Strong and Davila proposed the term cluneal syndrome. They started their research intrigued by the case of 2 soldiers that got their lumbar pain relieved after their lumbar fatty nodules were excised. They called the nodules episacroiliac lipomas (back mice was a term used after Peter Curtis’ article in the 90s). After their research they concluded that the really causative pain agent was more related to the cluneal nerve being embedded in fibrose stroma, not always they observed the existence of the palpable nodules. They did NOT observe any fatty herniation. That’s why they proposed the term cluneal syndrome, since it would include many different causes that in the end would result in low back pain due to cluneal neuropathy.
THIS ARTICLE IS IMPORTANT since it is the one that used the term ‘cluneal nerve syndrome’ for the first time as a title, as far as I know.
- They presented a detailed work with several tables with the information about 30 patients that underwent surgery related to cluneal neuropathy.
- They abandoned the titles related to the subcutaneous nodules since in some of their cases (50%) NO nodule was found, their related the pain to be due to the nerve and not to the macroscopic nodule. That’s why, despite they started their research focussing on the episacroiliac lipoma, they titled the article The Cluneal Nerve Syndrome.
- They suggested SURGICAL DEAFFERENTATION of the trigger area of tenderness or cluneal NEUROECTOMY as a treatment.
- They considered that the ‘fibrosis’ in the areolar tissue (fatty tissue) of the low back due to trauma, for example, would result in a nerve immobilization due to degenerative changes in the areolar tissue that would lead to later painfulness. Once the nerve is hypersensitised, then the pain is more intense. The movements that increase tension in that tissue aggravate the symptoms.
- The trigger point is the point where the nerve emerges from the deep dense fascia or musculature.
- They used the concept ‘trigger area’ more than ‘trigger point’.
- It seems they ‘invent’ the term cluneal syndrome, using the word cluneal from a famous anatomy book.
- They admitted they could not explain how come the LA injection gave longer relief than the one that should be expected by the pharmacological effect of the LA injection.
- They used the term ‘areolar tissue’ more than ‘fatty tissue’.
- They insisted that the fibrous stroma at the back is more abundant than in the abdomen and that the palpable nodules are NOT real lipomas; they are just PSEUDOENCAPSULATED fat through fibrous attachments.
- Despite they performed a detailed histological analysis of the excised fatty tissue, they could not find an abnormality that was common to the majority of cases. They deeply described some of the isolated findings that included increasement of the fibrous stroma, fat necrosis, some tissue inflammatory reactions, and even a calcified cyst. THEY ADMITTED that, nevertheless, the ‘normal histology’ of the lumbar areolar tissue was unknown, so it was difficult to draw certain conclusions.
- They explained the surgery technique in a very detailed manner.
- They included the concept of ‘physiologically hyper sensitised’ nerve to explain why the same pressure into different nerves produce different painfulness feeling.
- They referred to many authors that centred their studies on the presence of the fatty nodulations such as Copeman, Herz, Moes, Ries, Sutro, and even Orr and Usscher.
Notes on the article:
The Cluneal Nerve Syndrome, a Distinct Type of Low Back Pain
By E.K. Strong and J.C. Davila
Southern Pacific General Hospital, Department of Surgery
San Francisco, California
They started their article saying that while they were serving at an Overseas Station Hospital, Strong became interested in the relationship of low back pain to the presence of tender subcutaneous fatty nodules, such as those previously defined as ‘episacroiliac lipomas’ or ‘episacral fibrolipomas’.
Two soldiers intended for transfer because of persistent, disabling low back pain were relieved of symptoms by excision of such fatty nodules and returned to active duty status at their overseas station.
The results of the operative procedure were sufficiently impressive as to suggest further study.
During the first year of the study of 483 patients, 12 were diagnosed as having the cluneal nerve syndrome.
Table 1 showed the data of 39 operative cases in 30 patients that they treated surgically, some were operated a second time because of recurrence.
Their age varied from 28 to 67.
They concluded that the cluneal nerve syndrome was not related to occupation.
They present a review of literature about the Cluneal Syndrome
- They mention Ries as the first one to relate tender fatty nodules in the subcutaneous tissues of the lumbar and gluteal regions and low back pain.
- Sutro failed to demonstrate significant histopathological changes in ‘lumbosacroiliac nodules’.
- Then they mentioned the work of Copeman and Ackerman, Herz, Moes, Katz and Berk, who also described symptomatic relief of low back pain achieved by excision of tender subcutaneous fatty nodules.
- In 1938 Steindler suggested that the DEEP-SEATED CAUSES OF LOW BACK PAIN might be EXCLUDED where temporary relief of pain was obtained by superficial novocaine injections.
- In 1948 Orr, Mathers and Butt described 5 cases where confused intra-abdominal symptoms were relieved by excision of tender fatty nodules in the low back. They outlined the concepts of referred pain and discussed the viscerospinal syndrome previously postulated by Sir Thomas Lewis, Ussher, Wiulls, and Alsatt.
- In 1953 Dittrich suggested deafferentation of areas of fibrosed subfascial fat in the low back to achieve relief of both local and referred pain.
Anatomy notes from Strong and Davila
PIERSOL describes the cluneal nerves (L. Clunis, buttock) —also spelled clinical— as divided into three groups: the superior, the middle, and the inferior or lateral cluneal nerves. 
On line link to original book from Piersol: //archive.org/details/humananatomyincl19192pier/page/1282
IMAGE: Diagrammatic representation of the superficial dissection of the right buttock illustrating anatomical landmarks of the SCN and MCN.
For the purposes of their paper, they ignored the inferior cluneal group, since they arise from the posterior femoral cutaneous nerve.
The three superior cluneal nerves are the sensory branches of the dorsal rami of L1, L2 and L3.
The lateral branches of the 5th lumbar nerve and the first four sacral nerves unite in a series of loops from which the two (or possibly three) medial cluneal nerves arise.
Through surgery they could note that:
- The SCN emerge from the iliocostalis muscle through well defined foramina.
- The point of emergence of L1, L2 and L3 is at the level of the dorsal spinous processes of L2, L3, and L4.
- The dense fibrous aponeurosis of the iliocostalis is variable with regard to its cephalad extension so that in some instances the nerves emerge directly from muscle, and in others one or more of the nerves emerge through the aponeurosis.
- The cluneal nerves pass in a caudal direction between the iliocostalis muscle (aponeurosis and the posterior lamina of the lumbodorsal fascia).
- They pass through a well defined ostia in this layer of dense fascia at variable levels so that, in some cases, a line drawn across the three ostia will lie transversely at the level of the dorsal spinous process of L4.
- If the subject is required to ‘arch’ the two points, the ostia from the iliocostalis and the ostia of the thoracolumbar fascia OVERLIE each other; otherwise they are separated 0.5 to 1.5cm.
- The SCN are well defined when located at the areolar tissue deep to the superficial fascia at the level of the posterior iliac crest.
- The middle cluneal nerves are more difficult to identify in operative conditions.
Symptomatology of the cluneal syndrome according to Strong and Davila
- Low back pain was the cardinal symptom and was present in the 30 subjects of the study at several degrees.
- They described it as: ache, pressure, nagging sensation, or ‘something pushing on the bones’.
- Radiation of the pain was common around the buttock and back of the hip. Described as ‘spreading along here’ or ‘burning’ or ‘aching’.
- Localisation of the pain was difficult for the patient. The patient usually says ‘all across here’ while pointing out his low back. If the pain is radiated to the buttock, then he adds adding with the palm of the hand ‘and here’. Strong and Davila called this the ‘palm-on-buttock’ sign and considered it a corroborative sign in this syndrome.
- The referred pain is usually poorly outlined and localisation is difficult for the patient. Usually along the anterolateral aspect of the thigh or down the back of the thigh to the calf. They seem to search for the pain by gently massaging or squeezing the affected area. The patient is rarely aware of the presence of a trigger area in his back.
- Some postures and motion aggravate the back pain: sitting, bending, lying, and walking.
- 22/30 related the onset of symptoms with a trauma and used terms such as ‘sudden catch’, ‘jerk’, ‘twist’, and ‘snap’.
- Some related it to a direct ‘blow’ to the low back.
- The average of duration of symptoms was 6 months.
- 4 had the diagnose of pain due to herniated disc, 4 due to sciatica, 11 showed signs of osteoarthritis… The pain was also ascribed to other causes such as lumbosacral strain, old fracture, or myositis.
- Diagnoses of systemic illness other than as related specifically to the back did not show any uniform pattern.
Physical findings of the cluneal nerve syndrome according to Strong and Davila
A CONSTANTLY LOCATED TENDER AREA no larger than two centimetres located in the episacral areas was a REQUISITE to the diagnosis of the cluneal nerve syndrome.
Injection of 2cc of 1%procaine placed superficial to the deep fascia must eliminate the back pain. Injection relief that lasts less than half an hour should be questioned. However, relief lasting beyond the usual absorptive time of the drug is common. THIS PHENOMENON was also recognised to be poorly UNDERSTOOD.
The results from the injection sometimes could be ‘dramatic’: Strong and Davila said that the injection relief may be so pronounced as to make the examiner doubt the patient’s reliability, but experience teaches that bedridden patients with almost total restriction of spinal mobility may be urged out of bed and find themselves capable of a complete range of painless spinal mobility following successful injection of a trigger area.
They stated that the only diagnose technique for this syndrome would be:
the palpation with a single fingertip pressure of the painful trigger area + the back pain relief and the local tenderness by LA injection.
A subcutaneous fatty nodule at the site of the trigger occurred in 20 of the cases. But operative results were no more impressive in the group with the nodules than in the others.
The physical findings corroborative of the diagnosis of herniated intervertebral disc do not exclude the additional diagnosis of cluneal nerve syndrome. The patients may have both conditions. But as the injection of LA gave relief, the cluneal syndrome was the one giving the symptoms.
Pathology findings of Strong and Davila’s histological studies
NO IMPRESSIVE or CONSTANT FINDINGS: The pathological observations regarding the cluneal syndrome are rewarding only in a negative sense.
They performed meticulous stripping of the mass of areolar tissue from the under surface of the superficial fascia and the superficial aspect of the deep fascia. They described a PSEUDOENCAPSULATED MASS OF FAT; it was not a TRUE LIPOMA.
They described the fibrous stroma of the area as being more dense than that found over the abdomen and limbs.
THEY DID NOT observe any herniation of fat through the deep fascia. And they admitted that if the herniation occurred through the superficial fascia, it escaped their attention.
In thin patients, the localized trigger area would be the size of a ‘lead pencil eraser’.
Technique to identify the ‘hyper sensitised’ nerve: with a cross-hatch on the operative wound to mark the trigger, two-to three-centimeter segments of the superior cluneal nerves were dissected free of areolar tissue and left exposed and unaesthetised on the surface of the deep fascia. Blunt fingertip pressure on the nerve underlying the cross-hatch or trigger spot produced PAIN while equal pressure on the other two nerves produced only a mildly uncomfortable sensation (like leaning back in a hard chair). That suggested that the TRIGGER NERVE had become HYPER SENSITISED.
The largest elliptical mass of tissue excised measured 11x8x3.2 cm. No impressive histological abnormalities were found on the fatty tissue or the peripheral nerves. In some cases, they described findings such as: an increase in hyalin fibrous tissue stroma over what was considered ‘normal’ despite they admitted that the ‘STROMAL ARCHITECTURE OF THE SUBCUTANEOUS AREOLAR TISSUE of the low back at various ages was UNKNOWN by then’ (and by now).
They found some isolated abnormalities in some cases, such as inflammatory cellular infiltrates or giant cells.
One case that presented past history of trauma (10 weeks prior surgery) presented small cystic areas filled with creamy fluid, which was cultured and found sterile in the AREOLAR TISSUE. Histologically, it was described to be FAT NECROSIS with organisation.
They admitted that they had INADEQUATE UNDERSTANDING of the ‘normal histology’ of the subcutaneous tissue of the low back.
Strong and Davila’s treatment options
They offered surgery to all the cases. They explained the technique deeply.
They said that the detailed technique was not necessary and that just the simple removal of a sufficiently large mass of areolar tissue deep to the superficial fascia centred to the trigger area would produce effective deafferentation.
They had 3 recurrences. That’s why they recommended the nerves to be recognised and sectioned so that their stumps would retract back through the deep fascia.
The patients just showed small areas of hypoesthesia, but not anaesthesia.
The wound effusion occurred in six cases.
Strong and Davila’s RESULTS
They considered the results ‘excellent’. The patients returned to work soon.
They considered the palpable nodules not to be a herniation but rather a nodule due to a PSEUDOCAPSULE of ABNORMALLY increased fascial and stromal fibrous connective tissue. When the nodule is TENDER, it is because one or more of the cluneal nerves have been enmeshed in it. This ‘fibrosis’ was not found in every case, and then they could not conclude that the cluneal nerve syndrome was always due it to it.
Published by Marta Cañis Parera in January 2020