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Purpose: Non-convulsive status epilepticus (NCSE) is characterized by repetitive or continuous seizures without convulsions. Arterial spin labeling (ASL) is useful for assessing hyperperfusion due to neurovascular unit coupling in patients with NCSE; subarachnoid hemorrhage (SAH) impairs the neurovascular unit. We hypothesized that the sensitivity of ASL in detecting NCSE is low in patients with SAH during the acute phase. Methods: Based on ASL findings obtained within 48 h after the clinical suspicion of focal-onset NCSE, we divided 34 patients into ASL-negative (no hyperperfusion; n = 10) and ASL-positive (confirmed hyperperfusion; n = 24) groups. We further divided the two groups according to the NCSE etiology: patients who were diagnosed with NCSE within 14 days after SAH onset (acute SAH, n = 11) and patients with NCSE due to factors other acute SAH (n = 23) and compared their characteristics. Results: In 10 of the 34 patients (29.4 %) the ASL findings were normal. The rate of acute SAH was significantly higher in ASL-negative- (n = 8, 80.0 %) than ASL-positive patients (n = 3, 12.5 %). The rate of patients in aphasic status was significantly lower in ASL-negative patients (n = 1, 10 %) than in ASL-positive patients (n = 12, 50.0 %). Conclusion: Normal ASL findings alone should not be used to exclude a diagnosis of NCSE particularly in patients in the acute phase of SAH with deterioration or no improvement in consciousness.

A 64-year-old woman presenting with subarachnoid hemorrhage (World Federation of Neurosurgeons grade IV) from the rupture of a right large internal carotid-posterior communicating artery aneurysm suffered neuronal damage associated with post-ischemic hyperperfusion after neck clipping of the aneurysm under suction decompression. She did not completely recover consciousness after the operation. Diffusion-weighted imaging (DWI) performed on the first postoperative day showed subtle cortical hyperintensity in the parietal lobe. Arterial spin-labeling (ASL) and 123I-iodoamphetamine (123I-IMP) single photon emission computed tomography (SPECT) demonstrated hyperperfusion in the right temporo-parietal lobes. Delayed 123I-iomazenil (123I-IMZ) SPECT images showed a reduced IMZ uptake in the right temporo-parietal lobe corresponding to the hyperperfusion area on ASL images. DWI repeated on postoperative day 3 revealed progression of a hyperintensity lesion in the right parietal lobe. Blood pressure control and the use of a free radical scavenger relieved her symptoms. One month later, the area of reduced IMZ uptake was further expanded. Our findings suggest that post-ischemic hyperperfusion after suction decompression may result in neuronal damage demonstrated on 123I-IMZ SPECT images.