Peripheral nerves require extraordinary mobility in relation to surrounding tissues, sometimes sliding up to 2 centimetres as we move. This is because nerves are long (they are made up of the longest cells in our body) and often cross joints some distance from the axes of motion – think about driving round a round-a-bout- the further you are away from the centre the greater the distance you have to travel.
They need to slither and slide snake-like! A key connective tissue that facilitates this is the mesoneurium (Fig 1) – kind of like a condom around the nerve. Few people study it or are even aware of the mesoneurium – perhaps peripheral nerves just aren’t trendy enough for researchers these days.
The peripheral nerve surgeon, Hanno Millesi, who alerted us to it in the 1970’s is still the main voice for the mesoneurium. This overlooked bit of connective tissue is what makes a nerve feel slippery or flick away when palpated. The nerve slides in this sheath during movement and to some degree the mesoneurium will slide as well. Inflammation or scarring of the mesoneurium can lead to neuroimmune irritation and potential mid axon discharge. Those administering local anaesthetics to nerve should put it on and not inside the mesoneurium.
You won’t find much on the mesoneurium (aka. adventitia, paraneurium) in the literature – let us know if you do but this nugget is a reminder that early graded mobilisation post injury is so logical, and some local tenderness over nerves could involve this tissue. And next time you are watching someone dancing vigourously, pause and think “wow that nerve mesoneurium must be nice and slippery and smooth – it’s getting a real workout”.
For reviews of the mesoneurium see:
Butler DS (2000) The Sensitive Nervous System. Adelaide Noigroup Publications. Pp 103-104, 380, 405-410.
Millesi H, Zoch G and Riehsner R (1995) Mechanical properties of peripheral nerves. Clinical Orthopaedics and Related Research 314: 76-83 (and subsequent literature by Millesi H)
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