Long-term assessment of cerebral perfusion following STA-MCA by-pass in patients.

Abstract

SUMMARY A prospective study of mean hemispheric cerebral blood flow (CBF) correlated with clinical status has now been completed for the past 54 months. Thirty-eight patients underwent superficial temporal to middle cerebral artery (STA-MCA) by-pass. They were compared with 22 patients with similar arteriographic lesions and clinical symptoms, treated medically throughout the same interval of time. Assignment to either treatment group was not randomized but depended solely on choice of patient or treating physician. Both groups were matched for age, clinical symptoms, angiographic abnormalities, and CBF values. All patients had proximal occlusion of one internal carotid artery or intracranial occlusive disease of the internal carotid or middle cerebral arteries. CBF measurements and clinical evaluations were repeated at regular intervals up to 54 months following surgery or institution of medical treatment. Mean follow up interval after STA-MCA by-pass was 28.7 months and for medical treatment was 29.7 months. Mean hemispheric CBF values for STA-MCA patients became significantly increased 2 weeks after operation. After that, CBF flow values decreased. At 24 months after surgery, flow values for surgically treated patients were significantly higher than among those treated medically, although there were no differences in flow values between the two groups at 3, 6,12, 36 and 48 months. Prospective clinical evaluations after STA-MCA by-pass were as follows: 12 (32%) improved with cessation of TIAs and/or neurological improvement, 16 (42%) remained unchanged, 7 (18%) deteriorated (due to new or recurrent strokes) and 3 (8%) expired. Clinical results were the same for medical treatment: 6 (27%) improved, 10 (46%) unchanged, 4 (18%) deteriorated due to new or recurrent stroke, and 2 (9%) expired.

Cerebral haemodynamic changes after extracranial-intracranial bypass surgery.

“…6 [23][24][25][26][27][28][29][30][31][32] Most investigators have observed only modest rises of blood flow in a minority of patients studied, the change being often a transient phenomenon which is no longer demonstrable 3 or 4 months after the procedure.27 29 32 Some authors have suggested that a measurement of cerebral circulatory reserve, as judged by the capacity to increase blood flow in response to inhaled carbon dioxide, may be a more useful haemodynamic index than the level of blood flow itself.26 31 33 More recent studies using positron emission tomography (PET) have enabled measurements to be made not only of cerebral blood flow, but also of the metabolic demands of the brain, as reflected by regional oxygen consumption.3435 It has been shown that there are some patients with occlusive carotid artery disease in whom cerebral blood flow is inappropriately low in relation to the oxygen requirements of surviving brain.16 25 36 37 This critical haemodynamic state is characterised by a compensatory rise of fractional oxygen extraction (normally less than 50%), which maintains oxygen delivery to the tissues in the face of the reduced blood supply. A small number of patients have been reported in whom EC-IC bypass surgery was followed by restoration of blood flow and a fall to normal levels of a previously raised oxygen extraction ratio.16 25 Even when cerebral blood flow is still appropriately matched to metabolic demands, reduction of cerebral circulatory reserve may be evident as a regional increase of cerebral blood volume, consistent with focal vasodilatation in response to diminished cerebral per-fusion pressure.…”

“…36 37 Analysis of the relationship between blood flow, blood volume and oxygen extraction has suggested that the ratio ofcerebral blood flow to blood volume (a reflection of mean flow velocity) provides a more sensitive index of cerebral perfusion pressure than either variable considered alone. 36 38 In view of the apparently minor and inconsistent effect of bypass surgery of cerebral blood flow, [23][24][25][26][27][28][29][30][31][32] this study was carried out to establish whether other physiological variables, in particular the cerebral blood volume, might provide more information about the haemodynamic effect of the procedure.…”

The clinical utility of the Kopitnik arteriovenous malformation microclip during STA-MCA bypass surgery

“…The development of microsuture materials and surgical optical magnification has introduced new surgical possibilities [2] to treat ischaemic brain diseases [9, 15]. Although a range of surgical techniques can be used for STA-MCA bypass, e.g.…”

Assessing Success after Cerebral Revascularization for Ischemia

“…Whereas some have reported improvement in hemodynamic parameters following bypass, 47,[75][76][77][78][79] others found improvement only in a subset of patients, [80][81][82] or early improvement which was not long-lasting. [83][84][85] Improvements may be most prominent in patients with the greatest degree of compromise preoperatively and are more often seen in cerebrovascular reserve rather than resting CBF. 47,79,80 Nonetheless, changes in the postoperative setting are difficult to interpret definitively without comparison to similar nonoperated patients, given that even spontaneous improvement in hemodynamic parameters have been described, 86,87 presumably due to collateral formation.…”