Nystagmus and Vestibular Function
The direction of the endolymph flow is the slow phase of nystagmus. Caloric Testing - COWS (Cold Opposite Warm Same) - Fast phase of nystagmus is to the opposite side in cold caloric testing and to the same side in warm testing. Convection current in the 30 degree uptilted lateral canal causes endolymph flow to move anterosuperiorly towards the utricle with warm testing, resulting in positive stimulation of the ampulla. Posteroinferior flow, caused by cold convection, causes negative stimulation of the ampulla. Canal hypofunction - Aeroplane principle - if an airplane engine fails, but the other side continues, plane will veer to the side of the broken engine - vestibular hypofunction in right lateral canal, for instance, will cause drifting (in mobilising and also slow phase of nystagmus) to the right, with a resultant corrective fast phase)
