Physical Therapy Assistant Practice Exam

Diminished deep tendon reflexes (hyporeflexia) are characteristic of which type of disorders?

1. Upper motor neuron disorders

2. Lower motor neuron disorders

3. Cerebellar disorders

4. Peripheral nerve disorders

The correct answer is: Lower motor neuron disorders

Diminished deep tendon reflexes, or hyporeflexia, are indeed characteristic of lower motor neuron disorders. This phenomenon occurs because lower motor neurons are responsible for transmitting signals from the spinal cord to the muscles. When these neurons are damaged or dysfunctional, either due to injury, disease, or degeneration, their ability to effectively convey reflexive movements is impaired. As a result, reflex actions, which are typically swift and involuntary, become less pronounced or absent altogether. In contrast, upper motor neuron disorders typically present with hyperreflexia, which means increased reflex responses. This is due to the disruption of the descending pathways that normally modulate reflex activity, leading to exaggerated reflexes. Cerebellar disorders do not primarily affect deep tendon reflexes, as cerebellar function is more related to coordination and balance than to the reflex arcs being assessed. Peripheral nerve disorders can lead to hyporeflexia as well, but they are not exclusively characterized by it; they can also manifest symptoms such as pain or muscle weakness. Lower motor neuron involvement is more definitive for the specific presentation of diminished reflexes, which is why it is identified as the correct response.