When local anesthetic is administered, does the solution reach the core bundles first?

When local anesthetics are administered, they primarily reach the outer nerve fibers before penetrating into the core bundles. The outer layers of a peripheral nerve, where the smaller and more vulnerable fibers, such as those responsible for pain transmission, are located, will be involved first. As the anesthetic diffuses through the nerve sheath, the deeper core bundles will eventually be affected, but they are not the initial targets of the anesthetic solution. This sequence is crucial because it explains why certain sensations, such as pain, may be blocked before others, like proprioception or deep pressure sensation. The anatomical arrangement of nerve fibers, with smaller fibers on the outside and larger ones in the core, dictates the order in which different types of sensations are lost when local anesthetics are applied.