Question

Discuss the pathophysiology of benign paroxysmal positional vertigo (BPPV).

Hint:

The posterior semicircular canal is the most commonly involved canal in BPPV. Treatment options, such as the Epley maneuver, aim to reposition the displaced otoconia.

Answer 1

Step 1: Introduction to BPPV.
Benign Paroxysmal Positional Vertigo (BPPV) is a common cause of vertigo, characterized by brief episodes of dizziness triggered by specific head movements. It occurs due to the displacement of otoconia (calcium carbonate crystals) from the utricular macula into the semicircular canals, particularly the posterior canal. The displacement causes abnormal stimulation of the endolymph within the canal, resulting in the sensation of vertigo.

Step 2: Pathophysiology of BPPV.
- Otolith Displacement: Normally, otoconia (small crystals) are attached to the otolithic membrane in the utricle. In BPPV, these crystals become dislodged due to trauma, aging, or degenerative changes, and enter one of the semicircular canals, most commonly the posterior canal. - Canalithiasis: The crystals move freely within the semicircular canal, disrupting the flow of endolymph and causing abnormal stimulation of the cupula, leading to vertigo. - Cupulolithiasis: In some cases, the otoconia become adhered to the cupula (the sensory structure in the semicircular canal), causing persistent vertigo when the head is moved into certain positions. - Abnormal Sensory Input: The brain receives conflicting information from the vestibular system (inner ear) and visual system, resulting in a sensation of spinning (vertigo) when the head is moved.

Step 3: Clinical Manifestation.
The typical symptoms of BPPV include brief episodes of vertigo that are triggered by changes in head position, such as rolling over in bed, looking up, or bending over. The episodes usually last less than a minute but can cause significant discomfort.

Step 4: Conclusion.
BPPV is a mechanical disorder caused by the displacement of otoconia into the semicircular canals, disrupting the normal function of the vestibular system and leading to positional vertigo.