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Abstract

Brain lesions acquired during the prenatal and perinatal period cause different types of structural pathologies, depending mainly on the stage of brain development at the time of the insult [1]. Polymicrogyria and heterotopia originate from congenital disorders affecting neuronal migration (heterotopia) and organization (polymicrogyria) during fetal brain development in the first and second trimester of pregnancy [2] and may be of variable extent. If only one hemisphere is affected by a congenital lesion, the contralesional hemisphere has great compensatory potential, which can far exceed the reorganizational capabilities in the adult brain [3], [4]. With regard to the motor system, this includes (depending on the extent of a corresponding lesion) (re-)organization with ipsilateral corticospinal tracts [3].

To reveal the pattern of motor system organization and reorganization in affected patients, methods applied in children include functional magnetic resonance imaging and transcranial magnetic stimulation; diffusion-based tractography is used to visualize the pyramidal tracts. Because compensatory mechanisms in cortical maldevelopments are still largely unexplored, the authors applied these three methods in the present case, to further understanding of the functional architecture of the motor tracts in a malformed brain.