The coexistence of cupulolithiasis and canalolithiasis appears to be a possible mechanism of the spontaneous inversion of positional nystagmus.

A 63-year-old woman had disabling positional vertigo for four months. She showed intense direction-changing apogeotropic nystagmus. Conservative treatment failed to resolve her vertigo. From the findings of the nystagmus, cupulolithiasis of the right lateral canal was suspected. Plugging of this canal successfully eliminated the nystagmus and positional vertigo. Positional vertigo can sometimes be disabling and unresponsive to conservative therapy. Careful analysis of the nystagmus may allow selection of the most appropriate treatment.

Pupillary dilation in response to sound stimuli is well established and is generally considered to represent a startle reflex to sound. We believe that the auditory-pupillary response represents not only a simple startle reflex to sound stimuli but also represents a reaction to stimulation of other sense organs, such as otolith organs. Eight young healthy volunteers without a history of hearing and equilibrium problems and 12 subjects with bilateral deafness participated in this study. Computer pupillography was used to analyze the auditory-pupillary responses of both eyes in all subjects. We found that auditory-pupillary responses occurred even in subjects with bilateral deafness and that this response was comparable to those of normal subjects. We propose that the auditory-pupillary response also relates to vestibular function. Thus, assessing the auditory-pupillary response may be useful for evaluating the vestibulo-autonomic response in patients with peripheral disequilibrium.

A 16-year-old boy with rotatory positional vertigo and nausea, particularly when lying down, visited our clinic. Initially, we observed vertical/torsional (downward/leftward) nystagmus in the supine position, and it did not diminish. In the sitting position, nystagmus was not provoked. Neurological examinations were normal. We speculated that persistent torsional down-beating nystagmus was caused by the light cupula of the posterior semicircular canal. This case provides novel insights into the light cupula pathophysiology.

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