Levator ani syndrome is episodic rectal pain caused by spasm of the levator ani muscle. Vaginismus is a condition in which involuntary muscle spasm prevents vaginal penetration. Inflamed facets can cause a powerful muscle spasm. Spasm of coronary arteries, such as Prinzmetal's angina may cause blockage. Accommodative amplitude and facility may be reduced as a result of the ciliary muscle spasm. The causes of diffuse esophageal spasm is unclear. The local twitch response is not the same as a muscle spasm. Botulinum toxin injections can be helpful for the blepharospasm and for masseter spasm. Three theories exist to explain the facial nerve dysfunction found in hemifacial spasm. A true hypertonic spasm is caused by malfunctioning feedback nerves. During the May schedule of shooting, she suffered a muscle spasm. Additional mechanisms of peripheral artery disease including arterial spasm, thrombosis, and fibromuscular dysplasia. Various kinds of involuntary muscle activity may be referred to as a "spasm". It is theorized that spasm of lateral pterygoid causes anterior disc displacement. Other causes may include spasm of an artery.