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Many people experience their first attack of benign paroxysmal positional vertigo when waking up in the morning and are quite frightened by the intensity of the symptoms. The actual vertigo is usually of short duration (less than a minute) but the intensity of the sensation is so strong that the patient often reports experiencing a much longer attack. Most cases of benign paroxysmal positional vertigo resolve within a few weeks or months without any treatment. Often people can identify the exact movement that causes their vertigo and they tend to avoid making these movements in order to avoid the onset of symptoms.

The exact physiological mechanism responsible for benign paroxysmal positional vertigo is a subject of debate. There are two theories that prevail at the present time regarding the possible underlying mechanism responsible for causing this type of vertigo:

• Canalolithiasis theory
• Cupulolithiasis theory

Canalolithiasis Theory

This is a widely accepted theory which proposes that otoliths become displaced from the utricle and float into one of the semicircular canals (usually the posterior) due to gravitational pull. This causes abnormal movement of the endolymph resulting in the bending of the hairs floating below the cupula of the affected canal, despite cessation of actual movement. The prolonged bending of the hairs triggers impulses to the brain of the sensation of movement which conflicts with messages coming from the visual system and from the musculoskeletal system (no sign of movement). The result is vertigo.

Cupulolithiasis Theory

This theory is older than the canalolithiasis theory and suggests that the debris in the endolymph (the floating otoconia) are heavier than the endolymph itself and are, therefore, pulled down by gravity towards the cupula, to which they adhere. The free-floating debris becomes attached to the cupula and, because of the extra weight, gravity pulls them down forcing the hairs under the cupula to bend. The cupula over-responds to any movement of the head because it is not in its proper position and continues to respond even after the head has stopped moving.

The major difference between the two theories is whether the vertigo is caused by free floating debris or by debris that adheres to the cupula. Both theories are still the subject of debate since they do not adequately explain why the various maneuvers to dislodge the debris particles are not effective in some cases.