Intracranial Facial Nerve Crush Injury and Facial Motor Nuclei Cell Loss in Rats

Abstract

Objectives The purpose of this study was to (1) assess the degree of motoneuron cell loss and (2) the combinatorial effects of electrical stimulation (ES) and testosterone propionate (TP) on cell survival following an intracranial facial nerve crush injury and (3) compare these results to distal injuries. Study Design Prospective, randomized, controlled animal study. Methods Sprague-Dawley rats were randomly divided into 3 groups: intracranial sham surgery or intracranial crush injury with or without ES and TP treatments. The intracranial sham group underwent exposure of the meatal segment of the right facial nerve. The intracranial crush groups underwent a crush of the meatal segment following exposure with or without ES and TP treatment immediately following the injury and followed for 8 weeks. Brain sections were thionin-stained, and facial motor nuclei (FMN) were counted using light microscopy. Results were compared to intratemporal and extracranial facial nerve crush injuries. Results Intracranial crush injury resulted in a significant decrease in cell survival (n = 6) of 65.6% as compared to the sham group (99.4%; n = 9). The treatments increased cell survival to 93.8% (n = 2). The cell loss in the intracranial facial nerve injury is more substantial than the intratemporal (85.8%; n = 7) and extracranial (103.3%; n = 4) injuries. Conclusions Intracranial injury results in a more profound cell loss compared to the distal injuries. These data suggest a critical importance for the development of treatment modalities that can help improve cell survival following facial nerve injuries.