Thirty six cases with unilateral carotid artery occlusion were studied to elucidate the indication of surgical treatment by collateral circulation and CT findings.
There were three types of collateral pathway which were via Willis ring, via leptomeningeal anastomoses and transophthalmic collateral circulation. Classification of cerebral infarction by CT fiindings were IC territory type (17%), MC territory type (36%), perforators area (basal ganglionic region) type (8%), border zone type (33%) and no infarction type (6%). Angiographical fiindings of collateral circulation correlated well with the CT findings and clinical features. Transophthalmic and leptomeningeal anastomoses were insufficient and good collateral circulation through Willis ring was necessary to maintain the usefull life in many cases.
Eight cases (5 IC territory type and 3 MC territory type) developed severe brain swelling and neurological herniation signs. All conservatively treated cases died within a week after the onset due to secondary brain stem damage. In those cases, extensive surgical external decompression should be done not only for reducing mortality but also for improving morbidity. Decompression should be done until the early third nerve stage of downward transtentorial herniation.
Extra-intracranial arterial bypass (EIAB) was done in 14 cases (4 in acute stage and 10 in chronic stage). In 4 cases which were operated upon in acute stage, 2 cases of border zone type improved remarkably after bypass surgery. In 10 cases which the bypass operation was performed in chronic stage, 5 cases improved apparently and 3 cases were supposed to stop the deterioration of neuropsychological manifestations due to chronic low perfusion state. Border zone type by CT was good indication for bypass surgery. Perforators area type and no infarction type also have the indication for EIAB.
But in some cases, especially in acute stage, it is difficult to evaluate the effectiveness of collateral circulation and the functional reversibility after EIAB. Therefore, the analysis by the drug-induced EEG and somatosensory evoked potential (SEP)-tests which we have developed is important to decide the method of treatment.
