Reanimation of the hemiparalytic tongue.

Abstract

Tongue hemiparesis is the inevitable result when the freshly severed 12th nerve is anastomosed to the trunk of a paralyzed 7th nerve in the technique commonly used by neurosurgeons, head and neck surgeons, otologists, and plastic surgeons to treat unilateral facial paralysis. This author has reactivated hemiparalytic tongues after research on cats. The technique has now been proved to be successful on two human beings. The reanimation is based on a simple Z-plasty of tongue muscle across the midline. Two principles are established: (1) placing a normal muscle in direct contact with a denervated muscle stimulates axons from the normal side to penetrate into the denervated side, eventually restoring function, and (2) transposition of a flap of muscle from the normal side containing extrinsic tongue muscles could provide a motor apparatus to activate the paralytic side. Biopsy slides taken from the paralyzed side of the cat tongues after 18 months showed sprouting of multiple nerves. Nerve sprouting can be found in human tongues 1 year after Z-plasties. The two patients who experienced atrophy and hemiparesis after the 12th-7th nerve hookup regained full range of tongue movements by 2 months and 4 months, respectively, demonstrating that with time, motor axons from the normal side innervated the atrophic muscle side to form new neuromotor junctions resulting in tongue movements. EMGs of the reanimated tongue showed normal activity in both sides of the tongue. Biopsies of the interface between the normal and former paralyzed side taken 1 year later showed nerves crossing the scar barrier. Apparently, the role of additional extrinsic muscle to the paralyzed side played a minor role.