Flexor plantar responses in children with upper motor neuron lesions.

The usual plantar response in upper motor neuron lesions is extensor. As flexor responses were seen in a number of children with these lesions, a formal study was undertaken to assess the plantar reflex in affected children. Fifty-seven children with spastic cerebral palsy were examined. Ten had hemiplegias, so a total of 104 limbs were tested. Eighty-four (80.8%) of these had flexor and 12 (11%) had extensor responses. Half (3.9%) of the remaining eight responses were mute and half were variable. While exceptions to the extensor rule are known, this marked predominance of flexor responses is unusual. This may be the result of damage inflicted on the immature nervous system before full connections and myelination have been completed. Further studies, involving children who have sustained brain damage at different ages, will be needed to elucidate the various mechanisms involved.