Table 1 Grading of nerve conduction studies for carpal tunnel syndrome (Bland JD [7])
Grade | Findings |
|---|---|
Normal (grade 0) | |
Very mild (grade 1) | CTS demonstrable only with most sensitive tests |
Mild (grade 2) | Slow digit sensory nerve action potentials (SNAP) and normal terminal motor latency |
Moderate (grade 3) | Slow and attenuated digit SNAP + sensory potential preserved with motor slowing, distal motor latency to abductor pollicis brevis (APB) < 6.5 ms; prolonged terminal latencies |
Severe (grade 4 ) | Sensory potentials absent but motor response preserved, distal motor latency to APB < 6.5 ms |
Very severe (grade 5) | Terminal latency to APB > 6.5 ms |
Extremely severe (grade 6) | Sensory and motor potentials are effectively unrecordable (surface motor potential from APB < 0.2 mV amplitude) |