title: Unilateral cleft lip with or without cleft palate and handedness: is there an association?
abstract: OBJECTIVE
  The purpose of this study was to investigate the possibility of a relationship between the side of occurrence of unilateral clefting of the lip and/or palate and handedness, also taking into account the type of the initial cleft condition, a factor that has not been adequately assessed in previous studies.
  
  
  METHODS
  This was a retrospective study.
  
  
  METHODS
  Division of Orthodontics, The Hospital for Sick Children, Toronto, Canada, and Cleft Lip and Palate Program, Children's Hospital, Winnipeg, Canada.
  
  
  METHODS
  Subjects were 289 patients (176 males and 113 females) 9 years of age or older presenting with a history of unilateral clefts of the lip with or without the palate. Of these patients, 217 were recruited from the patient pool of the Orthodontic Clinic at the Hospital for Sick Children in Toronto. The remaining 72 were selected from the registry of the Cleft Lip and Palate Program of the Children's Hospital in Winnipeg. Any syndromic cases were excluded from the sample.
  
  
  METHODS
  Assessment of handedness was performed by asking the patients to fill out a multi-item questionnaire in which patients were asked to identify which hand they would use for different tasks. The side and type of the initial cleft condition were identified by reviewing each patient's hospital chart and by cross-referencing with clinical examination. Statistical evaluation of the results was performed by using the chi-square test.
  
  
  RESULTS
  There was a significantly larger number of left-sided clefts (198) in the sample than right-sided clefts (91), (p < .001). The proportion of left-sided clefts among left-handers (84.6%) was higher than that among right-handers (66.8%). However, the relationship between side of cleft and handedness was not statistically significant (p = .185). Clefts of the primary palate only seemed to occur on the left side 3.5 times more often than on the right, whereas the corresponding ratio of left:right manifestation for clefts of the primary and secondary palate was 1.8:1. The difference was statistically significant (p < .05).
  
  
  CONCLUSIONS
  The findings of this study confirm the affinity of unilateral clefts for the left side but suggest that there are differences between clefts of the primary palate only and clefts of the primary and secondary palate. Also, non-right-handed patients show a greater predilection for having a cleft on the left side than do right-handed patients.
authors.affiliation: Division of Orthodontics, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Daskalogiannakis
authors.forename: K L
authors.initials: KL
authors.lastname: Kuntz
authors.forename: A E
authors.initials: AE
authors.lastname: Chudley
authors.forename: R B
authors.initials: RB
authors.lastname: Ross
mesh_terms: D016009:Chi-Square Distribution; D002648:Child; D002971:Cleft Lip / Q000145:classification / Q000473:pathology*; D002972:Cleft Palate / Q000145:classification / Q000473:pathology*; D005260:Female; D007839:Functional Laterality / Q000145:classification* / Q000502:physiology; D006801:Humans; D008046:Lip / Q000473:pathology; D008297:Male; D009048:Motor Skills / Q000502:physiology; D009864:Ontario; D010159:Palate / Q000473:pathology; D012042:Registries; D012189:Retrospective Studies; D011795:Surveys and Questionnaires