Nucleus Caudalis

The nucleus caudalis is an elongated structure located on the dorsolateral surface of the cervicomedullary junction. It extends from the level of C2, in the upper cervical cord, rostrally to a region approximately 1 cm above the obex. It is anatomically homologous with the substantia gelatinosa in the dorsal horn of the spinal cord and harbors the second order neuronal cell bodies that project axons carrying pain and temperature sensation from facial sensory dermatomes, supplied by the branches of the trigeminal nerve, to the thalamus.

The nucleus caudalis has two main somatotopic organizations. The most fundamental organization is lateral-to-medial corresponding with tri-geminal divisions V1, V2, and V3, respectively. A less obvious organization, but one that is critical to the clinical success of the nucleus caudalis DREZ operation, is a rostral-to-caudal organization with a corresponding concentric target, or so-called "reptilian" or "onion skin'' dermatomal distribution. The perioral portions of V2 and V3 are found at the most rostral aspects of the nucleus, above the obex; whereas, the more peripheral facial regions away from the mouth are located progressively more caudally directed down to C2. Pain afferents from cranial nerves VII, IX, and X project to the most medial aspect of the caudalis nucleus, adjacent to the cuneate fasciculis.

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