Removal Of Spinal Cord In Adults

Removal of the spinal cord has been traditionally neglected by general pathologists but can be accomplished very easily within 10-15 min by the use of an oscillating saw, as described below. This should be part of every autopsy.

POSTERIOR APPROACH The body should be placed in the prone position with blocks under the shoulders. The head is rotated forward in a flexed position. Towels are placed under the face to avoid damage. A midline incision is placed over the spinous processes, muscles are resected, and bilateral laminectomies are made with the use of a saw (Fig. 6-5).

nal occipital protuberance (inion). If (A) is too low, there is danger of cutting into the roof of the orbit; if (B) is too low, saw will enter petrous portion of temporal bone. Either of these will make removal of skull vault difficult. When (D) is too low, saw line will be below attachment of the tentorium.

Fig. 6-4. Two methods of opening the calvarium in fetus and neonate. (A) illustrates Beneke's technique as described in text. In method shown in (B) and (B'), reflection of frontal bone flaps will result in fracture lines along their base. Optional cut may be made into posterior portion of these flaps as indicated by dots in (B).

Fig. 6-4. Two methods of opening the calvarium in fetus and neonate. (A) illustrates Beneke's technique as described in text. In method shown in (B) and (B'), reflection of frontal bone flaps will result in fracture lines along their base. Optional cut may be made into posterior portion of these flaps as indicated by dots in (B).

This methods allows easy exposure of the uppermost cervical spine and allows direct visualization of the craniocervical junction; it is therefore recommended in cases in which neck injuries are suspected (flexion and extension neck injuries), in cases of craniocervical instability and in special situations, for example, when an occipital encephalocele needs to be excised or in situ exposure of an Arnold-Chiari malformation is required. A myelomeningocele also can be removed more easily by the posterior approach (see below). Many morticians object to the routine use of this method, because embalming fluids tend to leak from the incision on the back. Therefore, if embalming is planned, this approach should be chosen only when strictly indicated. Posterior dissection reveals the posterior muscles of the neck, ligaments, vertebrae (spinous and transverse processes as well as the vertebral bodies), and vertebral arteries.

Spinal Cord Removal
Fig. 6-5. Posterior approach to spinal cord. The spinal cord inside the dura after the removal of vertebral arches C1-C7 is shown.

Deep contusions with blood extravasation, injuries to ligaments, and fractures of posterior parts of vertebral bodies also are demonstrated by this method (10). After the spinal cord has been removed, the spinal canal can be readily examined. With this approach, continuity between lower brainstem and upper cervical cord can be maintained, if indicated. To study sites of compression and related histologic abnormalities in the area, the cervical spinal cord and medulla may be removed inside the bony column, in continuity with the fora-men magnum (11).

Posterior dissection of the spinal cord may be limited to the upper thoracic and cervical cord or extended down to the sacral segments. However, compared with the anterior approach, this dissection method is much less suited for pursuing the course of peripheral nerves for any length in contiguity with the spinal cord. The posterior approach is used by us only on special occasions such as excision of an occipital encephalocele, in situ exposure of an Arnold-Chiari malformation, or removal of a spinal meningomyelocele (see below).

ANTERIOR APPROACH The anterior approach is simple and quick and does not require turning the body over. It also permits removal of the spinal cord and peripheral nerves in continuity when indicated. Immediate examination of the vertebral bodies is an added advantage. Kernohan's hemivertebral section method, devised as a quick anterior approach with the advantage of providing rigidity to the spinal column, fails to expose one side of the spinal cord (7). Consequently, it restricts removal of the spinal cord, nerve roots, and dural covering. For

Fig. 6-6. Anterior approach to spinal cord. Dotted lines between vertebral body and arch indicate planes of saw cut adjusted to shapes of different levels of vertebral column. (A) Cervical. (B) Thoracic. (C) Lumbar.

the preferred method, that is, complete removal of these structures, see below.

After evisceration is completed, the first cut is made across the uppermost part of the thoracic region (T-1 or T-2). The head is dropped back by removing the head support or placing a wooden block behind the back under the midthoracic region, which straightens the spinal column and facilitates the procedure. The next cut is placed on either side of the upper thoracic spine, caudal to the first, for approx 10-15 cm along the line indicated in Fig. 6-6A. The sawing should be stopped as soon as one feels a "give," to prevent cutting into the spinal cord. Sectioning over the proximal ends of the ribs (7) has the advantage of creating a wider opening for the spinal cord and of giving easier access to the spinal ganglia and the peripheral nerves. The freed portion of the thoracic spine readily snaps up toward the prosector, especially when the spine has been straightened as described earlier.

It is better to saw both sides of the spine for short distances, instead of one side all the way down to the lumbar area, followed by the other side. With the latter technique, one cannot be certain whether the line of cut is being placed properly. If the upper thoracic spine fails to snap up because of faulty sectioning, a remedied cut can be placed at this early stage. Grasping the freed spine with the left hand and pulling it toward the prosector makes the further caudal extension of the cuts easier.

As one proceeds toward the lumbar area, the angle of the blade should be changed by adjusting to the shape of the vertebrae as illustrated in Fig. 6-6B and C. The muscles in this area should be cut away from the spine, down to the level of emerging nerves but without dividing them before sawing. Since removal of the L-5 body with the rest of the spine is often difficult because of the angulation of the spine at this level, L5 can be removed separately from the sacral bone with relative ease but first, the lumbar spine at the L4-5 interspace must be transected with a slightly curved short knife. Twisting a broad chisel in the saw tracts helps to separate the vertebral bodies away from the rest of the spine. In most instances, the cauda equina roots can be transected at either L-4 or L-5.

Freeing the rest of the cauda equina from the sacral bone is time-consuming, because it is difficult to manipulate the saw within the pelvic cavity. In rare instances, one has to cut a wedge of bone near the midline with an oscillating saw blade and remove the remaining lateral portion of the sacral bone with a rongeur to avoid damage to the nerve roots in the foramina.

The exposed portion of the spinal cord and the cauda equina encased by the dura mater is lifted off the spinal canal with as many spinal ganglia as possible. When indicated, the spinal cord can be removed with all spinal ganglia and the nerves of the lumbar plexuses and beyond by extending the process of freeing these structures from the bony and soft-tissue encasement more peripherally (Fig. 6-7). A string and a label tied to one of the lumbar roots allows future identification.

The cervical spinal cord can be removed by Kernohan's extraction technique (see below), without removing the cervical spine. However, cervical spinal roots or posterior spinal ganglia cannot be obtained by this technique and therefore, when these structures must be examined, the dissection of the spine must be extended upward. The carotid arteries are pushed to the side and the cervical plexuses are exposed in the same manner as used in lumbar area. The spine is then cut along the plane shown in Fig. 6-8 on either side up to the level of C2-3 interspace, where it is transected with a scalpel blade (Fig. 6-8 upper). Alternatively, the cervical spine is simply reflected cephalad and fractured (Fig. 6-8 lower). This method should only be applied in the absence of important antemortem bony lesions in this area.

A slight lateral tilting of the blade facilitates the removal of the spinal ganglia in this region. With excessive tilting, accidental cutting of the spinal cord may occur. Another common mistake is to deviate the line of cutting toward the midline cephalad, ending up with the pointed tip. This easily results in damage to the underlying cervical cord. To facilitate the insertion of the oscillating saw blade underneath the skin flap, we have cut off the top portion of the circular blade. Adequate exposure of the neck region requires a primary chest incision from shoulder to shoulder and freeing the skin flap from the underlying muscles and connective tissue.

In order to remove the upper cervical cord and its roots from the intact bony canal one needs to approach it from the cranial cavity to free the dural attachment from the foramen magnum as high as possible. First, one makes a circular cut here. The dura is then peeled away from the bones caudad. Holding the freed dura taut with a hemostat or forceps facilitates this procedure. Usually, no special tools are required other than a pair of long scissors. On occasion, we have made use of semicircular chisels.

If the remaining portion of the spine needs to be removed, one can use a wire-saw passed through the spinal canal or a jigsaw with a long blade to complete the section. The latter instrument may injure the spinal cord, whereas the wire-saw can be used safely while the cervical cord is still in place. This will permit removal of the cervical spine in one piece. Although the upper cervical cord can be safely removed by the anterior approach, we would advocate the safer posterior approach if examination of higher cervical segments is critical.

After the cervical spine has been removed and the cervical cord exposed, the spinal cord and brain can be removed in continuity. This may be desirable in rare situations, as in the case of a tumor of the medulla and spinal cord. Of course, the usual transection at the lower medulla may not be made earlier. In this situation, it is better to expose and loosen the spinal cord completely before working on the removal of the brain (7).

Routinely or when difficulties are encountered in reaching the high cervical level, it is advisable to cut across the cervical spine at a lower level and to extract the spinal cord by Kerno-

han's method after cutting the dura circumferentially at the exposed edge and opening it longitudinally along the midline below this level. The spinal cord and dura are wrapped in a moist towel. The right hand grasps the lower portion of the spinal cord and provides a gentle, steady, caudad pull while the fingers of the left hand are placed close to the top of the exposed spinal cord to minimize angulation at this point. It is possible to remove most of the spinal roots from the cervical enlargement by this method. Although some plucking of the nerve roots (especially the posterior ones) from the cord occurs, the often-expressed fear that the cord itself may be seriously damaged by this method is unfounded, based on our experience. The most frequent damage is caused by an inexperienced prosector who places the right thumb over the upper thoracic cord and proceeds to bend the cord at this level instead of pulling it caudally along the long axis. This extraction method is a compromise to encourage the routine removal of the entire length of the cord. Finally, the posterior base of the skull also can be removed together with the cervical spine and spinal cord (11). For removal of the central nervous system in toto, undisturbed within the bony cage, see ref. (12).

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