A new study by physician researchers from Hasbro Children's Hospital and Children's Hospital Boston has identified an increased prevalence in left-handedness in children with a congenital disorder known as hemifacial microsomia (HFM).
The study was published in the March 2009 edition of the Journal of Craniofacial Surgery.
Overall, ten percent of the population is left-handed. A higher frequency has been associated with certain craniofacial malformations such as cleft lip and other conditions. Albert Oh, MD, director of pediatric plastic and craniofacial surgery at Hasbro Children's Hospital, along with researchers from Children's Hospital Boston, developed this study to determine if the frequency of left-handedness increased in patients with HFM. HFM is the second most common birth defect after clefts, and is a condition that affects the development of the lower half of the face. It most commonly affects the ears, mouth or jaw, and can occur on either side of the face or both.
A total of 86 patients who were diagnosed with HFM were studied and compared to a control group using several factors. The study group was 48 percent male, with an average age of 13.5 years. Of those patients, 49 percent had predominant right side involvement of HFM, while 38 percent had left side involvement and 13 percent had almost equal involvement on both sides. The control group included 96 children, 44 percent male with a mean age of 10 years.
When compared to the control group, the study group showed 26 percent were left-hand dominant for writing compared with only 11 percent in the control group. Also of note, for the patients who had bilateral involvement of their HFM, the side most affected was uniformly predictive of hand preference. The patients with left-predominant involvement of HFM were left-handed and the patients with right-predominant involvement were right-handed.
Albert Oh, MD, who is also a professor of surgery at the Warren Alpert Medical School of Brown University, says, "This study is significant in that it revealed a significant shift to left-hand preference in patients with HFM. This finding further emphasizes that the developmental abnormality that causes HFM is not isolated to the face."
Oh and the authors also note that the study should promote further discussion of the two major etiological theories of HFM: vascular disruption and abnormal proliferation or migration of neural crest cells (cells located in the neural plate in the embryo that migrate to their final destinations during embryo development). The study, while limited in size, found no correlations betweens the side of facial involvement and hand preference that would support the theory of vascular disruption.