62 



APPLIED ANATOMY. 



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, how- 

 ever, 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 



Ophthalmic 



Ophthalmic- 



Maxillary 



FIG. 70. Diagrams showing distribution of cutaneous branches of trigeminal and cervical spinal nerves (Piersol). 



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). 



Gushing 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 hem- 

 orrhage, 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 mandib- 

 ular 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. i, 1904, p. 943). 



