Human ulnar neuropathy at the elbow: clinical, electrical, and morphometric correlations.

This study explored and compared clinical, electrodiagnostic, and morphometric observations on bilateral ulnar nerves obtained at necropsy in a patient with severe bilateral ulnar compression neuropathy at the elbow. There was excellent correlation among all three evaluation techniques. On the patient's more symptomatic side, there was significant slowing of conduction velocity across the elbow, with sensory conduction unobtainable in the little finger. Morphometric results demonstrated loss of myelin, decreased nerve fiber diameter, and reduction in percent of neural tissue present in the compressed elbow segment of the ulnar nerve.

[Separation of undamaged single nerve fibers by using an ultrasonic microscalpel]. / Vydelenie nepovrezhdennykh odinochnykh nervnykh volokon s pomoshch'iu ul'trazvukovogo mikroskal'pelia.

A routine procedure for dissection of single nerve fibres with sharpened sewing needles is rather tiresome and occasionally traumatic because of poor efficiency in cutting interfibrous connective tissue and sticking out patches of it to preparative needles. The described method using microscalpel oscillating with ultrasonic frequency is free from these shortcomings. Voltage clamp tests proved an innocuous character of this method for excitable nodal membrane.

Multipotentiality of Schwann cells in cross-anastomosed and grafted myelinated and unmyelinated nerves: quantitative microscopy and radioautography.

Cross-anastomoses and autogenous grafts of unmyelinated and myelinated nerves were examined by electron microscopy and radioautography to determine if Schwann cells are multipotential with regard to their capacity to produce myelin or to assume the configuration seen in unmyelinated fibres. Two groups of adult white mice were studied. (A) In one group, the myelinated phrenic nerve and the unmyelinated cervical sympathetic trunk (CST) were cross-anastomosed in the neck. From 2 to 6 months after anastomosis, previously unmyelinated distal stumps contained many myelinated fibres while phrenic nerves joined to proximal CSTs became largely unmyelinated. Radioautography of distal stumps indicated that proliferation of Schwann cells occurred mainly in the first few days after anastomosis but was also present to a similar extent in isolated stumps. (B) In other mice, CSTs were grafted to the myelinated sural nerves in the leg. One month later, the unmyelinated CSTs became myelinated and there was no radioautographic indication of Schwann cell migration from the sural nerve stump to the CST grafts. Thus, Schwann cell proliferation in distal stumps is an early local response independent of axonal influence. At later stages, axons from the proximal stumps cause indigenous Schwann cells in distal stumps from the previously unmyelinated nerves to produce myelin while Schwann cells from the previously unmyelinated nerves to produce myelin while Schwann cells from the previously myelinated nerves become associated with unmyelinated fibres. Consequently, the regenerated distal nerve resembled the proximal stump. It is suggested that this change is possible because Schwann cells which divide after nerve injury reacquire the developmental multipotentiality which permits them to respond to aoxonal influences.