Special Techniques

ARTERIOGRAPHY Adequate examination of the extrac-ranial portions of the cerebral arteries is important. The simplest method consists of injecting water through the proximal stumps to test patency. This test is conclusive only when vessels are completely occluded; luminal narrowing cannot be appreciated by this method.

Many postmortem angiographic studies of cerebral arteries have been described (29-31). We remove the neck vessels in most instances and thus, angiographic studies are not performed routinely. When indications for them do arise, we clamp the external carotid arteries and inject 5-10 mL of warm barium sulfate-gelatin mixture into the common carotid arteries and roentgenograms are made in the autopsy room (Chapter 12). In a similar fashion, the vertebral arteries can be injected at their origins. Injection from the intracranial stumps of the internal carotid arteries also has been described (29). We have injected a 40% solution of potassium iodide in Karo corn syrup, approximately at systolic pressure. The contrast medium temporarily distends the injected vessels and then dissipates rapidly, which does not interfere with satisfactory embalming of the face and with proper evaluation of the arteries and brains by the pathologist.

To opacify the intracranial cerebral arteries, we prefer to inject them after removal of the brain, so that the lesions can be inspected first. We routinely use a barium sulfate-gelatin mixture (Chapter 12), with or without addition of red or blue dye. When a cerebral aneurysm or vascular malformation is suspected but not immediately visualized by external inspection and care ful flushing of the blood from the basal subarachnoid space, we prefer to inject the opacifying material before attempting to "dig out" the lesion. Successful roentgenographic demonstration (Fig. 6-16) obviates excessive "picking" of the brain substance. After roentgenographic demonstration of these lesions, the brain is best left intact until fixation is completed. Postmortem angiography is also useful in cases of surgically treated vascular lesions, for example, clipping of an aneurysm. Angiography shows whether the vascular system is patent, that is, whether contrast medium appears beyond the site of clipping.

VENOGRAPHY Injection of the venous system in situ or after removal of the brain appears to have little diagnostic use, although it provides background information for neuroradiol-ogists who study the deep cerebral venous system in order to localize lesions. Radiopaque material is injected into the straight sinus or vein of Galen, preferably through a buff hole, before the brain is removed from the cranial cavity. The external venous system of various cranial sinuses and the superficial cerebral veins can be examined directly.

VENTRICULOGRAPHY Outlining the ventricular system of the brain by injection of various materials has been attempted

Fig. 6-17. Intracranial freeing of internal carotid and vertebral arteries. Portion of basal cranial bones to be removed is shown. Horizontal portion of carotid artery is exposed first down to carotid canal. Latter is exposed along with entrance of vertebral artery.

Fig. 6-17. Intracranial freeing of internal carotid and vertebral arteries. Portion of basal cranial bones to be removed is shown. Horizontal portion of carotid artery is exposed first down to carotid canal. Latter is exposed along with entrance of vertebral artery.

in the past mostly for preparation of anatomic specimens. Because pneumoencephalography and ventriculography are of historical interest only, these casting methods have ceased to be of interest for diagnostic neuropathology. For the technique of making casts, see ref. (32).

REMOVAL OF NECK VESSELS For fear of interfering with subsequent embalming, neck vessels are rarely removed completely in the United States. We remove the neck organs and arteries after the embalming procedure, which is performed by private morticians in rooms adjoining the autopsy room. In some institutions, the common and internal carotid arteries are removed from the neck and a small rubber or plastic catheter is placed in the proximal external carotid artery for subsequent embalming at funeral homes (30).

After the primary incision, the skin flap is reflected over the face while subcutaneous tissue is severed by blunt dissection with scissors. Keeping the neck straight or slightly overextended facilitates the approach to the arteries. The common carotid arteries are followed upward by blunt dissection, with occasional snips of scissors, up to the bifurcation. Then, the external and internal carotid arteries are isolated and the dissection is continued along the latter up to as close to the base of the skull as possible. The cavernous and petrous portions of the arteries are freed from the bony enclosure intracranially by chiseling or rongeuring the bone away. The carotid canal may be enlarged and the artery freed from the soft tissue in this region. This can be accomplished by removing a vertical strip of bone mesial to the canal and just above the entrance of the vertebral artery. This is preparatory for the complete removal of the latter. Use of an oscillating saw in part will facilitate the procedure. Then, the neck arteries can be pulled down from below.

Dissection of the vertebral arteries is a little more time-consuming (33). First, portions of the occipital and temporal bones above the lateral and posterior parts of the atlas are removed intracranially by chiseling along the line shown in Fig. 6-17. We use the common bony defect to free intracranially the carotid and vertebral arteries. The posterior process of the superior articular surface of the atlas, which hides the artery, is chiseled

Fig. 6-18. Course of vertebral artery in neck.

away. The artery is then dissected free from the dura to the transverse process of the atlas. Second, in the neck (Fig. 6-18), the transverse foramina of the cervical spine up to the C-3 level are opened with a chisel; the transverse processes are broken, exposing the vertebral artery. The chisel should now be directed upward and laterally to follow the course of the artery in C-2. Because of the fibrous fixation of the artery to the transverse process of the atlas, the process is chiseled off medial to the artery and removed with the latter.

Alternatively, the cervical portion of the carotid and vertebral arteries can be removed together with the cervical spine (from the atlas to the seventh cervical vertebra), preceded by the injection of a barium sulfate-gelatine mixture (Chapter 12) into these arteries (7). Because this interferes with the embalming procedure, the method proved impractical in our institution.

The removed arteries are examined either before or after adequate fixation. A method of perfusing the neck arteries under constant pressure (120-150 mm Hg) (34) supposedly preserved the vessels in the shape and degree of distention present in the systolic phase. Longitudinal sections of these vessels reveal the nature and extent of an atheromatous process, but the degree of narrowing of affected arterial segments cannot be assessed by this method. Also, this method of opening will create artifac-

tual fractures on the surface of extensive plaques, and the condition of the luminal surface will be difficult to evaluate. Some particularly fragile atheromatous material will be lost. Of course, when occlusion is complete, this method of opening cannot be continued without destroying the pathologic process. To avoid these difficulties and to demonstrate the degree of luminal narrowing or the presence of thrombotic occclusion, cross-sec-Itioning is preferred and generally causes less regret. Calcified neck vessels can be fixed in a formalin solution containing ethyl-enediamine tetraacetic acid (EDTA); this greatly reduces crush artifacts at the time of sectioning.

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