Lingual numbness and speech articulation deviation associated with temporomandibular joint disk displacement.

A prospective investigation of 208 patients with painful, arthrographically verified temporomandibular joint disk displacement revealed that seven patients (3%) demonstrated lingual numbness associated with speech articulation impairment. The speech disorder was characterized primarily by a distortion in the production of /s,r,d, and t/. The lingual numbness and the speech disorder had in all cases started in association with a painful onset of permanent displacement of the temporomandibular joint disk. Local anesthetic blocking of the auriculotemporal nerve eliminated both joint pain and muscle pain and normalized tongue sensitivity and speech articulation. Placebo injections of saline solution resulted in no change. The explanation of the phenomenon is that the course of the lingual nerve for these seven patients was through the lateral pterygoid muscle rather than mesial to the muscle bundles and that an arthrokinetic myospasm resulted in compression of the lingual nerve. In order to test the hypothesis that the condition of lingual nerve entrapment in the lateral pterygoid muscle does exist, the course of the nerve was studied at dissection in 52 specimens from 26 cadaver heads. In 49 of the specimens, the lingual nerve descended deep to the lateral pterygoid muscle as has been traditionally defined. However, in three specimens, the nerve passed through the inferior belly of the muscle, revealing the condition of lingual nerve entrapment.