Developmental Neurorehabilitation  published research on the association between mental and motor functioning in children with CP.  This study looked at 78 toddlers with a diagnosis of cerebral palsy with GMFCS I-V.  The researchers determined that when motor and mental functioning did not develop at the same time,  it was always motor functioning that was more delayed than mental functioning.  No children performed better on the motor section than the mental section.

Reference:    Lotte Enkelaar ;  Marjolijn Ketelaar; Jan Willem Gorter Association between motor and mental functioning in toddlers with cerebral palsy Developmental Neurorehabilitation, Volume 11, Issue 4 2008 , pages 276 - 282 .