SUMMARY A patient is reported who during vigorous back bleeding after unclamping of the internal carotid artery during endarterectomy had EEG slowing and a postoperative increase in neurological deficit. This phenomenon, an apparent steal, has not been reported and suggests that EEG monitoring Is as vital at unclamping as it U after clamping. The patient also raises questions about the risk of early endarterectomy for those who have persistent deficits, even with unobstructed vessels. Stroke, Vol 11, No 3, 1980 EVALUATION by electroencephalography (EEG) of adequate collateral flow while cross-clamping during carotid endarterectomy has become an integral part of operative technique. It helps to make the decision for the need of a vascular shunt. 1 Usually the EEG changes rapidly if collateral flow is insufficient. In a recent patient, opening the internal carotid artery clamp during endarterectomy resulted in profuse backflow and was followed by slowing of a previously unremarkable EEG. The EEG rapidly became normal when the artery was again clamped. This episode suggests a steal phenomenon which, to our knowledge, has not been previously recognized.
Patient ReportThe patient is a 54-year-old right-handed male with hypertension, diabetes and hypertriglyceridemia who had 2 episodes of weakness and numbness in his right arm over 2 weeks. On physical examination 3 days after the most recent attack, the neurological examination was normal except for slight weakness of the right hand and patchy areas of decreased sensation over the right hand. No carotid bruit was heard. Transfemoral 4-vessel cerebral angiography showed a long shallow ulcerated plaque in the left internal carotid artery just above the bifurcation ( fig. 1). There was no other cerebrovascular lesion. The "watershed" between the middle and anterior cerebral artery circulations was in the mid-convexity ( fig. 2). The abnormal neurological signs cleared almost completely over the next 4 days.Endarterectomy was done one week later with 16 channel EEG monitoring. At the start of the record, while the patient was awake, the dominant frequencies were well regulated 9 to 10 cps alpha waves and there was no significant asymmetry. Pentobarbital was given causing transient bilaterally synchronous delta activity with the usual rapid clearing as the record reached level 3 anesthesia and then returned to level 2. Anesthesia was maintained with 60 percent nitrous ox- ide and one percent halothane. The posterior activity was moderately well regulated 8 to 9 cps waves mixed with 5 and 6 cps theta activity. The voltages of these wave forms were similar over the entire parasagittal regions.After administration of heparin, the external carotid artery was clamped with no visible change in the record. After the common carotid artery and internal carotid arteries were clamped, there was momentary bilateral voltage decrease posteriorly but no change in frequencies and no asymmetry. Throughout the initial period following artery clamping, the dominant posterior activity rem...
