Relationship Between Side of the Cleft and Handedness of the Patient

Abstract

The relationship between the type and side of the cleft and the left-right-handedness of the patient was evaluated in 706 patients with cleft, of whom 348 had unilateral cleft of the primary palate. The prevalence of left-handed persons in the group with left-sided cleft (14.5%) was more than three times as high as in the group with right-sided cleft (4.7%), a statistically significant difference. Among the 75 (10.6%) left-handed patients there were 38 unilateral clefts, of which 32 (84.2%) were on the left side; only 6 (15.8%) were on the right. Among the 631 right-handed patients there were 310 unilateral clefts, of which 122 (39.4%) were on the right and 188 (60.6%) were on the left side. Thus, the side of the cleft seemed to be associated with ipsilateral handedness. A large majority of left-handed patients have left-sided clefts, while right-handed patients are more heterogeneous in this respect. It appears universally true that approximately two-thirds of the unilateral clefts of the primary palate (CL(P)) occur on the left side, and one-third on the right (Fraser and Calnan, 1961; Ingalls et al, 1964; Campbell Wilson, 1972). The following clinical investigation considers the association of the left— versus right-handedness with the side and type of the cleft. MATERIAL AND METHODS Since 1980, the left-versus right-hand-edness of patients with clefts born be— tween 1954 and 1979 has been noted at the Finnish Red Cross Cleft Center outpatient clinic. The treatment of clefts in Finland is centralized to our unit, and the study comprises in principle all patients operated for either CL(P) or isolated cleft palate (CP). Only microforms not operated on, those who failed to appear at the The author is the Head of the Finnish Red Cross Cleft Center and an Assistant Professor of Plastic Surgery at the University of Helsinki and at the University of Turku in Finland. 34 follow-up, or patients in whom the hand-edness had not been recorded were excluded. A minimum age of four years was considered necessary for reliable determination of handedness, which was established by questioning (and observing) which hand the patient used for: eating, writing, playing with toys, and grasping. Persons using both hands indiscriminately were considered left—handed, partly due to findings in previous investigations (Humphrey, 1951) and partly because there still exists some social and cultural preference for right— handedness. Among the 706 patients with cleft studied , 459 (65%) had CL(P) and 248 (35%) had CP. Among the 459 CL(P) cases there were 111 (24%) bilateral and 348 (76%) unilateral clefts. Of the 348 unilateral clefts 220 (63%) were on the left side and 128 (37%) were on the right. The groups with CL(P) on the left side, CL(P) on the right side, CL(P) bilateral clefts, and CP were compared in relation to left-versus right-handedness of the patients using the Chi square (X2) test with