Ictal focal hyperperfusion demonstrated by arterial spin-labeling perfusion MRI in partial epilepsy status

Abstract

Dear Sir, Pulsed arterial spin-labeling (PASL) perfusion magnetic resonance imaging (MRI) is a noninvasive method of measuring regional cerebral blood flow (rCBF) without contrast medium and has been routinely applied in cerebrovascular diseases as a cerebral perfusion measurement [1]. In partial epilepsy, ictal cortical hyperperfusion is believed to be a useful marker for identifying epileptogenic zone, and singlephoton emission computed tomography (SPECT) is commonly used for evaluating differences between interictal and ictal cerebral perfusions. Few reports have described hemodynamic changes detected by PASL in interictal [2–4] and peri-ictal states [5, 6]. Recently, we had a rare opportunity to conduct PASL imaging and also diffusion-weighted imaging (DWI) of a patient both in partial epilepsy status (PES) and during the interictal state. Our patient, a 25-year-old man with normal development and no neurological deficits, had sometimes experienced a short-term feeling of visual distortion in the left half of his visual field since age 20 years. He had his first generalized convulsion and was admitted to our hospital. One week later, he complained of frequent occurrences of blurred vision or elementary visual hallucinations like flickering lights in the left half of his visual field, sometimes accompanied by rotating his head to the left. An electroencephalogram (EEG) recorded three ictal events during 30 min. The ictal pattern showed rhythmic bursting epileptic activities arising from the right occipital region, gradually reaching high amplitude and spreading to surrounding areas within approximately 2 min and then finished without generalizing (Fig. 1a). He presented with seizures at a frequency of five to six times per hour in the daytime, so-called PES. After starting carbamazepine administration, the seizures gradually decreased and had disappeared 3 days later. He experienced left visual field loss for a few days even after the seizures had disappeared but ultimately recovered from this deficit. MRI scans were performed on a 3 T MRI system (MAGNETOM Verio; Siemens AG, Munich, Germany) on the first day that frequent seizures occurred (Fig. 1b–d) and 1 week after the seizures had completely disappeared (Fig. 2). Cortical evaluation by reversed Short T1 inversion recovery (STIR) imaging indicated an anomaly consistent with a cortical malformation in the right medial occipital region (Fig. 1b). PASL was performed with a pulsed sequence, using QUIPSII perfusion mode [7] and the following parameters: nine slices; FOV read, 300.0 mm; FOV phase, 206.0; slice thickness, 10.0 mm; TE/TR/ Tl1/Tl2020/3,500/800/2,200 ms. PASL results were coregistered with FLAIR images. While focal hyperintense signals on DWI were observed in the limited area of the M. Oishi :Y. Fujii Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan