Background and Purpose-Dynamic cerebral autoregulation has been shown to be fast and effective, but it is not well known if the mechanism is symmetric, that is to say, it acts with equal compensatory action to upward as compared with downward abrupt changes in arterial blood pressure (ABP). Methods-Fourteen patients with head injuries and 10 normal subjects had bilateral transcranial Doppler and continuous ABP recording. Cyclic ABP stimuli were generated by large thigh cuffs, which were rapidly inflated above systolic pressure for 15 seconds alternating with 15 seconds of deflation. At least 8 such cycles were ensemble-averaged and the dynamic autoregulatory gain (AG up and AG dn ) was estimated separately for upward and downward changes in ABP. The results were compared with the autoregulation index using conventional leg cuff releases. Results-In normal subjects, AG dn was 0.74Ϯ0.18 and AG up was 0.77Ϯ0.17 (meanϮSD); the difference was insignificant.The correlation between AG dn and AG up , however, was weak (rϭ0.24). In the patients with head injury, AG dn was 0.30Ϯ0.21 and AG up was 1.27Ϯ0.76, the difference being highly significant (PϽ0.001). There was a negative relationship between AG dn and AG up (rϭϪ0.33). Autoregulation index correlated well with AG dn (rϭ0.79) and weakly negatively with AG up (rϭϪ0.47). Conclusions-A strongly asymmetric dynamic response of the cerebral autoregulation was seen the majority of patients with head injury. It might also have been present, albeit to a lesser degree, in the normal subjects. The findings suggest that nonlinear effects may be present in the operation of the cerebral autoregulation mechanism.
Early angiographic diagnosis with immediate endovascular treatment provided an effective approach for TICA detection and management. Endovascular therapy is versatile and offers a valuable alternative to surgery, allowing early aneurysm exclusion with excellent results.
The authors report the long-term results of a series of direct superficial temporal artery–middle cerebral artery (STA–MCA) bypass procedures in patients with moyamoya disease from the western US.
All patients with moyamoya disease treated at the University of Washington from 1990 through 2004 (39 patients) were included in this study. Patients underwent pre- and postoperative evaluation of cerebral perfusion dynamics. Surgical revascularization procedures were performed in all patients with impaired cerebral blood flow (CBF) findings.
The mean age of patients at diagnosis was 34 years (range 10–55 years). All 39 patients had impaired CBF and/or vasomotor reserve and underwent revascularization procedures: 26 patients underwent bilateral operations, 13 unilateral (65 total procedures). An STA–MCA bypass was technically possible in 56 procedures (86.2%); saphenous vein interposition grafts were required in 3 procedures (4.6%); encephaloduroarteriosynangiosis was performed in 6 procedures (9.2%). Three patients died due to postoperative complications, yielding a procedure-related mortality rate of 4.61%, and 8 experienced non–life threatening complications (for a procedure-related rate of 12.3%). Long-term follow-up appeared to indicate a reduction in further ischemic events in surviving patients compared with the natural history. Cerebral perfusion dynamics improved postoperatively in all 36 surviving patients.
Moyamoya disease may differ in the US and Asia, and STA–MCA bypass procedures may prevent future ischemic events in patients with this condition.
BNP plasma concentrations are elevated shortly after head injury and are continuously elevated during the acute phase in patients with more extensive SAH and in those with elevated ICP, and correlate with poor outcomes. Further studies should be undertaken to evaluate the role of BNP in TBI pathophysiology.
The present study suggests that, in general, quantitative measurements of rCBF and regional MTT by PCT show high concordance rates with the clinical course, vasospasm severity, and hemodynamic impairments in patients with cerebral vasospasm aneurysmal subarachnoid hemorrhage.
These results suggest that BNP secretion in SAH patients is closely related to the bleeding intensity and vasospasm severity as well as to development of DIND with a progressive and marked increase during the clinical course in patients who eventually develop cerebral ischemia. Taken together the local and systemic effects of BNP on CBF suggest that BNP might play a role in the pathophysiology of CVS through its systemic effects on blood pressure and plasma volume BNP leading to an aggravation of brain ischemia secondary to vasospasm.
These results suggest that DC may enhance survival in the presence of severe brain swelling, although it is unlikely to represent an adequate answer to mitochondrial damage responsible for cellular energy crisis and edema.
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