Abstract
Background: Prematurely born children are more often left-handed than their term born peers. It is unknown if this excess left-handedness, a marker for the extent of cerebral lateralisation, is caused by cerebral lesions.
Methods: In a cohort of 221 preterm born infants (gestational age <= 32 weeks and/or birth weight <= 1500 grams), brains were serially examined in the neonatal period using cranial ultrasound (US) to detect intraventricular haemorrhage (IVH), periventricular leukomalacia (PVL) and other abnormalities. At age 7 to 10 years, magnetic resonance imaging (MRI) was done, and hand preference and current IQ were measured. MRI and US were classified as normal, mildly abnormal, or severely abnormal, blinded to handedness data.
Results: Children with severely abnormal US (IVH grade III/IV, cystic PVL grade II/III, thalamic lesion, focal infarction or haemorrhage at the level of the convexity) had an increased chance to become left-handed: odds ratio (OR) severely abnormal US versus normal US 4.1, 95% CI 1.6 to 10.0, p=0.003. This was confirmed by MRI scans at school age: OR severely abnormal MRI versus normal MRI 4.0, 95% CI 1.5 to 10.7, p=0.005. Findings were attributable to IVH. Left-sided IVH showed a higher chance for left-handedness (OR left-sided IVH versus no IVH 4.4, 95% CI 1.7 to 11.3, p=0.002), whereas right-sided IVH did not. Neonates with left-sided mild IVH (grade I and II) still showed an increased chance for left-handedness: OR mild left-sided IVH versus no IVH 4.0, 95% CI 1.5 to 10.9, p=0.007. PVL was not related to left-handedness.
Conclusion: Our findings strongly indicate that even a small intraventricular haemorrhage affecting the left side of the brain induces left-handedness. This is likely related to the role of the subependymal germinal matrix in the developing brain.
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Ramadhani, M., Rademaker, K., Vries, L. et al. 301 Intraventricular Haemorrhage on the Left Side of the Brain Induces Left-Handedness. Pediatr Res 58, 406 (2005). https://doi.org/10.1203/00006450-200508000-00330
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DOI: https://doi.org/10.1203/00006450-200508000-00330