Neurophysiologic abnormalities in children with CMT 1A

[Guest guest]

J Peripher Nerv Syst. 2008 Sep;13(3):236-41.

Neurophysiologic abnormalities in children with Charcot-Marie-Tooth

disease type 1A.

Yiu EM, Burns J, MM, Ouvrier RA.

Children's Neuroscience Centre, Royal Children's Hospital, Melbourne,

, Australia.

Although Charcot-Marie-Tooth disease type 1A (CMT1A) initially

manifests in the first decade, there are no large studies describing

its neurophysiologic features in childhood.

We report neurophysiologic findings in 80 children aged 2-16 years

with CMT1A who underwent median motor and sensory nerve conduction

studies. Neurophysiologic abnormalities were present in all children.

Median motor nerve conduction velocity was invariably less than 33

m/s (mean 18.7 m/s, range 9.0-32.9 m/s), with conduction velocities

significantly slower in children aged 7-16 years compared with

children aged 6 years and below.

All children had prolonged distal motor latencies (mean 7.3 ms, range

4.0-12.3 ms). The compound muscle action potential (CMAP) amplitude

was reduced from an early age (mean 7.1 mV, range 2.1-13.5 mV), and

its normal increase with age was attenuated.

Median sensory responses were present in only seven children, all

aged less than 9 years and with slowed sensory conduction.

Neurophysiologic abnormalities are present in all children with CMT1A

from the age of 2 years. Motor conduction slowing progresses through

the first 6 years of life and thereafter remains stable.

CMAP amplitude is reduced from an early age, and the normal

physiologic increase with age is attenuated. Median sensory responses

may be recorded in younger children, and their presence does not

exclude the diagnosis of CMT1A.