Cerebral angiography.

Abstract

Intracranial angiography demonstrates the cerebral blood vessels by injection of radiopaque material into the circulation of the carotid and vertebral arteries. When the roentgenographic exposure is made during or immediately after the injection of contrast medium, an arteriogram is obtained. A venogram is obtained when the roentgen film is exposed three or four seconds later. Under normal conditions, only blood vessels of the injected side are shown. Angiography of the carotid artery is easily performed and of great practical importance. Vertebral angiography is technically more difficult and not often indicated. Technic For carotid angiography two methods are in use: the open or surgical and the closed or percutaneous method. The open method accomplishes surgical exposure of the carotid artery at the neck under local anesthesia. It has the advantage of greater accuracy and less chance of injury to neighboring structures or accidental paravascular injection. It permits separate injection of the external and internal arteries and requires only a small amount of contrast material. On the other hand, it is a time-consuming operation requiring a complete surgical set-up and several days hospitalization. The advantages of the closed method are its simplicity and speed. There is no need for hospitalization longer than a day. Percutaneous puncture of the carotid is, however, occasionally unsuccessful and sometimes fails to yield as excellent angiograms as those produced by the open method. Vertebral angiograms can be obtained by surgical exposure and direct injection of the vertebral artery, by indirect retrograde injection of this vessel via the subclavian or, finally, by percutaneous injection of the vertebral artery. It is always desirable to obtain angiograms in lateral and anteroposterior projections; for many purposes a stereoscopic pair of lateral films is valuable. With special mechanical equipment, multiple phase exposures can be made, recording the gradual progress of the contrast medium through the cerebral circulation. Persons frequently performing angiography should be protected from x-rays by lead screening. Contrast Media Two contrast media are available for angiography, but neither of them meets ideal specifications. The first, thorotrast, a 25 per cent colloidal suspension of thorium dioxide, produces excellent roentgenographic contrast and has no immediate ill effects, but it is radioactive and is permanently retained in the reticulo-endothelial system. Because of these undesirable properties, the total amount used should not exceed 35 c.c. The second medium is diodrast, a concentrated (35 per cent) solution of an organic iodine compound. It affords satisfactory x-ray contrast and is totally excreted. Since its injection is painful and may cause convulsions, general anesthesia or preliminary anticonvulsive medication is necessary; moreover, the patient must always be tested for sensitivity to this drug.