benign paroxysmal positional vertigo

**Pathophysiology:** Otoconia (calcium carbonate crystals) dislodge from the utricle and enter a semicircular canal. The posterior canal is involved in about 85-95% of cases because of its gravity-dependent position. Two mechanisms are proposed. In canalithiasis (the most common), free-floating particles move with head position changes, creating endolymph flow (a "plunger" effect) that deflects the cupula and produces vertigo. In cupulolithiasis, particles adhere to the cupula. Head movement produces inappropriate endolymph flow and cupular deflection, which causes a mismatch between the vestibular signals from the two sides. The result is vertigo and nystagmus.

**Clinical features:** - Brief episodes of rotatory vertigo lasting seconds to <1 minute. - Triggers include rolling over in bed, looking up, and bending over. - Nausea may occur. - There is NO hearing loss, tinnitus, or other neurologic deficits. - Episodes are often accompanied by a latency period, then crescendo-decrescendo symptoms. - Fatigability: symptoms lessen with repeated provocation.

**Risk factors:** Older age, female sex, head trauma, vestibular neuritis, prolonged bed rest, migraine, and osteoporosis/vitamin D deficiency.

**Diagnosis:** Clinical, with the **Dix-Hallpike maneuver** for posterior canal BPPV. The patient sits with the head turned 45° toward the test side and is then rapidly lowered supine with the head hanging about 20° below horizontal. A positive test produces torsional, upbeating nystagmus with latency (1-5 seconds), duration <1 minute, and fatigability. The **supine roll test** is used for horizontal (lateral) canal BPPV, which produces horizontal nystagmus. Imaging is not needed unless there are atypical features or central signs.

**Treatment:** - **Epley maneuver** (canalith repositioning) is first-line, with high success rates. The Semont maneuver is an alternative. - The Brandt-Daroff exercises can be done at home. - Vestibular suppressants (meclizine, benzodiazepines) are NOT recommended for routine treatment. They may be used briefly for severe nausea. - Surgery (posterior canal occlusion) is rarely needed for refractory cases.

**Differentiating from other causes of vertigo (high-yield for boards):** - **Vestibular neuritis:** Acute, continuous vertigo lasting days, often after a viral illness, with no hearing loss. Labyrinthitis adds hearing loss. - **Ménière disease:** Episodic vertigo lasting hours, with tinnitus, fluctuating sensorineural hearing loss, and aural fullness (endolymphatic hydrops). - **Central vertigo (posterior circulation stroke, cerebellar lesion, MS):** Direction-changing or vertical nystagmus, no latency or fatigability, and other neurologic signs. Use the HINTS exam in acute continuous vertigo. - **Vestibular migraine:** Episodic vertigo with migraine features.

**Key associations:** BPPV is the most common cause of vertigo overall. Central nystagmus is not suppressed by fixation, whereas peripheral nystagmus is suppressed by visual fixation. Recurrence is common (about 50% within 5 years), and patients should be counseled about fall risk, especially older adults.