Reversal of paradoxical stimulation (false inversion) in perforated tympanic membranes by increasing the time of warm stimulation, evidenced by a physical model.

OBJECTIVE: To measure the time required in patients with tympanic perforation to reverse paradoxical stimulation (reverse pseudo-nystagmus) and to create a physical model of the process. METHOD: An analytical, observational, cross-sectional study with vestibular evaluation (electronystagmography) of 52 individuals with tympanic membrane perforation without otorrhea or concomitant disease. Increased duration of caloric stimulation in the presence of paradoxical stimulation (reverse pseudo-nystagmus) reverses nystagmic responses. RESULTS: Reversal of nystagmus was observed in 90.9% of patients. The average reversal time was 105.5 seconds. The physical model we prepared provided supporting evidenced for the effects seen in these individuals: warm stimulation in a moist environment initially caused a decrease in temperature (nystagmus to the unexpected side, which characterizes paradoxical stimulation in the warm caloric test); but, as time passed by, the moisture evaporated, and the temperature gradually increased (reversal of nystagmus). CONCLUSIONS: Increasing the stimulation time can be used as a strategy to differentiate reverse nystagmus from paradoxical stimulation. Confusion is thus avoided in diagnostic findings, allowing peripheral alterations to be distinguished from central ones.