Wallerian degeneration and recovery of motor nerves after multiple focused cold therapies

Abstract

Introduction: A device has been developed to apply freezing temperatures to temporarily impede nerve conduction, resulting in inhibition of voluntary skeletal muscle contraction. This device was designed as an alternative to the neurotoxins usually used to treat movement disorders.

Methods: We evaluated the effects of single and 3 repeat treatments with a cryoprobe device (-55°C) on a sciatic nerve rat model. Long-term effects of repeated treatment were evaluated through assessments of physiological function and histological analysis.

Results: There was consistent weakening of physiological function after each treatment, with recovery of normal function by 8 weeks posttreatment. Histological findings showed axonal degeneration with no disruption to the epineurial or perineurial structures. Progressive axonal regeneration was followed by normal recovery by 24 weeks post-treatment.

Conclusions: Low-temperature treatment of motor nerves did not result in permanent or long-term changes to nerve function or structure.

Keywords: cryoprobe; cryotherapy; denervation; movement disorder; peripheral nerve; reinnervation.

© 2014 The Authors. Muscle Nerve published by Wiley Periodicals, Inc.

Figures

Figure 1

(A) Toe spread and (B) motor function assessment scores of single-treated versus untreated contralateral limbs. *Statistically significant (P < 0.05) when compared with control hindlimb. All other points are not significant (P > 0.05). Error bars represent mean ± SEM.

Figure 2

Samples of (A) 1-week, (B) 8-week, (C) 16-week, (D) 24-week, and (E) 32-week posttreatment H&E-stained cross-sections of single-treatment sciatic nerves. (F) Untreated controls are shown for comparison. Arrows indicate degenerated axons.

Figure 3

Immunofluorescence staining for neurofilaments (green, neuron), S-100 (red, Schwann cell), and nuclei (blue, DAPI) of (A) untreated control, (B) 1-week, and (C) 32-week posttreatment for repeat-treated nerves. Arrows indicate myelinated neurons.

Figure 4

(A) Toe spread and (B) motor function assessment scores of repeat-treatment versus untreated contralateral limbs. *Statistically significant (P < 0.05) when compared with control hindlimb. All other points are not significant (P > 0.05). Error bars represent mean ± SEM.

Figure 5

Overlay of (A) toe spread and (B) motor function scores to compare weakening and recovery after first, second, and third treatment in the repeat-treatment group. Error bars represent mean ± SEM.

Figure 6

Samples of (A) 8-week, (B) 16-week, (C) 24-week, and (D) 32-week posttreatment H&E-stained cross-sections of repeat-treatment sciatic nerves. Samples were collected at the indicated time intervals after the third cryotreatment. Arrow indicates degenerated axon. Arrowheads indicate epineurial structure of the nerve.