all vertigo cases. It is characterized by brief episodes of vertigo triggered by specific head movements. ### Diagnostic Criteria Met | Feature | Finding | Significance | |---------|---------|---------------| | **Onset** | Sudden, positional | Classic for BPPV | | **Dix–Hallpike maneuver** | Positive, reproduces symptoms | Pathognomonic for posterior canal BPPV | | **Nystagmus** | Spontaneous, rotatory with fast phase right | Indicates posterior canal involvement on right | | **Duration** | Hours (not days/weeks) | Consistent with BPPV, not neuritis | | **Hearing** | Intact | Rules out Menière disease | | **Gait/Romberg** | Normal | Rules out central cause | ### Pathophysiology **High-Yield:** BPPV results from **canalolithiasis** — dislodged otoconia (calcium carbonate crystals) from the utricle migrate into the semicircular canals, most commonly the posterior canal (90% of cases). When the head moves into the plane of the affected canal, the crystals shift, deflecting the cupula and triggering vertigo. ### Why Posterior Canal? - The **Dix–Hallpike maneuver** (head extended 20° below horizontal with neck rotated 45°) moves the head into the plane of the posterior semicircular canal. - Positive reproduction of vertigo with this maneuver is **pathognomonic** for posterior canal BPPV. - The nystagmus is **rotatory and upbeating** (torsional component toward the affected side). ### Management Algorithm ```mermaid flowchart TD A["Suspected BPPV"]:::outcome --> B{"Dix–Hallpike or Roll test positive?"}:::decision B -->|Yes| C["Confirm canal involvement"]:::action C --> D{"Posterior or lateral canal?"}:::decision D -->|Posterior| E["Epley maneuver (canalith repositioning)"]:::action D -->|Lateral| F["Semont or Barbecue roll maneuver"]:::action E --> G["Resolution in 80–90% after 1–2 sessions"]:::outcome F --> H["Resolution in 70–80% after 1–2 sessions"]:::outcome B -->|No| I["Consider central cause or other peripheral disorder"]:::action ``` **Clinical Pearl:** The **Epley maneuver** (canalith repositioning procedure) is the first-line treatment for posterior canal BPPV and achieves resolution in 80–90% of patients within 1–2 sessions. No medication is required for uncomplicated BPPV. ### Why Not Menière Disease? - Menière disease presents with **fluctuating hearing loss**, tinnitus, and aural fullness — hearing is normal here. - Episodes typically last hours to days, not minutes. - Nystagmus direction may vary with disease progression. ### Why Not Vestibular Neuritis? - Vestibular neuritis causes **continuous vertigo for days to weeks**, not brief positional episodes. - The Dix–Hallpike maneuver would not reproduce symptoms in neuritis. - Gait ataxia and positive Romberg are common in neuritis; both are normal here. ### Why Not Vertebrobasilar Insufficiency? - VBI causes **central signs**: dysarthria, diplopia, ataxia, or focal neurological deficits. - The Dix–Hallpike maneuver is not a trigger for VBI. - Hearing and gait are intact, excluding brainstem involvement. [cite:Harrison 21e Ch 21]