High frequency oscillations and high frequency functional network characteristics in the intraoperative electrocorticogram in epilepsy.

OBJECTIVE: High frequency oscillations (HFOs; > 80 Hz), especially fast ripples (FRs, 250-500 Hz), are novel biomarkers for epileptogenic tissue. The pathophysiology suggests enhanced functional connectivity within FR generating tissue. Our aim was to determine the relation between brain areas showing FRs and 'baseline' functional connectivity within EEG networks, especially in the high frequency bands. METHODS: We marked FRs, ripples (80-250 Hz) and spikes in the electrocorticogram of 14 patients with refractory temporal lobe epilepsy. We assessed 'baseline' functional connectivity in epochs free of epileptiform events within these recordings, using the phase lag index. We computed the Eigenvector Centrality (EC) per channel in the FR and gamma band network. We compared EC between channels that did or did not show events at other moments in time. RESULTS: FR-band EC was higher in channels with than without spikes. Gamma-band EC was lower in channels with ripples and FRs. CONCLUSIONS: We confirmed previous findings of functional isolation in the gamma-band and found a first proof of functional integration in the FR-band network of channels covering presumed epileptogenic tissue. SIGNIFICANCE: 'Baseline' high-frequency network parameters might help intra-operative recognition of epileptogenic tissue without the need for waiting for events. These findings can increase our understanding of the 'architecture' of epileptogenic networks and help unravel the pathophysiology of HFOs.

Visual function and compensatory mechanisms for hemianopia after hemispherectomy in children.

OBJECTIVE: Little is known about the functional visual outcome of children after hemispherectomy. Several case reports have described an anomalous head posture (AHP) and exotropia (XT) contralateral to the side of early brain damage, as possible compensatory mechanisms (CMs) for homonymous hemianopia (HH). The aim of this study was to determine visual outcome and the prevalence of such CMs in hemispherectomized children. METHODS: Patient files from all children who underwent hemispherectomy and had a postoperative ophthalmologic examination in the University Medical Center (UMC) Utrecht up to October 2012 were retrospectively reviewed. Preoperative and postoperative clinical information on visual fixation, visual acuity, visual fields, optic discs, head posturing, ocular alignment, and cognitive development was collected. Clinical characteristics were compared between children who developed CMs and those who did not. RESULTS: Forty-five children (21 male) underwent a hemispherectomy (22 right) at a median age of 2.1 years. Median ophthalmologic follow-up was 2.3 years. After hemispherectomy, visual fixation was present in all children, and 87% of the examined children had a normal visual acuity or a mild visual impairment. All children who underwent a visual field measurement had an HH. Anomalous head posturing and continuous or intermittent XT contralateral to the side of hemispherectomy were found in 53% and 38% of children, respectively. Children with CMs had more frequently right-sided surgery and earlier onset of epilepsy, and they tended to be younger when they underwent hemispherectomy than children without. SIGNIFICANCE: Despite HH, the majority of children who undergo hemispherectomy have a good visual outcome. Furthermore, they frequently develop AHP and continuous or intermittent XT contralateral to the hemispherectomy as part of a coping strategy to optimize the functional visual field. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.

Finger snapping during seizures.

We describe two patients who showed snapping of the right hand fingers during invasive intracranial EEG evaluation for epilepsy surgery. We correlated the EEG changes with the finger-snapping movements in both patients to determine the underlying pathophysiology of this phenomenon. At the time of finger snapping, EEG spread from the supplementary motor area towards the temporal region was seen, suggesting involvement of these sites.

Contralateral MRI abnormalities affect seizure and cognitive outcome after hemispherectomy.

OBJECTIVE: To explore whether EEG and MRI abnormalities in the "healthy" hemisphere influence seizure and cognitive outcome after functional hemispherectomy. METHODS: This is a retrospective consecutive cohort study of 43 children who underwent functional hemispherectomy between 1994 and 2008. Results of preoperative EEG recordings were reviewed for the existence of (inter)ictal epileptic or background abnormalities in the contralateral hemisphere. Preoperative MRIs were reexamined for the existence of unequivocal contralateral abnormalities. Postoperative seizure status was assessed, and of 34 children, IQ or mental developmental index (MDI) scores were obtained preoperatively and postoperatively. Seizure freedom was defined as Engel 1A. Contralateral EEG and MRI abnormalities were studied in relation to seizure and cognitive outcome. RESULTS: Thirty-three children achieved seizure freedom (77%). Of the 11 patients with contralateral MRI abnormalities, only 45% were seizure free, compared with 88% of the 32 patients without contralateral MRI lesions (p = 0.030). Children with contralateral MRI abnormalities more often were severely retarded after surgery (MDI/IQ <55; 90% vs 42%, p = 0.030). Postoperative MDI/IQ scores improved in none of the children with, but in 38% of those without contralateral MRI abnormalities (p = 0.034). Contralateral epileptic or background EEG abnormalities did not affect seizure outcome or postoperative cognitive performance. Four of 6 children with bilateral epileptic encephalopathy reached seizure freedom. CONCLUSION: Unambiguous contralateral MRI abnormalities are significantly associated with seizure recurrence, severe mental delay, and lack of cognitive improvement and may be considered a relative contraindication for hemispherectomy. Contralateral EEG abnormalities do not negatively influence postsurgical outcome.

Transferrin toxin but not transferrin receptor immunotoxin is influenced by free transferrin and iron saturation.

BACKGROUND: Cytotoxic agents can be targeted successfully to cancer cells. The efficacy of such novel and potent anticancer strategies may be influenced by variables of iron metabolism. METHODS: The in vitro cytotoxicity against glioma cells of transferrin (Tf)-based targeted toxins was compared with that of alpha-transferrin receptor (TfR)-immunotoxin. RESULTS: Of four Tf-based targeted toxins, Tf-gelonin, Tf-pokeweed antiviral protein, Tf-momordin and Tf-saporin, inhibitory concentration 50% values against glioma-derived cell lines HS683 and U251, ranged from [4.8 +/- 1.5] x 10(-10) m for Tf-saporin to [26.9 +/- 15.3] x 10(-10) m for Tf-gelonin in [(3)H]-leucine incorporation assays. Tf-saporin and alpha-TfR-saporin-immunotoxin had similar efficacy, even in the more quantitative clonogenic assay (4-5 log kill with 1 x 10(-9) m) using the myeloma cell line RPMI 8226 and glioma cell line U251. However, on RPMI 8226, the efficacy of Tf-saporin 1 x 10(-9) m was reduced by 90% in the presence of 150 microg mL(-1)(=20% of normal plasma value) competing diferric transferrin, whereas the efficacy of the corresponding immunotoxin was affected only marginally. In addition, the efficacy of Tf-based conjugates will depend on their iron saturation state. Iron desaturation of Tf-saporin was demonstrated by [(59)Fe]-labelling, subsequent CM-Sepharose chromatography and SDS-PAGE. Desaturation led to virtually complete loss of affinity for the transferrin receptor, as determined by flow cytometry, which could be largely restored upon resaturation. CONCLUSION: Transferrin-based toxin conjugates are strongly influenced by the presence of free transferrin and the iron saturation state. The corresponding alpha-transferrin receptor-immunotoxin does not show these disadvantages, has similar efficacy and should be preferred for further experiments.