A reproducible trigger for the measurement of trigeminal latencies elicited by a glabellar tap.

In order to develop a screening test of trigeminal latencies which could be used in the field, a stimulator which delivered a "tap" consisting of a focused puff of air to the glabella was compared with a tap delivered by means of a lightweight hammer with a piezoelectric trigger similar to that described by Shahani (Shahani and Young, 1972, Neurology 22, 149-154). Results were similar for both methods although the mechanical tap failed to elicit a response from the left side in one subject. The benefit of the air tap is in the reproducible force of the tap and better aim than is possible with the hammer.