Researchers have found a new way to monitor disease progression in people with Charcot-Marie-Tooth disease type 1 (CMT1), reports Charcot Marie Tooth News.

CMT1 is an inherited genetic condition that affects the communication of information between the brain and spinal cord, and the rest of the body. The condition affects people differently; some have mild symptoms that may go undiagnosed, while others experience considerable disability. Usually, the progression of CMT1 is slow and most people affected will not become dependent on wheelchairs. Symptoms of the condition usually begin to appear between the ages of five and twenty-five and can include muscle weakness and wasting, slow nerve message transmissions, and sensory loss. Those with the condition often have a high foot arch and a bilateral foot drop (difficulty lifting the front of the foot). People affected by CMT1 may be offered physical and occupational therapies, devices to help with movement, such as wheelchairs and canes, as well as special shoes or braces, pain medication, and, in some cases, surgery.

However, an on-going issue in the treatment of CMT1 is the lack of clearly defined stages to the condition that can be used to monitor disease progression. The recent research, published in the Journal of Clinical Neurophysiology, goes some way towards improving this. The researchers found that a method called Motor Unit Number Index (MUNIX) that is used to measure muscle electrical activity correlates with clinical disability in patients with CMT1, and so can be used as a marker of disease progression.

The French researchers carried out a trial on 56 patients with CMT, and 53 healthy controls. All participants were tested using MUNIX on three areas; a muscle in the hand, one on the side of the foot, and one on the side of the lower leg. The researchers also tested the same muscles using scales of strength and weakness. In patients with CMT1, the MUNIX scores of the three muscles were correlated with the scale score of the same muscle. Patients with CMT also showed a greater decrease in MUNIX scores compared to the healthy control group, and the researchers hypothesise that this is because those with CMT have lost more motor nerve fibres. Furthermore, the overall MUNIX score is associated with the CMTNSv2 and ONLS scales of clinical impairment.

Although more research is needed to corroborate these findings, this preliminary research indicates that the MUNIX score system could be useful for assessing patients with Charcot-Marie-Tooth disease type 1.

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