The presence of middle cluneal nerve (MCN) entrapment, a neuropathy characterized by buttock pain radiating to the posterior thigh, should be considered before recommending surgical intervention for patients with intractable low back pain (LBP), according to study results published in Acta Neurochirurgica.
The objective of the current study was to assess the incidence of LBP due to MCN entrapment, its clinical course, and the response to treatment.
The retrospective, single-center study included 383 patients (63 women; mean age, 64 years) who were assessed for LBP between May 2016 and August 2017.
After excluding 278 patients with LBP controlled by oral medication or diagnosed with radiologic findings, 105 patients were admitted for intractable LBP. After additional exclusion of subjects with no pain or tenderness at the MCN area, the diagnosis of MCN entrapment was established in 50 patients (13.1%), who reported reduced LBP in the MCN following MCN block.
In 43 patients, MCN entrapment was associated with other diseases, most commonly superior cluneal nerve entrapment (21 patients), sacroiliac joint pain (9 patients), radiculopathy (5 patients), or other diseases (8 patients).
Multiple MCN blocks (2 ml of 1% lidocaine) were administered during hospitalization to treat LBP from MCN entrapment. After discharge, the patients were followed on an outpatient basis for a median of 18.4 months.
Of the 50 patients with MCN entrapment who reported reduced LBP following MCN block, 22 patients required no additional treatment, while 19 required only conservative treatment. Only 9 patients whose MCN entrapment pain recurred after a transient relief by MCN blocks were considered candidates for microsurgical release of the MCN.
The study had several limitations, including the retrospective design, single-center study, lack of a control group, relatively small sample size, inclusion limited to hospitalized patients, diagnosis of MCN entrapment based on the effect of MCN block, and the short post-treatment follow-up.
“Before subjecting patients with intractable LBP to surgery, a differential diagnosis must be obtained and the presence of MCN EN [entrapment] must be assessed,” concluded the researchers.
Fujihara F, Isu T, Kim K, et al. Clinical features of middle cluneal nerve entrapment neuropathy. Acta Neurochir (Wien). Published online January 6, 2021. doi:10.1007/s00701-020-04676-0