Accurate Education – Low Back Pain: Superior Cluneal Nerve Entrapment

Low Back Pain:

Superior Cluneal Nerve (SCN) Entrapment

Over the last few years, there has been a growing appreciation of superior cluneal nerve (SCN) compression as a source of low back pain which has been previously under-diagnosed.  In particular, entrapment of the SCN has been estimated to be the source of up to 12-14% of low back pain. The SCN is a nerve derived from multiple branches of smaller nerves from the base of the thoracic spine to the base of the lumbar spine (the cutaneous branches of the dorsal rami of T11-L4). The SCN extends from the lower spine and travels over the pelvic bone (iliac crest) where it can be compressed by the fibrous tissues surrounding it.

 

Recognizing SCN entrapment as the source of pain can usually lead to succesful treatment and the avoidance of unnecessary surgery in many cases. As described below, identifying this condition generally does not require sophisticated or expensive testing nor does successful treatment usually require surgery.

  

See Also:

Low Back Pain (LBP) – Overview

LBP – Arachnoiditis

LBP – Superior Cluneal Nerve Entrapment

LBP – Disc Pain

LBP – Facet Pain

LBP – Failed Back Surgery Syndrome

LBP – Myofascial Pain

LBP – Sacroiliac (SI) Joint Pain

LBP – Sciatica

LBP – Spinal Stenosis

 

Treatment Procedures:

Epidural Injections

Facet Joint Injections and Nerve Procedures

Heat & Cold Therapy

Inversion Therapy

Massage Therapy

Physical Therapy

Trigger Point Therapy

  

LBP – Surgery:

Considering Surgery?

Failed Back Surgery

 

Low Back Pain:  Superior Cluneal Nerve (SCN) Entrapment

Clinical Picture

Although the chief complaint of those with SCN entrapment is usually LBP, approximately 50-84% of  SCN disorder patients have leg pain or tingling, including all areas of the leg. This percentage tends to be higher (up to 89%) in those that require surgery because of severe symptoms. It should be noted that in one study, 8 out of 19 cases that required surgical correction of SCN entrapment had a history of possibly unnecessary lumbar surgeries. In rare cases, the patient may have only an isolated area of pain in the lower extremity. Many patients indicate that the leg symptom are more severe than the LBP.

 

Clinical manifestations of the leg symptoms are quite variable and patients often find it difficult to describe precisely the location of their pain.  In the majority, pain radiates from the iliac crest down to the leg, but some have pain remote from the iliac crest.  Patients may complain of leg symptoms in a variety of areas from the groin to the sole of the foot, often creating the potential for confusing the diagnosis with sciatica, mimicking radiculopathy due to lumbar disc herniation or lumbar spinal canal stenosis.

 

In a definitive study published in 2014, 113 cases of SCN entrapment was identified in 834 patients assessed for low back pain (LBP). Of these 113 patients, 59 (52%) had only LBP, 53 (47%) had LBP associated with leg pain or tingling, and 1 (1%) had only leg pain. Various postures and motions aggravated both LBP and leg symptoms. The causes for worsening of pain included walking (39 cases), rising from a seated position (33 cases), standing position (25 cases), forward bending (16 cases), backward bending (11 cases), lying flat on the back (7 cases), sitting position (6 cases), any motion (4 cases), putting weight on the affected side (2 cases each), lifting something heavy (2 cases each), twisting motion (2 cases each), getting up out of bed (2 cases each), walking down the stairs (1 case), and lying on the stomach (1 case), while 5 patients stated no activity or posture aggravated their pain.

 

Sixteen subjects (84%) had leg pain or tingling. Of these 16 subjects, 10 reported that the leg symptom was more severe than the LBP. Fourteen subjects had leg symptoms spreading from the iliac crest buttock area and the remaining two had leg symptoms remote from the iliac crest.

 

Painful limping can be characteristic of SCN entrapment, the pain sometimes making it very difficult to walk.  Tightening of the buttock muscles can often worsen pain during walking, possibly due to constriction of the gluteus muscles squeezing the SCN. Patients may find that pushing above the iliac crest with their hands reduces symptoms associated with walking or bending at the waist, perhaps by relieving the tension on the nerve.  In the above study, 9 subjects demonstrated painful limping while two subjects could hardly walk because of leg pain. These patients consistently reported that they were unable to walk when asked to tighten their buttocks during walking.

 

Futher complicating the picture comes from the fact that branches of the middle cuneal nerve (MCN) may coalesce with branches of the SCN which may extend symptoms associated with sacral nerve branches including the foot, a symptomatic area not typical for the SCN (See Middle Cuneal Nerve entrapment, below).

 

Conditions that aggravate the pain such as changes in posture can also be quite variable. Limitation in range of motion  of the lower back is common. Symptoms tend to worsen with  bending forward, and coupling this bending forward with rotation to the opposite side further aggravates symptoms as this stretches the SCN.  Conversely, extension of the hip on the same side as the entrapment reduces pain with bending forward.  In some cases however, SCN patients may report that bending backwards worsens the symptoms. 

 

Diagnosis 

The key to diagnosing SCN entrapment is palpation over the SCN nerve at the posterior iliac crest and eliciting a maximally tender point that reproduces pain in a pattern that reproduces the patient’s symptoms, especially when the symptoms are remote from iliac crest. When palpation does reproduce symptoms, a local injection of an anesthetic such as lidocaine will confirm the diagnosis if symptoms resolve upon being anesthetized.

 

Differential Diagnosis – Sacral Iliac (SI) Joint Pain

SI joint pain presents with localized pain that may be similar to SCN entrapment symptoms although tenderness over the iliac crest would be atypical. The diagnosis of SI joint pain elusive due to a lack of definitive diagnostic features related to history, physical exam  and imaging studies. While the diagnostic standard for SI joint pain is resolution of the SI joint with an intrarticular injection of an anesthetic, studies also indicate that the anesthetic agent may diffuse from the joint into the area of the long posterior sacroiliac ligament (LPSL), a site of potential SCN or MCN entrapment. Thus it may be that even a “diagnostic” study of the SI joint pain may in fact resolve the pain through anesthetizing the SCN or MCN.

See: SI Joint Pain

 
Differential Diagnosis – Sciatica
Patients who have true sciatica due to radiculopathy from lumbar disc herniation or lumbar spinal canal stenosis also usually have tenderness in the gluteal regions (Valleix’s points). Although they may also have tenderness on the iliac crest, palpation of this point would not reproduce the leg symptoms and a local anesthetic injection over the SCN will not relieve symptoms.
 

Causes of SCN Entrapment

While it is not clear what precipitates SCN entrapment, many cases are associated with a history of trauma.  A history of vertebral fracture of the lower thoracic and lumbar spine are common in SCN entrapment. Any of the lower spinal vertebrae may be involved and it is thought that the traumatic event or the structural changes associated with the fracture result in stretching or tension on the SCN wiht subsequent development of adhesions to the surrounding tissues resulting in entrapment of the nerve.

 

SCN entrapment is also found not uncommonly as a complication of harvesting hip bone during spinal fusion surgery. It is believe that the entrapment is more commonly the result of subsequent adhesions of fascial tissues to the nerve rather than a direct nerve injury during bone harvest.

 

Treatment of SCN Entrapment

 Few studies have evaluated treatment of SCN entrapment, with only one large scale study published in 2014 that evaluated 834 patients with low back pain and identifying, 113 (14%) who met the criteria diagnostic of SCN entrapment.

 

As initial treatment, these 113 patients were given nerve block injections. Of these, 54 (49%) had leg symptoms. Ninety-six of the 113 patients (85%) experienced more than a 20% decrease of the pain scores following three injections and 77 patients (68%) experienced more than a 50% decrease in their pain scores. Surgery was performed in 19 patients who had intractable symptoms. Complete and almost complete relief of leg symptoms were obtained in five of these surgical patients.

 

Of the patients with leg symptoms, those with shorter duration of symptoms (3 years or less) had a significantly higher likelihood of excellent outcomes (complete or almost complete relief) than those with longer duration of symptoms (more than 3 years).

 

A complication of the injection, erectile dysfunction (ED), occurred in two cases. One was a 41-year-old male who experienced temporary ED during pain reduction after every injection that persisted the same time as the pain relief from the injection. The other case was permanent ED, which occurred immediately after the first injection in a 65-year-old male. The authors of the study were unable to explain the reasons for the ED.

 

Middle Cluneal Nerve (MCN) Entrapment

While pain syndromes resulting from the middle cluneal nerve (MCN) entrapment is likely rare compared with SCN entrapment, the middle cluneal nerves can become spontaneously entrapped where this nerve passes under the long posterior sacroiliac ligament (LPSL), adjacent to the SI joint. A case of MCN entrapment has been reported associated with severe low back pain.

 

In this case, a 48-year-old woman presented with LBP and buttock pain radiating to both legs that had gradually developed over 10 years. An L4-5 discectomy had been performed two years earlier and resulted in no improvement.The pain was continuous, severe and associated with greatly limited range of motion of the lower back in all directions because of pain.

 

This patient had significant tender points approximately 1.5 cm inferior to the palpable margin of the bilateral posterior superior iliac spine (the site typical for SCN entrapment), next to the long posterior sacroiliac ligament (LPS), consistent with the running course of the MCN.

 

As noted above, pain due to MCN entrapment may be diagnosed and treated as sacroiliac joint pain. Sacroiliac joint pain is thought to cause 15% to 30% of LBP and is often associated with buttock to lower extremity symptoms. Entrapment of the MCN by the LPSL adjacent to the SI joint would likely offer significant overlapping of pain symptoms. Anesthetic injections around the LPSL are successful in treating SI joint pain and in one study even more effective than injections into the SI joint, auggesting that there may be a definitive overlap in the diagnosis and treatment of SI joint pain and MCN entrapment pain. Furthermore, it suggessts that injections of the LPSL may offer an alternative to the management of SI joint pain that may avoid unnecessary SI joint fusion.

 

Resources

  1. Superior Cluneal Nerve:  You Tube Overview

 

References

 

LBP: Overviews

  1. Neuropathic low back pain in clinical practice -2016
  2. The evaluation of neuropathic components in low back pain. – PubMed – NCBI
  3. Low back pain of thoracolumbar origin. – PubMed – NCBI

 

LBP: Middle Cluneal Nerve Entrapment

  1. Entrapment of middle cluneal nerves as an unknown cause of low back pain – 2016

 

LBP: Superior Cluneal Nerve Entrapment

  1. Prospective study of superior cluneal nerve disorder as a potential cause of low back pain and leg symptoms – 2014
  2. Superior cluneal nerve entrapment. – PubMed – NCBI

 

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