Peripheral nerve lesions

. M.Samii

Although the operative microscope was developedin the early 1920's by HOLMGREN and «microsurgery»was used in otosurgery and ophthalmolgy for a longtime, the microscope and microtechnique was not in­troduced in peripheral nerve surgery until1963. JACOB­SON was the first to describe the advantages of themicrosurgical method in the repair of peripheral nerveinjuries. In 1964 SMITH, MICHON, MASSE and KURZEfurther introduced this modality in periheral and cranialnerve surgery, demostrating that the delicate handlingof tissue and the accurate approximation of nerve end(with fascicular orientation) were easily fulfilled withthe aid of the microscope.

Microsurgical techniques flourished (MILLESI,SAMII, RAKSTIAN, BRUNELLI, PALAZZI-COLL, etc.).New operative techniques developed, expanding the in­dications for peripheral nerve reconstruction and graftingprocedures and influencing positively the results.

We will analyze the two major groups of nerve in­juries; those in continuitY and with interruption of con­tinuity.

It is necessary befare beginning to remind that thesmallest surgical unit of a peripheral nerve is a fascic1e,consisting of nerve fibers and the endoneurium. Each .fascic1e is c10sed by the perineurium and aH fascic1es aresurrounded by connective tissue, the S0 caHed epineurium.

A) Nerve injuries in continuity

Three types of nerve injury in continuity can be dif­ferentiated from the miscrosurgical point of view. Thisdifferentiation is possible only intraoperatively.

Type 1: The fascic1es are in continuity and surroundedby scar tissue. Fibrotically changed epineurium is mainlylocated in the external sheet or in the interfasciculartissues between the individual fascic1es which can havea normal or altered size and formo This would corres­pond to SEDDON'S c1assification of neuroapraxia or ax­onotmesis. Rere the scar or fibrosis may prevent the

return of full normal function independent of functionalor optimal regeneration.

Type 2: The fascic1es c an either be interrupted withdevelopment of a neuroma or show signs of thickeningof the caliber, inside the perineurium (intrafascicularneuroma). This would correspond to seddon'sneurotmesis. In the region of the lesion there is alwaysan extensive fibrosis of the epineurium.

Type 3: There is a combination of Type 1 and 2,where several fascicles are in continuity while the restare interrupted.

A difficult decision confronting every surgeon ina case ofnerve lesion in continuity is 10 determine whetheror not the nerve fascicles and fibers are in continuity.Thickening and hardening of the nerve trunks is notsufficient proof of a neuroma caused by neurotmesis.Fibrotically altered connective tissue can also determinesuch a picture.

Under the microscope the epineurium in the intactpart proximal anddistal to the injured area is divided.The external sheet of the epineurium is removed andthe individual fascicles are exposed tracing them backto the site of injury.

Considering the aboye mentioned types in the Type 1lesions we totally remove the fibrosis (altered connec­tive tissue) liberating each individual fascic1e. Theperineurium of each and every fascicle should remainintact and not be traumatized.

In the Type 2lesions, we resect the damaged fasciclesup to the intact nerve tissue in order to accomplish anerve end-to-end suture or graft.

Finally in the presence of both type of injuries, oneshould first perform fascicular neurolysis and then resectthe altered fascicles and accurately approximate the endsdirectly or by nerve graft.

B) Nerve injuries with interruption oi continuity

The first question in cases of total interruption ofnerve continuity is the indication for primary and early

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secondary repair. A further important decision is thechoice between an end-to-end suture or application ofa nerve graft.

Primary treatment is indicated in a clean cut woundof the nerve trunk:. The reconstruction is executed afiersuture of possible concomitant vascular and tendon le­sion. In case of contusion of the sofi tissues and osseousdamage, primary nerve treatment is not indicated. Theadvantage of early secondary treatment (ca. 4-6 weeks)is to be seen in an already terminated wound healingand the nerve ends can be located in healthy tissue.

In primary nerve repair in a case of a clean andsharp transection of the nerve, there is an absolute in­dication for an end-to-end suture (without tension).When the surgical treatment is postponed the fibroticdegenerated tissue must be resected in order to obtainintact nerve stumps for suture. The use of a nerve graftis indicated in cases with more than 1,5 cm defecto

At the time of repair we therefore have the nervesuture and the nerve graft. As primary accepted suturetechniques there is the epineural conventional type andthe perineural or interfascicular suture for an accurateapproximation of the individual fascicles or fasciclegroups. After carefull and strategic dissection of thenerve stumps in preparation for the suture. Accordingto our microsurgical experience in peripheral and cranialnerve lesions we recornmend the following technical

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concept of nerve graft. The sural nerve should be thefirst choice for nerve grafts because of it's length anddepending on the nerve defect we remove both suralnerves. When confronted with long and broadgaps wenot only need both the sural nerves but also thecutaneous brachii and antebrachii medialis nerves. Atthe level of the brachial plexus we also have the inter­costal nerves for reconstruction procedures. For the per­formance of nerve grafiing, size and distribution of thefascicular structures of the nerve stumps are to be takeninto serious consideration. For adaptation and fixationof the individual grafi ends at the nerve stumps we per­form one or two using 10xO suture. In case of cranialnerve grafting in unaccessible areas fibrin glue can beused. According to the circumstances in one and thesame case either the epineural, perineural, epiperineuralor interfascicular suture techniques can be applied.

The general clinico-surgical principIes of peripheralnerve repair will explained and supported by drawings,case examples as wel1 as intraoperative findings andprocedures. Results will be analyzed and discussed bas­ed on the author's experience of over 20 years in thisfield.

Samii, M.: Peripheral nerve lesions. Neurocirugía,1991; 2: 293-294.