Final answer:
Tongue deviation can occur in lesions of the hypoglossal nerve or the tongue muscles. Upper motor neuron lesions result in spastic paralysis, while lower motor neuron lesions cause flaccid paralysis.
Step-by-step explanation:
Tongue deviation can occur in lesions that affect the hypoglossal nerve or the muscles of the tongue itself. Damage to the hypoglossal nerve, which controls the movement of the tongue, can result in the tongue deviating towards the side of the lesion. On the other hand, if there is a lesion in the muscles of the tongue, it can cause an imbalance in muscle control and lead to tongue deviation.
Upper motor neuron (UMN) lesions and lower motor neuron (LMN) lesions have different features. UMN lesions, which occur in the brain or spinal cord, often result in spastic paralysis. This is characterized by increased muscle tone, exaggerated deep tendon reflexes, and presence of the Babinski sign. In contrast, LMN lesions, which occur at or below the level of the spinal cord, typically lead to flaccid paralysis, decreased muscle tone, decreased or absent deep tendon reflexes, and muscle weakness.