The authors do a brief literature review about episakral lipoma (or back mice) and they present two case reports of 2 women that got better after local INTRANODULAR injection of the lumbar nodule.

Notes on the article:

[Episacral Lipoma: a Treatable Cause of Low Back Pain].

Erdem, H.R., Nacır, B., Özeri Z., Karagöz, A.

Agri. 2013; 25(2): 83-6. doi: 10.5505/agri. 2013. 63626. Turkish. PubMed PMID: 23720083. FREE online article

ORIGINAL abstract from the article by Erdem et al.

Episakral lipoma is a small, tender subcutaneous nodule primarily occurring over the posterior iliac crest. Episakral lipoma is a significant and treatable cause of acute and chronic low back pain. Episakral lipoma occurs as a result of tears in the thoracodorsal fascia and subsequent herniation of a portion of the underlying dorsal fat pad through the tear. This clinical entity is common, and recognition is simple. The presence of a painful nodule with disappearance of pain after injection with anesthetic, is diagnostic. Medication and physical therapy may not be effective. Local injection of the nodule with a solution of anesthetic and steroid is effective in treating the episakral lipoma. Here we describe 2 patients with painful nodules over the posterior iliac crest. One patient complained of severe lower back pain radiating to the left lower extremity and this patient subsequently underwent unsatisfactory disc operation. The other patient had been treated for greater trochanteric pain syndrome. In both patients, symptoms appeared to be relieved by local injection of anesthetic and steroid. Episakral lipoma should be considered during diagnostic workup and in differential diagnosis of acute and chronic low back pain.

Erdem et al. start commenting previous studies

-Various studies have shown that episakral lipomas are one of the important causes of acute and chronic low back pain.

-In studies to understand the pathophysiological mechanisms leading to low back pain, little attention has been paid to the connective tissue forming the facial surface of the back, and pathologies such as fat nodulation and herniation in the thoracodorsal fascia have remained only in sporadic case presentations.

-It has been reported that this disease can produce severe pain -similar to discopathy- and that, therefore, unnecessary disc surgery can be performed erroneously. The pain persists after this unnecessary surgery.

-These episakral lipomas have also been reported to lead to different referral pain patterns such as major trochanteric pain syndrome (BTE) and abdominal pain, which cause confusion in the diagnosis.

–Episakral lipoma is a deeply subcutaneous, rubber-like fat nodule, often mobile, round or oval in shape, localized in the lumbosacral region.

-The original description of these nodules as episacroiliac lipomas was first made by Ries in 1937..

-Copeman and Ackerman used the term lumbar fascial fat herniation to give a definitive anatomical explanation to these nodules for the first time in 1944.

-In clinical practice, these nodules, called the Copeman nodules, are one of the major causes of acute and chronic low back pain.

-They are subfascial fatty tissue that has become a hernia through thoracodorsal fascia.

–Episakral lipoma is common in the general population and is often asymptomatic. Singewald said that these nodules are present in 16% of the population and that only 10% of these individuals are symptomatic.

Erdem et al. PRESENT 2 cases

 Case 1– A 50-year-old woman complaining of left leg pain. The patient was operated on of a disc lesion three years before with the same complaints, and after the operation the pain still persisted. On the patient’s examination, there was scar in the lumbar region from previous surgery; waist flexion was restricted and painful.

Straight leg stretching test was negative and neurological examination was normal. A careful palpation of the lumbar region revealed a nodule with a diameter of approximately 2 cm, near the left posterior iliac crest, partially movable, exquisitely sensitive nodule. Local palpation and palpation of the nodule exacerbated the pain. The patient’s pain was detected with a Visual Analogue Scale (0-10). Disability due to back pain was calculated as 21 with the Roland Morris Disability Questionnaire Form (0-24). Lumbar magnetic resonance imaging of the patient revealed a L5 vertebral laminectomy defect and amelia-related granulation tissue. The patient was injected with 1 cc local anesthetic (LA) into the nodule region by preliminary diagnosis of episacral lipoma with these examination findings. Following injection, the diagnosis of episacral lipoma was confirmed with a significant degree of pain relief.

Technique: The nodule was stabilized with a finger and penetrated into with a green tip (21G diameter 38 mm) needle to allow penetration of the nodule. The needle was retracted slightly under the skin and infiltrated into the mixture of 2 cc of prilocaine, 20 mg of methylprednisolone by puncturing through 4-10 different sites. Pressure was applied for 30 seconds after the needle retracted.

Case 2– A 60-year-old woman was admitted to our outpatient clinic with severe left calf and lateral thigh pain. The patient had a 3- to 4-year-old mild-to-moderate chronic low back pain with a bilateral left large trochanter and lateral thigh pain. Extreme sensitivity to the left large trochanter palpation. Neurological examination was normal. There was no pathology in laboratory findings. The patient was evaluated as a major trochanteric pain syndrome. Local injection of LA and steroid mixture was applied to the large trochanter area of the patient. Then, on the patient’s examination, a deep nodule with a diameter of 1-2 cm was detected with deep palpation in the groin area in addition to the sensitivity on the great trochanter. The pressure on the nodule exacerbated the pain in the large trochanter and lateral thighs while leading to local pain. The patient’s pain was assessed as 7. The patient underwent intranodal injection with the technique previously described with the diagnosis of episakral lipoma. Following injection, the patient’s pain was significantly reduced. At the first month of follow-up, the value of the pain was 2.

POSSIBLE ETIOPATHOGENIC explanations and pain mechanisms from Erdem et al.

These hernias occur near the posterior superior iliac spine in the sacroiliac region, just above the posterior iliac crest and along the sacro-spinal muscle margin. In these regions, due to trauma or hereditary weakness of the fascia and due to the fact that neurovascular foraminae of the cutaneous nerves exist, THERE CAN BE subfascial fat tissue that herniates from the subfascial location to between the superficial and deep fascia, then it becomes compressed and inflamed.

The mechanism of pain in episacral lipoma is not fully understood. It may be trauma, it may be hereditary. In both of their presented cases, there was no serious trauma story.

If the fat’s level of distension reaches a sufficient level, the blood supply may deteriorate, edema and sometimes hemorrhage could occur. These events start the symptoms. The strangulation of the herniated fat lobules stalk could be the cause of the symptoms. The enlargement of the fat herniation within the rigid fibrous capsule, which is not flexible, can cause pain by stretching the fibrous capsule. According to Curtis, the cause of pain is increased intranodular pressure.

Episakral lipoma can be seen in both sexes, but it is approximately three times more frequent in women, especially in middle-aged obese women.

Both of their cases were female and body mass indexes were 25.

Episakral lipoma is single or multiple, usually 1-3 cm in size. In both of our cases, there was a unilateral single nodule.

Why can the episacral lipoma be confused with other pathologies such as disc pathology according to Erdem?

Patients with episakral lipoma usually present severe pain on one side and a back pain complaint on the other. Often, there is pain spreading to the hips and thighs.

It should be kept in mind that episackral lipoma may be associated with other causes of back pain such as lumbar spondylosis and disc lesion, which lead to similar complaints. Therefore, this disease can be treated with unnecessary disc surgery, as in their first case. Since referred pain originating from the episakral lipoma is sclerotomally spread.

In their second case, the main complaint was delayed due to the large trochanteric pain syndrome. It should be known that episacral lipomas formed in the sacroiliac region may cause complaints involving pudendal neuropathic leg and foot pain by compressing the middle cluneal nerves of the dorsal rami of the upper sacral nerves.

They should not be confused with TRIGGER POINTS and other nodules according to Erdem et al.

Episakral lipomas should be distinguished from trigger points defined by Traveell, although their location is similar. Episakral lipoma refers to a specific nodule at the border rather than the cushioned tortuous band. They are also different to “lipomas” (more superficial, softer with palpation) and sebaceous cysts (more superficial and circular) seen in similar anatomic localizations, of course they should be considered in the differential diagnosis.

The cluneal nerve entrapments

It should also be kept in mind that the cluneal nerve may pass through the fibro-osseous tunnel between the thoracolumbar fascia and the iliac crest at 7-8 cm of the midline, leading to complaints similar to episacral lipoma.

General treatment

Treatment of episakral lipoma involves applications such as hot application, massage, electrical stimulation, manipulation, dry needling, local anesthetic and steroid injections. Surgical excision and fascia repair of fat nodule is recommended in severe cases where these treatments are inadequate. In our cases, intranodal injection with LA steroid mix has been effective with multiple punching techniques; long-term follow-up of our patients is still ongoing. Rapid reduction of pain with multiple drilling techniques may confirm that the pain is caused by intranodular pressure.

Erdem et al. THEORIES about the PUNCHING TECHNIQUES

The beneficial effect of local anesthetic can be attributed to local cleansing chemicals such as substance P, removal of metabolites by local vasodilatation, and disruption of the neural feedback mechanism. Analgesic and anti-inflammatory effects of steroids also increase the efficacy of injection therapy.

Published in June 2018 by Marta Cañis Parera   

Some REFERENCES

• Erdem HR, Nacır B, Özeri Z, Karagöz A. [Episacral lipoma: a treatable cause of low back pain]. Agri. 2013;25(2):83-6. doi: 10.5505/agri.2013.63626. Turkish. PubMed PMID: 23720083.
• Curtis. In search of the ‘back mouse’. J Fam Pract. 1993 Jun;36(6):657-9. PubMed PMID: 8505609.
• 1944 Copeman, W.S.C. and Ackerman, W. Fibrositis of the back (1944) . Quart.J.Med. 13,37.
• Singewald. Another cause of low back pain: lipomata in the sacroiliac region. Trans Am Clin Climatol Assoc. 1966;77:73-9. PubMed PMID: 4223124; PubMed Central PMCID: PMC2441105.