Definition of Upper motor neuron

Upper motor neuron: A neuron that starts in the motor cortex of the brain and terminates within the medulla (another part of the brain) or within the spinal cord. Damage to upper motor neurons can result in spasticity and exaggerated reflexes. There is no standard laboratory test for upper motor neuron disease.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=33871
Last Editorial Review: 6/14/2012