Because of the electrical properties of the myelin sheath, and the concentration of sodium channels at nodes of Ranvier, conduction velocities in myelinated axons are much greater than those in unmyelinated axons.1
Clinical considerations: The diagnosis of peripheral neuropathy is very common.6 The subsets of nerve fibres affected can vary so symptoms can vary from person to person and can include numbness (particularly in the feet), weakness and imbalance.6,7 There are many causes of neuropathy but in general they affect either the axon or myelin.6 A prototypic demyelinating neuropathy is Guillain-Barré syndrome in which peripheral myelin is disrupted leading to profound weakness.8 Duplication of the PMP22 gene (abundantly expressed in myelin) gives rise to a form of Charcot-Marie-Tooth disease, a demyelinating neuropathy that causes progressive weakness beginning in the legs.9
References:
1. Grider MH, Belcea CQ, Covington BP, et al. Neuroanatomy, nodes of Ranvier. [Updated July 2023]. In: StatPearls [internet]. Treasure Island (FL): StatPearls Publishing; 2023. Available at: https://www.ncbi.nlm.nih.gov/books/NBK537273/.
2. Basic plan of the nervous system. In: Squire L, Berg D, Bloom FE, Lac Sd, Ghosh A, Spitzer NC. Fundamental Neuroscience. 4th edition, 2012. Burlington: Elsevier Science.
3. Stifani N. Motor neurons and the generation of spinal motor neuron diversity. Front Cell Neurosci 2014; 8: 293.
4. De Hert S, De Baerdemaeker L, De Maeseneer M. What the phlebologist should know about local anaesthetics. Phlebology 2014; 29 (7): 428–441.
5. Hedges V. Spinal motor control and proprioception. In: Introduction to Neuroscience. Available at: https://openbooks.lib.msu.edu/introneuroscience1/. Accessed December 2025.
6. Hammi C, Yeung B. Neuropathy. [Updated October 2022] In: StatPearls [internet]. Treasure Island (FL): StatPearls Publishing; 2022. Available at: https://www.ncbi.nlm.nih.gov/books/NBK542220/.
7. Beaulieu ML, Müller MLTM, Bohnen NI. Peripheral neuropathy is associated with more frequent falls in Parkinson’s disease. Parkinsonism Relat Disord 2018; 54: 46–50.
8. Bellanti R, Rinaldi S. Guillain-Barré syndrome: a comprehensive review. Eur J Neurol 2024; 31 (8): e16365.
9. Stefanski KM, Wilkinson MC, Sanders CR. Roles for PMP22 in Schwann cell cholesterol homeostasis in health and disease. Biochem Soc Trans 2024; 52 (4): 1747–1756.