Which response by a client after a traumatic brain injury indicates upper motor neuron damage?

The response indicating upper motor neuron damage is the presence of the Babinski response, which is characterized by the fanning of the toes and dorsiflexion of the big toe when the sole of the foot is stimulated. This reflex is normally present in infants but typically disappears as the nervous system matures, indicating proper functioning of the corticospinal pathways. In adult individuals, the reemergence of the Babinski response after a traumatic brain injury suggests dysfunction in the upper motor neuron pathways, as these pathways are responsible for voluntary movement control as well as reflex actions.

In contrast, clonus—such as bilateral ankle clonus—also indicates upper motor neuron involvement, but it is more specific to persistent rhythmic contractions following sudden stretch. Decreased sensation in the limbs generally points towards lower motor neuron damage or peripheral nerve issues since upper motor neuron lesions usually do not directly affect sensation. Loss of reflexes is characteristic of lower motor neuron damage, where the reflex arc is interrupted, resulting in reduced or absent reflexes. Therefore, the presence of the Babinski response serves as a clear indicator of upper motor neuron damage, making it the best choice among the options provided.