Which of the following is NOT a characteristic of spastic dysarthria?

The hallmark features of spastic dysarthria primarily arise from bilateral damage to the upper motor neurons that affects the muscles responsible for speech production. One of the defining characteristics of spastic dysarthria includes increased muscle tone, which results in muscle stiffness. This stiffness can lead to increased speech effort, a slowed rate of speech, and reduced phonation duration as the muscles may struggle to manage the necessary movements fluidly.

Fluctuating volume levels, on the other hand, are not a common trait of spastic dysarthria. This characteristic is more often associated with other types of dysarthria, such as ataxic dysarthria, which involves more variability in muscle control and timing. In spastic dysarthria, the speech output generally demonstrates a more consistent pattern, albeit with effort and slowness, rather than the irregularities seen with fluctuations in volume. Therefore, identifying fluctuating volume levels as not characteristic of spastic dysarthria is accurate, as it highlights a distinction between the motor control issues associated with different types of dysarthria.