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Published in Bobby Krishnachetty, Abdul Syed, Harriet Scott, Applied Anatomy for the FRCA, 2020
Bobby Krishnachetty, Abdul Syed, Harriet Scott
The ramus communicans is a communicating branch that connects two other nerves. With respect to the sympathetic nervous system, it is the branch that transmits signals between the spinal nerves and the sympathetic trunk. There are two types of rami communicantes – white and grey. The white rami communicantes appear white as they have more myelinated fibres than the grey. These only exist in the intermedio-lateral column, T1 to L2, and contain preganglionic fibres from the spinal cord to the paravertebral ganglia.The grey rami exist at every level throughout the spinal cord and contain postganglionic fibres, they connect from the sympathetic trunk to the spinal nerves.
Autonomic Nervous System
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The short sympathetic preganglionic fibres pass via ventral roots and white rami communicantes (myelinated fibres) to the sympathetic chain where they synapse with the long postganglionic fibres in the paravertebral and prevertebral ganglia. Grey rami communicantes (unmyelinated fibres) carry postganglionic sympathetic fibres from the sympathetic ganglia to the spinal nerves (Table 10.1). In the adrenal medulla, the chromaffin cells form the postganglionic cells and are directly innervated by preganglionic sympathetic fibres.
The Spinal Cord and the Spinal Canal
Published in Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand, Pediatric Regional Anesthesia, 2019
Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand
Rami communicantes are bundles of bidirectional fibers which connect the ventral ramus of each spinal nerve to the sympathetic chain (Figure 1.38). They convey (1) efferent (myelinated) preganglionic fibers to the sympathetic chain (white ramus communicans), (2) efferent (unmyelinated) postganglionic fibers (gray ramus communicans) that reenter the ventral primary ramus and migrate with its (efferent) fibers, and (3) afferent fibers from viscera to spinal ganglia (white ramus communicans).
Cervical nerve root variant: report of two cases under the cervical endoscopy and review of clinical literature
Published in British Journal of Neurosurgery, 2023
Bin Sun, Changgui Shi, Huiqiao Wu, Ying Zhang, Nicholas Tsai, Zeng Xu, Xiao-Dong Wu, Wen Yuan
Lumbosacral nerve root anomalies are relatively common but they are unusual in the cervical spine with few reports were previously published.1,2 Anatomical study has shown that intradural rami communicantes are commonly in the lumbosacral region, but less so in the cervical region, and most were between dorsal roots.3 Only five cases of cervical nerve root variants have been reported observed at surgery.1,2,4–6
Selective block of grey communicantes in upper thoracic sympathectomy. A feasibility study on human cadaveric specimens
Published in British Journal of Neurosurgery, 2020
Vicente Vanaclocha, Nieves Sáiz Sapena, Marlon Rivera, Juan Manuel Herrera, José María Ortiz-Criado, Ana Monzó-Blasco, Ricardo Guijarro-Jorge, Leyre Vanaclocha
The parietal pleura was incised perpendicular to the ribs and 1cm lateral to the sympathetic chain. The grey rami communicantes could be found running between the intercostal nerve and their corresponding sympathetic ganglia. The intercostal veins crossed the sympathetic chain in 63.33% (19/30) of the sides, 12/19 of them being on the right side. These intercostal veins could be dissected free and coagulated with harmonic scissors. No clips were used to clip the veins to prevent them from impeding further surgical manoeuvres. Each level had at least one grey ramus communicans (Figure 4), occasionally two (Figure 5). In all of the dissected chains, all the levels had one grey and one white ramus communicans, shaped as described previously. The incidence of ascending grey rami communicantes was 30% (9/30) and that of the descending ones was 16.66% (5/30). Two grey rami communicantes could be seen at T2 in 26.66% (8/30 sides). One of the rami communicantes connected with the same level sympathetic ganglion, and the other with the ganglion above (five cases, 16.66%) or below (two cases, 6.66%), and in one case it connected both above and below (3.33%). At T3 two grey rami communicantes could be seen in 13.33% (4/30 sides). One of the ramus communicans connected with the same level sympathetic ganglion and the other with the ganglion above (3 cases, 10%) or below (1 side, 3.33%). At T4 two grey rami communicantes could be seen in three of the sides (10%); two were ascending (6.66%) and one descending (3.33%) (Tables 1 and 2). We did not dissect any lower than T4 because this it is not done in real life surgery. The number of accessory rami communicantes was higher at T2 than at lower levels. The number of cases was insufficient to draw any statistical conclusions about which side had more accessory grey rami communicantes. The diameter of the grey rami communicantes was 0.87 ± 0.76 SD.