Chronic localized back pain due to entrapment of cutaneous branches of posterior rami of the thoracic nerves (POCNES): a case series on diagnosis and management

Key points

1. 0181% of patients had more than 50% pain reduction after a diagnostic lidocaine injection
2. 02Long-term success (VRS 1-2) was achieved in 57% of the full study population at median 29 months follow-up
3. 03Neurectomy succeeded in 7 of 11 operated patients (64%) at long-term follow-up
4. 04Median diagnostic delay before POCNES was identified was 22 months
5. 056 of 14 patients had previously had a neurectomy for the related anterior nerve entrapment syndrome (ACNES)

How it was conducted

Design

Prospective case series at two Dutch tertiary-referral surgery centers

Participants

14 patients (12 female, 2 male) meeting at least 4 of 5 predefined POCNES diagnostic criteria; median age 26 years (range 18-73)

Observation period

January 2013 to September 2016

Diagnostic intervention

2-5 mL 1% lidocaine injection below the thoracolumbar fascia at the point of maximal pain

Primary outcome

More than 50% reduction on NRS (0-10) after injection; long-term satisfaction on VRS (1-5)

Surgical procedure

Neurectomy of the cutaneous branch of the posterior ramus via a 5 cm transverse incision over the pain point

What they found

• NRS pain scores dropped from median 8.0 (IQR 7.0-8.0) pre-injection to median 3.0 (IQR 1.5-3.5) post-injection (P<0.001) in 13 of 14 patients
• 10 of 13 assessed patients (81%) reported more than 50% pain reduction after the diagnostic injection
• At 6-week post-operative review, 7 of 11 neurectomy patients (64%) were very satisfied or satisfied (VRS 1-2) and 3 (27%) reported attenuated pain (VRS 3); surgery was unsuccessful in 1 (VRS 4)
• At long-term follow-up (median 29 months, range 5-48 months), 7 of 11 operated patients (64%) remained satisfied (VRS 1-2)
• Overall long-term efficacy across the entire study population was 57% (8 of 14 patients achieved VRS 1-2)
• All patients had a DN4 score of at least 3 (median 3, range 3-5), confirming neuropathic pain
• Positive pinch test was found in 86% (12 of 14) of patients
• In half of cases (7 of 14), the point of maximal pain corresponded with the T12 dermatome

Limitations

• Very small sample of 14 patients from two tertiary referral centers limits generalizability and introduces selection bias
• No control group or comparison with standard back pain treatments
• Retrospective data accrual and lack of objective neurophysiological tests (laser evoked potentials, quantitative sensory testing, nerve biopsy)
• Results may not apply to general clinical practice as the diagnosing centers have specialized expertise in neuropathic trunk pain syndromes

Why it matters

For patients

Patients with chronic localized back pain that has not responded to standard investigations and treatment should ask their doctor whether nerve entrapment (POCNES) might be the cause, especially if there is a small, predictable tender spot with abnormal skin sensation nearby.

For clinicians

POCNES should be included in the differential diagnosis of chronic localized back pain; a structured clinical assessment followed by a diagnostic lidocaine injection at the tender point can confirm the diagnosis, and neurectomy offers durable relief in roughly two thirds of surgical candidates.

For readers

This is a small, first-in-kind case series describing a newly recognized neuropathic back pain syndrome; evidence is preliminary and larger comparative studies are needed before routine clinical adoption.