Typical nerve conduction study abnormalities seen with axon loss or demyelination
| Axon loss | Demyelination | |
|---|---|---|
| It is not necessary to have all the features of axon loss or demyelination to come to a conclusion. Some conditions only affect motor or sensory nerves, and some processes are length dependent and others universal. It can sometimes be quite difficult to decide whether a process is primarily demyelinating or demyelinating with secondary axonal changes as features of both may coexist. | ||
| Sensory responses | Small or absent | Small or absent |
| Distal motor latency | Normal or slightly prolonged | Prolonged |
| CMAP amplitude | Small | Normal (reduced if conduction block or temporal dispersion) |
| Conduction block/temporal dispersion | Not present (responses may disperse slightly) | Present |
| Motor conduction velocity | Normal or slightly reduced | Notably reduced |
| F waves minimum latency | Normal or slightly prolonged | Significantly prolonged |