Accurate Education – Low Back Pain: Superior Cluneal Nerve 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.

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.

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. 

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.

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).