A Radiologic and Pathologic Study of Embolism of the Internal Carotid-Middle Cerebral Arterial Axis

In the course of a survey of a large number of cases of clinically suspected stroke referred to the neurological unit of St. Vincent's Hospital, Melbourne, a comparison of the accuracy of clinical diagnosis as measured against the results of radiological investigation showed that in a large number of cases, the clinical diagnosis was in error (2). The majority of apparent missed diagnoses were found in the category of “embolism of the middle cerebral artery.” The radiologic finding of a classic picture of embolic occlusion of the trunk of the middle cerebral artery was a rarity when compared with the large number of suspected cases and, although in most patients in this category some pathological lesion was demonstrated, there were still a substantial number with no angiographic indication of vascular block. Closer study revealed that not only was suspected middle cerebral artery embolism due to embolic occlusion of the internal carotid artery in many cases, but in addition the embolus could migrate up the axis formed by the internal carotid and middle cerebral arteries. A much larger proportion of strokes are probably caused by internal carotid-middle cerebral embolism than is currently realized. Methods of Study Angiography: After thorough clinical assessment, all cases of suspected stroke were submitted immediately to unilateral carotid angiography, followed in most instances by study of the contralateral carotid system. In the course of the next twenty-four to forty-eight hours, completion of the investigation of the cerebral vascular status was undertaken by aortography and vertebral angiography. Only if the patient's condition were rapidly deteriorating was this not performed. If an occlusive embolic lesion was demonstrated, repeat carotid angiography on the appropriate side was carried out twenty-four hours and seven to ten days after the first injection. Operative findings: Part of the survey on cerebral vascular disease entailed the application of vascular surgery to strokes. Accordingly, all cases of embolism of the internal carotid artery were assessed for embolectomy if the patient's condition warranted the procedure. By this means angiographic findings were checked, and by catheter injection of contrast medium at operation, the intracranial portion of the internal carotid artery was outlined. The actual site of the embolic block could thus be determined radiologically (Fig. 3). Autopsy findings: All cases coming to postmortem examination were investigated by total carotid angiography. Contrast material, normally solid at room temperature, was heated to the liquid stage and injected under pressure into the origins of the common carotid and vertebral arteries in situ.