Jury Still Out on Value of Vitamin C in CMT1A

An Australian trial yields mixed results, and a U.S. trial nears completion.

by Quest Staff on July 27, 2009 - 5:00pm

A recent trial has shown inconclusive results from various doses of vitamin C (ascorbic acid) in patients with the peripheral nerve disease type 1A Charcot-Marie-Tooth disease (CMT1A), and the jury remains out on this form of treatment, says Michael Shy, an MDA grantee at Wayne State University in Detroit.

Shy, a neurologist, is conducting a trial of high-dose vitamin C in CMT with neurologist Richard Lewis, also an MDA grantee at Wayne State. That trial is now closed, and results are under analysis.

According to results published in the June 2009 issue of Lancet Neurology, a one-year trial of high-dose vitamin C in 81 children ages 2 to 16 with CMT1A in Australia showed the treatment was safe and well tolerated but not effective.

Doctor and child
Neurologist and MDA grantee Michael Shy conducts research and sees patients at Wayne State University in Detroit.

However, some of the mildly affected patients in that trial appeared to perform better on relatively low doses of vitamin C in the Australian trial than children taking a placebo. (Their story was highlighted on Australian television on May 28. See the Webcast CMT Disease.) For most patients, the results were neutral.

Shy expressed concerns about the design of the study in a commentary in the same issue of Lancet Neurology in which the results were reported.

Shy says the Australian study was conducted in growing children, which makes the analysis particularly difficult to interpret. (The MDA-supported study includes adolescents and adults ages 13 to 70.)

"Kids grow, and they grow at different rates at different ages," he says. "There's this whole field of how to evaluate children with neuromuscular disease that's evolving. We're in the process of creating ways of evaluating children with CMT, through a study that's in part funded by another MDA grant. One of the aims is to develop a CMT pediatric scoring system."

He says the outcome measure the Australian researchers used was based on an electrodiagnostic measurement called nerve conduction velocity (the speed at which nerve impulses travel), values for which have been shown not to correlate with impairment in movement or sensation in children with CMT.

The Australian study used varying doses of vitamin C in the children, but they "never got to a high dose."

"Kids are an important group," says Shy, "but they need to be studied in a more complete and carefully designed manner."

Other studies now under way, Shy says, may show there isn't much effect of 1 gram of vitamin C per day on CMT. However, he says, most of these studies are limited by small numbers of participants and short durations.

Shy and Lewis note that results of a French study, presented at a meeting in Antwerp, Belgium, in July 2009, suggest that a trial of 3 grams of vitamin C per day in people with CMT is "looking positive" but that this trial also may not have been designed to yield a definitive answer.

"The bottom line is that the definitive study is going to be the MDA-supported CMTA study," Shy says, noting that he and Lewis agree. "It's 4 grams a day, which is a high dose, and is powered [has enough participants and lasts long enough] to give a meaningful result."

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The MDA-supported CMT North American Database for patients with all types of CMT was established in 2001 by investigators at Wayne State University and Indiana University. Registration involves filling out forms about family and medical history, consenting to have medical records reviewed, and having a physician report results of the patient's physical examination. Registrants may be invited to participate in future research projects.

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