17/06/2024
Dobrze pokazana radikulopatia- czyli inaczej ucisk korzenia rdzeniowego przez w tym przypadku "przepuklinę". Popularną radikulopatią w odcinku lędźwiowym jest tak zwana rwa kulszowa- czyli ucisk i podrażnienie nerwu kulszowego. Ucisk, podrażnienie powoduje stan zapalny toczący się w okolicy ujścia korzeni rdzeniowych nerwów obwodowych. Objawowo daje to ból oraz uczucie napięcia i sztywności okolicznycn tkanek. Czasami dochodzi do uszkodzenia nerwu rdzeniowego co objawia się niedowładem mm unerwianych przez uciskany nerw oraz osłabienie odruchów ścięgnistych.
The Pathophysiology of Radicular Pain 💡
👉 Radicular pain is a form of pain caused by irritation of the sensory root or the dorsal root ganglion (DRG) of a spinal nerve (https://link.springer.com/referenceworkentry/10.1007/978-3-540-29805-2_3710).
👉Radicular pain is not nociceptive pain, for the neural activity arises from the dorsal root, and not from stimulation of peripheral nerve endings. Therefore, it is not synonymous with somatic pain or somatic referred pain and needs to be distinguished from them. Nor is radicular pain synonymous with radiculopathy. Whereas radicular pain is caused by the generation of ectopic impulses, radiculopathy is caused by the blocking of conduction along sensory and motor axons, and is characterised by loss of nerve function (https://link.springer.com/referenceworkentry/10.1007/978-3-540-29805-2_3710).
👉 Mechanistically, radicular pain is characterized by spreading of the afferent nociceptive input combined with complex cellular and molecular processes that initiate and maintain the increased nociceptive signal input. Furthermore, both anatomical (https://pubmed.ncbi.nlm.nih.gov/10568867/, https://pubmed.ncbi.nlm.nih.gov/17850967/) and electrophysiological (https://pubmed.ncbi.nlm.nih.gov/20147564/) studies suggest that the spreading of radicular pain involves adjacent spinal segments. This supports the common clinical observation of involvement of multiple nerve roots, despite a single level of pathology.
👉 Although the spreading of the radicular afferent signal is a complex phenomenon, a certain sequence in the inflammatory cascade is apparent (s. figure, https://pubmed.ncbi.nlm.nih.gov/24553305/). Beginning with the disc degenerating nerve, proinflammatory cytokines are released at the site of lesion and at a distance through Wallerian degeneration (WD). During degeneration of the distal axon by WD, TNF-α is released by Schwann cells, endothelial cells, mast cells, and resident macrophages at the site of nerve injury. This causes ectopic firing at the dorsal root ganglion (DRG)), leading to an increased release of neurotrophins and ectopic firing at the dorsal horn, eventually leading to central sensitization (https://pubmed.ncbi.nlm.nih.gov/14624855/, https://pubmed.ncbi.nlm.nih.gov/15120588/, https://pubmed.ncbi.nlm.nih.gov/2388084/, https://pubmed.ncbi.nlm.nih.gov/10366647/).
👉 The cellular-molecular cascade may also start form the herniated disc material. The extrusion of material from the nucleus pulposus onto the spinal nerve leads to edema and ischemia. Experimental work has shown that exposure of nerve root (proximal to the DRG) to material from the nucleus pulposus material increased endoneurial fluid pressure and decreased blood flow into the DRG with secondary edema (https://pubmed.ncbi.nlm.nih.gov/9854750/). A key mediator released after disc herniation is the proinflammatory cytokine TNF-α. When TNF-α reaches the nerve root, production of the neurotrophic factor (NGF) in the surrounding inflamed tissue is initiated (https://pubmed.ncbi.nlm.nih.gov/9179382/, https://pubmed.ncbi.nlm.nih.gov/14615047/, https://pubmed.ncbi.nlm.nih.gov/12237190/).
👉 This, in turn, induces the production of another neurotrophin ,brain-derived neurotrophic factor (BDNF), in the DRG (https://pubmed.ncbi.nlm.nih.gov/12237190/, https://pubmed.ncbi.nlm.nih.gov/22280975/).Besides their neurotrophic qualities, such as the induction of nerve sprouting, both NGF and BDNF are also recognized as important factors in the development of central sensitization (https://pubmed.ncbi.nlm.nih.gov/16543102/) and may play important role in the pathophysiology of radicular pain. The release of cytokines may also directly interfere with both activity and expression of various ion-channels in the DRG (https://pubmed.ncbi.nlm.nih.gov/19339603/).
👉 In radicular pain, ectopic discharges can be generated at different locations of the nervous system. from electrophysiological analysis, it was calculated that approximately 75% of the overall ectopic firing was generated at the DRG and only 25% at the lesion or neuroma (https://pubmed.ncbi.nlm.nih.gov/10781925/). Cytokines and neurotrophins can initiate modulation and phosphorylation of ion channels, which forms the basis for generation of ectopic action potentials or ectopic firing (https://pubmed.ncbi.nlm.nih.gov/7999002/, https://pubmed.ncbi.nlm.nih.gov/21525373/). Because repetitive firing of the pain afferents forms the physiological reason for central sensitization (https://pubmed.ncbi.nlm.nih.gov/15120588/), this clearly contributes to the clinical syndrome of radicular pain (https://pubmed.ncbi.nlm.nih.gov/24553305/).