Nerve Conduction Changes Not Linked to Quality of Life and Hand Function in CMT1A Patients, Study Says

Muscle wasting and nerve conduction deficits are not associated with alterations in health-related quality of life (HRQoL) and hand function in people with Charcot-Marie-Tooth disease type 1A (CMT1A), a new study suggests.

Still, the findings also indicated the importance of assessing changes in hand function as early as possible to minimize deformations in these patients.

The study, “Multidimensional evaluation is necessary to assess hand function in patients with Charcot-Marie-Tooth disease type 1A,” was published in the journal Annals of Physical and Rehabilitation Medicine.

Because it affects the myelin sheath — the insulating layer of nerve fibers — CMT type 1 is associated with slow signaling between nerve cells. People with CMT1A, the most prevalent form of CMT, typically experience a deficit in hand function and loss of grip strength.

Although several studies have assessed the relationship between loss of axons (long projections of nerve cells that conduct electrical impulses in neuronal communication) and CMT1A progression, the impact of axonal loss on hand skills and HRQoL is unknown.

To address this knowledge gap, researchers at the Clermont-Ferrand University Hospital, France, used a technique called electroneuromyography to record nerve conduction and electrical activity in the hands of 33 participants with CMT1A (average age 47).

Researchers hypothesized that the severity of axonal loss — as demonstrated by electromyoneurography results — would correlate with loss of hand function and worse HRQoL.

Specifically, grip and pinch strength were evaluated with devices called dynamometers. Hand dexterity was evaluated with the Sollerman, Jebsen, and Nine-hole Peg tests.

The impact of CMT on well-being was assessed with the Medical Outcomes Study Short Form 36 (SF-36), Beck Depression Inventory, and the Fatigue Severity Scale.

Results showed high frequency of electroneuromyography impairment (more than 80%) — as manifested by loss of myelin and axonal loss — and amyotrophy (muscle loss, 70%). Yet, these changes were not correlated with alterations in HRQoL, autonomy in activities of daily living and hand function, which remained relatively preserved.

“Electrophysiological [electrical activity] follow-up seems to be of little relevance to follow HRQoL in individuals with CMT1A and manual function related to functional objectives for everyday physical medicine and rehabilitation practice,” the scientists wrote.

Pinch strength was associated with better hand skills, according to the Sollerman test.

Next, the investigators assessed which factor was most detrimental for hand function and quality of life.

Results indicated that grip strength on the dominant hand and median compound muscle action potential (the composite electric activity within a muscle) were the only factors associated with altered function.

Overall, the preserved hand function “suggests patients’ ability to compensate for impairments of the hand’s intrinsic muscles and the interest of detecting these deficits as early as possible to limit deformations,” the researchers wrote.

“Further work is needed to evaluate the effectiveness of rehabilitative or surgical treatments on objective functional criteria to improve manual function and develop early management protocols in CMT1A,” they added.