Practical pathology

by Aldred Scott Warthin

After the removal of the posterior wall of the spinal canal the peridural adipose tissue and the dural sac are exposed in the canal. The cord may now be removed with dural sac intact, and when the cord is soft this should be done, but in so doing the spinal fluid is likely to be lost; and, as it is very important to obtain a knowledge of the amount and character of this fluid, care should be taken to preserve it. With the block placed under the cervical region to keep the cervical and dorsal vertebræ higher than the lumbar the dural sac may be opened in the median line from above downward. The cervical dura is grasped with a pair of forceps and lifted so that a cut can be made in it with the small bent, probe-pointed shears. The blunt probe-point is then introduced into the subdural space and the dura cut in the median line downward toward the sacrum. With care the arachnoideal sac with its fluid may be preserved intact. What fluid there is in the subdural space will collect in the lumbar region and may be secured while the lumbar dura is cut. The fluid in the subarachnoideal space will likewise collect in the lower portion of the cord, and it is best at this stage of the operation to introduce a sterile pipette through the delicate arachnoid and draw up the fluid, preserving it for bacteriologic and microscopic examination.

The thirty pairs of spinal nerves are now cut from above downward, beginning on the right side. The cut edge of the dura or a dural fold, if the dura is left uncut, is seized with the dissecting forceps and pulled over to the left, so that as much of the nerve can be secured as possible. A long, narrow, sharp-pointed scalpel is inserted, outside of the dura, into the intervertebral foramina, as far as possible, and the nerves are cut while traction is made upon the dura to the opposite side. The same procedure is then carried out upon the left side. When all of the spinal nerves are cut, the scalpel is introduced in the spinal canal upward, as near to the foramen magnum as possible, and the cord and dura are cut transversely. The cord should be held by the dura; direct pressure with forceps or fingers upon the soft substance of the cord should never be made. If the forceps cannot be used to hold the dura with advantage, then the cord enclosed in the dural sac may be gently but firmly held in the palm of the left hand and lifted and drawn downward towards the sacrum with the greatest care. As the cord is removed the fibrous attachments between the dura and the longitudinal fascia of the anterior wall of the canal are cut with the small scalpel by means of oblique cuts upon the bodies of the vertebræ. Any fragments of bone impeding the removal of the cord should be trimmed off with the bone-forceps. The forcing of the cord through a tight aperture in the open canal may ruin that portion of the cord. In some cases it may be better to sever the dura and cord at the sacral end, below the cauda equina, and remove it toward the head, using the same method of holding the dura, and cutting the spinal nerves and peridural tissue. When this is done the importance of saving the spinal fluid should be borne in mind. Some prosectors prefer to sever the dura and cord above before cutting the spinal nerves, and to cut these and the epidural fascia while removing the cord. An experienced operator may save time in this way, but there is greater danger of injuring the cord. The cord may also be removed by severing the spinal nerves and vessels inside of the opened dura and lifting the cord out of the dura, but it is more likely to be damaged by this method. When the brain has been removed before the cord the dural attachments as high as the foramen magnum should be severed and the cord removed up to the point where it was severed from the brain. If it is desired to remove the cord attached to the brain, the cord is first loosened throughout its length from below up to the foramen. It is then carefully protected while the skull is opened; and after the brain-connections have been severed it is drawn up through the foramen as the brain is lifted out of the skull. After its removal from the body the cord is stretched out upon table or board and the dura opened in the median line both anteriorly and posteriorly, if the latter cut was not made before its removal from the body. If it is desired to make sections of both cord and dura for microscopic study the dura may be left uncut or attached to the cord after it has been opened in the median line. It then helps to hold the pieces of cord together after the latter has been cut. Otherwise the dura may be removed from the cord by cutting the nerve-roots and denticulate ligaments on both sides. The cord is now examined by making transverse cuts through it with a clean knife which is dipped into clean water before each cut. The cord is allowed to hang over the index-finger of the left hand while the knife is drawn across it, severing it down to the underlying pin which is left uncut to hold the pieces together. The cuts are usually begun in the cervical region and are made at the level of the spinal nerves. When the dura is left attached to the cord it may be laid back and the cord cut within it, or if it has not been opened, the cuts may be made through it and the cord at the same time, if a very sharp knife is used. Areas of softening should not be cut, but should be preserved intact for examination after fixation and hardening. If the segments of cord are left attached to the dura or pin the cord and membranes may be fixed and hardened en masse so as to permit future orientation.

Examination of Cord Anteriorly. After the complete examination of the neck, thoracic and abdominal organs the spinal column is divested of all remaining tissues, including the psoas muscles. A block is then placed beneath the lumbar vertebræ. With the belly of the cartilage-knife held transversely across the spinal axis the intervertebral disks on both sides of the next-to-the-last lumbar vertebra are cut down to the level of the canal. If the lumbar vertebræ are sufficiently elevated by the block placed beneath the abdomen, the cutting of the disks allows the neighboring vertebræ to spring away, so that the body of the vertebra thus separated can be cut out by the bone-forceps or chisel. The spinal canal is thereby exposed; so that the Brunetti chisels may now be used in cutting the pedicles and stripping off the vertebral bodies. As this stripping progresses upward the block is moved toward the head so that the cutting is always down hill. The chisels are driven through the pedicles of five or six vertebræ at a time; the handle is forced down until the long chisel-blade is nearly parallel with the vertebræ. At the same time the cutting-edge must be sent forward at a uniform level, just high enough to expose the canal. If the cut is too high the chisel will enter the body of the vertebra, if too low the probe-point will be pushed into the cord. When the cervical vertebræ are being cut the head of the cadaver must be steadied by an assistant. As the sections of vertebræ are loosened the intervertebral disks are cut with the cartilage-knife and the pieces of bone pulled away with the bone-nippers. When the canal is fully exposed the examination of the dura and the removal of cord and dura proceed as when the canal is opened posteriorly. The straight chisel and the bone-forceps are also used to open the spinal canal anteriorly, but the Brunetti chisels are especially recommended for this operation.

Examination of Spinal Ganglia. While these may be examined when the canal is opened posteriorly, they can be exposed with less danger of damage in the anterior examination. To expose them in the posterior examination they must either be drawn forcibly through the intervertebral foramina, or the articular processes must be cut away with the chisel.

When it is desired to remove a part of the spinal column for preservation as a specimen, the intervertebral cartilages and the cord above and below the portion to be removed are cut through with the knife, and the ribs severed with a chisel, while the adherent soft parts are cut away. The saw or chisel is then used to complete the disarticulation if necessary and the loosened portion is removed. The entire spine may be removed, if desired; and may be bisected with a band-saw. A stick of wood may be put in the place of the spine and covered with plaster-of-Paris.

After the cord and dura have been removed the inner surface of the canal should be examined. The character of the cut surface of the vertebral bodies is also noted, and the bones examined for pathologic conditions.

2. POINTS TO BE NOTED IN THE EXAMINATION OF THE SPINAL COLUMN.

1. Dorsal Incision. Note color of skin as it is cut, number of bleeding points, moisture, bedsores, amount and character of panniculus, color and blood-content of muscles, hemorrhages, purulent and tuberculous processes (usually infiltrations from diseased vertebræ) trichina in spinal muscles, etc.

2. Vertebrae. Necrosis from bedsores, surfaces smooth or rough, purulent and tuberculous processes (most common anteriorly), exostoses, curvatures, fractures, dislocations, erosions, malformations (spina bifida and supernumerary vertebræ most common), neoplasms (secondary carcinoma, primary sarcoma, myeloma and chloroma most common), actinomycosis, syphilis, rachitis, etc.

3. Dura. Note epidural tissue first, then dura, its thickness, color, translucency, blood-content, intradural pressure, character of inner surface (normally it is grayish-white, smooth and shining). defects, bone-formation, organizing blood-clots, hæmatoma, gumma, neoplasm, etc. Most common pathologic conditions are chronic pachymeningitis, syphilis, tuberculosis, traumatic lesions and secondary carcinoma. Primary tumors (sarcoma) and parasites (echinococcus and cysticercus) are rare. Teratomata occur in sacral and coccygeal regions. A diffuse formation of adipose tissue is common, as is also the development of bony plates in the dura in old chronic pachymeningitis (usually syphilitic). Note character and amount of contents of subdural space (blood, pus, serous exudate, etc.).