2016 Bicket

Bicket et al. emphasized the importance of CONSIDERING the epi-sacro-iliac lipoma or back mice as a CAUSE OF LOW BACK PAIN. They reviewed existing literature, including treatment options and presented a CASE REPORT. They finished saying that no recognizing back mice can lead patients to receive the INCORRECT DIAGNOSIS OF NON-SPECIFIC low back pain.

Notes about the article:

The Best-Laid Plans of “Back Mice” and Men: A Case Report and Literature Review of Episacroiliac Lipoma.

Bicket MC, Simmons C, Zheng Y.

Pain Physician. 2016 Mar;19(3):181-8. Review. PubMed PMID: 27008292.

Bicket et al. start with a mention to “low back pain problem

They start commenting that low back pain represents a common, costly and disabling condition. Still with unclear causes.

Low back pain patients have been categorized in 3 cohorts:

-nonspecific low back pain

-back pain associated with radiculopathy/spinal stenosis

-back pain associated with another specific spinal cause

They present a case report and a literature review that may help to describe one potentially treatable cause of back pain: “back mice

About epi-sacro-iliac lipoma or  “back mice”

Bicket et al. described “back mice” as palpable, freely movable, fatty tissue nodules found commonly in the sacroiliac region.

“Back mice” and other monikers

Back mice” have received various monikers over time: the most common of which is “episacroiliac lipoma” or (epi-sacro-iliac lipoma)

List of alternative names for back mice or epi-sacro-iliac lipoma:

-Episacral lipoma

-Sacroiliac lipomata

-Subcutaneous fatty nodes

-Lumbar subcutaneous nodule

-Tender rheumatic nodule

-Fibrositis nodule

-Multifundus triangle syndrome

-Iliac crest pain syndrome

Some notes about old references

-First description dates from 1935 from Sutro’s work.

-In the late 1930s and 1940s work with corpses was characterized by their occurrence’s pattern with nodules located in areas where fatty tissue herniates through fascial layers (especially Copeman and Ackerman’s work)

epi-sacro-iliac lipoma

-The areas correspond with: lumbar parespinal musculature, sacroiliac area and posterior superior iliac crest… but they have also been described in thoracic areas.

The name back mice

The sobriquet of back mice developed out of the need to communicate with patients about the mobile nature of the nodule, the rubbery consistency, and ABILITY TO CHANGE SIZE OVER TIME.

Bicket et al. CASE REPORT

epi-sacro-iliac lipoma

A 47-year-old woman with a 2-year history of persistent axial LOW BACK PAIN, with a 2-week period of exacerbation. No low extremities involvement. No trauma. The pain was described as intermittent, sharp, localized, bilateral in low back. Intermittent numbness. Pain triggers included twisting and walking. Soothing factors resting and laying down.

Physical examination revealed 2 mildly tender, distinctly palpable, freely movable nodules, measuring 4x2x3cm.

Deep palpation of nodules reproduced the patient’s sensations of pain as the numbness in posterior thigh.

The rest of examinations show no findings.

epi-sacro-iliac lipoma

They injected local anesthetic and corticosteroid under ultrasound visualization with no good response.

They repeated infiltration with a dry needling technique with good results after one month following up.

DISCUSSION

-The prevalence of these nodules is yet not clear since the result of the studies vary.

-The pain pattern that they present and the physical examination can help to differentiate from other etiologies.

-In comparison to myofascial trigger points, back mice lay superficial to muscle bands.

-Pain from back mice can radiate to leg, but there is absence of other neurological deficit, reflexes are intact, and no lack of sensory findings.

Back mice can give referred pains to the hip or the abdominal site.

-The injection and the repeated needling seem to be the best initial approach. Despite other studies focused on surgery that should be considered in case that injection does not give permanent relief. Despite sometimes pain persists even after surgery. Other described techniques have been radiofrequency or cryoablation.

-Nevertheless, the pain mechanisms of this entity are not yet clarified, pressure, tension or torsion have been suggested.

-They explained the only randomized trial of Collée that compared injection therapy with local anesthetic or with isotonic saline.

-Bicket et al. propose injection with local anesthetic and corticoisteroid with repeated needling as first treatment approach.

Published in May 2018 by Marta Cañis Parera   ORCID iD icon

REFERENCES by Bicket et al.

  1. Hoy D, March L, Brooks P, Blyth F, Woolf A, Bain C, Williams G, Smith E, Vos T, Barendregt J, Murray C, Burstein R, Bu- chbinder R. The global burden of low back pain: Estimates from the Glob- al Burden of Disease 2010 study. Ann Rheum Dis 2014; 73:968-974.
  2. Hoy D, Bain C, Williams G, March L, Brooks P, Blyth F, Woolf A, Vos T, Bu- chbinder R. A systematic review of the global prevalence of low back pain. Ar- thritis Rheum 2012; 64:2028-2037.
  3. Martin BI, Deyo RA, Mirza SK, Turner JA, Comstock BA, Hollingworth W, Sul- livan SD. Expenditures and health status among adults with back and neck prob- lems. JAMA 2008; 299:656-664.
  4. Chou R, Qaseem A, Snow V, Casey D, Cross JT Jr, Shekelle P, Owens DK. Diag- nosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med 2007; 147:478-491.
  5. Sutro CJ. Subcutaneous fatty nodes in the sacroiliac area. Am J Med Sci 1935; 190:833-837.
  6. Ries E. Episacraliliac lipoma. Am J Obstet Gynecol 1937; 34:490-494.
  7. Copeman W, Ackerman W. ‘Fibrositis’ of the back. Q J Med 1944; 13:37-52.
  8. Copeman W, Ackerman W. Edema or herniations of fat lobules as a cause of lumbar and gluteal ‘fibrositis.’ Arch Intern Med 1947; 79:22-35.
  9. Harman JB. Fibrositis and pain. Ann Rheum Dis 1940; 2:101-107.
  10. Curtis P. In search of the ‘back mouse.’ J Fam Pract 1993; 36:657-659.
  11. Motyka TM, Howes BR, Gwyther RE, Curtis P. Treatment of low back pain as- sociated with “back mice”: A case series. J Clin Rheumatol 2000; 6:136-141.
  12. Swezey RL. Non-fibrositic lumbar subcu- taneous nodules: Prevalence and clinical significance. Br J Rheumatol 1991; 30:376- 378.
  13. Earl DT, Lynn JC, Carlson JM. “Back mice” – a prevalence study. J Tenn Med Assoc 1995; 88:428-429.
  14. Collée G, Dijkmans BA, Vandenbroucke JP, Rozing PM, Cats A. A clinical epide- miology study in low back pain. Descrip- tion of two clinical syndromes. Br J Rheu- matol 1990; 29:354-357.
  15. Collée G, Dijkmans BA, Vandenbroucke JP, Cats A. Iliac crest pain syndrome in low back pain: Frequency and features. J Rheumatol 1991; 18:1064-1067.
  16. Curtis P, Gibbons G, Price J. Fibro-fatty nodules and low back pain. The back mouse masquerade. J Fam Pract 2000; 49:345-348.
  17. Pace JB, Henning C. Episacroiliac lipoma. Am Fam Physician 1972; 6:70-73. Herz R. Herniations of fascial fat as a cause of low back pain. JAMA 1945; 129:921-924.
  18. Herz R. Herniation of subfascial fat as a cause of low back pain: Report of thir- ty-seven cases treated surgically. Ann Rheum Dis 1946; 5:201-203.
  19. Herz R. Herniation of subfascial fat as a cause of low back pain: Results of sur- gical treatment in thirty-one cases. J Int Coll Surg 1946; 9:339-347.
  20. Hucherson DC, Gandy JR. Herniation of fascial fat. Am J Surg 1948; 76:605-609. Hittner VJ. Episacroiliac lipomas. Am J Surg 1949; 78:382.
  21. Herz R. Differential diagnosis of low back pain based on a study of two hun- dred and eighty-one cases. J Fla Med As- soc 1950; 37:289-292.
  22. Katz KH, Berk MS. Episacroiliac lipoma as a cause of low-back pain. N Engl J Med 1950; 243:851-852.
  23. Herz R. Subfascial fat herniation as a cause of low back pain: Differential di- agnosis and incidence in 302 cases of backache. Ann Rheum Dis 1952; 11:30-35.
  24. Bonner CD, Kasdon SC. Herniation of fat through lumbodorsal fascia as a cause of low-back pain. N Engl J Med 1954; 251:1102-1104.
  25. Bauwens P, Coyer AB. The multifidus triangle syndrome as a cause of re- current low-back pain. Br Med J 1955; 2:1306-1307.
  26. Wollgast GF, Afeman CE. Sacoiliac (episacral) lipomas. Arch Surg 1961; 83:925- 927.
  27. Singewald ML. Another cause of low back pain: Lipomata in the sacroiliac re- gion. Trans Am Clin Climatol Assoc 1966; 77:73-79.
  28. Faille, RJ. Low back pain and lumbar fat herniation. Am Surg 1978; 44:359-361. Fischer PM. “Back mouse.” J Fam Pract 1993; 37:328.
  29. Min Ko S, Ali RK, Chacko J, Ryu J. Superior cluneal nerve entrapment due to fibro-fatty nodule: A case report. PM&R 2009; 1:S176.
  30. Collée G, Dijkmans BA, Vandenbroucke JP, Cats A. Iliac crest pain syndrome in low back pain. A double blind, random- ized study of local injection therapy. J Rheumatol 1991; 18:1060-1063.
  31. Bond, D. Chiropractic treatment of the back mouse. Dynamic Chiropractic 2004; 22:20.