Researchers have found that children affected by Charcot-Marie-Tooth disease type 1A (CMT1A) have lower function, strength, and sensation in the upper limbs and hands.
The study, titled “Established and novel measures of upper limb impairment in children with Charcot-Marie-Tooth disease type 1A and Riboflavin Transporter Deficiency type 2,” was published in the Journal of the Peripheral Nervous System.
The study’s findings suggest these patients could benefit from therapies targeting upper limb and hand function.
It’s common for children with diagnosed CMT1A to show lower upper limb strength and hand function impairment. However, little is known about the involvement of upper limbs in this disease.
With the first signs appearing as early as age 3, there are several methods to evaluate motor dysfunction in these patients. Some of these test the capacity of the child to accurately and effectively use their fingers and hand, such as the Functional Dexterity Test, the Nine-Hole Peg Test and Grip strength test, tip and pinch strength, and the handwriting speed test.
To improve the knowledge of hand and upper limb function in CMT, a research team led by Joshua Burns, PhD, professor of pediatric neuromuscular rehabilitation at the University of Sydney, conducted a pilot study in which they used established and new outcome measures.
They measured hand function, strength, and sensation in four children with CMT1A, four with riboflavin transporter deficiency (RTD2) – a progressive neurodegenerative disease that affects the motor and sensory functions – and four healthy age and sex-matched controls. They also determined fatigue and muscle activity in all participants.
The team found that both CMT1A and RTD2 children presented wide-ranging hand and upper limb impairment compared to the control group. In particular, the affected children presented weakness in the small muscles of the hands, which was only detected with the use of force transducer and hand-held dynamometer instead of common manual muscle testing.
CMT1A and RTD2 children were also found to be unable to compensate during fatiguing contractions in comparison to the healthy children. This may in part be due to the lower strength and inability to recruit muscle action. This feature also correlates with the previously described slower writing speed and worse performance on hand function tests.
“A decline in muscle activity while force remained constant showed that controls [healthy children] compensated with other muscles during the fatigue task while children with CMT1A and RTD2 did not have this compensatory ability,” the researchers wrote.
Overall, this pilot study showed that children with CMT1A have significant hand and upper limb impairment compared to children without CMT.
The researchers believe that “these results suggest the upper limb should be a focus of rehabilitative therapy in affected children using sensitive outcome measures of strength and sensation, as well as functional activities of daily living, which are most relevant to the patient.”