Interarterial shunts in the cerebral circulation

Preoperative evaluation of patients with extracranial carotid disease. Plethysmographic criteria for the use of a shunt, and for avoidance of surgery

Eighty five angiographically studied patients (mean age 52) with carotid artery disease were preoperatively evaluated for the type and adequacy of their collateral circulation by the use of supraorbital photo-electric plethysmography (SPP). According to certain criteria we identified the candidates for surgery with or without shunt or for conservative treatment. Sixty patients presented evidence of extracranial collateral mainly from the ipsilateral superficial temporal artery (49 of 60), 11 patients revealed evidence of intracranial collateral mainly from the contralateral internal carotid artery (9 of 11), while in the rest, 14 patients, the source of the collateral circulation was undeterminable. Furthermore, an adequate circle of Willis was found in 67 patients and an inadequate one in the rest 7 (4 of 60, and 3 of 14). The majority of the surgically treated patients (74 of 81) were subjected to surgery without shunt (91%) while only 7 necessitated the use of a shunt (9%). No neurological complication was encountered and the single death (1.3%) was not directly related to the surgery itself. According to the present study, the careful preoperative determination of the collateral circulation, with the simple technique of SPP and the identification of patients at high risk under certain criteria could help the surgeon to decide about the advisability of a shunt or not and about the avoidance of surgery as well. This technique may be valuable where other more sophisticated forms of monitoring, such as EEG, evoked potentials or blood flow, are not readily available.

Assessment of the capacity of cerebral collateral circulation using ultrasonic Doppler technique

A new non-invasive method for the assessment of cerebral collateral circulation via the circle of Willis using an ultrasonic directional Doppler flowmeter is described. The technique was found useful in measuring the capacity of cerebral collateral circulation and would be applicable not only in internal medicine but also in neurosurgery.

Contribution of the circle of Willis to the subclavian steal syndrome

The arteriograms and other findings in 42 patients with the subclavian steal syndrome were statistically evaluated to determine which factors predisposed to vertebrobasilar ischemia. Evidence of disconnection of the circle of Willis between the territories of the carotid and vertebral arteries was found in a significantly higher proportion of the patients with vertebrobasilar insufficiency. This finding was interpreted to mean that in these patients one of the major routes normally available for compensating for the basilar ischemia produced by the steal was not present.

It is suggested that this or similar mechanisms may be necessary before the subclavian steal produces symptoms in individual patients.