Final answer:
A lesion that presents as tongue deviation is typically associated with damage to the hypoglossal nerve or a lower motor neuron lesion in the brainstem. Upper motor neuron lesions are characterized by spastic paralysis, increased muscle tone, and exaggerated reflexes, while lower motor neuron lesions lead to flaccid paralysis, muscle atrophy, and decreased reflexes.
Step-by-step explanation:
A lesions that presents as tongue deviation is often associated with damage to the hypoglossal nerve (CN XII) or a lower motor neuron (LMN) lesion in the brainstem where the cell bodies of these neurons reside. If the lesion affects the upper motor neurons (UMN), it can result in a variety of symptoms, including muscle weakness, strong deep tendon reflexes, decreased control of movement or slowness, pronator drift, a positive Babinski sign, spasticity, and the clasp-knife response. On the other hand, LMN lesions, which may involve the hypoglossal nerve directly, lead to flaccid paralysis of the tongue on the affected side, causing the tongue to deviate towards the side of the lesion when protruded.
Upper motor neuron lesions are known for causing 'spastic paralysis' due to the loss of inhibitory signals that lead to increased muscle tone, exaggerated tendon reflexes, and the presence of pathological reflexes like clonus or Babinski sign. Contrastingly, lower motor neuron lesions typically result in 'flaccid paralysis,' muscle atrophy, fasciculations, and decreased or absent muscle reflexes due to the loss of the nerve supply to the muscles.