A new concept.
The most unknown and yet the most frequent of neuropathies.
Indeed, a recent study carried out by a Parisian pain center found an incidence of between 2.5% and 5% of operated patients.
They therefore affect around 500,000 people per year in France (1).
It is linked to trauma, a wound or surgery.
It gives variable tables, from a simple gene to a persistent handicap.
- Appears in the months following a trauma, surgery.
- The pain is accompanied by dysesthesias, paresthesias, burns, electric shocks sometimes a sensation of bone pain.
- the clinical examination finds hyperesthesia and / or hypoesthesia in the area.
- Depending on the affected area, an accompanying myofascial syndrome is not uncommon.
- Additional examinations are normal (blood test, x-ray, ultrasound, CT scan, MRI)
- Only the bone scintigraphy is sometimes positive but has no value in this context.
- The electromyogram and the evoked potentials are normal.
The size of the surgery or the trauma does not in any way prejudge the size of the painful area and its consequences.
- May be responsible for visceral symptoms depending on the location of the cutaneous involvement: constipation, bladder instability.
- The diagnosis is only clinical.
- Local examination of the patient finds the neurological signs described above.
- The affected territory may correspond to a known neurological path but often truncated (absence of complete involvement of the territory: truncated sciatica, truncated intercostal neuralgia) or be divided into an "oil stain".
- In the painful area there is even a minimal scar (trocar path for example)
- examination of the scar area by the rolling palpate method triggers a sharp pain which sometimes reproduces all of the pain described by the patient.
- May join the neurological picture of vasomotor signs and sometimes edema leading to true algodystrophy (CRPS)
An algorithm helps you to suspect the diagnosis. (Go to the algorithm)
Treatment and diagnostic confirmation:
- Infiltration of the scar area with 1% lidocaine confirms the diagnosis. This infiltration is done by tracing infiltration under the scar and sometimes deeper in the subcutaneous plane
- Short kissing needles can be used (especially in the abdominal area) which allow you to feel the areas containing fibrosis and the changes in tissue density.
- The injection, if the scar is responsible, is painful or even very painful, which is a good diagnostic sign.
If the scar is not responsible, the injection is not very painful.
- In the minutes which follow the pains related to this scar disappear and confirm the diagnosis.
- To get an idea of the neurological picture of some patients, we invite you to look at the clinical cases described on this site.
- If effective, the injection must be repeated if the pain has subsided over a long enough period (1,2,3 weeks or even several months). The repetition of the injections allows in 2 thirds of the patients to obtain a clear improvement in the long term (2). Sometimes a single injection may suffice.
- If the injection is effective but only 2 hours, it was made near the responsible area and it is the diffusion of the lidocaine that causes the relief.
Do not forget to treat an associated myofascial syndrome with physiotherapy.
Action mechanism :
Scarring neuropathy is probably the result of suffering from small nerves sheathed in scar fibrosis.
The latter evolves by contracting and hardening realizing in a few weeks or months a real compressions of these small nerves, which explains the delay between surgery or trauma and the appearance of these pains.
Lidocaine infiltration probably has a mechanical effect by dissecting this fibrosis and relieving the compression of these small nerves.
The anesthetic also probably defuses central phenomena linked to this permanent pain.
This mechanism of action remains to be confirmed.