Monday, December 10, 2007

What about neurapraxia, axonotmesis and neurotmesis?

Many clinicians would have learnt the classification system of peripheral nerve injury listed in the title. It comes from Seddon in 1943. Others may be familiar with the similar Sunderland (1951) system where nerve injury it is graded from 1-5, with 1 being neurapraxia, a conduction block.

However, most clinicians would never use these classifications unless they are working in specialist areas such as peripheral nerve surgery.

What has become apparent, is that there are many nerve injuries which can be painful, and debilitating, yet they may never rate a classification of neurapraxia and rarely show up on nerve conduction studies. Sunderland was aware of this and referred to it as “perversions of function” of nerves and other researchers such as Lundborg (1988) have referred to “pre category 1 classifications”.

It is these “preneurapraxias” which we are likely to find with skilled neurodynamic testing. The neurobiology of the preneurapraxias is related to mid axon abnormal impulse generation, i.e. ion channel accumulation at injured sites along the peripheral nerve. The cardinal sign of these nerve injuries will usually be mechanosensitivity, not failing conduction. They are a possible contribution to a range of syndromes including tennis elbow, de Quervain’s tenosynovitis, plantar fasciitis and hamstring pain. With good handling, clinicians will ‘find’ these pathologies.

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