A rare local anesthetic misadventure. Case report and anatomic considerations.

When the mouth is fully opened, the depth to which the needle is inserted need not be great in order to pass through the submandibular gland capsule, and insertion of the needle behind the second molar tooth would result in passage behind the posterior border of the my-ohyoid muscle. The discussion indicates the relative ease with which fluid may penetrate the parapharyngeal space, particularly if pressure is used in injecting. Fluid diffusing into the region of the carotid triangle may have been responsible for the various symptoms, and anesthesia of the hypoglossal nerve, nerve, thyrohyoid nerve, internal and external laryngeal nerves, and carotid body possibly occurred. Anesthesia of the vagus is a remote possibility.