Biology Reference
In-Depth Information
1. INTRODUCTION
The degree of functional recovery after peripheral nerve reconstruc-
tion is often nonsatisfying although the neurons of the peripheral nervous sys-
tem have the machinery to regenerate their axons and no general inhibitory
environment develops in the distal nerve stumps or target tissue (
Deumens
et al., 2010
). Functional recovery ismost complete if regeneration occurs after
crush injury, and it can still reach a valuable degree after tension-free end-to-
end suture (
Deumens et al., 2010
). But whenever severe trauma or tumor
resection leads to long distances between transected peripheral nerve stumps,
the mechanisms impeding timely and appropriate target reinnervation
become seriously obstructing (
Ray & Mackinnon, 2010
).
As reasons for insufficient functional recovery, the increasing irreversible
muscle atrophy with time and the long period axonal sprouts, extending
from far proximal lesion sites, need to reach distal motor targets were pre-
viously discussed (
Fu & Gordon, 1997; Gordon, Sulaiman, & Ladak, 2009
).
Recently,
Tessa Gordon
and colleagues have defined the main factors imped-
ing axonal regeneration in more detail as (1) the slow growth of regenerating
axons across surgical coaptation sites and nerve gaps, (2) the decline in regen-
erative capacity of axotomized neurons with time, and (3) the limited time in
which denervated Schwann cells can successfully contribute a regenerative
milieu for regenerating axons (
Gordon, Sulaiman, & Ladak, 2009; Gordon,
Tyreman, & Raji, 2011
).
Furthermore, only when regenerating axons are not misguided into the
wrong distal pathways and appropriate target reinnervation occurs, a suffi-
cient degree of functional recovery can be expected (
Valero-Cabre &
Navarro, 2002
).
Electrical stimulation was conceived as one therapeutic strategy to expe-
dite regenerative axonal growth of regenerating axons across surgical repair
sites and to improve regeneration accuracy especially of motor axons
(
Gordon, Sulaiman, & Ladak, 2009
).
Different ways to apply electrical stimulation protocols with the aim to
increase peripheral nerve regeneration are described in the following.
2. WAYS TO APPLY ELECTRICAL STIMULI TO THE
RECONSTRUCTED NERVE
2.1. Transcutaneous/percutaneous stimulation
Transcutaneous electrical stimulation (TENS) is used clinically as rehabili-
tation treatment
in order
to recover
impaired muscle functionality
