National Physical Therapy Examination (NPTE) Practice Exam

In a sensory nerve conduction velocity test for a patient with a lesion proximal to the dorsal root ganglion, the conduction times will reveal what finding?

1. Decreased in amplitude

2. Markedly decreased

3. Markedly increased

4. Within normal limits

The correct answer is: Within normal limits

In a sensory nerve conduction velocity test, a lesion proximal to the dorsal root ganglion primarily affects the sensory pathway before the nerves enter the spinal cord. When assessing conduction times in this scenario, it is essential to understand the mechanism of nerve conduction and the role of the dorsal root ganglion. The sensory nerve conduction involves the activation of receptors, the conduction of the impulse through the peripheral sensory nerves, and the transmission to the central nervous system. A lesion proximal to the dorsal root ganglion may not affect the conduction velocity of impulses traveling through the remainder of the sensory nerve, as the dorsal root ganglion primarily serves as a relay point for sensory information entering the spinal cord. Therefore, conduction times measured distal to the lesion would likely be within normal limits because the nerve fibers themselves maintain their integrity, retaining their ability to conduct impulses effectively. As a result, while there may be changes in sensory perception or other clinical symptoms due to the lesion, the conduction velocity and times in a properly conducted test would typically not show significant alterations, indicating that the test results would be consistent with normal findings. This understanding is critical when interpreting nerve conduction studies, especially in distinguishing between different types of nerve injuries and their anatomical locations.