How can I interpret the results of nerve conduction studies to differentiate between peripheral neuropathy and radiculopathy?

Interpreting nerve conduction studies (NCS) to differentiate peripheral neuropathy from radiculopathy involves assessing the pattern and location of abnormalities in nerve function. In peripheral neuropathy, NCS typically show abnormalities in the distal segments of peripheral nerves, such as reduced amplitude of sensory and motor responses, slowed conduction velocities, and prolonged distal latencies, reflecting diffuse or multifocal nerve involvement NICE NG211 Lee et al. 2004. Conversely, radiculopathy primarily affects the nerve root proximal to the dorsal root ganglion, so sensory nerve action potentials (SNAPs) are usually preserved because the sensory neuron cell bodies remain intact; motor responses may show reduced amplitude or conduction block if the motor root is involved, but sensory abnormalities on NCS are generally absent or minimal NICE NG211 Choi & Di Maria 2021.

Key distinguishing features include:

• Peripheral neuropathy: Abnormalities in both sensory and motor nerve conduction studies, often symmetrical and distal, with reduced SNAP amplitudes and slowed conduction velocities indicating axonal loss or demyelination NICE NG211 Lee et al. 2004.
• Radiculopathy: Normal sensory nerve conduction studies due to intact dorsal root ganglion neurons, with possible motor conduction abnormalities; needle electromyography (EMG) is often required to detect denervation changes in muscles supplied by affected roots NICE NG211 Choi & Di Maria 2021.

Therefore, NCS alone may not definitively diagnose radiculopathy but can effectively identify peripheral neuropathy. Combining NCS with needle EMG enhances diagnostic accuracy by detecting denervation in radiculopathy, which is not evident on NCS alone NICE NG211 Lee et al. 2004Choi & Di Maria 2021.