Practical neurology--4: Dizziness on head movement.

Benign positional vertigo (BPV) is the most common cause of episodic vertigo. It results from activation of semicircular canal receptors by the movement of calcium carbonate particles (otoconia) which dislodge from the otolith membranes. During changes in head position, the otoconia either float freely within the semicircular canal duct (canalithiasis) or adhere to and move with the cupula of the canal (cupulolithiasis). BPV from canalithiasis evokes brief spells of vertigo lasting seconds and can be diagnosed at the bedside by provoking paroxysmal vertigo and nystagmus on tilting the head in the plane of the affected canal. The nystagmus has a unique rotational axis perpendicular to the affected canal. The Dix-Hallpike test is a simple means of confirming the diagnosis in patients presenting with episodic vertigo or imbalance. Audiovestibular tests are only indicated if a symptomatic primary underlying inner ear disease is suspected. In over 80% of patients, BPV can be treated successfully with a single bedside Epley (particle-repositioning) manoeuvre, which can be performed by any medical practitioner.