Which of the following symptoms would be expected from an upper motor neuron (UMN) lesion?

An upper motor neuron (UMN) lesion results in a specific set of symptoms that include spasticity. This is characterized by increased muscle tone and exaggerated reflexes. The underlying mechanism involves the loss of inhibitory control of spinal cord reflexes, leading to excessive contraction of the muscles. As a result, movements can become rigid and stiff, which is commonly observed in conditions such as stroke or multiple sclerosis where UMN lesions are prevalent.

In contrast, symptoms such as muscle cramps, hypotonicity, and atrophy are more associated with lower motor neuron (LMN) lesions or other conditions. Muscle cramps often indicate muscle fatigue or irritation rather than a clear UMN issue. Hypotonicity involves decreased muscle tone and is also linked with LMN disorders, while atrophy signifies muscle wasting due to disuse or degeneration of the motor neurons, which is typically seen in LMN lesions. Therefore, spasticity is the primary symptom that aligns with an upper motor neuron lesion.