Review of sorne surgical concepts in the treatrnent of

Review of sorne surgical concepts in the treatrnent of peripheral nerve lesions
G. Penkert; W. Bini* andM. Samii
Neurosurgical Dept., Nordstadt Hospital / Hannover-Germany; *Neurochirurgia, Ospedale Civico / Lugano-Switzerland
diagnósticos y la sofisticación quirúrgica. Claros conceptos anatomo-clínicos y quirúrgicos deben de guiarnos a la hora de planear un tratamiento en este campo
The treatment of peripheral nerve lesions still reel cual ha sido en parte «olvidado» por la neurocirugía
presents a challenge in spite of today's diagnostic and
clínica. Si bien los resultados pueden ser espectaculasurgical sophistication. Clear anatomo-clinical and
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res, con mucha frecuencia tendremos la información
surgical notions
must guide the treatment planning in
decisiva sólo después de haber expuesto el campo quithis field which has been somewhat «neglected» by clirúrgico, es decir, «in situ». El principio básico es obtenical neurosurgery. The results can be spectacular, nener o crear condiciones óptimas para la regeneración
vertheless the decisive information will often be acquired only after surgical exposure that is in situ. The baaxonal.
sic prerequisite or principIe is to be able to create optiPALABRAS CLAVE: Nervios periféricos. Cirugía de las
mal conditions for axonal regrowth.
lesiones de los nervios periféricos.
KEY WüRDS: Peripheral nerves. Surgery of peripheral
nerve lesions.
Introduction
Resumen
As in other areas of neurosurgical practice, in peripheral nerve surgery treatment planning must begin with an
El tratamiento de lesiones de los nervios periféricos
accurate anatomical and neurological orientation in order
sigue representando un desafío a pesar de los avances
Summary
lower extremity
upper extremity
axillary nerve - - - - - - - - - - - - obturator nerve
musculocutaneous nerve
femoral nerve
with cut. antebrachii lat. nerve - - - - - with cutaneous branch (saph. nerve)
median nerve
medial plantar nerve
ulnar nerve
lateral plantar nerve
<
superficial branch
radial nerve
deep branch
(post. inteross. nerve)
superficial brauch
>
tibial nerve
>
\
.• )
sciatic uerve
fíbular uerve
I
deep branch
Scheme 1: Comparison of ramification of upper and lower extremity nerves
255
Review oí sorne surgical concepts in the treatment oí peripheral nerve lesions
_S_ED_D_O_N_l_94_3_....;I
SU_N_D_E_RL_A_N_D_l_9_51
Neurapraxia - - - - - grade I - - focal demyelinisation
I
Axonotmesis
~
:
Neurocirugía
grade TI - - continuity ofaxons interrupted
grade III - - architecture of endoneurium destroyed
grade IV - - architecture of perineurium destroyed
I
_
~
WALLERian
degeneration
of the
/ nerve fiber
Neurotmesis - - - - - grade V - - continuity of aH nerve structures interrupted
Scheme 2: Nerve lesions according to Seddon and Sunderland
to judge which nerve or combination of nerves have been
1. Anatomical Considerations
injured 1•4 •5 • Por
this prerequisite
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compare the nerve ramifications of the upper and lower
The smallest anatomical unit of a nerve is the axon.
extremity. Each nerve of the arm will correspond to a speAround the axon membrane we find the myelin sheath and
it' s Schwann cells. These components together form the
cial nerve of the leg and important distinctions do not
exist with exception of the level of ramification (see scheso-called nerve fiber. Each nerve fiber is enclosed in two
me 1).
or more layers; one with latticed and the other with longi-
Fig. 1.- Severe acute tra!tmatic median nerve compression at the wrist.
256
Neurocirugía
Review of sorne surgica! concepts in the treatrnent of periphera! nerve lesions
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Fig. 2.- Interfascicular dissection (multifascicular arrangement).
tudinal collagen· and elastic elements (the endoneurium).
If we transect a nerve, its stumps will always retract due
to these elastic elements. A bundle of nerve fibers together with their endoneurium is again surrounded by connective tissue and this is referred to as a fascicle. This
truly represents the surgical unit.
The numerous fascicles of each nerve are arranged into groups of fascicles, changing theif arrangement or distribution from centrallevels to the periphery. Nerve roots
consist of fewer but thicker fascicles which can be divided
into sorne sectors whereas more in the periphery the nerve
has its typical group arrangement with 3-5 groups of fascieles. Between these groups only loose connective tissue
with longitudinal oriented vessels is presento At the peripheral end these groups further subdivide into many small
fascieles so that the nerve structure acquires a multifascicular nature. In summary, the nerve begins mono or oligofascicular containing a typical group arrangement and at
the end this is lost in favour of multiple small no longer
distinguishable fascicle groups. The surgeon has to be
aware of this changing arrangement. An interfascicular
microsurgical neurolysis is only possible in the segment
with group arrangement, whereas at the root level a dissection of fascieles would damage their continuity.
Following nerve transection all elements constituting
the nerve fiber degenerate from the level of the lesion until the periphery. Only the Schwann cells remain viable
and are able to build up a new myelin sheath when new
axons find their way to sprout. Our surgical efforts presently aim at establishing as optimal conditions as possible lor the axon sprouting over the level of the lesion to
achieve its distal target2•
Depending on the amount of compressing and injuring
forces, Seddon, in 1943 established the well known idea
of neurapraxia, functional block of the- electrical conductivity due to myelin degeneration; axonotmesis, interruption of continuity of the axons and neurotmesis, complete
interruption of nerve continuitt. In comparison, Sunderland7 distinguished five degrees of lesion in 1951. We
consider this latter elassification to be much more useful
in understanding the different disturbing events which occur within the nerves and is still valid today:
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Review of sorne surgical eoncepts in the treatrnent of peripheral nerve lesions
Neurocirugía
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Fig. 3.- Transected median nerve with a neuroma at the proximal stump.
Fig. 4.- Separation 01 the lascicle groups.
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Review of sorne surgical concepts in the treatrnent of peripheral nerve lesions
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1~,,",
~."",.'
~
~"...~-
Fig. 5.- Site after neuroma resection.
Fig. 6.- Coaptation ojthe sural graft (proximal suture Une).
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Review of sorne surgical concepts in the treatment of peripheral nerve lesions
Neurocirugía
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Fig. 7.- Median nerve reconstructed withfive grafts.
Grade 1.- Sunderland's grade I lesions are identical
with Seddon' s neurapraxia. The myelin sheath is the most
sensitive part of the nerve fiber thus focal demyelination
occurs at first. The rearrangement of the myelin sheath
lasts 3-4 weeks. After this short period, the nerve regains
it' s function.
Grade II.- due to more compressing forces the axons
undergo wallerian degeneration.
Nevertheless, each axon remains enclosed by it's basal
membrane and endoneurium so that durlng axon sprouting
it will reach its former muscle end-plate. This process will
last sorne months but the end results is nearby a restitutio
ad integrum.
Grade III.- in this degree of lesion we find the endoneural structures progressively destroyed so that motor
axons may sprout into a sensitive pathway or vice a versa.
This leads to a certain amount of miss-sprouting with the
corresponding functional defects.
Grade IV.- because of disarranged perineural structures the degree of miss-sprouting determines for example
that antagonistic muscles will be innervated simultaneously. The compressing fibrosis causes that a certain
amount ofaxons sprouts are blocked completely and a
260
neuroma in continuity without nerve function results. This
is comparable to a nerve interruption.
The quality of regeneration, the number ofaxon
sprouts, the amount of miss-sprouting and the functional
results at the end of regeneration depend on the degree of
fibrosis and on the possible disintegration of the group
arrangement of all the fascicles. Therefore the idea ofaxonotmesis contains a wide field of different types of nerve
lesion and we are now able to explain the possible unexpected poor results after neurolysis.
Grade V.- a grade V lesion is again identical with
Seddon's neurotmesis, that means complete interruption
of the whole nerve (see scheme 2).
The time span between nerve lesion and possible regeneration will often last several months.
During this period we can test the' beñáviour of the
axon sprouts only by eliciting the «Tinelsign». The palpation of the nerve and where sprouting occurs triggers an
electric pain which is experienced in the sensitive area
previously belonging to the injured nerve. If the trigger
point moves downward (distally) during the period of several months, outgrowth ofaxons is taking place. This is a
positive prognostic factor.
Review of sorne surgical concepts in the treatment of peripheral nerve lesions
Neurocirugía
n. Operative Procedure
of a grade IV lesion the post-traumatic tissue fibrosis
compresses the axons to such a point that their outgrowth
is partially or even totally hindered.
In a very simplified way we have used to distinguish
Without surgical intervention, regeneration wiU fail.
between nerve lesions with and without continuity. In reaPrimary causes are: gun shot wounds, sharp injuries
lity we often enough find a nerve which seems to be in
and severe traction trauma due to fractures or joint distorcontinuity but by means of microsurgical dissection we
tion. Especially after distortion injuries we must expect to
discover a complete destruction of the nerve structure.
have to bridge defects of 20-30 cm. The nerve stumps reOn the other hand we can find a markly thickened nertract due to their elastic elements.
ve segment similar to a large neuroma but the dissection
Additionally, we always have to resect long fibrotic
shows only scar tissue between the fascicle groups (pseuand neuromatous segments to find viable stumps. In reladoneuroma). Thus the microsurgical findings often intion to nourishment and revascularization there doesn't
fluence the therapeutical actions.
exist any argument against the use of long free nerve
grafts 3 •
A. Lesions without loss of continuity
The treatment of choice is to restore the nerve contiThese are lesions which can be overcome by axon
nuity. If we would try an end-to-end suture, we would be
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faced
two
desadvantages.
On one
hand
we would
trapment syndromes
in anatomically
narrowed regions ie.
have to overcome strong tension forces which tend to pull
carpal tunnel, supinator canal, median nerve under the
at the nerve stumps due to the elastic nerve fibers and sepronator teres, interosseous anterior nerve entrapment,
condly, after resection of fibrotic segments the nerve demeralgia paresthesica and the thoracic outlet syndrome are
fect increases. Alternatively, since the last thirty years
examples of this type of lesiono Furthermore numerous
free autologous nerve grafts are used for interposition
chronic nerve lesions due to repeated traction forces such
between the nerve stumps. In case of nerve segments with
as the ulnar tunnel syndrome existo
the typical, previously mentíoned group arrangement
The best condition for optimal regeneration is when
each fascicle group can be coaptated to one nerve graft
only a fibrosis of the epineurium is present. In more seve(Fig. 3-7). This method ensures control on the individual
re cases also the epineurium between the fascicle groups
(epifascicular perineurium) can be fibrotic perhaps even
coaptation and avoids any disturbing tension which induces tíssue fibrosis in the ara of the junctíon. One suture
the epifascicular endoneurium.
In treatment the first step is to open the outer epineuthrough the epineurium of the sural nerve graft and through the epineurium of each fascicle group is sufficient
rium in a longitudinal direction from proximal and distal
to avoid foreign body granulomas. If the nerve is unifastowards the level of the lesiono If we observe a persisting
cicular or multifascicular the grafts have to be coaptated
compression we will have to peel and remove the surrounover the whole cross section of the nerve stump. Fibrin
ding epineurium. In cases of an interfascicualr fibrosis we
glue does hinder a timely revascularization in the suture
will have to dissect between the fascicle groups (Fig. 1-2).
area for sorne days. The question of increased scar tissue
If the fascicles themselves remain fibrotic due to scarred
formation by glueing or stitching is often discussed conendoneurium rather easily palpable between two finger
troversially but not completely answered till now. The intips one must decide if resection of the neuromatous segtroductíon of laser techniques to seal the coaptatíon
ment and nerve grafting should be performed.
should always consider the excess costs of this method.
Our goal is always to achieve a sufficient decompresImportant to remember is that the patient's own fibrin
sion in order to enable the axon sprouts to overcome the
lesion and reach again their target. In cases of pseudoneuwill maintain the coaptation naturally after 10-20 mino
Post-operative immobilisation of the site is advisable for
roma, microsurgical neurolysis will be the treatment of
sorne days.
choice but in case of a real neuroma, perhaps affecting
only one fascicle group, resection and grafting for this
Conclusion
group has to be carried otu (see scheme 2).
Intraoperative nerve stimulation is fundamental to conIf we tend to judge and treat peripheral nerve lesions
firm fascicles which are still anatomofunctionally intacto
we must have a clear idea of the anatomical ramification
of the nerves of the upper and lower extrernities compleB. Lesions with loss of continuity
ted by an assessment of the degree of the nerve lesiono
These lesions which can not be bridged by axon
Our surgical goal should be to create conditíons for resprouts, that is completely interrupted nerves but also cagrowth ofaxon sprouts. We have to decide between seveses with real neuromas, have a loss of functional contiral microsurgical techniques and this often remains an innuity. As mentioned prev~ously it can happen that in cases
261
Review of sorne surgical concepts in the treatrnent of peripheral nerve lesions
traoperative decision rnaking. AH options rnust be discussed with the patients preoperatively.
References
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2. Millesi, H.: Microsurgery of periphera1 nerves. En: B.
McKibbin ed. Recent Advances in Orthopaedics. Edinburg,
Churchill Livingstone, 1983; 1-22.
3. Penkert, G., Bini, W., Samii, M.: Revascularization of
nerve grafts: an experimental study. J. Reconstr. Microsurg.
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Neurocirugía
4. Robertson, S.C., Trayne1is, V.: Acute management of
Compressive Peripheral Nerve Injuries. En: C.M. Loftus ed.
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6. Seddon, H.-J.: Three types ofnerve injury. Brain 1943;
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