Positional Testing & BPPV
Benign Paroxysmal Positional Vertigo accounts for roughly a quarter of all dizziness presentations. The pathophysiology is mechanical and the cure is mechanical — making it among the most satisfying diagnoses in vestibular medicine.
Otoconia are calcium carbonate crystals normally embedded in the otolith membranes of the utricle and saccule. With age or trauma they can dislodge, drift into a semicircular canal — most often the posterior — and there generate inappropriate cupular deflection with head movement.[Dix & Hallpike 1952][Bhattacharyya et al. 2017]
Patient seated, eyes open with VNG goggles on. No nystagmus at baseline. Otoconia sit in the dependent posterior canal, near the ampulla.
The classic test for posterior canal BPPV. The head turn aligns the right posterior canal with the sagittal plane; rapidly laying the patient back with head extended brings the canal into the gravitational vertical, and free-floating otoconia migrate. The resulting endolymph movement excites the canal afferents, producing the diagnostic torsional + up-beating nystagmus.[Dix & Hallpike 1952]