Lateral Cutaneous Nerve Entrapment Syndrome (LACNES): A previously unrecognized cause of intractable flank pain.

BACKGROUND AND AIMS: Chronic abdominal pain may occasionally be due to terminal endings of intercostal nerves (ACNES, abdominal cutaneous nerve entrapment syndrome) that are entrapped in the abdominal wall. Spontaneous neuropathic flank pain may also be caused by involvement of branches of these intercostal nerves. Aim is to describe a series of patients with flank pain due to nerve entrapment and to increase awareness for an unknown condition coined Lateral Cutaneous Nerve Entrapment Syndrome (LACNES). METHODS: Patients possibly having LACNES (constant area of flank tenderness, small point of maximal pain with neuropathic characteristics, locoregional altered skin sensation) presenting between January 2007 and May 2016 received a diagnostic 5-10mL 1% lidocaine injection. Pain levels were recorded using a numerical rating scale (0, no pain to 10, worst possible). A >50% pain reduction was defined as success. Long term effect of injections and alternative therapies were determined using a satisfaction scale (1, very satisfied, no pain - 5, pain worse). RESULTS: 30 patients (21 women, median age 52, range 13-78) were diagnosed with LACNES. Pain following one injection dropped from 6.9±1.4 to 2.4±1.9 (mean, p<0.001) leading to an 83% immediate success rate. Repeated injection therapy was successful in 16 (pain free n=7, pain acceptable, n=9; median 42 months follow-up). The remaining 14 patients received (minimally invasive) surgery (n=5) or other treatments (medication, manual therapy or pulsed radiofrequency, n=9). Overall treatment satisfaction (scale 1 or 2) was attained in 79%. CONCLUSIONS AND IMPLICATIONS: LACNES should be considered in patients with chronic flank pain. Injection therapy is long term effective in more than half of the population.

Pulsed radiofrequency or anterior neurectomy for anterior cutaneous nerve entrapment syndrome (ACNES) (the PULSE trial): study protocol of a randomized controlled trial.

BACKGROUND: Some patients with chronic abdominal pain suffer from an anterior cutaneous nerve entrapment syndrome (ACNES). This somewhat illusive syndrome is thought to be caused by the entrapment of end branches of the intercostal nerves residing in the abdominal wall. If ACNES is suspected, a local injection of an anesthetic agent may offer relief. If pain is recurrent following multiple-injection therapy, an anterior neurectomy entailing removal of the entrapped nerve endings may be considered. After 1 year, a 70% success rate has been reported. Research on minimally invasive alternative treatments is scarce. Pulsed radiofrequency (PRF) treatment is a relatively new treatment for chronic pain syndromes. An electromagnetic field is applied around the nerve in the hope of leading to pain relief. This randomized controlled trial compares the effect of PRF treatment and neurectomy in patients with ACNES. METHODS: Adult ACNES patients having short-lived success following injections are randomized to PRF or neurectomy. At the 8-week follow-up visit, unsuccessful PRF patients are allowed to cross over to a neurectomy. Primary outcome is pain relief after either therapy. Secondary outcomes include patient satisfaction, quality of life, use of analgesics and unanticipated adverse events. The study is terminated 6 months after receiving the final procedure. DISCUSSION: Since academic literature on minimally invasive techniques is lacking, well-designed trials are needed to optimize results of treatment for ACNES. This is the first large, randomized controlled, proof-of-concept trial comparing two therapy techniques in ACNES patients. The first patient was included in October 2015. The expected trial deadline is December 2017. If effective, PRF may be incorporated into the ACNES treatment algorithm, thus minimizing the number of patients requiring surgery. TRIAL REGISTRATION: Nederlands Trial Register (Dutch Trial Register), NTR5131 ( http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5131 ). Registered on 15 April 2015.