The mechanism of the pain in trigeminal neuralgia.

Trigeminal neuralgia (tic douloureux) is characterized by brief paroxysms of pain limited to the facial distribution of the trigeminal nerve and is precipitated by stimuli to sensory endings in the trigeminal receptive area. The condition is relieved by blocking the afferent input of the trigeminal nerve. According to Wyburn-Mason (1953) and Crue, Shelden, Pudentz, and Freshwater (1956), attacks of trigeminal neuralgia can in some cases be abolished by interruption of adjacent cervical nerves. The neurophysiological mechanism underlying trigeminal neuralgia is still obscure (cf. List and Williams, 1957). King and Meagher (1955), King and Barnett (1957), and King, Meagher, and Barnett (1956) described alterations of trigeminal nerve potentials associated with over-reaction to tactile facial stimulation in cats produced by applying alumina gel or strychnine to the spinal trigeminal nucleus. The electrical potential changes in the human trigeminal system associated with the paroxysmal pain, however, remain to be investigated. Moreover, the finding of a correlation between the clinical syndrome of tic douloureux and the electrophysiological phenomena presupposes a detailed knowledge of the clinical events. Since the mechanism of the paroxysmal pain is intimately associated with afferent discharges we have studied with semiquantitative methods the relation between the attack of pain and stimuli applied to the skin trigger zone. The effect of anti-epileptic drugs, such as hydantoin and lidocain, has also been investigated.