THE EXAMINATION OF THE SPINAL CORD.
1. =METHODS OF EXAMINATION.= The spinal cord may be opened anteriorly
or posteriorly. The choice of method is largely a matter of
convenience or of individual skill in using certain instruments,
such as the Brunetti chisels. The method of opening posteriorly is
more commonly used in this country, as it requires less skill. It
necessitates, however, an additional long skin incision that must
be tightly stitched together to prevent leakage of blood and fluids
after the restoration of the body. For this reason it is not as
clean a method as the anterior opening, which requires only the one
main skin-incision. In private practice the latter method is often
advisable, as by it an examination of the cord can often be secured
when the relatives would not consent to its removal posteriorly, on
the ground of undue mutilation of the body. The anterior examination
also permits a better inspection and an easier removal of the spinal
ganglia and nerves.
=Examination of Cord Posteriorly.= For the _opening of the spinal
cord posteriorly_ the cartilage-knife, bone-forceps, bone-nippers and
rhachiotome are necessary; in place of the latter the single saw,
double chisel, Brunetti chisels or single chisel may be employed. The
posterior examination of the cord should take place at the beginning
of the autopsy, after the external inspection of the cadaver, before
the thorax and abdomen are examined. The removal of the sternum
gives a loss of resistance to the manipulations upon the back of the
cadaver, and the turning-over of the body after it has been opened
anteriorly is usually an unpleasant procedure because of the dripping
of blood and other fluids. When it is found necessary to examine the
cord posteriorly after the opening of thorax and abdomen it is better
to fill these cavities with tow or excelsior, replace the sternum and
sew up the anterior skin-incision before turning the body over.
The cadaver is placed face downwards, with medium-sized blocks
beneath the cervical and lumbar regions, the arms being folded
underneath the body. With the cartilage-knife an incision is then
made through the skin and subcutaneous tissues in the median line,
over the spinous processes, beginning above at the occipital
prominence and ending at the lower border of the sacrum. The skin
and subcutaneous tissues are then dissected back by bold slashing
strokes for a distance of a hand’s breadth on both sides of the
spine, thus laying bare the muscles of the neck and back. The muscles
may be stripped back with the skin, but the heavy flaps thus formed
are very likely to fall back and cover the seat of operation. Chain
retractors may be used to hold the skin flaps back, particularly in
the case of a very fat individual, but usually the separate stripping
of the skin and muscles is sufficient. To remove the muscles the
cartilage knife is set close against the spinous processes of the
uppermost vertebræ and a deep cut made on each side of the spine
throughout its entire length, severing the vertebral attachments of
all muscles and tendons. About four finger-breadths outside of these
cuts there should now be made from above downwards on both sides
another deep cut through the muscles parallel with the first two
incisions. The bundles of tendons and muscles between these parallel
cuts on both sides of the spine are then separated from the bones as
cleanly as possible, beginning either above or at the sacral end,
severing the muscle-mass at the end at which the separation begins,
but leaving it attached at the other end, where it is laid over the
side of the body out of the way, and replaced after the examination
of the cord is completed; or the two bundles of muscle may be cut off
at both ends and disposed of without further trouble. Portions of
tissue clinging to the vertebræ should then be scraped or cut away
with the chisel or knife.
When the vertebræ are bared the next step is the removal by saw,
bone-forceps or chisel of the posterior bony wall of the spinal canal
in such a manner as to expose the cord and permit of its removal
without causing any damage to it, either from the instruments or
from fragments of broken bone. A single-bladed saw with curved ends
may be used to saw through the laminæ on both sides of the spinous
processes; or even the small bone-saw (Fig. 9) may be used for this
purpose. The blade of the saw should be held obliquely against the
spinous processes with the sawing edge directed outward so as to
cut the laminæ close to the medial borders of the ascending and
descending transverse processes. The sawing is complete when the
spinous processes become movable. The straight-edged chisel may be
used to cut any adhesions left after sawing, and the bone-forceps
may be used to cut the atlas and axis. When the laminæ have been cut
through on both sides of the spinal column for its entire length,
including the sacrum, the posterior ligament between the atlas and
occiput is cut with the cartilage knife; and the strip of bone and
ligaments loosened by sawing is torn off from above downward by
grasping it in the upper cervical region with a pair of bone-nippers
and jerking it off forcibly downward toward the sacrum, thus exposing
the spinal canal. It may be taken off in the opposite direction by
cutting the ligament between the last lumbar vertebra and the sacrum
and stripping upward.
The use of the single saw is not advised, however, as it is too
time-consuming. The laminæ on both sides of the spinous processes
may be cut at the same time by the use of _Luer’s rhachiotom_e (Fig.
11). The blades are separated according to the size of the vertebral
arches and are set so as to include the spinous processes and cut the
outer border of the laminæ close to the transverse processes in such
a manner as not to injure the cord. Since the spinal canal is broader
in the cervical and lumbar regions than in the dorsal, the distance
between the saw-blades must be regulated accordingly. The dorsal
portion is first sawed. The sawing should be in long cuts without too
great pressure, the instrument being steadied by placing the left
hand on the upright bar. As soon as the spinous processes become
movable on slight pressure the sawing should be stopped. Should the
blades become caught in the saw-cuts great care should be taken to
avoid injuring the cord while releasing them. The straight-edged
chisel may be inserted into the cuts and any parts still adherent
may be carefully sprung apart. This is necessary particularly in the
upper cervical region. The entire posterior wall of the canal may be
loosened in this way, the sacrum being also sawed, when it is desired
to open this part of the canal. When all the spinous processes are
movable the attachments either above or below are cut with the
cartilage-knife, and the spinous processes and laminæ torn off by the
bone-nippers in one piece, either toward the head or sacrum as is the
more convenient.
The laminæ may be cut by a chisel instead of a saw. The
straight-edged or curved single chisel, the “tomahawk” chisel, or
the double-bladed chisel of _Esquirol_ may be employed. The latter
instrument has adjustable chisel-blades that can be set to include
the spinous processes. These blades are very strong and short, and
have convex cutting edges. The use of a wooden mallet (Fig. 17) is to
be preferred to that of the steel hammer in driving chisels of any
type. The straight, curved and tomahawk chisels are held with their
cutting edges directed slightly outwards. The _Amussat rhachiotome_
is a chisel-knife with a curved metallic handle, the cutting edge
running along the length of the chisel. When set at an angle of 45°
to the laminæ it is driven through them by means of blows from a
wooden mallet delivered upon the chisel-back over the cutting edge.
The _Brunetti chisels_ are shown in Fig. 15. In using these to open
the spinal cord posteriorly, a block should be placed beneath the
abdomen so as to raise the lumbar vertebræ above the level of the
dorsal. The intervertebral ligaments of the last lumbar vertebræ
are then cut through with the belly of the cartilage-knife held at
right angles to the spine. The laminæ and spinous process of the last
lumbar vertebra are then cut out with the straight-edged chisel or
bone-forceps, exposing the canal. The _right_ and _left_ Brunetti
chisels are then alternately used, beginning usually with the “left”
chisel, the blunt probe-point being introduced into the canal, while
firm pressure downward is made upon the handle, while at the same
time the cutting edge is driven through the outer borders of the
vertebral arches by blows from a wooden mallet delivered upon the
head of the handle. Great care must be taken to keep the cut at the
same level throughout. It is better, however, to cut too high rather
than too low. In the latter case the cord may be injured, while in
the former the bone may later be easily trimmed off sufficiently
without causing any damage. The arches of three to four or even more
vertebrae may be cut without removing the chisel. The same thing is
then done on the other side, using the “right” chisel. The loosened
portion of bone and ligaments is then cut or torn off with the
bone-forceps or nippers. The cut bone should not be touched with the
hands because of the danger of injury and subsequent infection from
the sharp spicules and splinters of bone. As the canal is opened the
block under the body is pushed towards the head, the object being
always to cut _down hill_ and not upward. When the cervical region is
reached the head of the cadaver should be firmly held by an assistant
so as to give sufficient resistance to the blows of the mallet. The
skilful use of the Brunetti chisels is difficult to acquire and a
great deal of practice is necessary, but when once the knack is
obtained the spinal canal can be opened in this way more quickly than
by any other method. In private practice the noise made by the hammer
upon the head of the handles of the chisels is unpleasant, and should
be avoided by the use of felt or something else on the head of the
chisel or mallet to deaden the sound.
Another easy and convenient way of opening the spinal canal
posteriorly is the cutting of the laminæ by means of special
bone-forceps designed for this purpose. The cutting-edges may engage
the laminæ from without or the lower blade may be introduced into
the canal as a blunt probe, while the upper blade cuts down upon it
through the side of the arch. Such bone-forceps should be very strong
and have long handles to give sufficient purchase, as a good deal of
force is necessary to cut through the laminæ. With a good instrument
the canal can be opened in this way in about 10-15 minutes. It
requires much less skill than is needed for good and quick work with
the Brunetti chisels, and for that reason is recommended, as is also
the use of Luer’s rhachiotome, for the general practitioner.
In the case of marked curvatures of the spine it may be impossible
to use either rhachiotome or Brunetti chisels. The straight single
chisel and small saw can be used on the concave and convex sides of
the curvature respectively. In children and young adults the canal
can be easily opened with the bone-forceps.
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.).
4. =Inner Meninges.= Normally gray, transparent, delicate. Note
intrameningeal pressure, contents of subarachnoid space, color,
thickness and translucency of arachnoid and pia, blood-vessels,
presence of blood, pus, fibrinous exudates, localized thickenings,
calcification, etc. Most common pathologic conditions are acute and
chronic leptomeningitis, results of trauma, hemorrhage, syphilis,
tuberculosis, cerebrospinal meningitis, leprous meningitis, etc.
Bony plates (osteomata) are found in the arachnoid of the majority
of people over forty-five years of age. In small number and size
they have no pathologic significance; they are often large and very
numerous in old cases of syphilitic leptomeningitis, sometimes
encasing the cord. Primary tumors (fibroma, myxoma and sarcoma) are
rare. Teratoid tumors (lipoma, myolipoma, neuroma) are occasionally
found in the lumbosacral region, often associated with spina bifida.
Secondary carcinoma and sarcoma, and metastases of the so-called
glioma of the eye are also rarely found.
5. =Cord.= Size and form. Average length about 45 cms.; weight, 30
grms.; weight of cord to that of brain, 1:48.
Anteroposterior diameter of cervical cord 0.9 cm.
Anteroposterior diameter of dorsal cord 0.8 cm.
Anteroposterior diameter of lumbar cord 0.9 cm.
Transverse diameter of cervical cord 1.4 cm.
Transverse diameter of dorsal cord 1.0 cm.
Transverse diameter of lumbar cord 1.2 cm.
Adhesions to inner meninges, consistence (should be uniform; changes
in form and consistence are often the results of postmortem changes),
color (gray-white, as seen through the pia), translucency (sclerotic
areas in the white matter are firmer, depressed and gray or
brownish-gray in color, and more translucent when present in the gray
matter), moisture, color and blood-content of cut surface, relation
of white and gray matter, symmetry of parts, size of central canal,
presence of cavities, areas of softening (soft, yellowish-white,
loss of structure), hemorrhages, congestion, anæmia, œdema, gumma,
tubercle, tumors, parasites, etc. The normal consistence of the lower
portion of the cord is usually somewhat firmer than that of the upper
part. The “butterfly-figure” should stand out distinctly on the
freshly-cut surface; the outlines between the white and gray matters
should be sharp, and the gray matter should be grayish-red in color.
Normally the white matter tends to rise above the gray. Inasmuch
as the cord is often injured accidentally during its removal it is
important to distinguish such artefacts from pathologic softenings.
This can be easily done by taking a small portion of the doubtful
area and examining in the fresh state under the microscope. In true
softening numbers of “fat-granule” cells and also capillary walls
showing fat-degeneration are seen.
The pathologic lesions of the cord easily recognized by the naked-eye
are areas of sclerosis or gray degeneration, yellow degeneration,
hemorrhage, anæmia, œdema, congestion, tabes dorsalis, amyotrophic
lateral sclerosis, acute poliomyelitis, syringomyelia, ascending
and descending degenerations, glioma, gumma, tubercle, certain
malformations, neoplasms and parasites. Other important pathologic
conditions are: Malformations (myelocele, hydrorrhachis interna,
diastematomyelia, etc.), atrophy, myelitis, sclerosis, effects
of trauma, syphilis and intoxications, infections, tuberculosis,
etc. Primary tumors are: Glioma, gliosarcoma, gliomyxoma, sarcoma
(spindle-cell, myxo-, angiosarcoma, etc.), neuroepithelioma,
neuroma, diffuse gliosis, etc. All are rare with the exception of
the gliomata. Metastatic carcinoma and sarcoma are relatively rare.
Cysticercus and echinococcus are rare.
The thickness, color, consistence and translucence of the spinal
ganglia should be noted. Atrophic nerves are smaller, more gray and
more translucent.
6. =Inner Surface of Vertebrae.= The remains of the epidural tissue
and the inner surface of the spinal canal should also be carefully
examined, noting the consistence of the vertebræ, the character of
the ligaments, fascia, periosteum, etc. The anterior wall of the
canal should be smooth, the color of the vertebræ grayish-red, that
of the intervertebral disks grayish-white. Caries, tuberculosis and
syphilis lead to roughening of the bony wall of the canal.