Lateral Cutaneous Nerve Entrapment Syndrome: Newly Described Cause of Flank Pain

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Overall, mean pain scores were lower after the lidocaine injection with patients reporting a >50% reduction in pain score.
Overall, mean pain scores were lower after the lidocaine injection with patients reporting a >50% reduction in pain score.

Lateral cutaneous nerve entrapment syndrome (LACNES), a newly defined syndrome characterized by flank tenderness, may successfully be treated with lidocaine injections and alternative treatments, according to the results of research published recently in the Scandinavian Journal of Pain.

In this single-site study, patients who presented with constant area of flank tenderness, small point of maximal pain with neuropathic characteristics, and locoregional altered skin sensation were considered to present with LACNES. Patients who met inclusion criteria received a lidocaine injection (5-10 mL; 1%), and their pain levels were monitored with a numerical rating scale.

Pain reduction >50% indicated treatment success. A satisfaction scale (with a value of 1 for lack of pain and a "very satisfied" patient and a value of 5 for worsening pain) was used to evaluate the long-term effects of lidocaine injection and alternative therapies.

During the almost 10-year study period, 30 patients met the diagnostic criteria for LACNES, and all consented to the diagnostic lidocaine injection. Overall, mean pain scores were lower after the lidocaine injection (2.4 vs 6.9; P <.001). A total of 83% of patients reported a >50% reduction in pain score after the diagnostic injection.

In addition, 17% of patients experienced long-term pain relief after a single injection (median, 60 months). Multiple injections (between 1 and 3) resulted in long-term pain relief for 23% of patients, with a satisfaction score of 1. Acceptable pain relief (satisfaction score of 2) was achieved in 30% of patients with injections alone.

Alternative therapies included pulsed radiofrequency therapy and surgery. Patients treated with surgery had a 75% success rate (satisfaction score, 1-2).

According to the study authors, "the most important finding is that this novel syndrome [LACNES] should be considered in the differential diagnosis of chronic flank pain." They added that "injection therapy using a combination of local anaesthetic agents with or without steroids is long term effective in over half of this population. Further research is needed to establish a standardized treatment protocol and investigate the effect of a local surgical exploration in treating LACNES patients."

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Reference

Maatman RC, Papen-Botterhuis NE, Scheltinga MRM, Roumen RMH. Lateral cutaneous nerve entrapment syndrome (LACNES): A previously unrecognized cause of intractable flank pain. Scand J Pain. 2017;17:211-217.

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