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compensates for the tension generated by movement and End‑neuromas, which are associated with similar
requires an intact gliding surface between the nerve and symptoms, and neuromas‑in‑continuity without residual
its surrounding tissue. function, are not addressed in the present review, because
their management is fairly well established: the former
Clearly, the movement also stretches perineural and
intraneural vascular structures, inducing vessel strain and may benefit from relocation to deep, protected areas,
reducing blood flow. A healthy gliding system prevents whereas for the latter the initial treatment of choice is
excessive stress from being exerted on vessel walls and reconstruction with nerve grafts or conduits.
ensures a sufficient blood supply to axons and Schwann cells. This review describes and discusses the main diagnostic
Preclinical studies have demonstrated that an 8% increase in and therapeutic approaches to neuropathic pain due to
nerve tension induces a 50% reduction in intraneural blood neuroma‑in‑continuity and peripheral nerve compression
flow, whereas tension exceeding 15% of the baseline value in scar tissue based on the literature and the authors’
induces an 80% reduction. In a study of rat sciatic nerves personal experience. The condition is complex and
[4]
subjected to crush lesions, Boyd et al. documented nerve difficult to treat, and there is no consensus on the most
[5]
tension exceeding the intraneural microvessel compression appropriate surgical approach.
threshold due to physiological movements, and found Different surgical procedures and products that limit
that it resulted in perineural scar formation and reduced scar formation and reduce pain are also reviewed, and
intraneural vascularization.
a treatment algorithm based on the type of pain, lesion
Similarly, in the clinical settings formation of a perineural type, number of previous operations, and imaging data is
scar for any reason increases the tension on the nerve proposed. Finally a review of the literature for treatment
and may lead to prolonged ischemia. Wilgis and Murphy outcomes, with emphasis on the resolution of pain
[6]
described an association between reduced longitudinal symptoms, is presented.
gliding of the peripheral nerve and symptom recurrence
following surgical decompression. In 1979, McLellan and EPIDEMIOLOGY
Swash reported that impaired linear gliding can induce
[7]
a nerve lesion at a distance from the compression area, Perineural scarring and consequently traction neuropathy
thus introducing the notion of traction neuropathy. The have traditionally been considered to be complications
term indicates a condition related to impaired nerve of nerve decompression surgery. Nerve tethering in the
gliding, whereas in Hunter 1991 description, it designates surgical scar is still the main cause of symptoms related
[8]
neurological symptoms due predominantly to the movement to perineural scarring. For instance, 7‑20% of patients
of the affected nerve. However, traction neuropathy may subjected to primary median nerve release report pain
be too narrow a definition, given that some patients with and symptom recurrence. The condition is difficult to
[13]
extensive perineural fibrotic reactions experience constant manage, so much so that according to different reports
pain both at rest and in the absence of movement. The compression symptoms persist after 40‑90% of revision
condition is likely due to a fibrotic response that is, procedures, and 20% of patients actually require a
[14]
initially perineural and eventually becomes intraneural due third operation. Clinical failure rates of 25% have been
[14]
to compression secondary to chronic scarring. Perineural reported after ulnar nerve release at the cubital tunnel,
[15]
fibrosis can induce ischemic stress in the involved fascicles, and a review of 50 studies found symptom recurrence in
followed by degeneration of distressed axons, the repair approximately 75% of treated patients. As noted above,
[16]
process may subsequently lead to formation of an 5% of nerve sutures have been estimated to induce a pain
in‑continuity neuroma with residual nerve function whose syndrome. [11]
[9]
symptoms also involve pain at rest. Pain at rest may also
be related to a perineural scar associated with intraneural However, the problem is not confined to peripheral
scarring due to a traumatic Grade III or IV injury or to a nerves. Indeed, one of the most common complications
Grade V lesion (nerve transection) according to Sunderland’s of microdiscectomy and laminectomy, found in 15‑20%
[10]
classification. A painful neuroma at the suture site has of patients, is failed back syndrome, which seems to be
[11]
been described in nearly 5% of repaired nerves. We, related to the formation of scars entrapping the released
[17]
therefore, agree with Elliot that “traction neuropathy” is nerve roots. These patients often undergo additional
[9]
a somewhat limited definition, whereas “scarring neuritis” procedures for the new symptoms.
or “scar neuropathy” encompass all the conditions related Besides compression syndrome recurrence, neurogenic
to formation of perineural and intraneural fibrotic tissue pain may be related to the formation of a neuroma‑in‑
involving neurological symptoms and induced by a nerve continuity associated with a partial lesion or severance of
injury (intraoperative lesion, cut injury, stretching, or the peripheral nerve. This condition is found in 60‑70% of
extrinsic compression due to fracture or hematoma). [12] traumatic injuries involving a peripheral nerve. [18]
Based on our experience and the pathophysiology of nerve
injuries, both fibrosis around a nerve (traction neuropathy) CLASSIFICATION OF SCARRING
and inside/outside it (as in neuroma‑in‑continuity) can NEURITIS
be classified as scarring neuritis/scar neuropathy, whose
distinctive symptom is pain due to the pathological Millesi et al. have extensively investigated peripheral
[19]
condition affecting the nerve. nerve gliding and devoted considerable effort to describing
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