A 77-year-old man developed cerebral hyperperfusion syndrome with temporal deterioration of consciousness and worsening of left hemiparesis on the 6 th postoperative day following superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis for right M 1 occlusion. Electroencephalography (EEG) revealed frequent ictal discharges in the right hemisphere, although convulsive seizures were not apparent. Administration of anticonvulsants was performed based on the diagnosis of non-convulsive status epilepticus (NCSE). Complete recovery from hyperperfusion syndrome was achieved with rapid improvement of EEG findings. The present case demonstrates the pathophysiological mechanism of hyperperfusion syndrome associated with NCSE after STA-MCA anastomosis.

Nonconvulsive status epilepticus (NCSE) is generally defined as a change in behavior and/or mental process from the baseline, which is associated with ongoing seizure activity or continuous epileptiform discharges on electroencephalography (EEG) in the absence of convulsive seizures. The present study investigated NCSE incidence using serial EEG during the perioperative periods of cerebrovascular surgery at a medium-sized, local hospital. A total of 54 patients were admitted to our department and underwent various neurosurgical procedures over a course of one year. If clinical symptoms worsened without clear explanation, EEG was performed, resulting in a diagnosis of NCSE in four patients (7.4%). The EEG abnormalities included periodic lateralized epileptiform discharges in 1 patient, triphasic waves in 2 patients, and repeated ictal discharges in 1 patient. Improved mental status and consciousness level, together with disappearance of EEG abnormalities, after appropriate anticonvulsant treatment supported the diagnosis of NCSE. The present study stressed the importance of EEG if no adequate explanation for neurological deterioration can be determined from the clinical course, laboratory data, or neuroimaging examination.

Low-flow bypass, such as superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis, can result in cerebral hyperperfusion syndrome (CHS). The present study evaluated the pathophysiological conditions of CHS through the use of repeated electroencephalography (EEG). Among a total of 22 patients who underwent STA-MCA anastomosis over a course of 4 years, 3 patients were diagnosed with CHS based on clinical symptoms and neuroradiological examinations, including cerebral blood flow evaluation. Case 1 and Case 2 developed CHS on postoperative day 1, when EEG demonstrated focal slow waves on the frontal region of the operated side, indicating cortical dysfunction in these areas. Although prompt recovery of these EEG findings was noted with improvement of the clinical symptoms in Case 1, Case 2 developed an intracranial hemorrhage on postoperative day 5, when EEG clearly depicted persistent nonconvulsive status epilepticus (NCSE) after control of convulsive status epilepticus. In contrast, the clinical onset in Case 3 was delayed to postoperative day 6 and EEG revealed frequent ictal discharges in the operated hemisphere, although convulsive seizures were not apparent. Administration of anticonvulsants was performed after the diagnosis of NCSE, and complete recovery from CHS was achieved. Although the pathophysiology of CHS is cortical dysfunction, ictal hyperperfusion associated with NCSE could be included. The present findings emphasize the importance of repeated EEG examinations in the differential diagnosis of the various types of pathophysiological conditions of CHS.

The champagne bottle neck (CBN) sign refers to a reduction in the diameter of the proximal portion of the internal carotid artery that resembles a CBN, and is a characteristic feature of Moyamoya disease. A 43-year-old woman with an infarction of the posterior limb of the left internal capsule was diagnosed with Moyamoya syndrome associated with Graves' disease. The CBN sign was observed bilaterally. Cerebral revascularization surgery was performed, including left-sided superficial temporal artery to middle cerebral artery anastomosis. During four years of follow-up, she maintained a euthyroid state and did not have any further cerebral ischemic events. The CBN signs remained unchanged on both sides during this time. This is the first report of the CBN sign in a patient with Moyamoya syndrome associated with Graves' disease.

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