Medial rectus muscle palsy after dental anesthesia.

A 42-year-old woman developed a transient partial third cranial nerve palsy after a supraperiosteal injection in the area of the middle superior alveolar nerve with mepivacaine HCl for dental anesthesia. This effect may have been caused by direct extension through a bony defect rather than by inadvertent intravascular injection of the anesthetic. Dentists and ophthalmologists should be aware of this phenomenon, which can result in permanent ocular palsy and even amaurosis.