Temperature effect on antidromic and orthodromic sensory nerve action potential latency and amplitude.

The measurement of sensory nerve action potential (SNAP) latency and amplitude is often necessary to accurately diagnose disorders of peripheral nerves. The sensory evoked response can be obtained using either the antidromic (AD) or orthodromic (OD) technique. In a previous study we demonstrated that in healthy subjects the AD SNAP distal latency of median and ulnar nerves at 14 cm distance is approximately 0.2 msec slower than the OD SNAP distal latency at 32C. The AD SNAP amplitude was also two times greater than the OD SNAP amplitude. In this study we observed that these differences between the AD and OD SNAP latency and amplitude varied significantly as temperature changed. The AD median nerve SNAP distal latency was delayed by .06 msec/degree with cooling. The OD median nerve SNAP distal latency was delayed by .03 msec/degree with cooling. These values represent less of a slowing per degree centigrade cooling than has been previously noted in the literature. The median nerve SNAP amplitude was found to increase with upper extremity cooling with the AD and OD technique by 3.5 microV and 0.5 microV per degree, respectively. For accurate interpretation of SNAP latency and amplitude, the electromyographer must be familiar with the technique used and the differing effect of the temperature with each technique.

Detachable cast pylon technique for rigid dressings on below-knee amputee patients.

The attachment of a pylon and prosthetic foot to a postoperative rigid dressing can be beneficial in the management of a below-the-knee amputation. Recently, a rigid, removable dressing has been used to allow easy inspection of the stump during healing. The removal of the pylon and prosthetic foot at night, preventing unsupervised ambulation, is accomplished by a disconnecting mechanism, which is permanently attached to the end of the rigid removable dressing. This disconnecting mechanism adds to the bulk and weight of the rigid dressing, increasing the shear force on the stump. We are introducing the detachable cast pylon technique, in which a fabricated sleeve attached to the pylon is easily and completely attached and detached from a rigid dressing. It is lightweight, less bulky, easily fabricated, and inexpensive. It offers a quick disconnect system for either the Otto-Bock attachment plate or uniquely with PVC tubing. In addition, this technique affords consistency in shaping the stump, as the same rigid dressing can be used for both rest and training. Its intent is for in-hospital use or when ambulation is restricted to supervised situations.

The value of propoxyphene hydrochloride (Darvon) for the treatment of hyperhidrosis in the spinal cord injured patient: an anecdotal experience and case reports.

Hyperhidrosis is a condition affecting the spinal cord injured (SCI) patient that often does not respond well to medical management. While the aetiology of hyperhidrosis in SCI patients is not completely understood, the standard form of treatment is aimed at interrupting the sympathetic cholinergic eccrine sweat glands. It has been our experience in treating this condition that many patients will have a significant decrease in hyperhidrosis using propoxyphene hydrochloride (Darvon) 65 mg once or twice per day. Two of these patients are presented. While the mechanism of action is purely speculative, there is evidence to support the concept that opioids may act as a weak ganglionic blocking agent. We have found that a trial of this medication for SCI patients suffering from hyperhidrosis may produce very gratifying results. Further investigation into the treatment of this condition with propoxyphene hydrochloride is indicated.

Orthodromic vs antidromic sensory nerve latencies in healthy persons.

Sensory nerve action potentials may be evoked antidromically (AD) by stimulating a nerve proximally and recording distally, or orthodromically (OD) by stimulating distally and recording over the nerve trunk proximally. The objective of this study was to compare OD and AD distal latencies in healthy subjects. Fifty-two volunteers (average age 30 years) were tested. Orthodromic and AD sensory distal latencies of the median and ulnar nerves of the nondominant hand were obtained. Hand temperature was controlled at 32C. Six subjects were also tested at a hand temperature of 24C. In all subjects tested the OD latency was shorter than the AD latency. Median nerve AD = 3.14 +/- 0.20 (mean latency in ms +/- 1 standard deviation); median nerve OD = 2.94 +/- 0.20; ulnar nerve AD = 3.07 +/- 0.22; ulnar nerve OD = 2.85 +/- 0.19. Mean difference between the latencies obtained (OD vs AD) for the median and ulnar nerves was statistically significant (p less than 0.001). In addition, this difference was over twice as great at 24C compared to 32C for both median and ulnar nerves. Because of the difference between OD and AD sensory latencies, the standard values obtained using one method cannot be rigorously applied when utilizing the other method. Individual laboratories should develop their own normal values for both OD and AD methods, or be specific in performance of the studies when utilizing standards from the literature.