Distance of the motor cortex from the coronal suture as a function of age

Objective: This study was performed to investigate whether the distance from the motor cortex to the coronal suture changes with age. Methods: We performed a retrospective review of the charts of pediatric patients who had undergone frontoparietal implantation of subdural grids for long-term video-EEG monitoring during an evaluation for seizure surgery from 1995 to 2001. Cortical mapping was performed in 17 patients to localize the motor cortex. On postimplantation lateral skull radiographs, the coronal suture was identified at its medial aspect, and the anterior-posterior distance was measured to the electrodes overlying motor cortex. Results: Ages ranged from 10 months to 14.6 years with a mean of 8.6 years. The mean distance from the coronal suture to the motor cortex was 31.5 mm (±7 mm). The location of the motor cortex correlated significantly with age (r_s = 0.84, p < 0.0005) and increased at a rate of 1.5 mm per year. All patients aged <6 years had distances of <3 cm from the coronal suture to the motor cortex. Conclusions: The distance from the coronal suture to the motor cortex increases with patient age. This variability has implications for determining the location of eloquent structures based on this anatomical landmark.