Back Mouse, aka Episacroiliac Lipoma

Often misdiagnosed, pain relief from back mice can be illusive

Back of the pelvis including sacroiliac area.
Back of the pelvis including sacroiliac area. SCIEPRO / Getty Images

Back mouse is a condition characterized by painful bumps in and around the hips, sacrum and low back. Diagnosing it accurately often stumps doctors and other health practitioners. Because of that, it's a good idea to very carefully consider the treatment recommendations you are offered, should you find yourself with these painful nodules. Let's sort out the known facts so there's a reference for dealing with this back problem effectively.

A Back Mouse by Any Other Name

Back mice have been known to surgeons since 1937 when Reis reportedly named them episacroiliac lipoma. Since then, the condition has been attributed a number of names including: Iliac crest pain syndrome, multifidus triangle syndrome, lumbar fascial fat herniation and lumbosacral fat herniation. Many authors believe that of all the terms used to identify back mice, the last two - lumbar fascial fat herniation and lumbosacral fat herniation - are the most accurately descriptive.

So What is a Back Mouse, Anyway?

A back mouse is a fat mass that protrudes abnormally through the lumbodorsal fascia. The lumbodorsal fascia is a big diamond-shaped sheath of connective tissue in the lumbar and thoracic spine area of your back.  Back mice also occur in the hip bones in back, as well as the sacroiliac region.

Related:  What is the Lumbodorsal Fascia?

You might think that a simple fat mass couldn't cause much pain, but generally speaking, that's not so.

Patients and their surgeons often report excruciating pain from back mice. Along with the pain, telltale symptoms may include visibly notable nodules in the low back and sacral areas, and, when the nodules are touched or pressed, a reproduction of the type of pain that likely drives you to seek treatment in the first place.

Very little medical research has been done on back mice, and that may be a reason why little is known about it. In the meanwhile, the word on the internet street is that articles written by chiropractor David W. Bond provide the most comprehensive information available on this subject. Bond reports that moderately obese women seem to be at a higher risk for back mice than others. He also says that often people with back mice quite often go through a battery of treatments with no pain relief to show for it.

Back Mice?  Or Sciatica? 

As I mentioned above, it's not uncommon for doctors to misdiagnose back mice. In fact, the condition is commonly mistaken for sciatica. While pain from back mice starts locally, at the nodules themselves, it often, like sciatica, radiates to other areas. Like sciatica, back mouse pain tends to be unilateral, and can increase depending on your position. The pattern of pain radiation is generally not uniform.

Related:  Got Sciatica?  Here's what to do.

Bond says that irritation due to back mice doesn't show up on nerve root tests - unless you also have a herniated disc.

He adds that the condition may be accompanied by spasms in your paraspinal muscles, as well as decreased lumbar range of motion. Pain intensity can vary, as can how long it lasts (duration.)

Related:  What is a Spinal Nerve Root?

Back Mice?  Or Trigger Points?

While it's possible to pinpoint back mouse pain and/or tenderness by touching one, back mice are not trigger points. Trigger points present themselves as taut bands muscle while back mice are felt as masses or nodules.

Back mice are not tight muscles, so pressing down on them will not contribute to their cure or management. In fact, this kind of treatment causes pain, Bond says. this means that a deep massage will likely not be the correct treatment.

Diagnosis and Treatment - The 2015 State of the State

One way to diagnose back mice is by injection (or surgery.) If injecting a local anesthetic relieves the pain - albeit temporarily - the diagnosis is suggested. Case studies from the 1940s show that when back mice are surgically removed, this almost always fully relieves the pain.

Currently, surgery (excision of the mice, followed by repair of the fascial openings through which they emerged) appears to be the only way to achieve durable pain relief from back mice. The problem is, often hundreds of back mice may be present, which complicates achieving full pain relief using this method. That said, Bond believes this condition may be successfully treated by combining acupuncture and spinal manipulation.

Sources:

Denman C. Hucherson, M.D., Joe R. Gandy, M.D., Herniation of fascial fat: A Cause of Low Back Pain. The American Journal of Surgery. November 1948.

Rosati E1, Mariani D. The role of episacroiliac lipomas as a cause of pseudolumbago-sciatica syndromes. Arch Putti Chir Organi Mov. 1990.

Bond, D. Chiropractic Treatment of the Back Mouse. Dynamic Chiropractic. September 2004. http://www.dynamicchiropractic.com/mpacms/dc/article.php?id=46427

Bond, D. Low Back Pain and Episacral Lipomas. Dynamic Chiropractic. September 2000. http://www.dynamicchiropractic.com/mpacms/dc/article.php?id=31867

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