Positional plagiocephaly

Positional plagiocephaly, also known as deformational plagiocephaly or flathead syndrome, is a condition most commonly found in infants and is characterized by a flat spot on the back or one side of the head caused by remaining in one position for too long.

Causes
It can be caused by a condition called torticollis in which neck muscles on one side of the head develop differently, causing the head to tilt to one side, but more commonly it happens in infants of ordinary development who sleep in one position for long periods of time.

In 1992 the American Academy of Pediatrics started a program called "Back to sleep" which encouraged parents to keep their infants on their backs while sleeping instead of their front as had been conventional wisdom. This reduced the risk of SIDS by nearly 40% but increased the incidence of positional plagiocephaly by 600%.

Prognosis and treatmnt
Prognosis for this condition is excellent and can be reversed in most cases before one year of age. Treatment can be as simple as occasionally repositioning the child's head while sleeping and increasing the time spent on their belly. In extreme cases special fitted helmets can be used. Once a child starts moving on their own, the condition can improve rapidly by itself.

The flattening of the head, while alarming, does not typically harm the brain or hinder its development.

Similar conditions
Another, similar condition called craniosynostosis occurs when bones in the skull fuse together too soon. This is a much more serious condition that requires surgery.