Neurobiology of the trigeminal ganglion in comparison to the dorsal root ganglion

ABSTRACT: The trigeminal ganglion (TG) represents the craniofacial counterpart of the dorsal root ganglion (DRG) in the peripheral nervous system (PNS). TG and DRG are clusters of cell bodies of highly specialized sensory neurons, with TG neurons innervating the head and face and DRG neurons innervating the body. TG and DRG neurons are essential for detecting various mechanical, thermal, and chemical stimuli and relaying these internal or external signals to the central nervous system (CNS). Despite sharing fundamental similarities, TG and DRG differ significantly in many aspects under pathophysiological states. This review provides a comparison between these 2 types of ganglia by highlighting their distinctions across anatomical locations, embryological origins, cellular compositions, gene expression profiles and molecular signatures, ratios of A/C fibers, connections with the CNS, sympathetic fiber sprouting, ectopic discharges, biophysical properties of ion channels, and neuron-glia interactions. These divergences may contribute to certain differences in intensities and responses to the same stimuli or treatments between TG- and DRG-mediated pain. Acknowledging their neurobiological distinctions underscores the importance of identifying potential pain targets within each system independently and developing targeted therapeutic strategies for craniofacial vs somatic pain.