What Nerves Traceable
Any spinal nerve may be traceable for at least a part of its course. The cranial nerves are made inaccessible to palpation by their location, except the spinal portion of the spinal accessory and the terminal portions of the nerves to the face. Likewise the sympathetic trunks, except perhaps in the neck, are untraceable.
Nerve-tracing is comparatively easy in the upper and lower extremities, neck and back. The superficial nerves of the scalp are hard to follow on account of the hair. The superficial nerves of thorax, abdomen, and pelvis are accessible under the conditions mentioned below; the deep or visceral branches, never.
Of those nerves mentioned as traceable, only such as are irritated and consequently swollen and tender, can be followed. If a nerve is very heavily impinged, especially if the impingement be chronic, it is partially or wholly paralyzed and not traceable. If the heavy impingement be acute, or if there be a light impingement serving as a mechanical irritant, nerve-tracing is a real aid to diagnosis.