Recovery of intellectual function after a brain injury: a comparison of longitudinal and cross-sectional approaches

The goal of this study was to investigate recovery of intellectual function as a function of age at the time of a brain lesion. Participants with unilateral cortical lesions were selected from an initial data base of 685 patients. Ninety-six participants formed a longitudinal cohort for a first study and 314 participants formed a cross-sectional cohort for a second study. Participants of each study were split into two age groups according to the age at the time of the lesion: (1) before 7 years, (2) 7 years or more. Results showed a significantly different recovery profile as a function of age in the longitudinal study. Older participants manifested recovery on VIQ and PIQ, while younger participants presented stable profiles. The longitudinal and cross-sectional studies revealed differing recovery profiles as a function of age. Results are discussed in the context of the Kennard principle and with regard to the methodological approaches.