Nerve crush but not displacement-induced stretch of the intra-arachnoidal facial nerve promotes facial palsy after cerebellopontine angle surgery

Abstract

Little is known about the reasons for occurrence of facial nerve palsy after removal of cerebellopontine angle tumors. Since the intra-arachnoidal portion of the facial nerve is considered to be so vulnerable that even the slightest tension or pinch may result in ruptured axons, we tested whether a graded stretch or controlled crush would affect the postoperative motor performance of the facial (vibrissal) muscle in rats. Thirty Wistar rats, divided into five groups (one with intact controls and four with facial nerve lesions), were used. Under inhalation anesthesia, the occipital squama was opened, the cerebellum gently retracted to the left, and the intra-arachnoidal segment of the right facial nerve exposed. A mechanical displacement of the brainstem with 1 or 3 mm toward the midline or an electromagnet-controlled crush of the facial nerve with a tweezers at a closure velocity of 50 and 100 mm/s was applied. On the next day, whisking motor performance was determined by video-based motion analysis. Even the larger (with 3 mm) mechanical displacement of the brainstem had no harmful effect: The amplitude of the vibrissal whisks was in the normal range of 50°-60°. On the other hand, even the light nerve crush (50 mm/s) injured the facial nerve and resulted in paralyzed vibrissal muscles (amplitude of 10°-15°). We conclude that, contrary to the generally acknowledged assumptions, it is the nerve crush but not the displacement-induced stretching of the intra-arachnoidal facial trunk that promotes facial palsy after cerebellopontine angle surgery in rats.

The Anticancer Properties of Tanshinones and the Pharmacological Effects of Their Active Ingredients

“…The pathological examination indicated that these cells often exhibit atypical mitosis (Machado et al, 2016). Patients with advanced cancer often exhibited severe systemic symptoms and high recurrence rate after surgical excision, causing a big challenge for cancer therapy (Bax et al, 2016;Bendella et al, 2016;Frohman et al, 2016). In view of the enormous harm caused by cancer, the development of new antitumor treatments has become a research hotspot.…”

Clinical Studies and Pre-clinical Animal Models on Facial Nerve Preservation, Reconstruction, and Regeneration Following Cerebellopontine Angle Tumor Surgery–A Systematic Review and Future Perspectives

“…Based on the current review, the rat (Bendella et al, 2016) and the rabbit model (Maurer and Mika, 1983;Lumenta et al, 1988;Widick et al, 1994;Braun and Richter, 1996;Telischi et al, 1999) seem to be the most feasible rodent models for manipulation of the intra-arachnoidal FN in the CPA. Mice were used for stereotactically guided injection of modified Schwann cells to create CPA-tumors (Bonne et al, 2016;Dinh et al, 2018;Chen et al, 2019).…”

“…Beside a proper head fixation, even when working under microscopic magnification, the amount of required maneuverability depends on the FN-reconstruction techniques used. The smallest animal reported in the current review, where cranial nerves of the CPA were manipulated, was the rat (Table 7; Mattsson et al, 1999;Burgette et al, 2012;Amine et al, 2014;Bendella et al, 2016;Bonne et al, 2016;Dinh et al, 2018;Chen et al, 2019), followed by the New Zealand rabbit or guinea pig (Table 8; Maurer and Mika, 1983;Lumenta et al, 1988;Levine et al, 1993;Widick et al, 1994;Braun and Richter, 1996;Telischi et al, 1999), cats, dogs and monkeys (Table 9; Chinn and Miller, 1975;Mangham and Miller, 1979;Sekiya et al, 1985Sekiya et al, , 1990Fisch et al, 1987;Sekiya and Moller, 1988;Lusk et al, 1990;Greiman and Lusk, 1991;Glasby et al, 1995). However, the rat model published by Amine et al (2014) and Burgette et al (2012) for intracranial FN injury required extensive petrous bone drilling, FN rerouting and removal of the cochlear structures to sufficiently expose the FN, on the other hand efficiently creating a post-operative intracranial FN palsy (Table 7).…”

“…The 2nd (meatal) intra-arachnoidal segment extends from the IAP to the fundus of the internal acoustic canal (IAC). Within the 3rd (labyrinthine) segment, being the shortest in humans, the FN occupies a small rostro-dorsal portion of the IAC, and extends from the fundus of the IAC to the geniculate ganglion (Lescanne et al, 2002 ; Bendella et al, 2016 ). Within these first three segments, the neuronal axons are individually myelinated.…”

“…Protection mostly occurs via the cerebrospinal fluid (CSF), the arachnoid layer and the cisternal anatomy. However, even in a physiological state, the intra-arachnoidal FN is strained and exposed to pulsatile forces within the subarachnoid space (Lescanne et al, 2002 ; Bendella et al, 2016 ).…”