The effects of bipolar electrode montage on conduction velocity estimation from the surface electromyogram.

This study examines the influence of the bipolar electrode montage on conduction velocity (CV) estimation. Electrode montage refers to the combination of two parameters, the inter-electrode distance (IED), the distance between the two electrodes of a bipolar pair, and the inter-signal distance (ISD), the distance between two bipolar signals used to calculate CV. Data from the biceps brachii (BB) and tibialis anterior (TA) of healthy subjects are analysed. Two approaches are used for CV estimation. The first returns a single value per epoch. The second is based on finding velocity values from individual peaks in the signal and results in a peak velocity (PV) distribution being generated per epoch. It is concluded that CV estimation is significantly dependent on the choice of the (IED, ISD) electrode montage. The main results are that the electrode montage affects (1) the mean PV and CV estimates, (typically P < 0.001), (2) the degree of spatial variability, and (3) the width of the PV distributions. The combination of a small IED and large an ISD is recommended.

Bilateral absence of the ulna in twins as a manifestation of the split hand--split foot deformity.

Bilateral absence of the ulna and ulnar rays in twin female infants are described as a manifestation of the split hand--split foot deformity (ectrodactyly). Family history revealed the father had a unilateral split hand. Given the wide variability of expression of this disorder and the availability of prenatal diagnosis, there is a need for obstetricians and pediatricians to recognize parents with this malformation and appreciate the potential for severely affected offspring.