A trigger (from the Dutch trekken, meaning to pull) is a lever which, when pulled by the finger, releases the hammer on a firearm. In a database, a trigger is a set of Structured Query Language (SQL) statements that automatically fires off an action when a specific operation, such as changing data in a table, occurs. A trigger consists of an event (an INSERT, DELETE, or UPDATE statement issued against an associated table) and an action (the related procedure).
Other conditions sometimes associated with Chiari malformation include hydrocephalus, syringomyelia, spinal curvature, tethered spinal cord syndrome, and connective tissue disorders such as Ehlers-Danlos syndrome and Marfan syndrome. Chiari malformation is the most frequently used term for this set of conditions.
Chiari malformation type III is extremely rare and more severe than Chiari malformations types I and II. This form is associated with an encephalocele, a condition in which a portion of the brain and its surrounding membranes (meninges) protrude through a defect in the skull.