The Science and Art of Nerve Fiber Teasing for Myelinated Nerves: Methodology and Interpretation

Abstract

Nerve fiber teasing is a sensitive technique utilized in diagnostic neuropathology practice, laboratory research, and animal toxicity studies for characterizing changes in single myelinated nerve fibers over extended distances. In animal toxicity studies, a nerve portion (approximately 10 mm in length) is stained with Sudan black for 24 to 48 hours and then transferred into a drop of viscous medium (eg, glycerin) mounted on an adhesive-coated glass slide, positioning it such that the proximodistal orientation is known. Individual fibers are removed using fine forceps while the sample is viewed under a stereomicroscope. In general, lesions can be identified during teasing, but more detailed characterization and photodocumentation is undertaken once nerve fibers have been dried and coverslipped. Nerve fiber teasing is particularly useful for distinguishing early stages of axonal degeneration (which presents as ovoid fiber fragments in the midinternodal region) from segmental demyelination (which presents as loss of original myelin segments and their replacement by thinner, shorter segments in the absence of axonal damage). The slow, laborious nature of nerve fiber teasing dictates that the technique will be employed on a few samples as an auxiliary method to better define the pathogenesis of nerve lesions first identified by conventional histopathologic assessment.

Proliferative and Nonproliferative Lesions of the Rat and Mouse Central and Peripheral Nervous Systems: New and Revised INHAND Terms

“…Teased fiber preparations, applicable to PNS axons and myelin. 8,9 Demyelination can be demonstrated in teased fiber preparations in the form of paranodal or segmental demyelination. Ultrastructural (TEM) evaluation to distinguish the main lesion: axonal degeneration versus demyelination.…”

“…Teased fiber preparations, applicable to PNS axons and myelin. 8,9 Differential diagnoses: degeneration, axonal; demyelination.…”

“…6 Cytoskeletal demonstration in axons by histological stains (eg, silver impregnation [Bielschowsky’s, Bodian’s]) or IHC (eg, anti-NFP). Myelin demonstration by histological stains (eg, LFB, Marchi technique, osmium impregnation) or IHC (eg, anti-MBP). Teased fiber preparations, applicable to PNS axons and myelin. 8,9 …”

Comparative Pathology of the Peripheral Nervous System

“…Schwann cells may be replenished if the insult is removed, but conduction velocity may remain slow since commonly more than one new Schwann cell is needed to cover the denuded axons. 21…”

Special Issue on Toxicologic Neuropathology of the Peripheral Nervous System: A Special Compendium of Past, Present, and Future Developments in a Neglected Field

“…Dr Danielle Brown’s 62 group provided a detailed review of theoretical and practical aspects of stereology as applied to PNS specimens. The art of nerve fiber teasing is covered by Bolon and Pardo 63 in a piece that includes exquisite diagrams and photomicrographs depicting normal and neuropathological features of myelinated nerve fibers in teased preparations. A histopathological end point (intraepidermal nerve fiber density) for sensory neuropathy evaluation is compared between species in an article by Mangus et al 56 In addition to these pathology-focused articles, a review of electrophysiological end points that are often used to evaluate the functional significance of morphologic data is included in an article by DaSilva and Arezzo .…”