Chronic middle cerebral artery occlusion: a hemodynamic and metabolic study with positron-emission tomography

Abstract

Background and purpose: Chronic middle cerebral artery (MCA) occlusion is more common than generally thought. It is important to assess the cerebral hemodynamic status in patients with this chronic condition. We investigated the cerebral hemodynamic and metabolic disturbances in these patients in relation to the development of the collateral vasculature.

Materials and methods: We studied 13 patients with chronic unilateral MCA occlusion who had a minor or no stroke by using positron-emission tomography (PET). PET was performed by the oxygen 15 ((15)O) gas steady-state inhalation method. The intracranial arteries were evaluated by digital subtraction angiography. We divided the patients into 2 subgroups according to whether they had a normal or increased oxygen extraction fraction (OEF) in the occluded MCA territory and compared the 2 groups.

Results: Of the 13 patients, 9 were classified into the normal OEF and 4 were classified into the increased OEF group. In the increased OEF group, the mean OEF values were also increased in the territories of the ipsilateral anterior cerebral artery, ipsilateral posterior cerebral artery, and contralateral MCA. The patients in the increased OEF group had more than 1 steno-occlusive lesion in the major intracranial arteries (P = .008). Three of the 4 patients in the increased OEF group also had vascular lesions in the collateral pathways to the MCA territory.

Conclusion: Most patients with chronic MCA occlusion did not show severe hemodynamic impairment. Those with increased OEF tended to have other areas of severe hemodynamic impairment and other vascular lesions, especially in the collateral pathways.

Fig 1.

Locations of regions of interest: cortical territories of the ACA, MCA, PCA, and the corona radiata. The watershed areas between the ACA and MCA (AWS) and the watershed areas between the MCA and PCA (PWS) were excluded from the analysis.

Fig 2.

Angiographic assessment of the patients. This diagram shows schematic representations of the circle of Willis and the major intracranial vessels in each patient. Black lesions indicate the location of the stenosis or occlusion. Acom indicates the anterior communicating artery; Pcom, the posterior communicating artery; Rt; right, Lt; left; M1-M3, collaterals reconstituting the M1, M2, or M3 segments; None, little or no significant reconstitution of the territory of the occluded vessel.