Chronic Localized Back Pain Due to Posterior Cutaneous Nerve Entrapment Syndrome (POCNES): A New Diagnosis

Abstract

Most patients with chronic back pain suffer from degenerative thoracolumbovertebral disease. However, the following case illustrates that a localized peripheral nerve entrapment must be considered in the differential diagnosis of chronic back pain. We report the case of a 26-year-old woman with continuous excruciating pain in the lower back area. Previous treatment for nephroptosis was to no avail. On physical examination the pain was present in a 2 x 2 cm area overlying the twelfth rib some 4 cm lateral to the spinal process. Somatosensory testing using swab and alcohol gauze demonstrated the presence of skin hypo- and dysesthesia over the painful area. Local pressure on this painful spot elicited an extreme pain response that did not irradiate towards the periphery. These findings were highly suggestive of a posterior version of the anterior cutaneous nerve entrapment syndrome (ACNES), a condition leading to a severe localized neuropathic pain in anterior portions of the abdominal wall. She demonstrated a beneficial albeit temporary response after lidocaine infiltration as dictated by an established diagnostic and treatment protocol for ACNES. She subsequently underwent a local neurectomy of the involved superficial branch of the intercostal nerve. This limited operation had a favorable outcome resulting in a pain-free return to normal activities up to this very day (follow-up of 24 months). We propose to name this novel syndrome “posterior cutaneous nerve entrapment syndrome” (POCNES). Each patient with chronic localized back pain should undergo simple somatosensory testing to detect the presence of overlying skin hypo- and dysesthesia possibly reflecting an entrapped posterior cutaneous nerve. Key words: Chronic pain, back pain, posterior cutaneous nerve entrapment, peripheral nerve entrapment, surgical treatment for pain, anterior cutaneous nerve entrapment