The compound muscle action potential (CMAP) scan is “a promising tool” for detecting early nerve dysfunction in people with type 1 diabetes, 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 participants, plus matched healthy controls:
- Group 1: 13 participants 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 participants in this group would not be expected to have subclinical DPN.
- Group 2: 17 participants 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 participants might be expected to have subclinical DPN.
- Group 3: 13 adult participants (aged 20-70 years) with established clinical DPN.
- As a result of the 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 type 1 diabetes, 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 participants in Group 3 and their matched controls.
- The researchers concluded that motor nerve axonal excitability…