The ventrolateral surgical approach to labyrinthectomy in rats: anatomical description and clinical consequences.

UNLABELLED: Destruction of the inner ear in rats for medical research has been performed since 1936. Nevertheless, descriptions of the technique used and clinical analysis are poor and often involve coagulation of the stapedial artery. We suggest a description of a surgical ventrolateral approach to labyrinthectomy in rats, with preservation of the stapedial artery.
METHODS: Twenty-five Wistar rats were operated on via a right ventrolateral approach to the bulla, followed by labyrinthectomy with preservation of the stapedial artery. Clinical observation and tests were carried out from the time of the surgery until day one. Twenty-four hours after the surgery on the right side, the same surgery was performed on the left side, followed by clinical observation. Twenty-five other rats were used as controls, with sham surgery. Histologic analysis of the vestibular nerve with silver staining was performed in six rats 3 or 7 days after the labyrinthectomy.
RESULTS: The ventrolateral approach made it possible to reach the middle- and inner-ear with preservation of nervous and vascular elements such as the facial nerve and stapedial artery. Unilateral labyrinthectomy induced ocular skew deviation, head torsion and limb asymmetry. Dynamic signs were first rolling, then rotation, which increased considerably during tail suspension. Bilateral labyrinthectomy produces instability with major body oscillation. Animals show head and neck dorsiflexion with limb extension, sometimes followed by fast backward walking.
CONCLUSION: The ventrolateral approach is an efficient technique for surgical labyrinthectomy with stapedial artery preservation. Clinical analysis shows a wide range of signs to evaluate the functional destruction of the vestibular organ.