Relationship between side of the cleft and handedness of the patient.

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.