In the sacral plexus, entrapment of the sciatic nerve at the greater sciatic foramen (piriformis syndrome) may be secondary to asymmetry of the piriformis muscle
size or anatomic variations in the course of the sciatic nerve relative to the piriformis muscle
(Figure Obtaining a sequence perpendicular to the piriformis muscle
is crucial in identification of these anatomic variants.
Botulinum toxin type A use in piriformis muscle
syndrome: a pilot study.
The onset is gradual, caused not only by wallets, but by any object (like carrying golf balls around) that presses on the piriformis muscle
in the buttocks.
Assessments of the complaint included such aspects as visual signs of dysfunction, piriformis impingement analysis, piriformis muscle
length test and piriformis strength test.
Special imaging for nerves with magnetic resonance neurography can detect piriformis muscle
syndrome--a condition in which the narrow piriformis muscle
irritates or pinches the sciatic nerve.
A rare cause is entrapment syndrome of the SGN as a result of compression by tendinous fibers of the piriformis muscle
(Kountouris & Okur, 1982; Plihal, Saudan, Vischer, & Roth, 1989; Rask, 1980).
Sciatic pain due to nerve pressure has three possible sources: bony spurs on the vertebrae pressing on the nerve, pressure from a damaged spinal disk, and muscle spasms--particularly in the piriformis muscle
, which may tighten enough to press on the nerves and cause pain.