Increased occurrence of left-handedness after severe childhood bacterial meningitis: Support for the pathological left-handedness hypothesis

The hypothesis that brain damage during infancy causes pathological left-handedness was tested by assessing handedness in 182 survivors of childhood non-Hemophilus influenza type b bacterial meningitis in the Netherlands (mean age of 9.7 years). These children were selected randomly after clustering them into those with or without parental report on academic and behavioural problems. Medical records were obtained from the hospitals, while handedness and neurodevelopmental outcome were assessed at school age. Logistic regression analysis was used to study the relationship between a severity score of bacterial meningitis and handedness. Fifteen percent were left-handed. Severity of childhood bacterial meningitis was related to left-handedness (Odds ratio (OR) 6.2, 95% confidence interval (CI) 2.0–18.6 for those with a total severity score above the median as compared to those below). Compared to non-left-handed children, left-handed children had lower IQ (mean difference −6.6, 95% CI −12 to −1.2), tended to have lower vocabulary scores on WISC-r (−1.0, −2.1 to 0), and lower Beery scores on visual-motor integration (−4.9, −10.1 to 0.4). Left-handed children also tended to have more combined academic and behavioural limitations (OR 2.7, 95% CI 0.9–8.6), lower manual speed of the dominant hand (mean difference −9 taps, p < 0.05) and better manual steadiness in the non-dominant hand (mean difference of contact's time −2.7 s, p < 0.05). Left-handed post-meningitic children generally have worse neurodevelopmental outcome than non-left-handed survivors. Our results support the role of early life brain damage in left-handedness.