THE FACE 1345 



Sensory nerves. — The cutaneous nerve areas of the face are shown in fig. 774. 

 The supraorbital nerve, the main sensory branch of the ophthalmic, emerges from 

 the orbit with its companion artery through the notch (occasionally a foramen) 

 at the junction of the medial third and lateral two-thirds of the supraorbital 

 margin. A line drawn from the supraorbital notch downward across the interval 

 between the bicuspid teeth will cross the infraorbital foramen from which emerges 

 the infraorbital nerve, the main terminal division of the maxillary, at a point 

 1 cm. below the orbital margin. The mental foramen, the point of exit of the 

 mental nerve, a branch of the inferior alveolar, is found on a prolongation of the 

 same line midway between the upper and lower margins of the mandible in the 

 adult. In the infant in whom the alveolar element of the jaw is relatively 

 large, the mental foramen is nearer the lower margin, while in the edentulous 

 jaw of old age it is found much nearer the upper margin. 



In trephining to expose the inferior alveolar (dental) nerve, one of the common 

 seats of neuralgia and one in which a peripheral operation is justified from the 

 results, the ascending ramus is opened midway between its anterior and posterior 

 borders, on a level with the last molar. 



The semilunar ganglion lies at a depth of 5.5-6 cm. (2j in.) u^der the eminentia articularis 

 at the base of the zygoma. In exposing it for the purpose of excision for intractable nem-algia 

 the following structures are encountered: (1) Skin and superficial fascia with branches of the 

 superficial temporal artery; (2) temporal fascia and muscle with deep temporal vessels; (3) 

 squamous bone and great wing of sphenoid, which are trephined, the floor of the middle fossa 

 being gouged away; (4) middle meningeal vessels and dura mater. By elevating the dura mater 

 and superimposed temporal lobe, and securing the middle meningeal artery, the ganglion is 

 exposed, lying in a separate compartment [cavum Meckelii] of the dura, which contains cerebro- 

 spinal fluid. The motor nerve of the muscles of mastication lies on the lower and medial 

 aspect of the ganglion, and should not be divided. 



Injection of the mandibular nerve with alcohol, by means of a long stout hypodermic needle 

 is practised in cases of intractable neuralgia as an alternative to excision of the semilunar gang- 

 lion. A vertical line is drawn on the cheek downward from the junction of the posterior and 

 middle thirds of the zygomatic arch, and the needle is entered on this line at a point 1.5 cm. 

 from the lower border of the zygoma. It is directed upward and medially so as to pass through 

 the lowest part of the mandibular notch. If the mouth is opened the notch is depressed and more 

 room gained. The needle impinges first against the inferior surface of the great wing of the 

 sphenoid bone, and when the point is lowered a little it engages in the foramen ovale at a depth 

 of 4-4.5 cm. In most cases the needle can be passed through the foramen ovale into the semi- 

 lunar ganglion. (Harris.)* 



The maxillary nerve may be injected by passing a needle along the floor of the orbit from its 

 infero-lateral angle in a direction backward and sUghtly medially to the foramen rotundum 

 which lies 4.5 cm. from the surface. 



Facial nerve. — In the petrous bone the course of this nerve is first outward 

 and forward, then, having entered the facial canal, backward and downward 

 along the medial wall of the tympanum, above the fenestra ovalis. Emerging 

 from the stylo-mastoid foramen the nerve takes first the line of the posterior 

 belly of the digastric, running forward and a little downward from the anterior 

 border of the mastoid where this meets the auricle. (Godlee.) Entering at 

 once the posterior part of the parotid, it crosses the neck of the mandible at the 

 level of the lower border of the tragus. 



The frequent paralysis of this nerve may thus depend upon — (1) cerebral causes; (2) dis- 

 ease of or injury to the petrous portion; (3) affections after its exit — ^Bell's paralysis. A diag- 

 nosis may be arrived at by attention to the foUownng. In cerebral disease the lower part of the 

 face is chiefly affected, the eyelids usually escaping. In all the other forms the whole side of 

 the face is paralysed. Hemiplegia of the opposite side of the body and paralysis of the sixth 

 nerve are usually present. In petrous paralysis, owing to involvement of the chorda tympani, 

 there may be interference with the saliva and taste, affecting especially the anterior part of the 

 tongue. The auditory nerve may also be affected. Here and in (3) there will be a history of 

 disease or injury. In complete paralysis the smooth side of the face and forehead, the absence 

 of power of expression, to frown, to blow, or whistle, the open eyelids and epiphora, and subse- 

 quent liability to mischief in the cornea, the dropping of the angle of the mouth and dribbling 

 of saUva, the interference with mastication from paralysis of the buccinator, are the chief points. 



Mandible. — Dislocation of the temporo-mandibular joint is referred to on 

 p. 217. In the usual dislocation, from muscular action, the jaw is suddenly 

 brought forward against the anterior part of the capsule, which tends, by the 

 action of the depressors, to give way; the elevators then pull up the mandible, a 

 sequence that must be remembered in reduction. In the commonest fracture of 



♦Lancet, Jan. 23, 1912. 



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