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.
Neuralgia involving the face below the line of the mouth, the lower teeth, and side of the tongue requires the removal of the inferior dental and lingual nerves. To do this, a curved incision following the lower edge of the mandible is made. It ends anteriorly in front of the mandibular foramen, and posteriorly it stops a centimetre below the ear to avoid wounding the facial nerve. The masseter muscle is raised from the bone, and, with the parotid gland, is drawn up. The ramus of the jaw is trephined in its middle, rather high up toward the coronoid notch. The outer table of bone is then to be chiselled off, from the trephine opening as far down as the mental foramen. A delicate, curved, haemostatic forceps is then made to grasp both nerves through the trephine opening, and on rotating very slowly the nerves are wound around the forceps and are gradually torn loose from the base of the skull above to their ultimate branches below (see Fig. 68).
Fig. 68. - Excision of the lingual and mandibular (inferior dental) nerves.
The Gasserian ganglion lies in its capsule, formed by a splitting of the dura, on the anterior surface of the apex of the petrous portion of the temporal bone and on the root of the greater wing of the sphenoid. From its posterior extremity, which rests on the ridge separating the anterior and posterior surfaces of the petrous portion of the temporal bone, to the foramen rotundum anteriorly is 2.5 to 3 cm. (1 to 1 1/4 in.). The foramen ovale, which transmits the third or mandibular branch is midway between these two points, and corresponds on the outside of the skull to the eminentia articularis or root of the zygoma. Therefore, in removing the ganglion one works not only inward but also backward. Rose first operated on the ganglion from below. He removed the zygoma and coronoid process, ligated the internal maxillary artery, and trephined the skull in front of the foramen ovale. This operation was succeeded by that of Hartley and Krause. They went in through the temporal fossa. A large horseshoe-shaped flap, with its base above the zygoma, was cut and deepened with chisels through the bone to the dura. This was elevated by breaking across its base, and turning it down. The dura was then lifted from the base of the skull, and the maxillary and mandibular nerves recognized as they passed into the round and oval foramina. The capsule having been incised, these were seized with forceps, and as much of the ganglion as possible torn away.
Other surgeons, like Doyen, Quenu, Poirier, and Cushing, have combined these pterygoid and temporal routes. The bone flap, as made by Hartley and Krause.
embraced the region of the pterion or junction of the coronal with the temporo-sphenoidal sutures. As the bone was lifted from the dura at this point the middle meningeal artery was torn and troublesome bleeding ensued. Also the point of its breaking was too uncertain. Sometimes it broke too high up, sometimes too low down involving the base. It was also found unnecessary to replace the bone as the cavity left was filled up with fibrous tissue. For this reason Tiffany, of Baltimore, advocated the making of an opening in the skull above the zygoma with a trephine or gouge and mallet, and enlarging it with the rongeur forceps; the bone was not replaced. This is the procedure now used.
The operators who used the pterygoid route, by displacing the zygoma downward, were enabled to approach the ganglion from below instead of from above, therefore, a high temporal section of the bone was unnecessary and it has been abandoned; the bone section keeping below the pterion and not wounding the middle meningeal artery thus avoids hemorrhage from that locality. Cushing (Journ. Am. Med. Assoc., April 28, 1900) showed that the extensive removal of bone on the base of the skull was unnecessary, and that a displacement of the zygoma and temporal muscle downward, and removal of the bone down to and including part of the infratemporal crest gave sufficient access. Murphy found it unnecessary to resect the zygoma, and this has been our experience.
Fig. 69. - The upper portion of the illustration shows the operation of removal of the Gasserian ganglion (ganglion semilunare). The lower portion shows the pterygoid muscles.
One of the main difficulties has been the question of bleeding. It has caused death and not infrequently has necessitated the packing of the wound and the deferring of the completion of the operation for two or more days. This bleeding came from the soft parts, the bone, the middle meningeal artery, the veins running from the dura mater to the bone, the cavernous sinus, and the blood-vessels to the ganglion itself. These as given by Cushing are a branch from the middle meningeal soon after its entrance to the skull, a small branch from the carotid, a small branch from the ophthalmic, the small meningeal through the foramen ovale, and occasionally one through the foramen rotundum. He calls attention to the septa in the cavernous sinus as rendering wounds to it less serious than they otherwise would be. If the skin incision is cast too far back, the temporal artery may be cut in front of the , ear. Its position can be determined by its pulsation. It or its branches are divided in the upper portion of the incision and bleeding is very free. Division of the temporal muscle is followed by hemorrhage from the deep temporal. The bleeding from the bone is usually not troublesome, but the general oozing from the veins of the dura mater as it is detached from the bone is sometimes free. If an osteoplastic (bone and skin) flap is raised, the middle meningeal will be torn at the pterion. This is a large vessel and bleeds freely. It may also be torn, while isolating the mandibular division of the nerve, at the foramen spinosum. This foramen is usually a couple of millimetres posterior and to the outer side of the foramen ovale and generally the nerve can be isolated without injuring the artery. In some cases, however, the artery lies so close to the nerve that it is almost certain to be torn. The posterior portion of the ganglion lies on the carotid artery in the middle lacerated foramen, of course separated by a layer of dura mater. Care should, therefore, be taken not to injure the carotid artery. The cavernous sinus has often been injured. This occurs principally in those cases in which it is attempted to excise the ophthalmic division. It is to be avoided by working from behind forward instead of attempting to attack it laterally. Bleeding from the middle meningeal artery can be avoided by biting the skull away with the rongeur forceps and refraining from detaching the dura from the bone where the artery enters it (see Fig. 23).
Fig. 70. - Diagrams showing distribution of cutaneous branches of trigeminal and cervical spinal nerves (Piersol).
Cushing states that he makes an opening in the bone only 3 cm. in diameter. Such a small opening is used when the zygoma has been divided and pushed down or removed. Fowler and others have resorted to a preliminary ligation of the external carotid artery. This, while obviating to a great extent troublesome hemorrhage, cuts off the blood supply to the flap and sloughing has followed. In order to overcome this objection, the writer (Journ. Am. Med. Assoc, April 28, 1900) after ligating the external carotid artery above its posterior auricular branch made a temporal skin flap with its base up. The temporal muscle was then divided and turned down and the bone removed with the trephine and rongeur. Haemostasis was perfect and no ill effects followed the ligation.
It is comparatively easy to isolate the maxillary and mandibular divisions of the nerve. This having been done, the capsule of the ganglion is opened by a cut joining the two. A blunt dissector is then introduced and the upper layer of the dura, less adherent than the lower, is raised from the ganglion. The blunt dissector is then worked beneath the ganglion beginning between the maxillary and mandibular divisions and it is loosened from behind forwards. The sixth nerve is in such close relation to the ophthalmic that a temporary paralysis of it usually follows, causing internal squint. Anaesthesia of the whole side of the face from just in front of the ear to the median line follows complete removal. Frazier and Spiller have divided the root posterior to the ganglion instead of removing the ganglion itself (Journ. Am. Med. Assoc., Oct. 1, 1904, p. 943).