The sciatic nerve can sometimes be compressed, irritated or entrapped as it runs through the soft tissues of the buttock. Traditionally, sciatic pain (neuralgia) generated from issues within the buttock has been termed “Piriformis Syndrome” (see Figure 5.7 to view the piriformis muscle and the sciatic nerve).
This was based on a finding that in about 20% of the population, all or part of the sciatic nerve runs through the piriformis muscle. Compression of the nerve within the piriformis muscle was thought to be the problem in all cases of nerve related buttock and leg pain that could not be associated with a problem in the back.
It is now thought that this is the case in only a relatively small number of cases and that this condition has been over-diagnosed. So much so, that some believe it does not exist at all.
The term “Deep Gluteal Syndrome”has been suggested recently as an alternative term to piriformis syndrome. It refers to any irritation of the sciatic nerve in the deep gluteal space, beneath the gluteus maximus muscle.
In this space, the sciatic nerve may be compressed or irritated at the level of the piriformis, as it runs over the deep external rotator muscles or by fibrous bands anywhere along its path through the buttock. The nerve can also be irritated as it leaves the pelvis to head down into the thigh.
Here it runs through a tunnel (ischial tunnel), between the outer side of the sitting bone (ischial tuberosity) and the upper thigh bone (femur) (Figure 5.7).
In this tunnel it may be squeezed between the bones or irritated by unhealthy hamstring tendons (tendinopathy).
Cluneal Nerve Neuralgia
Of the cluneal nerves, the superior and inferior are more likely to be at risk of compression.The superior cluneal nerve branches run from the spine, over the top of the back of the pelvis and down into the buttock.
They usually run through fibrous tunnels as they cross the top edge of the pelvis.This is where the small nerves may become compressed or irritated.
This is usually associated with a fairly localised area of pain in the upper buttock, in the region of its skin supply (Figure 5.8).
The inferior cluneal nerve branches run across the lower buttock, right over the sitting bone (ischial tuberosity). They can be compressed and irritated by a hard fall onto the bottom or sitting for prolonged periods on a hard surface, particularly if you don’t have much gluteal muscle bulk to cushion the bone.
Again, associated symptoms are usually fairly localised to the area of skin supply (Figure 5.8). Sometimes the nearby posterior femoral cutaneous nerve can also be affected. Symptoms may then extend into the back of the thigh (see Figure 5.8 for region of this nerve supply).