Aspects on pathophysiology of nerve entrapments and nerve compression injuries.

The microanatomy of the neuron and the peripheral nerve, which is a composite tissue, should be considered when discussing the pathophysiology of nerve compression injuries. Acute and chronic compression of peripheral nerve can induce changes in intraneural microcirculation and nerve fiber structure, increase vascular permeability with subsequent edema formation, and impair anterograde and retrograde axonal transport, which all contribute to the clinical symptoms and deterioration of nerve function. Morphologic and functional changes in the nerve cell bodies can be observed after compression which may be due to inhibition of axonal transport. The latter findings might be a theoretical explanation for double crush syndromes. Diabetes mellitus may confer on the peripheral nerve an increased susceptibility to compression injuries. Clinical stages of compression syndromes, such as carpal tunnel syndrome, may be related to specific pathophysiologic events occurring in the nerve.