The effect of mild head injury in 78 preschool children on their cognitive performance, especially reading ability, evaluated one year after injury and at 6.5 years of age was investigated at the Department of Neurosurgery, Auckland Hospital, New Zealand. Compared to a control group with minor injury not involving the head, head injured preschoolers showed impairment of interpretation of visual puzzles, a visual closure test, and increased incidence of reading difficulties at 6 and 12 months after injury and at age 6.5 years. Another head injury occurred within 6 months in 14% of the head injured group compared to <1% of the control group. Reading ability was correlated with the scores on visual closure at one year after injury. 
COMMENT. Mild head injury, not sufficient to require admission for observation, may result in cognitive deficits and impairment of reading and school performance. In this study, the development of visual skills necessary for reading appeared to be interrupted by the injury.
In a previous report reviewed in Progress in Pediatric Neurology I, (PNB Publishers, 1991, p408), mild head injury in 114 school aged children did not have an adverse effect on global measures of cognition and achievement at one to five years after injury. Children with head injuries were indistinguishable from uninjured children on all tests except the teachers’ report of hyperactivity which was 4/10 of a standard deviation higher . Hyperactivity noted after head injury might be significant and worthy of careful follow-up and management.