Causes
The trigeminal nerve is a mixed cranial nerve responsible for sensory data such as tactition (pressure), thermoception (temperature), and nociception (pain) originating from the face above the jawline; it is also responsible for the motor function of the muscles of mastication, the muscles involved in chewing but not facial expression.Several theories exist to explain the possible causes of this pain syndrome. It was once believed that the nerve was compressed in the opening from the inside to the outside of the skull; but leading research indicates that it is an enlarged or lengthened blood vessel – most commonly the superior cerebellar artery – compressing or throbbing against the microvasculature of the trigeminal nerve near its connection with the pons. Such a compression can injure the nerves protective myelin sheath and cause erratic and hyperactive functioning of the nerve. This can lead to pain attacks at the slightest stimulation of any area served by the nerve as well as hinder the nerves ability to shut off the pain signals after the stimulation ends. This type of injury may rarely be caused by an aneurysm (an outpouching of a blood vessel); by an AVM (arteriovenous malformation); by a tumor; such as an arachnoid cyst or meningioma in the cerebellopontine angle; or by a traumatic event, such as a car accident.Short-term peripheral compression is often painless. Persistent compression results in local demyelination with no loss of axon potential continuity. Chronic nerve entrapment results in demyelination primarily, with progressive axonal degeneration subsequently.
Uterine tachysystole is a condition of excessively frequent uterine contractions during pregnancy. It is most often seen in induced or augmented labor, though it can also occur during spontaneous labor.Because contraction counts are often measured over periods of ten minutes but averaged over periods of thirty minutes, there can be slight differences in how the cutoff is calculated. Generally it is defined as more frequently than once every two minutes. Although definitions may vary among studies, most use the terms defined by the American Congress of Obstetricians and Gynecologists (1999a) to describe increased uterine activity as follows:

Uterine tachysystole is defined as  more than 5 contractions in 10 minutes, averaged over a 30-minute window. Uterine hypertonus is described as a single contraction lasting longer than 2 minutes. Uterine hyperstimulation is when either condition leads to a nonreassuring fetal heart rate pattern.The American Congress of Obstetricians and Gynecologists amended these definitions in 2008. Uterine tachysystole is defined as more than 5 contractions in 10 minutes, averaged over a 30-minute period. The terms "hypertonus" and "hyperstimulation" are not recommended to be used. Uterine tachysystole has been reported to follow vaginally administered Prostaglandin E2 in 1 to 5 percent of women (Brindley and Sokol, 1988; Rayburn, 1989). It can be associated with placental abruption and perhaps with uterine leiomyomas. It can also refer to hyperstimulation with oxytocin. == References ==