抄録
Proton MR spectroscopy (MRS) is valuable for identifying metabolic changes occurring during brain ischemia. Although it has been shown that N-acetylaspartate (NAA) measurement by MRS is useful to detect neuronal damage in the acute stage of cerebral ischemia, the clinical significance and the availability of the NAA measurement in the chronic stage of cerebral ischemia are still obscure. We examined a serial change of NAA/Creatinin (Cr) ratio in patients who underwent EC-IC bypass in the chronic stage of ischemia and investigated the influence of revascularization surgery on the brain metabolism. Nine patients who underwent EC-IC bypass, five patients with symptomatic occlusive main cerebral arteries who received conservative treatment, and three healthy volunteers were studied. 1H-MRS was obtained using Philips Achieva 3.0T. Multi-voxcel spectra were recorded using a SE-2D-CSI sequence (TR/TE=2000/288 ms). The volume of interest was placed in the frontal white matter of both hemispheres axially above the lateral ventricles. Surgery was done on average 45 days after onset. 1H-MRS was performed before and one week, one month and three months after surgery, and the serial change of ischemia/contralateral side ratio (I/C ratio) of NAA/Cr between the bypass group and conservative treatment group was compared. In the healthy volunteer group, neither laterality of NAA/Cr nor the serial change was seen. Six patients in the bypass group had significant lower NAA/Cr on the affected side compared to the contralateral side at one month after onset. In these patients, the I/C ratio of NAA/Cr increased 11 percentage point three months after surgery. All patients in the conservative treatment group also had significantly lower NAA/Cr on the affected side, but I/C ratio of NAA/Cr increased three percentage points at three months after onset. The improvement range of I/C ratio of NAA/Cr was significantly higher in the bypass surgery group.
The present study demonstrated that decreased NAA/Cr shown in the chronic stage of cerebral ischemia is reversible. MRS may provide useful information of impaired metabolic states that can be treated with revascularization surgery.
