Which of the following conditions is associated with both upper motor neuron and lower motor neuron injuries?

Paralysis of muscles is indeed a condition associated with both upper motor neuron and lower motor neuron injuries. When there is an upper motor neuron injury, it affects the pathways that originate in the brain and connect to the lower motor neurons in the spinal cord. This can lead to paralysis or weakness of the muscles innervated by the affected lower motor neurons.

On the other hand, lower motor neuron injuries directly impact the neurons that connect the spinal cord to the muscles. Damage here can also lead to muscle paralysis because the signals from the lower motor neurons to the muscles are disrupted. In practice, conditions such as amyotrophic lateral sclerosis (ALS) can demonstrate both upper and lower motor neuron involvement, resulting in muscle paralysis.

Other options, while they hold clinical significance in neurology, do not uniquely encapsulate the dual aspect of both upper and lower motor neuron involvement. For instance, hypotonia relates more to decreased muscle tone, which can occur in lower motor neuron lesions but is not characteristic of upper motor neuron lesions. Hypertonia involves increased muscle tone due to upper motor neuron lesions, while absent deep tendon reflexes are typically associated with lower motor neuron damage. Therefore, paralysis of muscles is the most encompassing answer regarding both types of neuron injury.