Table 1

Peripheral nerve conduction studies

Patient (sex, age)NerveMotor NCSSensory NCS
Distal CMAP amplitude (mV)Distal latency (m/s)NCV (m/s)SNAP amplitude (μV)NCV (m/s)
II–2 (F, 46 y)Median135.21-150 492.61-150 381-150
Tibial6.34.2391-150
Sural6.51-150 361-150
III–1 (F, 25 y)Median19.54.31-150 545.81-150 421-150
Tibial20.23.450
Sural25.351
III–2 (M, 21 y)Median8.55.11-150 351-150 0.51-150 241-150
Tibial3.01-150 5.1321-150
Sural4.81-150 321-150
III–3 (M, 19 y)Median2.21-150 7.91-150 281-150 0.91-150 311-150
Tibial2.61-150 5.31-150 311-150
Sural0.71-150 341-150
III–4 (M, 13 y)MedianNDNDNDNDND
Tibial8.64.5301-150
SuralNRNR

  • ↵1-150 Pathological values; ND=not done; NR=no response upon stimulation; CMAP=compound muscle action potential; SNAP=sensory nerve action potential; NCV=nerve conduction velocity.

  • Although not clinically affected, the transmitting mother (II-2) showed slight abnormalities in sensory and motor NCVs. The unaffected daugther (III-1) has subtle signs of a (clinically asymptomatic) carpal tunnel syndrome, which is not related to the CMTX mutation. The carriers of the mutation show pathological motor and sensory NCVs .