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Neuromas
Definition: Nodule developing on damaged nerve.
Onlysensory nerve neuroma become painful
20 – 30% of neuroma are symptomatic
Pathogenesis
 The nodule forms as a result of injury to schwann cell endoneural barrier that
confines the axons to their endoneural tubes
 Once the barrier is destroyed the regenerating axons escape into the surrounding
tissue in a disorganized fashion and are accompanied by proliferating fibroblasts,
schwann cells and blood vessels
Anatomy
 Sunderland stressed the importance of the endoneural barrier in containing the axons
after injury
 If the barrier is broken , the regenerating axons grow out of the end of the severed
nerve in an attempt to reenter their original endoneural tubes distally to reach the end
organs they originally innervated. If the barrier is not broken regenerating axons
remain in their original endoneural tubes and grow distally until they reach their
respective end organs
 After injury the axons regrow in the proximal portion and when they reach the end of
the endoneural tubes and escape into a mass of tissue containing fibroblasts, schwann
cells macro, and capillaries
 The axons grow out in many directions and branch irregularly seeking to restore
continuity with the trunks and a result they zig zag through the tissue in a
disorganized fashion and branch irregularly to form whorls, spirals and convolutions
 The distal stump axons degenerate as cell bodies are proximal and thus is unable to
regenerate. there is cellular response in the area of schwann cell injury and
fibroblastic proliferation resulting a small nodule that is known as a glioma
 The size of the neuroma depends primarily in the amount of axonal ingrowths but
also on amount of proliferatiing connective tissue fibroblasts, schwann cells, vessels
and macrophages. Axonal growth is more active the closer the lesion is to the cell
body and thus they tend to be larger in nerves injured proximally and smaller in those
injured distally
 Many unknown factors influence the development of neuromas ie one digital nerve
may develop one and one wont in an amputation
Classification of neuromas
I) neromas in continuity
a. spindle neuromas: lesions in which the perineurium is not damaged
b. lateral neuromas: lesions in which the perineurium of some funiculi is
broken
c. neuroma following nerve injury
II) neuromas in completely severed nerves
III) amputation stump neuromas
Neuromas in continuity
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neuromas in a nerve that has not been completely severed and are of two main
types ie those in which the perineural sheath is intact and those in which the nerve
is only partly damaged
Spindle neuromas
 not a true neuroma
 Swellings or enlargements in an intact nerve secondary to chronic irritation,
friction, or pressure.
 histologically the bulbous area contains increased connective tissue and with
repeated trauma fibrous tissue proliferation constricts the nerve interfering with
its nutrition and eventually get a large colagonized mass with fibrotic replacement
of nerve fibers and vessels
 Examples of this are mortons neuroma, the neuroma of the UDN in bowlers
thumb, the occipital nerve as it pierces the trapezial fascia, the lat cut nerve in
meralgia paraesthetica
Lateral neuromas
 Occur when part of a nerve is damaged and the size of this neuroma depends on
the number of faniculi that are damaged and the distance between the faniculi.
 If there is minimal retraction of ends the gap is bridged rapidly by proliferating
schwann cells and fibroblasts reestablishing the tubes to allow regenerating axons
to find their way to the proper distal sheaths and end organs. If the funicular are
gaps are too large the area is not bridged quickly allowing regenerating axons to
escape quickly from their sheaths and thus form a true neuroma on the side of an
otherwise intact nerve
Neuromas following nerve repair
Neuromas in completely severed nerves
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Forms on the proximal stump of any severed peripheral nerve
Amputation stump neuroma
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The neuroma that forms in the amputation stump is the same as that of a
completely severed nerve but two important differences
1) in the amputation stump if the nerve lies near the end of the stump and secondary
healing occurs it is subject to increased fibrosis
2) it is subjected to repeated trauma from friction pressure and concussion which
leads to increased size, edema fibrosis and increased sensitivity
To avoid this surgeon should transect the nerve in such a way to allow it to retract
into a bed of healthy tissue away from the working surface of the amputation
stump. If the tissues are not satisfactory the nerve should be transferred to as area
away from the working surface of the stump usually dorsally
Diagnosis
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Direct tapping over the nerve elicits painful paraesthesia
A palpable mass that is tender to palpate and pressure of this mass may recreate
the patients symptoms
The pain produced is has a peculiar intensity and unpleasant quality
In WC pts may use differential blocks ie with saline first and then lidocaine (
suggested by green in his personal communications)
Nb occasionally a mass over a nerve such as a inclusion cyst may fool one
Treatment
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There is no procedure that is completely successful in the treatment of neuromas
and thus there are many techniques that are described
Prevention
 Almost any nerve will form a neuroma if it is severed and the best way to
minimize this is by careful repair or nerve graft to allow the axons to reach the
distal faniculi
 Greater amounts of internal collagen(scarring) with perineural repairs than with
epineural repairs .
 Ie suggested that epineural repair is the best method of minimizing the neroma
formation
 With amputations, shorten the nerve and allow retraction into deep soft tissues
Nonoperative techniques
 Desensitisation - Tapping, massage
 U/S transcutaneous electrical stimulation have been tried but no proven studies
thus operative repair with repair or translocation is the best method
Surgical Techniques
Resection/ retraction
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Resection of an acutely severed nerve allowing to retract back into an area of
uninjured tissue is the most commonly preferred treatment for irreparable nerve
injury esp in amputation stumps and also can be used in an area of old injury
With 65 % showing good result from single neurectomy in injured nerves and
increasing to a 78 % with second neurectomy
Operative technique
 identify nerve in area of normal anatomy isolate the neuroma and dissect the
nerve proximally . the proximal limit of the dissection should be an area of
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normal tissue. Gentle traction then applied to the nerve(excessive traction will
lead to intraneural tears and additional neuroma formation)
the nerve then sectioned as far as possible with a sharp knife, scissors and
allowed to retract into healthy bed
Crushing
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Attempting to suppress axonal regrowth at the end of the severed nerve by
crushing the end of the nerve.
It has been proven to be ineffective in neuroma formation. (Mr H uses this
method in combination with resection and retraction but times the crush by the
clock for one min)
Multiple sectioning
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Not recommended by Sunderland as it may result in neuroma formation at
multiple sites
Thought by others that resection and repair of the nerve proximal to the site of
the neuroma will stop many of the axons finding there way to the stump
Ligation
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Controversial
Sunderland believes it is of value
The rationale being that ligation will result in closure of the faniculi by sutures
thus preventing axonal re-growth
This requires the ligature to be placed around the nerve 5-10 cm above the cut end
and tied tightly enough to close them but not too tightly to cut through the
perineurium – forming new sites for neuroma formation
Radioactive ligatures have been used in animals with good results
Epineural closure
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Epineural closure alone has not been successful
Combination of fanniculectomy and epineural closure has shown 81 good results
Method
 microscope used
 the epineurium is carefully peeled back and each faniculi is carefully
identified and sectioned
 the epinurium is then redraped and then sutured with 6/0 nylon and placed
in healthy tissue
Transposition
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The neuroma is excised and then the distal end is turned back on itself and placed in
an a area devoid of scar.
A neuroma will still develop but will be in an area free of scar tissue.
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Care must be taken not to twist the nerve as a neuroma may develop at the point of
twist if a schwann cells are damaged at this site
Nerve may also be transposed into other tissues:
1. Implantation into same nerve (neurocampsis)
a. The nerve stump is coapted into the same nerve more proximally through
an opening in the epineurium.
b. may get neuroma in continuity at this site
2. Implantation into muscle
a. 82 % success rate but much poorer results with digital neuromas
b. not recommend to implant these into intrinsic muscle of the hand –
discomfort from traction on nerve end with movement and muscle
contraction
c. Others have found high reoperation rate
3. Implantation into bone
a. The nerve end is implanted within the medullary cavity of the bone
b. The objective are
i. contain the nerve within a restricted space thus limiting the size of
the neuroma
ii. protect the nerve from direct trauma
c. Drawback is that the nerve may be irritated by movement
i. Widely mobilize the nerve
ii. no tension on the nerve
iii. acute angle should be avoided as it enters the bone
iv. avoid implantation of the nerve just distal to a joint
4. Implantation into another nerve
a. The axons will not grow down the other nerve but will proliferate within
the epineural repair resulting in a neuroma in continuity
b. Need to have faniculi of the same size for this to be successful
Relocation of the intact neuroma
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The neuroma is kept intact with surrounding cuff of tissue and transposed enbloc
with a surrounding cuff of tissue to an unscarred area – preferably in a web space for
finger neuromas and between shafts of adjacent metacarpals for neuromas in palm
A dorsal site is preferable to a palmer location for fingers
Good success rate with this method
Coagualtion
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Aim to seal the funicular ends
Many methods used including hot water, cauterization, freezing , chemical coagulants
and radioactive substances
Sunderland feels that these methods are usually not successful as it is almost
impossible to suppress axonal growth
CO2 laser photocoagulation has shown promise
Capping of the neuroma
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The divided ends are capped with various materials including silicone, gold foil, glass
caps methlymethacrylate arterial wall tissue
Most not successful and elicit a foreign body reaction
Silicone capping
 Some success shown
 The neuroma is trimmed and then passed into the distal cap which is not too tight and
the length to diameter of the cap is 5:1 to reduce backward growth of the nerve
 Transfer stump to healthy tissue
 Failure may result from nerve ends growing out the proximal end of the cap
Soft tissue cover
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Salvage operation
Rather than moving nerve to healthy tissue, vascularised soft tissue is transferred to
the area to provide a protective cover for the neuroma
Greens preferred method
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If possible to repair the nerve, repair the nerve with or without nerve graft
Where ned is healthy - resects and allows the cut end to retract into healthy tissue.
If the bed is not adequate, translocate the nerve
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In formed neuromas, relocate the intact neuroma with surrounding cuff to an
unscarred protected area
Sood and Eliott (J Hand Surg (Br) 1998)
. Zones of the hand as a guide to relocation of painful nerves of the hand and wrist.
Zone 1 – the digits: Pain from the digital nerves, their dorsal branches and the terminal
branches of the nerves innervating the dorsum of the hand. First choice of relocation – the
proximal phalanx or metacarpal.
Zone 2 – the body of the hand: Pain from the common digital nerves, the palmar
cutaneous branches of the median and ulnar nerves and the dorsal branch of the ulnar
nerve. First choice of relocation – pronator quadratus muscle.
Zone 3 – the radial border of the wrist and the forearm: Pain from the superficial radial
nerve, the lateral cutaneous nerve of the forearm, the medial cutaneous nerve of the
forearm and the posterior cutaneous nerve of the forearm. First choice of relocation –
muscles of the forearm and arm, especially brachioradialis.