[Orbicular eye reflex (R3) and the valsalva manoeuvre]

Different kinds of tests have been devised to evaluate the autonomic nervous system, including the changes in heart rate and arterial blood pressure after carrying out Valsalva s manoeuvre. However, to date, the behaviour of the three responses to the orbicular eye reflex during this manoeuvre was not known and this was the reason for carrying out our study.

We evaluated 12 neurologically normal persons before and after doing a Valsalva manoeuvre by studying the orbicular eye reflex using the method of Kimura and recording the three responses: R1, R2 and R3.

The late results (R3) of this reflex, but not those of short (R1) or medium (R2) latency were significantly modified whilst the manoeuvre was carried out (p< 0.05).

Inhibition of the gamma motor neurones during this inspiratory manoeuvre, which are also related to activity of the facial muscles, seems to be the mechanism most likely to explain the findings during the practice of BREATH (Blink reflex autonomic testing in humans). Studies which evaluate only the first two responses to this reflex whilst the manoeuvre is carried out should not be taken too seriously since they may lead to dangerously erroneous conclusions.