We report a case with AVM who was studied by TCD and SPECT to evaluate the hemodynamic changes before and after treatment (feeder embolizations followed by surgical resection) . A 23 -year -old man was admitted to our hospital with convulsive seizures. Preoperative cerebral angiogram showed left parieto-occipital AVM fed from the MCA and PCA branches. A preoperative SPECT study showed decreased blood flow in the area surrounding the AVM. SPECT with acetazolamide challenge showed a decrease of

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... rebrovascular response at the left parieto -occipital lobe. A TCD study showed an increase of the left middle cerebral artery mean flow velocity (MCAmFV) and a decrease of the pulsatility index (PI). TCD after hyperventilation (5 min) showed a decrease of the right MCAmFV and an increase of PI. Conversely, left MCAmFV and PI were not changed. These findings indicated a potential risk of post -operative hyperemic complications from a single -stage resection of the AVM. We performed feeder embolization (TAE) as the first step. SPECT with acetazolamide challenge showed improvement of the cerebrovascular response at the parieto -occipital lobe. A TCD study after embolization also showed a decrease of the left MCAmFV and an increase of PI. The changes in mFV and PI after hyperventilation returned to the normal response. Surgical resection was performed uneventfully one week after embolization and the patient returned to normal life. TCD is a useful monitoring tool to evaluate hemodynamic changes and guide the selection of the optimum surgical treatment of high flow AVM.