This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The pain involves the cheek from the eye to the mouth and as far forward as the median line, also the upper gums and hard palate. The operations devised for its relief are both numerous and intricate, and necessitate an accurate anatomical knowledge of the parts. The maxillary-nerve is the second division of the fifth cranial nerve. It leaves the skull cavity by the foramen rotundum, then crosses the sphenomaxillary fossa, enters the sphenomaxillary fissure and infra-orbital canal to emerge on the cheek, opposite the middle of the lower edge of the orbit and about 6 mm. below it. The intracranial portion is 6 to 8 mm. in length. From the sphenomaxillary fossa to the infra-orbital foramen is about 5 cm. (2 in.). Its branches are as follows: one or two small branches to the dura mater, the orbital or sphenomalar branch to the cheek and anterior temporal region, sphenopalatine branches going to Meckel's ganglion, the posterior, middle, and anterior dental to the upper teeth, and the terminal branches, labial, nasal, and palpebral, on the face.
Its anterior portion has been removed through an incision on the face, and its posterior portion with Meckel's ganglion has been operated on either anteriorly through the maxillary sinus or laterally through the temporal fossa, after removing the zygoma. The writer has removed the intracranial portion by entering the anterior cerebral fossa through the temporal region. Removal of the infra-orbital portion of the nerve is so liable to be followed by recurrence of the pain and interferes so much with the more complete procedures, as it destroys the guide (the nerve itself) which leads the operator to Meckel's ganglion, that it is doubtful whether it should ever be resorted to. The posterior dental branches are given off so far back that they are not apt to be removed in this operation.
Fig. 65. - Exposure of the infra-orbital nerve and artery.
An incision 3 cm. in length is made along the lower edge of the orbit. This divides the orbicularis palpebrarum muscle. Arising from the bone, between the infra-orbital foramen and the edge of the orbit, is the levator labii superioris muscle. This should be carefully detached, and the foramen with its artery and nerve will be found opposite the middle of the lower edge of the orbit and about 6 mm. (1/4 in. ) below it, on a line drawn from the supra-orbital notch to between the premolar teeth. The position of the foramen having been located, the palpebral ligament and periosteum are divided and the contents of the orbit raised. The canal is next to be opened. This can be done either by chiselling away its roof from the opening on the face and following it backward or by breaking through its upper wall. This latter procedure is liable to give trouble, because if the track of the canal is not encountered the instrument breaks into the maxillary sinus, the roof of which is very thin. The infra-orbital canal does not pass directly backward but backward and outward, striking the sphenomaxillary fissure about 2 cm. (in a large skull) behind its anterior extremity. Sometimes the roof of the canal is fibrous, in which case the groove so formed can be readily felt, but in others it is bony. The nerve is hooked up and cut as far back as one can, so as to remove, if possible, the posterior dental branches. The terminal branches are then pulled off from the cheek, and the nerve drawn out from the front. It is in the highest degree desirable to avoid wounding: the artery, as death is said to have followed it. and there may be bleeding into the orbit, causing protrusion of the eye and serious interference with its sight. A better way of removing the nerve, the method of Thiersch ( Verhand. der Deutschen Gesell. fur Chir., 18 Congress, Berlin, 1889, p. 44), is to grasp it with a pair of slender, curved forceps, then by rotating the forceps very slowly (about 1 turn a minute) both the distal and proximal ends are wound around it and an extremely long portion of the nerve can be removed.
Fig. 66. - The fifth or trifacial nerve with its various branches.