Abstract
Somatosensory information (concerning, e.g., touch, pressure, pain) from the head, face, and oral cavity are received by the endings of primary afferent neurons with processes in the fifth cranial (trigeminal) nerve, and with cell bodies in the trigeminal (or Gasserian) ganglion. The central axon terminals of these ganglion neurons synapse within the trigeminal nuclear complex (TN) in the brainstem (see Figure 1). This complex is a long, sausage-shaped set of subnuclei extending from the caudal pons to the caudal medulla. Its two major histologically defined subdivisions include the most rostral nucleus principalis or main sensory trigeminal nucleus (MTN) and the immediately caudal spinal nucleus of the fifth cranial nerve (SPV). SPV itself has been subdivided into three subnuclei, which from rostral to caudal levels, respectively, include subnucleus oralis (SO), subnucleus interpolaris (SI), and subnucleus caudalis (SC). The primary afferent fibers entering the brainstem from the trigeminal ganglion descend laterally along side of the entire long nuclear complex in the primary descending trigeminal tract (TT), projecting terminating fibers into the nuclear complex from MTN to the most caudal SC region of SPV. Axons of secondary afferent neurons in TN relay the information and sweep medially through the brainstem mostly to the contralateral side as they ascend to the ventrobasal complex of thalamus for final relay to somatosensory cortex.
Published Version
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