Practical pathology

by Aldred Scott Warthin

5. Examination of the Orbit. When the eye-ball cannot be enucleated anteriorly the orbit may be opened by removing its roof with small bone-chisel and hammer according to the lines of incision given in Fig. [32]. The dura is, of course, first removed. The bony plate covering the orbit is thin and easily splintered, so that the chisel should be very carefully used. The pieces of bone should be removed with the forceps. The optic foramen and the superior orbital fissure may be opened at the same time. After the removal of the roof of the orbit the orbital fat and muscles are dissected away until the optic nerve and eye-ball are exposed. The sclera is then seized with the forceps and the eye-ball pulled back and cut quickly around its equator with sharp shears or scalpel. The head should be held so that the eye looks downward, so that when cut the vitreous humor falls out, leaving the retina well spread out over the posterior half of the bulb. If the retina is thrown into folds it may be straightened by blowing into it or filling it with water. After the retina has been examined it may be washed off from the chorioid, leaving it attached around the papilla. The pigment-layer remains attached to the chorioid, and when the latter is examined for the presence of tubercles it should be removed. When removed for microscopic studies the eye should be placed at once in a suitable fixing fluid.

Fig. 33.—Tympanic cavity after removal of tegmen. an, mastoid antrum; ha, hammer-anvil articulation; s, tendon of musc. tens. tymp.; t. musc. tens. tymp.; g, genu of facial nerve; a, auditory nerve; f, facial nerve; n, nerv. petros. superfic. major. (After Politzer.)

6. Examination of the Ear. The dura is removed from over the temporal bone and the tegmen tympani cut off with chisel and hammer as indicated in Fig. [32], 1, 2, 3, 4, 5, thus exposing the tympanic cavity as shown in Fig. [33]. When the tegmen tympani is very hard and compact the hammer and chisel are used to remove that portion of the tegmen lying laterally to the eminence formed by the upper semicircular canals. As the ear-ossicles lie immediately beneath the roof of the tympanic cavity care should be taken not to injure them with the chisel, and this can be best accomplished by beginning to chisel so far posteriorly that the tegmen of the mastoid antrum is first cut away, and from this opening the cut is extended carefully until the tegmen tympani is removed. When the tegmen of the tympanic cavity is very thin and porcelain-like, as is often the case, it may be most quickly and expediently removed by means of the pointed bone-forceps. A complete view of the tympanic cavity is obtained by removing the coverings of the mastoid antrum posteriorly and the bony canal anteriorly after first drawing out the musc. tensor tymp. from the canal. The mastoid process may be opened with the saw or with chisel and hammer. The labyrinth may be exposed by cutting anteriorly with the chisel held horizontally in such a way as to spring off the upper half of the bony labyrinth, exposing the vestibule and cochlea. The superior and posterior semicircular canals come off, and from their open spaces the membranous semicircular canals can be lifted out with the forceps and then examined in water.

The external auditory canal may be opened and the outer surface of the ear-drum examined by carrying the anterior flap of the scalp downward and forward until the entrance into the bony canal is reached. The external ear is then cut off close to the bone, using slight pressure so as to avoid tearing out the lining of the canal or injuring the tympanum. The anterior bony wall of the canal, and a part of the lower, are then carefully chiseled away until the membrane is exposed. Any bony projections on the thicker upper or lower wall of the canal may be trimmed off to give an unobstructed view. When pathologic changes are present upon any part of the wall of the canal the latter should be opened from the other side so as to expose the condition fully.

For the removal of the auditory apparatus and its examination outside of the body a number of methods are advised. The temporal bone may be resected by extending the scalp-incision half-way down the neck along the anterior edge of the trapezius. The anterior flap with the external ear is carried forward as far as the middle of the zygoma and below to the angle of the lower jaw. The posterior flap is carried backward to the middle of the occipital bone. All soft parts are cut as closely to the bone as possible. A saw-cut is now made across the posterior cranial fossa, beginning just behind the mastoid process and extending to the median line of the clivus half-way between the anterior border of the foramen magnum and the sella turcica. The sinus sigmoideus is thus included in the part to be removed. A second saw-cut is then made across the middle cranial fossa, in a line nearly parallel with the transverse diameter of the skull, cutting the middle of the zygomatic arch, the anterior portion of the squama, the great wing of the sphenoid and the pterygoid process, to the tuberculum sellæ. The median ends of the two saw-cuts are then united by a chisel-cut in the median line of the sella and clivus. All bony connections remaining are then cut with the chisel. The soft parts are then cut, beginning with those attached to the mastoid process; the loosened bone is then raised and pulled anteriorly so that the posterior capsule of the maxillary joint can be cut and the jaw-bone disarticulated. All remaining soft parts of neck and nasopharynx are now cut and the temporal bone with the complete ear-apparatus and neighboring portion of nasopharynx is removed. When both temporal bones are removed the saw-cuts should not be carried to the median line, but should stop at the borders of clivus and sella, and then united on each side by sagittal chisel-cuts made along these borders, leaving the clivus and sella as a firm connecting bridge between anterior and posterior portions of the skull. The resected bone may now be examined by means of a saw-cut made perpendicularly through the apex of the eminence of the superior semicircular canals and parallel with the crista of the petrous bone. The tegmen should be removed before the saw-cut is made and the covering of the tympanic cavity and the outer wall of the external auditory canal also removed. The tendon of the tensor tympani is cut and the anvil-stapes articulation severed so that the saw-blade passes between the drum, hammer and anvil on one side and the head of the stapes on the other without damaging or displacing the ossicles. This can be accomplished by pushing outward the drum with hammer and anvil so that the saw-blade can pass between the anvil and the head of the stapes. The bone should be held in a vise and a fret-saw used. On one side of the cut will be seen the drum, hammer, anvil and anterior portion of the mastoid cells; on the other the stapes, wall of the labyrinth and posterior half of the mastoid cells. The Eustachian tube may be easily worked out from the tympanic cavity or from the pharyngeal opening.

A sagittal section of the middle ear may be made, giving pictures as shown in Figs. 34, 35. The temporal bone is resected as above, the tegmen tympani removed and the bony covering of the Eustachian tube removed with hammer and chisel until the tube is exposed from its pharyngeal opening to the isthmus. The temporal bone is then divided into an outer and an inner half by cutting the roof of the tube with fine straight scissors from the pharyngeal mouth to the bony portion and then cutting the membranous floor of the canal likewise. The bony canal, the floor of the tympanic cavity and the mastoid process are then cut sagittally with a fine fret-saw, passing between the lower annular segment of the sulcus tympani and the inner wall of the tympanic cavity. By altering the direction of the saw-cut the Eustachian tube may be removed in connection with either outer or inner portion of the temporal bone.

Fig. [34].—Sagittal section through left middle ear, outer half. an, mastoid antrum; n, niche of the hammer-anvil body; op, mouth of Eustachian tube; te, Eustachian tube; it, isthmus of tube; mt, tympanum; ww, mastoid cells. (After Politzer.)