The compound muscle action potential (CMAP) scan is “a promising tool” for detecting early nerve dysfunction in patients with T1DM, the researchers involved in this cross-sectional pilot study concluded.
They investigated the potential of the test for detecting subclinical diabetic peripheral motor neuropathy by scanning the peroneal nerve in three groups of patients with T1DM, plus matched healthy controls:
- Group 1: 13 patients aged 8-25 years with a disease duration of 2.5-5 years, an HbA1c level consistently below 8% since diagnosis, and without clinical diabetic peripheral neuropathy (DPN). The patients in this group would not be expected to have subclinical DPN.
- Group 2: 17 patients aged 10-25 years with a disease duration of 10 years or more, an HbA1c level above 8.5% on at least three occasions, and/or early signs of microvascular complications such as retinopathy or microalbuminuria, but without clinical DPN. These patients might be expected to have subclinical DPN.
- Group 3: 13 adult patients (aged 20-70 years) with established clinical DPN.
- As a result of the patient criteria for the three groups, the researchers expected to observe a trend towards higher stimulus intensity (SI) – reflecting reduced motor nerve atonal excitability – from Group 1 to Group 2 to Group 3.
- As expected, higher SI values were observed in Group 2 compared with Group 1. However, some aberrant values were seen in Group 1, compared with controls: the researchers said this suggests that “reduced axonal excitability (whether stand-alone or as part of subclinical DPN) occurs in some individuals in a very early stage of T1DM, despite appropriate glycemic control and the absence of other microvascular complications”.
- Overall, in both Group 1 and Group 2, motor nerve axonal excitability was significantly lower compared with the control groups.
- Differences in the CMAP scan measures of axonal loss and re-innervation were seen only between the patients in Group 3 and their matched controls.
- The researchers concluded that motor nerve axonal excitability “seems to be reduced early in T1DM, even in well-controlled young patients, and probably before (irreversible) axonal damage occurs”. They added that these changes can be measured by the CMAP scan, “which makes this a promising tool for detecting nerve dysfunction in T1DM”.
For PubMed abstract click here.