October 1, 2021
Node of Ranvier
The patient is a 70-year-old male with recent bilateral foot drop. Laboratory studies showed normal/negative pANCA, cANCA, and MPO. His symptoms partially responded to treatment with prednisone. Nerve biopsy was performed to evaluate for vasculitis.
What is the structure indicated by the arrow in the image?
B. Myelin incisure
C. Traction artifact
D. Node of Ranvier
Answer: Node of Ranvier
Peripheral nerve “nodes of Ranvier” are small gaps between adjacent segments of myelin sheath formed by individual Schwann cells. The specialized regions are rich in voltage-gated sodium ion channels and act as “booster stations” for the rapid propagation of action potentials via saltatory conduction.
Autoantibodies formed against proteins of the node of Ranvier are associated with the immune-mediated neuropathies CIDP (chronic inflammatory demyelinating polyradiculoneuropathy) and GBS (Guillain-Barré Syndrome).
Vural A, Doppler K, Meinl E. Autoantibodies Against the Node of Ranvier in Seropositive Chronic Inflammatory Demyelinating Polyneuropathy: Diagnostic, Pathogenic, and Therapeutic Relevance. Front Immunol. 2018 May 14;9:1029. doi: 10.3389/fimmu.2018.01029. PMID: 29867996; PMCID: PMC5960694
Propagation of action potential in the periaxonal space has recently been documented.
Cohen CCH, Popovic MA, Klooster J, Weil MT, Möbius W, Nave KA, Kole MHP. Saltatory Conduction along Myelinated Axons Involves a Periaxonal Nanocircuit. Cell. 2020 Jan 23;180(2):311-322.e15. doi: 10.1016/j.cell.2019.11.039. Epub 2019 Dec 26. PMID: 31883793; PMCID: PMC6978798.
Lim BC, Rasband MN. Saltatory Conduction: Jumping to New Conclusions. Curr Biol. 2020 Apr 6;30(7):R326-R328. doi: 10.1016/j.cub.2020.02.037. PMID: 32259510.