Diffusion-weighted MRI (DWI) and perfusion MRI (PI) have been mainly applied in acute stroke, but may provide information in the peri-ictal phase in epilepsy patients. Both transient reductions of brain water diffusion, namely a low apparent diffusion coefficient (ADC), and signs of hyperperfusion have been reported in experimental and human epilepsy case studies. We studied 10 patients with complex partial status epilepticus (CPSE) with serial MRI including DWI and PI. All patients showed regional hyperintensity on DWI, and a reduction of the ADC in (i) the hippocampal formation and the pulvinar region of the thalamus (six out of 10 patients), (ii) the pulvinar and cortical regions (two out of 10), (iii) the hippocampal formation only (one out of 10), and (iv) the hippocampal formation, the pulvinar and the cortex (one out of 10). In all patients a close spatial correlation of focal hyperperfusion with areas of ADC/DWI change was present. In two patients hyperperfusion was confirmed in additional SPECT (single photon emission computed tomography) studies. All patients received follow-up MRI examinations showing partial or complete resolution of diffusion and perfusion abnormalities depending on the length of the follow-up interval. The clinical course, EEG and SPECT results all indicate that MRI detected changes related to prolonged epileptic activity. Combined PI and DWI can visualize haemodynamic and tissue changes after CPSE in the hippocampus, thalamus and affected cortical regions.

It is the purpose of this review to critically consider and organize the literature dealing with the ephemeral electroencephalographic (EEG) pattern periodic lateralized epileptiform discharges (PLEDs). Although the retrospective nature of these studies limits their ability to discuss accurately the clinical and pathophysiological aspects of this EEG entity, the available data strongly emphasize stroke as the dominant etiology and its high association with seizures. Recent evidence, particularly from functional neuroimaging studies, strongly suggests that PLEDs might reflect a key pattern for focal hyperexcitability in the penumbra zone of ischemic stroke. The authors prefer to consider PLEDs as an EEG signature of a dynamic pathophysiological state in which unstable neurobiological processes create an ictal-interictal continuum, with the nature of the underlying neuronal injury, the patient's preexisting propensity to have seizures, and the co-existence of any acute metabolic derangements all contributing to whether seizures occur or not. This review underlines the need for further sophisticated prospective controlled studies implementing early continuous EEG monitoring in order to contribute to an understanding of the incidence, dynamics, and relevance of this pattern.

Our data confirm that ipsilateral PET hypometabolism may be an indicator for good postoperative outcome in presurgical evaluation of drug-resistant TLE, although the actual diagnostic added value remained questionable and unclear. PET does not appear to add value in patients localized by ictal scalp EEG and MRI. Prospective studies limited to non-localized ictal scalp EEG or MRI-negative patients are required for validation.