Figure 2.

Proposed pathways for discogenic pain and referred orchialgia, using L4 discogenic pain as an example. Intervertebral discs are innervated by the sinuvertebral nerve (Shayota et al, 2019), which carries pain impulses from the injured disc to the sympathetic ganglion at the same level (L4). Any afferents from the L3 to S1 lumbosacral regions must detour up the paravertebral sympathetic trunk before re-entering the dorsal horn at upper lumbar (L1 or L2) level where rami communicantes are found (Das & Roy, 2018). Afferent impulses eventually ascend to the brain via the spinal cord. Different afferent fibers from the same spatial entry contribute to the mental picture of referred pain (Jinkins, 2004). The final stage of pain pathway involves integrating the ascending information into pain perception that elicits fight or flight behaviors (Patel, 2017).