[Structural characteristics of sural nerve myelin from patients with chronic inflammatory demyelinating...

Using the X ray diffraction technique and the mathematical analysis developed by Luzzati and Mateu, we have studied the structure of nerve myelin from patients with chronic inflammatory demyelinating polyneuropathy (CIDP) in order to quantitatively evaluate the changes occurred in the myelin sheath at structural level.

Sural nerves from 4 patients filling the criteria for CIDP were studied and the results compared to those of 4 other sural nerves extracted from patients who died in the Hospital with no symptoms of peripheral nerve diseases. The structural parameters determined by the mathematical analysis were: the repeat distance between the myelin membranes pairs (D) and its mean standard deviation (sigmaD); the mean number of membrane turns per axon ; the fraction of total myelination (alpha myel) in the nerve, the fraction of membrane pairs not packed in a crystallite (alpha loose) and the degree of disorientation (sigmaw) of the myelin membrane pairs with respect to the fiber axis.

The alterations found in pathological nerve myelin were: 1) increase in the packing disorder sigmaD and in the fraction of disordered myelin alpha loose; 2) decrease in the percentage of myelination alpha myel and in the mean number of membrane turns around the axons .

Our results indicate that with these techniques it is possible to detect and quantify demyelination produced by CIDP in human peripheral nerves. In consequence it should be possible to use a similar approach to study other types of polyneuropathy.