The Pterygo-Maxillary OR Zygomatic Fossa is a comparatively small space, bounded anteriorly by the zygomatic surface of the superior maxilla ; internally by the external pterygoid plate and pterygo-spinous ligament, which frequently ossifies ; posteriorly by a line from the foramen spinosum to the tubercle of the zygoma ; and externally by the zygomatic arch and ramus of the inferior maxilla. Above it is partially bounded by the great wing of the sphenoid and a small portion of the squamous of the temporal, and it is quite open below. It communicates anteriorly with the sphenomaxillary fossa by the pterygo-maxillary fissure (which is a vertical fissure between the superior maxilla and the external pterygoid plate), and with the orbit by the spheno-maxillary fissure (which is a horizontal fissure running at right angles to the pterygo-maxillary, separating the great wing of the sphenoid from the orbital margin of the maxilla). Above it is continuous with the temporal fossa beneath the zygoma, and below with the parotid region. Indirectly the space is continuous with the nasal fossa through the spheno-palatine foramen (from spheno-maxillary to nasal fossa), and with the cranial cavity through the sphenoidal fissure (from cranial cavity to orbit), and thus suppurative processes may find their way through it to or from the nasal, orbital, temporal, parotid, or cranial regions. Zygomatic abscess may point on the face, neck, or in the pharynx. The pterygo-maxillary fossa is occupied by the two pterygoid muscles and a small portion of the temporal, the internal maxillary artery and branches, the pterygoid venous plexus, and the third division of the fifth nerve.

The temporal muscle, which is inserted into the coronoid process of the lower jaw, is situated chiefly in the temporal fossa, and is covered externally by a dense fascia, the temporal fascia. This fascia is continuous above with the occipito-frontalis aponeurosis, which is attached along the temporal crest and covers the muscle as far as the zygoma, to which it is attached in two layers, a quantity of fat intervening between them. This fascia is very dense, and, like the occipito-frontalis aponeurosis, may, when cut through, give the sensation of broken bone to the examining finger. Anteriorly the deep fascia loses itself on the face, and posteriorly it forms the thin masseteric fascia and the thicker parotid capsule. Lying behind the temporal fascia and muscle is a quantity of fat, continuous with that in the pterygo-maxillary fossa, the absorption of which produces the prominent malar bone and zygoma seen in extreme emaciation. Fracture of the zygoma may be due to direct or indirect violence. There is generally little displacement, owing to the attachment of the temporal fascia above and masseter muscle below, but a fragment may be detached and driven into the temporal muscle, and cause pain on mastication. Abscesses in the temporal fossa tend to point in the pterygo-maxillary region or in the neck. The external pterygoid muscle runs backwards from its origins from the great wing of the sphenoid and external pterygoid plate, to be inserted into the neck of the lower jaw and the interarticular fibro-cartilage, and has the internal maxillary artery on its outer side, as a rule, while the branches of the third division of the fifth nerve surround it. The internal maxillary artery gives off the middle meningeal artery, which ascends through the foramen spinosum, at which point it is sometimes caught in fracture of the skull, and the inferior dental, which enters the inferior dental canal, and numerous muscular and other branches.

The pterygoid venous plexus is situated chiefly beneath the upper origin of the external pterygoid, its blood being removed by the internal maxillary vein. It forms a venous communication between nose, orbit, and cranium, including the cavernous sinus. The internal pterygoid muscle, arising from the deep surface of the external pterygoid plate and from the tuberosity of the upper jaw, is quadrilateral in form, and is directed downwards and backwards on the deep surface of the external pterygoid to the inner surface of the lower jaw near the angle.

The third division of the fifth nerve is joined by the motor root immediately after its exit from the foramen ovale. At this point it lies on the deep surface of the external pterygoid, and then breaks into two divisions, an anterior, which is almost entirely motor, and supplies the muscles of mastication, excepting the buccinator (which is supplied by the facial), and a posterior sensory, which gives off the auriculo-temporal nerve to the parotid gland, ear, etc.; the inferior dental, which supplies the teeth, and gives off a mental branch; and the lingual, which crosses between the ramus of the jaw and external pterygoid to the tongue, sublingual and submaxillary glands. While it supplies the tongue with sensation, it also has some taste fibres derived from the chorda tympani. The inferior dental nerve is sometimes divided for neuralgia, being reached .either through the mouth by a vertical incision along the inner side of the ascending ramus of the jaw or by trephining through the central point of the ascending ramus, and so reaching the nerve as it enters the canal. The lingual nerve is sometimes sectioned for the relief of pain and salivation in carcinoma linguae. It may be reached through the mouth by an incision inch below and behind the last molar tooth, or through the neck by an incision similar to that for ligature of the lingual artery, after which the capsule of the submaxillary gland is divided, the gland turned up, and the nerve found at the point at which it is connected with the submaxillary ganglion. The inferior maxillary trunk, and also the Gasserian ganglion, have been attacked through the pterygo-maxillary space. The zygoma is cut and turned down with the masseter, the coronoid process is cut and turned up with the temporal, and the external pterygoid is shelled from its attachments. If the Gasserian ganglion is to be attacked (Rose's operation), it is further necessary to trephine the skull close to the foramen ovale. In these operations haemorrhage from the internal maxillary artery and pterygoid venous plexus is generally very great, frequently necessitating postponement of the complete operation, and even ligature of the common carotid. The Gasserian ganglion has also been attacked by turning down a large flap of bone from the temporal region (Hartley-Krause method), but here also the haemorrhage is generally very great. Attention has already been drawn to the method of attacking the ganglion through an incision in the face (p. 13).