Autonomic nervous system activity associated with postural disturbances inpatients with perilymphatic fistula: Sympathetic or vagal origin?

The study focused on patients suffering from perilymphatic fistula (PLF), w hether they had undergone surgery or not. Vestibular disturbances can be ha rmless but are associated with varying symptoms, demonstrating disorders wi thin the autonomic nervous system (ANS). The aim was to test whether the or thosympathetic is involved as the vagal part is often suspected of elicitin g a feeling of sickness. Non-invasive and uninterrupted recording of ANS ac tivity represents an objectivation technique to evidence such disturbances. Etectrodermal activity, thermovascular variables, instantaneous cardiac ra te and blood pressure were recorded. Discomfort was triggered experimentall y by applying various stimulations successively to the intact ear then to t he PLF (or operated) side. Twelve subjects took part in the experiment. Two types of ANS activity were distinguished: (1) phasic responses during stim ulation and (2) tonic evolution thereafter. Results show strong activation in orthosympathetic variables when the PLF side was stimulated. No further significant difference between the two sides was to be observed following s urgery. After stimulation, a sudden increase in skin resistance was observe d, associated with slight bradycardia. No vagal signs having been evidenced , actual nausea may result from brief inhibition of sympathetic activation resulting, in turn from primary over-activation of this system. (C) 2000 El sevier Science Inc.