Analysis of cerebral perfusion and metabolism assessed with positron emission tomography before and after carotid artery stenting

Object The authors analyzed cerebral perfusion and metabolism in patients with internal carotid artery stenosis before and after carotid artery stenting (CAS).Methods Sixteen patients with internal carotid artery stenosis (> 70%) underwent PET scanning before CAS, 1–7 days after CAS, and 3–4 months after CAS to assess a variety of parameters related to cerebral perfusion and metabolism.Results Cerebral blood flow at rest (CBFrest) significantly increased in the immediate postoperative stage before returning to normal levels over the long term; this trend was also recognized on the contralateral side. In contrast, there was gradual improvement in the rate of CBF variation on acetazolamide administration (% CBFaz). Cerebral perfusion pressure (CBF/cerebral blood volume) increased rapidly during the acute stage and decreased in the long term, and the oxygen extraction fraction decreased slightly during the acute stage before normalizing over the long term. The cerebral metabolic rate of oxygen (CMRO2) increased slightly after stenting over both the short and long term. The ratios of ipsilateral to contralateral values (asymmetry index) for CBFrest, % CBFaz, cerebral blood volume, oxygen extraction fraction, and CMRO2 tended to approach 1.0 over time.Conclusions Repeated PET scanning revealed improvements in CBF, perfusion pressure, and oxygen metabolism after CAS. In particular, the vascular reserve tended to improve gradually, while CBF, cerebral perfusion pressure, and CMRO2 increased rapidly and peaked soon after CAS. These results suggest that a large discrepancy between rapidly increased CBF, perfusion pressure, and a small increase in vascular reserve in the acute stage after CAS could cause hyperperfusion syndrome