Middle Cluneal Nerve Entrapment

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The cluneal nerves are a group of pure sensory nerves (superior, medial or middle, and inferior) that provide sensory supply to the buttocks. This article covers middle cluneal nerve entrapment. See also the more common superior cluneal nerve entrapment, as well as inferior cluneal nerve entrapment.

Anatomy

Sensory supply of the cluneal nerves. SCN: superior cluneal; MCN: middle cluneal nerve; ICN: inferior cluneal nerve

The cluneal nerves are divided into the superior cluneal nerve (SCN), middle cluneal nerve (MCN), and inferior cluneal nerve (ICN). The middle cluneal nerves are sensory nerves derived from the lateral branches of the dorsal rami of S1-S3. It has also been described as arising from the posterior sacral nerve plexus formed by S1-S3 dorsal rami. The nerves exit the sacral foramina and travel inferolaterally under the PSIS and across the long posterior sacroioliac ligament. The nerve route is variable, with the MCN travelling underneath the LPSP or superficial to it. The MCNs pierce the gluteus maximus and travel to the dorsal sacrum. The MCNs supplies sensory innervation overlying the intermediate medial gluteus maximus. There may be an anastamosis between the MCN and SCN. The most superior branch of the MCN often anastamoses with the medial SCN distally, and this may explain why leg symptoms are common as the MCN comprises of the sensory branches of the dorsal rami of S1-S3.

See Konno et al for an open access anatomical study of middle cluneal nerve entrapment.

Pathophysiology

Superior and middle cluneal nerves with typical entrapment sites. Multiple branches of the superior cluneal nerves can be entrapped where they pierce the thoracolumbar fascia over the iliac crest. Middle cluneal nerve entrapment can occur where it passes under or through the long posterior sacroiliac ligament.

The MCN can become trapped while passing underneath or through the long posterior sacroiliac ligament (LPSL).

Epidemiology

The epidemiology is largely unknown.

Clinical Features

The pain is aggravated by short and long periods of standing, lumbar flexion, rolling, prolonged sitting, and especially by walking. The clinical features are similar to other causes of low back pain, especially sacroiliac joint pain and sciatica. The S1 to S2 composition could explain why most patients with MCN entrapment get leg symptoms.

There should be maximal tenderness and a Tinel-like sign approximately 35mm caudal to the PSIS at a slightly lateral point at the edge of the iliac crest (corresponding to the area of nerve compression). An important diagnostic finding is the patient reporting numbness and radiating pain upon palpation over the compression zone.

Diagnosis

Isu et al offer the following diagnostic criteria for MCN entrapment:

1. Low back pain involving the buttocks
2. Symptoms exacerbated by lumbar movement or posture
3. Trigger point 35 mm caudal to the posterior superior iliac spine at a slightly lateral point at the edge of the iliac crest (corresponding to the nerve compression zone)
4. Patients report numbness and radiating pain in the MCN area (Tinel sign) when the trigger point is compressed
5. Symptom relief by MCN block at the trigger point

Note that a positive sacroiliac joint block could still indicate long posterior sacroiliac ligament (LPSL) pain or MCN entrapment if there is dorsal extravasation of the local anaesthetic.

Treatment

See Matumoto et al for a well documented minor surgical MCN decompression technique.

Literature Review

Literature Review

Reviews from the last 7 years: review articles, free review articles, systematic reviews, meta-analyses, NCBI Bookshelf

Articles from all years: PubMed search, Google Scholar search.

TRIP Database: clinical publications about evidence-based medicine.

Other Wikis: Radiopaedia, Wikipedia Search, Wikipedia I Feel Lucky, Orthobullets,