The most common type of posterior crossbite to occur is the unilateral crossbite which occurs in 80% to 97% of the posterior crossbite cases. Posterior crossbites also occur most commonly in primary and mixed dentition. This type of crossbite usually presents with a functional shift of the mandible towards the side of the crossbite. Posterior crossbite can occur due to either skeletal, dental or functional abnormalities. One of the common reasons for development of posterior crossbite is the size difference between maxilla and mandible, where maxilla is smaller than mandible. Posterior crossbite can result due to

Upper Airway Obstruction where people with "adenoid faces" who have trouble breathing through their nose. They have an open bite malocclusion and present with development of posterior crossbite. Prolong digit or suckling habits which can lead to constriction of maxilla posteriorly
Prolong pacifier use (beyond age 4)

Unilateral posterior crossbite
Unilateral crossbite involves one side of the arch. The most common cause of unilateral crossbite is a narrow maxillary dental arch. This can happen due to habits such as digit sucking, prolonged use of pacifier or upper airway obstruction. Due to the discrepancy between the maxillary and mandibular arch, neuromuscular guidance of the mandible causes mandible to shift towards the side of the crossbite. This is also known as Functional mandibular shift. This shift can become structural if left untreated for a long time during growth, leading to skeletal asymmetries.
Muscle loss increases with age naturally, but it is even more significant with nemaline myopathy. Current research
New research resources have become available for the NM community, such as the CMDIR (registry) and the CMD-TR (biorepository). These two resources connect families and individuals interested in participating in research with the scientists that aim to treat or cure NM. Some research on NM seeks to better understand the molecular effects the gene mutations have on muscle cells and the rest of the body and to observe any connections NM may have to other diseases and health complications. History
"Rod myopathy" was first identified by Douglas Reye, an Australian physician, in 1958. However, Reyes results were never published because another doctor dismissed his finding of rods in the muscle tissue as an artifact of the biopsy. Forty years later, Reyes "rod myopathy" patient was confirmed to have nemaline myopathy. Another group of Australian researchers has since published an article recognizing Reye for his work. "Nemaline myopathy" was first named in a published paper in 1963 by North American researchers P.E. Cohen and G. M. Shy. Shy and his team discovered rod- like structures in muscle fibers of  patients with muscle weakness by performing muscle biopsies on multiple patients. Laboratories performing research on NM are located around the world, notably in the United States, Canada, England, Finland, and Australia. Society and culture
In 1999, the first website on nemaline myopathy was launched, and in October 2004, the first Nemaline Myopathy Convention was held in Toronto, Canada.