Microneurovascular allotransplantation of the canine tongue

Introduction: Reconstruction of the tongue with existing methods of tissue transfer often leaves glossectomy patients with significant deficits in spe ech and swallowing. The critical role of the tongue is implied by its uniqu e structure and function. This paper reports the development of an animal m odel of hemitongue allotransplantation and documents functional and anatomi c outcomes of this procedure. Methods: Ten pairs of unmatched clogs underwe nt reciprocal exchange of the left hemitongue with microneurovascular repla ntation. The unoperated hemitongue acted as the control. Under cyclosporine immunosuppression, animals surviving long term underwent clinical observat ion, before electromyography, force transduction studies, and histological evaluation being euthanized. Results: Five animals survived between 6 and 1 3 months for long-term evaluation. The remaining group were euthanized beca use of or died of overwhelming infection or uncontrollable transplant rejec tion. The latter sometimes resulted from difficulty in the delivery of the cyclosporine. Clinical recovery of tongue function was observed, as well as resumption of motor unit potential activity on electromyography. Contracti le force recovery of the transplanted tongue averaged 68% of control (range , 47%-97%), and histological study of the hypoglossal and lingual nerves de monstrated anatomic evidence of reinnervation. Preservation of muscle, muco sal, and stromal ultrastructure was seen with light microscopy of the trans planted tongue. Conclusions: Allotransplantation of the hemitongue and asso ciated neurovascular apparatus is possible in a large mammalian model, with long-term survival of tissue being accompanied by partial recovery of cont ractile properties. Anatomical and clinical evidence also points to sensory recovery. These data support the future possibility of employing a similar technique in glossectomy patients.