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In an antero-posterior skiagram of the skull, the light shadows formed by the ethmoidal cells are seen to occupy the well-defined area bounded on either side by the still lighter shadow of the orbital cavities and above by the dense horizontal shadow of the cribriform plate, which occupies the frontier line between these sinuses and the frontal sinuses. Anteriorly the ethmoidal area is overlapped by the vertical shadow caused by the frontal processes of the maxillæ and by the ridges of the lacrimals. Not infrequently the ethmoidal cells will be seen to extend into the roof of the orbit, while inferiorly and laterally they come into close relation to the superior and medial angle of the shadow formed by the maxillary sinus. The comparative transparency of the area of the ethmoidal cells is accounted for by the fact that it is superimposed upon that of the sphenoidal sinuses.
In a profile skiagram the ethmoidal area is seen to extend from the frontal process of the maxilla backwards across the orbits to the sphenoidal sinuses, with which they are contiguous. This area is crossed about its middle by the vertical shadow caused by the lateral margin of the orbit. In front of this, and occupying, therefore, the light area of the orbital cavity, are the anterior ethmoidal cells; while behind it are the posterior ethmoidal cells. In a profile view of the skull, the posterior ethmoidal cells, the sphenoidal sinuses, and the hypophyseal fossa all lie from before backwards in the axis of those rays which pass through the thinnest portion of the cranial box, namely, the anterior part of the temporal fossa; hence the possibility of being able to identify them even in a skiagram taken from a living subject.
The sphenoidal sinuses are so deeply placed behind the upper half of the piriform aperture of the nose that their outlines cannot be identified in an antero-posterior skiagram. If the sinuses be filled with bismuth before the skiagram is taken, it will be seen that they produce a well-defined and slightly oval black shadow, about the size of a shilling, situated opposite the superior half of the piriform aperture, the superior limit of the shadow reaching just up to the transverse curvilinear line already referred to, while laterally the shadow reaches cm. medial to the inferior half of the medial margin of the orbit (Logan Turner). In a profile skiagram of the skull the light shadow produced by the sphenoidal sinus is seen immediately inferior to and in front of the characteristic well-defined cup-shaped shadow formed by the concave floor of the hypophyseal fossa. Inferiorly the sinus area is bounded and to some extent overlapped and obliterated by the dense shadow which corresponds from latero-medially to the tuberculum articulare and the horizontal portion of the great wing of the sphenoid, that is to say, to the floor of the middle fossa of the base of the skull. This dark shadow is continuous, posteriorly, with that which is caused by the dense petrous portion of the temporal bone. Anteriorly is the shadow of the posterior ethmoidal cells (blurred by that produced by the vertical portion of the great wing of the sphenoid), while posteriorly it is limited by the shadow produced by that portion of the body of the sphenoid which lies inferior to the dorsum sellæ.
The topography of the sella turcica, which lodges the hypophysis cerebri, is of importance now that surgery has succeeded in dealing with certain tumours and enlargements of this organ. The fossa hypophyseos lies immediately behind the superior part of the sphenoidal sinuses, and, in a median sagittal section of the skull, the anterior half of the fossa is seen to project into what would correspond to the supero-posterior angle of the sinuses. The more the sphenoidal sinuses project backwards, beneath the sella turcica, the thinner is the plate of bone which separates the sinus from that part of the posterior fossa of the base of the skull which supports the pons. When, on the other hand, the sphenoidal sinuses are small and do not extend backwards below the sella turcica, the latter may be difficult to identify. In order to reach the hypophysis surgeons have abandoned the intra-cranial route, partly on account of the damage produced in the brain, and partly because, when the hypophysis
enlarges, it frequently does so by projecting downwards towards the sphenoidal sinuses rather than upwards into the cranial cavity.
The sphenoidal sinuses constitute the surgeon's guide to the hypophysis To reach them he traverses the upper portions of both nasal cavities, removing, from before backwards, the upper portion of the septum nasi, the superior and middle conchæ, and the anterior and posterior ethmoidal cells. The rostrum sphenoidale, situated at the superior and most posterior part of the nasal septum, serves as a guide to the anterior wall of the sphenoidal sinuses; after removing it the sinuses are opened up by removing their anterior walls and the septum. The hypophysis is then exposed by breaking down the anterior portion of the floor of the sella turcica, which forms a bullous-like projection into the superior and posterior part of the sinuses. In making the opening from the sphenoidal sinuses into the hypophyseal fossa, the surgeon must keep strictly to the median plane, so as to avoid opening into the cavernous sinus; if the roof of the sinus be penetrated in front of the fossa the optic chiasma would be injured and the cranial cavity opened, while if the posterior wall of the sinus be penetrated below the level of the fossa hypophyseos the spongy tissue of the body of the sphenoid would be opened into, and if the sinus happened to extend unusually far back, the anterior part of the posterior fossa of the base of the skull would be opened into opposite the basilar artery and the ventral surface of the pons.
According to Stanley Gibson, the average distance from the nasion to the anterior superior margin of the sphenoidal sinus is 13 inches, while the distance. from the anterior superior boundary of the sinus to the anterior superior margin of the sella turcica is a little more than inch, so that the total distance from the nasion to the hypophysis is from 2 to 2 inches. The average distance from the anterior nasal spine to the hypophysis is 78 cm. (practically 3 in.). The floor of the hypophyseal fossa is on a level with a plane projected backwards from the nasion to the inion. The fossa measures inch in its antero-posterior diameter.
In a profile skiagram of the skull, the outline of the cup-shaped sella turcica is marked out by a crescentic linear shadow, the anterior and posterior horns of the crescent being represented by the shadows of the anterior and posterior clinoid processes. Below and in front of the fossa the outlines of the sphenoidal sinuses may be distinctly traced. (Plate I.)
Enlargements of the hypophysis cerebri can often be clearly demonstrated by an increase in the depth and antero-posterior diameter of the skiagraphic outline of the sella turcica, and by the unusual extent to which the fossa encroaches upor the sphenoidal sinus.
The skin of the face is thin, vascular, and rich in sebaceous and sweat glands. it is intimately connected with the subcutaneous tissue, in which are imbedded the facial muscles as well as the main blood-vessels. Owing to its elasticity and to the presence of the main blood-vessels in the lax subcutaneous tissue, the face is an admirable site for plastic operations, as the flaps do not necrose in spite of considerable tension. The laxity of the tissues accounts for the marked swelling which attends œdematous and inflammatory conditions about the face. Whenever pos sible, incisions should be made along the line of the natural furrows and creases of the skin, so as to render the resulting cicatrix less noticeable.
The bony landmarks of the face which may be readily palpated are: the superciliary ridges and the glabella, the nasion (fronto-nasal junction), the bridge of the nose, the osseous piriform opening and the anterior nasal spine, the supra- and infra orbital margins, the zygomatic process of the frontal bone, the medial angular process the anterior part of the temporal crest, the zygomatic bone, the zygomatic arch, and the region of the canine fossa of the maxilla.
Immediately inferior to the root of the zygoma, and in front of the super part of the tragus, is the condyle of the mandible. By pressing with the point of the finger upon the condyle while the mouth is being widely opened, the bone will
elt to glide forwards, while the finger sinks deeply into the hollow corresponding o the mandibular fossa. The close relation of the first part of the internal maxillary rtery to the medial aspect of the neck of the mandible must be kept in mind in operations calling for disarticulation or excision of the condyle. The ramus of the nandible is sandwiched between the masseter and the pterygoid muscles, and can be removed without opening into the mouth. Passing downwards from the condyle, one can palpate the anterior and posterior borders of the ramus and the angle and body of the mandible. The anterior border of the coronoid process is felt n front of the upper part of the anterior border of the masseter, immediately below Che anterior part of the zygomatic arch.
The pulsation of the external maxillary artery may be felt as the vessel crosses the inferior margin of the mandible at the anterior border of the masseter, 11 in. in front of the angle of the mandible. To map out the course of the artery upon the face, draw a line from this point to a point in. lateral to the angle of the mouth, and thence to a point a little behind the ala nasi and along the side of the nose to the medial angle of the orbit. The anterior facial vein lies posterior to the external maxillary artery, and takes a straighter course from the medial palpebral commissure to the anterior inferior angle of the masseter. The vessel is devoid of valves, hence infective phlebitis and thrombosis are liable to spread along it to the cavernous sinus by way of the ophthalmic and pterygoid veins.
A line projected downwards from the supra-orbital notch (junction of medial and intermediate thirds of the supra-orbital margin) to the inferior border of the mandible opposite the interval between the two lower premolar teeth, will cross the infra-orbital and mental foramina, the former in. below the infra-orbital margin, the latter midway between the superior and inferior borders of the mandible. In performing the operation of neurectomy for the relief of trigeminal neuralgia, these foramina furnish the guides to the correspondingly-named branches of the fifth nerve. It should be remembered that the nerves in question, after emerging from, their respective foramina, lie, in the first instance, beneath the facial muscles. The supra-orbital and infra-orbital nerves are not infrequently represented each by two branches, one of which passes through an accessory foramen situated lateral to the normal opening. Neurectomy of the inferior alveolar nerve is performed by trephining the ramus of the mandible midway between its anterior and posterior borders, on a level with the crown of the last molar tooth, the nerve being reached as it enters the inferior alveolar canal: the lingual nerve, which lies a little anterior to the inferior alveolar, can be exposed through the same opening.
The relations of the maxillary and mandibular divisions of the trigeminal nerve have become of increased importance to the surgeon since the introduction of the treatment of trifacial neuralgia by the injection of alcohol into these nerves immediately after their exit from the cranial cavity. According to Symington, in order to reach the maxillary nerve as it lies in the pterygo-palatine fossa, the skin should be punctured immediately below the zygomatic arch, about 4 cm. in front of the anterior wall of the external acoustic meatus. The needle should be directed medially with a slight inclination upwards and backwards. After perforating the masseter and temporal muscles, the instrument enters the fatty tissue of the infra-temporal fossa, embedded in which is the internal maxillary artery and some veins. By passing the needle still more deeply, it is made to penetrate between the two heads of the external pterygoid muscle through the pterygo-maxillary fissure into the pterygo-palatine fossa. If the instrument be passed too far forwards it will strike the maxillary tuberosity; if too far backwards, the lateral pterygoid lamina. The cedema of the eyelids which not infrequently follows the operation is due to some of the fluid passing upwards into the orbit through the inferior orbital fissure. The distance from the skin to the nerve, as it lies in the pterygo-palatine fossa, is practically 2 in. Should the needle, after perforating the masseter, strike the coronoid process of the mandible, the latter may be depressed by opening the mouth.
The mandibular nerve is injected immediately beyond its exit from the foramen ovale, which lies 4 cm. from the skin in the same vertical frontal plane
as the tuberculum articulare. When the mouth is opened widely the condyle of the mandible travels forwards and can be distinctly felt immediately belowe the tubercle. To avoid entering the mandibular joint the needle is intro-s duced through the skin immediately below the zygoma, a little in front of the eminence. It is pushed medially and slightly backwards through the sigmoid notch of the mandible, and thence through, or immediately above, the external pterygoid muscle, into the nerve. Symington points out that "the chief dangers connected with this operation are dependent upon the needle being passed in too far. Thus, if it be directed straight inwards beyond the depth of the nerve (4 cm.) it would penetrate the tensor veli palatini and the auditory tube and open on the lateral wall of the naso-pharynx; or, if directed somewhat upwards, it might pass through the foramen ovale, and even reach the cavernous sinus and the internal carotid artery, as the medial boundary of the foramen slopes upwards and inwards."
The facial nerve, after emerging from the stylo-mastoid foramen, is embedded in the parotid gland, where it is superficial to the external carotid artery; the nerve can be rolled under the finger as it crosses the posterior border of the ramus of the jaw at the level of the lower margin of the tragus; incisions continued along the ramus above this point should be only skin deep if the nerve is to be avoided. To expose the trunk of the nerve an incision is made from the anterior border of the mastoid process to the angle of the mandible. Incisions upon the cheek should, whenever possible, be planned so as to run parallel with the branches of the nerve; these radiate from the inferior end of the tragus. The nerve may be paralysed by wounds of the cheek and by malignant tumours of the parotid, as also by intra-cranial and middle-ear lesions.
The parotid gland is surrounded by a fascial envelope, the strongest portion of which is continued from the deep cervical fascia over its superficial aspect to become attached to the zygoma (Fig. 1085); hence abscesses in the parotid tend to burrow deeply towards the pterygo-palatine fossa and the superior part of the pharynx (Fig. 1085); the pus should therefore be evacuated by Hilton's method, through an early incision over the angle of the mandible. A study of the relations of the gland explains the surgical difficulties which attend its complete removal.
The parotid duct can be rolled beneath the finger as it crosses the masseter, rather less than a finger's breadth below the zygoma. After winding round the anterior border of the muscle it soon pierces the buccinator, and opens into the mouth opposite to the second molar tooth of the maxilla. The duct corresponds to the intermediate third of a line drawn from the inferior margin of the concha to a point midway between the ala nasi and the margin of the upper lip.
Superficial to the parotid and a little in front of the tragus is the pre-auricular lymph gland, which is frequently found to be inflamed in children suffering from eczematous conditions of the eyelids, face, scalp, and external ear. In opening an abscess connected with this gland care must be taken to make the incision as low down as possible, so as to avoid the parotid duct.
The deep parotid lymph glands which lie partly in the substance of, and partly deep to, the inferior part of the parotid, form the highest group of the medial superior deep cervical lymph glands. They are especially liable to become infected secondary to tuberculous disease of the middle ear and to malignant affections about the root of the tongue, the fauces, and the naso-pharynx. In removing them it is generally impossible to avoid dividing the cervical branch of the facial nerve, which pierces the cervical fascia immediately below and behind the angle of the mandible. This nerve supplies the platysma and the depressor labii inferioris muscles, 80 that its division gives rise to inability to depress the lower lip on the affected side At the same operation some trouble may be caused by bleeding from the posterior facial vein and its divisions, which traverse the substance of the gland.
Eyelids. The skin of the eyelids, more especially of the upper, is very thin and connected with the orbicularis oculi muscle by delicate and lax subcutaneous tissue destitute of fat; hence the marked swelling which occurs in a "black eye" and in oedema of the lids. Along the anterior edge of the free margins of the lids are the eyelashes and the orifices of the sebaceous glands, suppurative inflammation of which gives rise to a "stye"; along the sharp posterior edge of the free margins
re the minute orifices of the tarsal glands. These glands, embedded in the deep urface of the tarsi, are seen through the palpebral conjunctiva as a row of parallel, ellowish, granular-looking streaks. From the deep position of the glands it follows hat the skin over a Meibomian cyst is freely movable, and that to reach the cyst an incision should be made through the conjunctival surface of the lid.
The palpebral conjunctiva is closely adherent to the ocular surface of the tarsi; at the fornix it is loose and contains small lymph follicles, which become hypertrophied in the condition known as granular conjunctivitis. The ocular conjunctiva is thin, transparent, and loosely attached to the sclera, so that in operating upon the eye a fold of the membrane can be picked up with forceps to steady the eyeball.
In inflammatory affections of the eye the state of those vessels which are visible gives important information as to the seat of the mischief. For example, in inflammation of the conjunctiva the posterior conjunctival vessels (derived from the palpebral arteries), scarcely visible normally, appear as a close network which fades away towards the corneal margin; these vessels move freely with the conjunctiva, and do not disappear under pressure. In superficial inflammations of the cornea the anterior conjunctival vessels (the most superficial of the terminal branches of the anterior ciliary arteries) are seen to spread in a freely branching manner into its superficial layers. In iritis and deep inflammations of the cornea there is a pink circumcorneal zone of vascular dilatation consisting of delicate straight vessels which disappear under pressure and do not move with the conjunctiva; they are the subconjunctival (episcleral) terminations of the anterior ciliary arteries; in health they are invisible.
Lacrimal Apparatus. The lacrimal gland, situated behind the lateral part of the supra-orbital margin, cannot be felt unless enlarged. By everting and raising the upper eyelid, the accessory (palpebral) portion of the gland is seen to project beneath the lateral third of the fornix, in which situation also the minute orifices of the lacrimal ducts may be detected. By gently drawing downwards the lower lid, the small punctum lacrimale is seen situated upon a slight papillary elevation of its margin about 4 min. from the medial palpebral commissure; the corresponding orifice of the upper lid is placed a little nearer the commissure. Normally the puncta are directed towards, and accurately applied to, the ocular conjunctiva immediately lateral to the lacrimal caruncle. By drawing the lids laterally the medial palpebral ligament is put upon the stretch, and can be felt as a narrow tense band passing transversely medially to be attached to the frontal process of the maxilla. The ligament is a guide to the position of the lacrimal sac, which it crosses a little above its centre. Continuous with the inferior end of the lacrimal sac is the naso-lacrimal duct, which passes downwards and slightly backwards and laterally, to open into the inferior meatus of the nose, under cover of the anterior end of the inferior concha. The lacrimal sac and naso-lacrimal duct each measure about in. in length; the latter is slightly contracted at its commencement and termination, and it is in these situations that pathological strictures of the duct are commonest. Spontaneous rupture of an abscess of the lacrimal sac almost invariably occurs just below the medial palpebral ligament; it is in this situation that the abscess should be opened, the incision being made a little lateral to the angular termination of the external maxillary artery.
The canaliculi lacrimales, which convey the tears from the puncta to the lacrimal sac, run for the first 1-2 mm. almost vertically to the free margins of the lids, and thence parallel to them. Between the canaliculi is the lacrimal caruncle. In the various morbid conditions which give rise either to misdirection of the puncta or to stricture at any part of the lacrimal drainage apparatus, overflow of the tears (epiphora) is the chief symptom. In passing a probe along a canaliculus the instrument, in consequence of the bend upon the duct, is passed at first vertically to the margin of the lid, and afterwards parallel to it, until the point is felt to strike against the medial wall of the lacrimal sac; to pass the instrument onwards along the naso-lacrimal duct the handle is rotated forwards and upwards through a quarter of a circle, and then pushed gently downwards and slightly backwards and laterally into the inferior meatus of the nose.