Origin of early waves evoked by infraorbital nerve stimulation in man.

The origins of early waves recorded from the scalp of man after stimulation of the infraorbital nerve have been investigated by simultaneous recording from the scalp and from the trigeminal pathway in patients undergoing thermocoagulation rhizotomy. It has been found that the surface-recorded W1, W2 and W3 waves correspond respectively to the activity of the point of entry of the maxillary nerve into the gasserian ganglion, the point of entry of the trigeminal root into the pons and the presynaptic portion of the trigeminal spinal tract. It is remarked that depth recording during surgery may provide useful information about the positioning of the thermocoagulation electrode.