Operating From The Side Through The Pterygoid Fossa

Both the maxillary and mandibular branches have been reached by this route; the former at the foramen rotundum and the latter at the foramen ovale. Lücke, of Strasburg, was the pioneer of the operation on the maxillary nerve, and Joseph Pancoast, of Philadelphia, on the mandibular. Lücke's operation was modified by Lossen, of Heidelberg. Recently, Mixter, of Boston, has again advocated the method. A convex flap, base down and reaching 1/2 inch below the zygoma, is cut from the external margin of the orbit to the lobe of the ear. The zygoma is sawed through, and, with the masseter, pulled downward. Maurice Richardson, in describing Mixter's operation (Internal. Textbook of Surg., vol. i, p. 863), says that "if the operator is skilled enough in the subsequent manipulations, he may omit cutting the temporal muscle." It will be easier, however, to divide the coronoid process and turn the temporal muscle upward, clearly exposing the infratemporal crest. Detach the upper head of the external pterygoid muscle and push it downward, exposing the external pterygoid plate. Chisel off the spur at the anterior extremity of the infratemporal crest, and immediately in front and to the inner side is the superior maxillary nerve, with the terminal portion of the internal maxillary artery just below it. Immediately posterior to the root of the pterygoid plate is the foramen ovale and mandibular nerve, with the middle meningeal artery a little posterior to it.

Anatomical Comments

The incision at its posterior extremity can be made to avoid cutting the temporal artery by feeling its pulsations, about a centimetre or less in front of the ear, as it passes over the zygoma. The incision should not involve the deep structures - only the skin and superficial fascia. Therefore, the facial nerve and parotid duct (a finger's breadth below the zygoma) will not be injured.

In clearing the upper surface of the zygoma, it will be necessary to cut through the layers of the temporal fascia; between them the orbital branch of the temporal artery may be encountered and may bleed. The temporal muscle arises not only from the deep layer of the temporal fascia, but may also be attached anteriorly to the inner surface of the zygoma, and in loosening it free bleeding from the deep temporal arteries, branches of the internal maxillary, may be encountered. No trouble need be expected in sawing through the anterior end of the zygoma, but care should be taken not to injure the parotid duct, or the socia parotidis if it is present. In making the division of the posterior end of the zygoma, one must guard against opening the temporomaxillary articulation, for, when the head of the mandible is back in the glenoid fossa, the capsule of the joint extends considerably in front of it. Therefore, it is better to open the mouth and push the jaw on that side forward until it rides on the eminentia articularis, then the anterior limit of the joint can be recognized and avoided. Before one can reach the spur on the anterior extremity of the infratemporal crest, the temporal muscle must be detached from the bone. The upper head of the external pterygoid muscle arises from the bone just below the pterygoid ridge (infratemporal crest), and must be loosened from the bone to obtain access to the nerves (see Fig. 67).

Fig. 67.   Operating through the pterygoid fossa. The skin with the zygoma and masseter have been turned down. The coronoid process is divided and turned up. The upper head of the external pterygoid has been detached and turned down. The maxillary nerve is in front of the pterygoid plate (processus pterygoideus) and the mandibular nerve and middle meningeal artery just behind it.

Fig. 67. - Operating through the pterygoid fossa. The skin with the zygoma and masseter have been turned down. The coronoid process is divided and turned up. The upper head of the external pterygoid has been detached and turned down. The maxillary nerve is in front of the pterygoid plate (processus pterygoideus) and the mandibular nerve and middle meningeal artery just behind it.

The coronoid process rises almost as high as the infratemporal crest, and, therefore, in order to gain space it will be necessary to depress the jaw. Running upward and inward over the internal pterygoid muscle, and passing just in front of the origin of the upper head of the external, is the internal maxillary artery and pterygoid plexus of veins. These vessels lie directly below the maxillary nerve as it crosses the sphenopalatine fossa, and it is to be expected that free hemorrhage will accompany the attempt to fish out the nerve.

In operating in this region, one surgeon found the bleeding so severe as to require the ligation of the external carotid artery.

Intracranial operations are hardly ever done for maxillary neuralgia alone. The mandibular and often the ophthalmic divisions are also usually affected in cases requiring to be approached from the inside of the skull.