Evidence for a Peripheral Etiology of Trigeminal Neuralgia

B ECAUSE the paroxysmal nature of trigeminal neuralgia suggests an epileptic discharge, Kinnier Wilson 177 proposed that trigeminal neuralgia was due to a paroxysmal discharge of centrally-located trigeminal neurons. This concept has met with considerable favor and is an acceptable working hypothesis, provided it is not interpreted as an argument for a central etiology. As a matter of fact the organization of the central nuclei of the fifth cranial nerve provides one of the impor tan t lines of evidence in favor of a peripheral etiology for trigeminal neuralgia. The por t ion of the fifth spinal nucleus extending several millimeters below the level of the obex is primari ly concerned with pain and temperature. The evidence for this in man stems f rom SjSqvist's section of the spinal tract of the trigeminus; 14s it has further been shown by H a m b y that an incision as far as 10 m m below the obex level gives satisfactory trigeminal analgesia. 69 Thus only a small caudal por t ion of the nucleus, located mainly in the C-1 and C-2 segments of the spinal cord, is the major relay for pain in this system. Brodal TM demonstrated thermanalgesia of the glossopharyngeal and vagal nerves in SjSqvist 's patients and concluded that the corresponding sensory relay must reach the spinal nucleus of the trigeminus below the obex level. Caja112 demonstrated fibers of the ninth and tenth cranial nerves joining the spinal tract of the fifth nerve, but Ingram and Dawkins s~ could not trace them below C-1 or follow them to their termination in the nucleus. The manner of termination of the three divisions of the trigeminal nerve and of nerves 7, 9, and 10 in the subnucleus caudalis (pars spinalis)* of the fifth nerve has recently been demonstrated in considerable detail. 9~ Whereas all of the divisions of the trigeminal nerve are laminated throughout their course