Alternobaric Vertigo

In underwater diving, alternobaric vertigo is dizziness resulting from unequal pressures being exerted between the ears due to one Eustachian tube being less patent than the other. This might have occurred due to barotrauma of descent, and/or the effects of nasal decongestants. It is due to unequal increase in middle ear pressures on ascent, is usually mild, and most often cleared by further ascent. When the pressures in both ears reach ambient levels, the stimulus for the dizziness stops. Although most often mild, the vertigo can persist until the diver reaches the surface continuing the unequal pressures, which can damage the inner ear or ear drum.
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Vertigo /ver·ti·go/ [L.] a sensation of rotation or movement of one's self or of one's surroundings in any plane; sometimes used erroneously to mean [more]Alternobaric vertigo - Community and Resources