Birth trauma or intrauterine malposition is considered to be the cause of damage to the sternocleidomastoid muscle in the neck. Other alterations to the muscle tissue arise from repetitive microtrauma within the womb or a sudden change in the calcium concentration in the body which causes a prolonged period of muscle contraction.Any of these mechanisms can result in a shortening or excessive contraction of the sternocleidomastoid muscle, which curtails its range of motion in both rotation and lateral bending. The head typically is tilted in lateral bending toward the affected muscle and rotated toward the opposite side. In other words,  the head itself is tilted in the direction towards the shortened muscle with the chin tilted in the opposite direction.Congenital Torticollis is presented at 1–4 weeks of age, and a hard mass usually develops. It is normally diagnosed using ultrasonography and a colour histogram or clinically through evaluating the infants passive cervical range of motion.Congenital torticollis constitutes the majority of cases seen in clinical practice. The reported incidence of congenital torticollis is 0.3-2.0%. Sometimes a mass, such as a sternocleidomastoid tumor, is noted in the affected muscle. Torticollis does not resolve on its own and may result in plagiocephaly. Acquired torticollis
Noncongenital muscular torticollis may result from scarring or disease of cervical vertebrae, adenitis, tonsillitis, rheumatism, enlarged cervical glands, retropharyngeal abscess, or cerebellar tumors. It may be spasmodic (clonic) or permanent (tonic). The latter type may be due to Potts Disease (tuberculosis of the spine).
Conclusions derived from face mirroring, however, have been called into question, because it has been shown that mirroring face-halves creates artificial features. For example, if the nose of an individual is slightly bent to the right side, then mirroring the right side of the face will lead to an over-sized nose, while mirroring the left side will lead to an unnaturally small nose. Attractiveness
Facial symmetry has been found to increase ratings of attractiveness in human faces. More symmetrical faces are perceived as more attractive in both males and females, although facial symmetry plays a larger role in judgments of attractiveness concerning female faces.While studies employing the composite faces produced results that indicate that more symmetrical faces are perceived as more attractive, studies applying the face-half mirroring technique have indicated that humans prefer slight asymmetry. Also, studies have shown that nearly symmetrical faces are considered highly attractive as compared to asymmetrical ones. The symmetry of the nose seems to be more important than that of the lips. Dynamic asymmetries
Highly conspicuous directional asymmetries can be temporary ones. For example, during speech, most people (76%) tend to express greater amplitude of movement on the right side of their mouth. This is most likely caused by the uneven strengths of contralateral neural connections between the left hemisphere of the brain (linguistic localization) and the right side of the face. Facial averageness vs. symmetry
Experiments suggest that symmetry and averageness make independent contributions to attractiveness. Aging
Facial symmetry is also a valid marker of cognitive aging.