Figure 4.

When canalolithiasis of the short arm of the horizontal semicircular canal near the ampulla occurs (left ear), a similar nystagmus (bilateral apogeotropic) as in the cupulolithiasis cases is observed during the supine roll test (the involved left horizontal canal is colored black). (a) Patient in supine position with debris in the short arm of the left horizontal canal. (b) When rotating the head towards the affected side, the particles move away from the cupula, which will undergo an ampullofugal (inhibitory) deflection, triggering an apogeotropic horizontal nystagmus. (c) When rotating the head towards the healthy side, the particles move towards the cupula, which will undergo an ampullopetal (stimulatory) deflection, triggering a more intense apogeotropic nystagmus.