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Cluneal nerve entrapment / syndromes

Summary:

The superior and middle cluneal nerves are purely sensory nerves which dominate sensation in the lumbar region and the buttocks.


Epidemiology:

Superior cluneal nerve (SCN) entrapment occurs in 1.5 - 15% of LBP.

SCN and MCN entrapment produce leg symptoms in 50-85% of cases and 82% of LBP patients.


Anatomy:

The SCN and MCN are comprised of 4-6 branches that may be connected


SCN:

SCN arises in the lower thoracic and lumbar posterior nerve root.

Their course is superior-medial to inferior-lateral

At the iliac crest it penetrates the thoraco-lumbar fascia 3-4 cm (medial branch) and 7-8 cm (middle branch) from the midline.

A portion of the SCN traverses through a tunnel created by the thoraco-lumbar fascia and the iliac crest


Nerves coming from lower thoracic and upper lumbar nerve roots


Area the nerves run through into the buttock region

Superior cluneal nerve coming through the thoracolumbar fascia

Thoracolumbar fascia


MCN:

Originates at S1-S4 and passes below and sandwiches the long posterior sacroiliac ligament between the PSIS and the posterior inferior iliac spine and courses over the iliac crest to the buttocks. It has been suggested that due to the anatomical path, the MCN cannot become entrapped but others suggest it could be as lateral branches penetrate the long posterior sacroiliac ligament.


Arising locations for the middle cluneal nerves

Middle cluneal nerves seen on the lower medial aspect


Epidemiology:

SCN entrapment in studies varies from 5% to 30% - it is quite unclear

Females are slightly more common than males

Average age in 55-70yo

MCN entrapment is unknown


Symptoms:

LBP due to SCN entrapment is exacerbated lumbar movement such as extension, bending, rotating, prolonged sitting, walking and rolling. It can occasionally have claudicant features.


Tinel sign at 3-4cm for medial branch and 7-8 cm for middle branch (from the midline)

Patients often experience numbness and radiation of pain with trigger point compression.


LBP due to MCN-e is also affected by non-specific lumbar movements. You can appreciate a tinel sign 35mm caudal to the PSIS at a slightly lateral point edge of the iliac crest.


Diagnosis:

CT and MRI are unhelpful because the nerves are very thin

Tinel sign and removal of pain with anaesthetic block are the best tests


Treatment:

Diagnostic blocks themselves, up to three, can actually provide LBP relief

Surgical interventions with microscopic releases can be performed


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