part of part of has part has part characteristic of inheres in has modifier neuron Upper motor neuron dysfunction A functional anomaly of the upper motor neuron. The upper motor neurons are neurons of the primary motor cortex which project to the brainstem and spinal chord via the corticonuclear, corticobulbar and corticospinal (pyramidal) tracts. They are involved in control of voluntary movements. Dysfunction leads to weakness, impairment of fine motor movements, spasticity, hyperreflexia and abnormal pyramidal signs. Corticospinal tract dysfunction UMLS:C1839042 UMLS:C1504405 HP:0002493 Pyramidal tract dysfunction A functional deficit of the tract that conveys nervous impulses from the motor cortex of the brain to the spinal cord. The corticospinal tract mediates discrete voluntary skilled movements. Clinical features of corticospinal tract dysfunction may include spasticity and weakness, particularly affecting the lower limbs, as well as hyperreflexia, clonus at the ankles and knees, and extensor plantar responses (Babinski response). Abnormal central motor function abnormal decreased functionality primary motor cortex