The morphology of high frequency oscillations (HFO) does not improve delineating the epileptogenic zone

Publication date: April 2016
Source:Clinical Neurophysiology, Volume 127, Issue 4
Author(s): Sergey Burnos, Birgit Frauscher, Rina Zelmann, Claire Haegelen, Johannes Sarnthein, Jean Gotman
ObjectiveWe hypothesized that high frequency oscillations (HFOs) with irregular amplitude and frequency more specifically reflect epileptogenicity than HFOs with stable amplitude and frequency.MethodsWe developed a fully automatic algorithm to detect HFOs and classify them based on their morphology, with types defined according to regularity in amplitude and frequency: type 1 with regular amplitude and frequency; type 2 with irregular amplitude, which could result from filtering of sharp spikes; type 3 with irregular frequency; and type 4 with irregular amplitude and frequency. We investigated the association of different HFO types with the seizure onset zone (SOZ), resected area and surgical outcome.ResultsHFO rates of all types were significantly higher inside the SOZ than outside. HFO types 1 and 2 were strongly correlated to each other and showed the highest rates among all HFOs. Their occurrence was highly associated with the SOZ, resected area and surgical outcome. The automatic detection emulated visual markings with 93% true positives and 57% false detections.ConclusionsHFO types 1 and 2 similarly reflect epileptogenicity.SignificanceFor clinical application, it may not be necessary to separate real HFOs from "false oscillations" produced by the filter effect of sharp spikes. Also for automatically detected HFOs, surgical outcome is better when locations with higher HFO rates are included in the resection.



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2. Follow-up of five cases with Rasmussen encephalitis with magnetoencephalography

Publication date: April 2016
Source:Clinical Neurophysiology, Volume 127, Issue 4
Author(s): D.S. Rossi, E. Visani, D. Duran, F. Rotondi, L. Canafoglia, E. Freri, F. Ragona, T. Granata, F. Panzica, S. Franceschetti
Magnetoencephalography (MEG) recordings of interictal and/or ictal discharges can provide valuable information about the location of the epileptogenic area in the brain. Rasmussen Encephalitis (RE) is characterized by intractable epilepsy, progressive hemiparesis, and unilateral hemispheric atrophy. The progression of the symptoms to significant neurological impairment usually occurs within months to a few years. Five patients (mean age at first observation 7.6±3years) fitting Bien's criteria for the diagnosis of RE were enrolled for the study and follow-up for at least 1.5years (4–7MEG measures per patient), in order to evaluate correlations between the evolution of clinical picture, neuroradiological and MEG findings. MEG data were visually inspected and interictal spikes were selected for the source localization by means of equivalent current dipoles (ECDs). Cortical thickness was evaluated from Magnetic Resonance Imaging (MRI). All patients showed ictal/interictal multifocality, reduction of background cortical magnetic activity, and progressive focal cortical atrophy on MRI of the affected hemisphere. Moreover, our preliminary data showed that dipole clusters were found mainly in the most atrophic cortical regions, suggesting a close relationship between MRI and MEG alterations.



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6. Sensory-motor networks’ topology in multiple sclerosis fatigue

Publication date: April 2016
Source:Clinical Neurophysiology, Volume 127, Issue 4
Author(s): F. Miraglia, F. Vecchio, C. Porcaro, C. Cottone, A. Cancelli, P.M. Rossini, F. Tecchio
The large majority (80%) of people with multiple sclerosis (MS) complain of fatigue, which is the most disabling symptom in half of them. While the few drugs used to treat MS fatigue are limitedly useful, it was recently observed the efficacy of a personalized neuromodulation treatment, supporting the concept that interventions modifying the sensorimotor network activity balances could be suitable non-pharmacological treatments for MS fatigue. Aim of the present study is to strengthen knowledge of the brain unbalances, which proper neuromodulations should target to compensate. We collected electroencephalographic (EEG) data in 18 people with mild MS, while they were in resting state with open eyes. To ensure a wide range of fatigue, we enrolled patients to have Higher- or Lower-Fatigue based on scores of the modified Fatigue Impact Scale (mFIS). We selected the graph theory small-world index, calculated on networks of cortical nodes estimated by eLORETA, to evaluate the characteristics of left and right frontal (Motor) and parieto-occipital-temporal (Sensory) brain networks separately. Fatigue symptoms increased together with the small-world index in the Sensory network of the left dominant hemisphere. This finding hones understanding of the targets of neuromodulation interventions, indicating the sensory network of the dominant left hemisphere as a specific target.



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10. Visual electrophysiology. A good friend can help you in need

Publication date: April 2016
Source:Clinical Neurophysiology, Volume 127, Issue 4
Author(s): M.C. Tozzi, S. Silipo, S. Monaco, L. Bertolasi
Scotopic and photopic full field-Electroretinogram (ERG), pattern electroretinogram (PERG) and visual evoked potential (VEP) are stimulating and recording methods to evaluate the functionality of the different layers of retina and of the visual pathway from retina to visual cortex of the brain. Visual electrophysiology is a useful diagnostic tool which aids in cases of unexplained visual loss if the clinician is well-versed in this techniques. Furthermore the new ocular imaging tests such us OCT give only morphological informations about retina and the head of optic nerve that need functional correlations with the symptoms of the patient. We review the diagnostic protocol for neurophysiological assessment of afferent visual system performed in our lab and describe normative data from 30 healthy subjects.



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14. An abnormal transduction of the chromatic stimuli from the outer to the inner retinal layers may contribute to the mechanism of photophobia in migraine

Publication date: April 2016
Source:Clinical Neurophysiology, Volume 127, Issue 4
Author(s): G. Coppola, L. Corso, A. Di Renzo, A. Fadda, F. Martelli, C. Di Lorenzo, V. Parisi, J. Schoenen, B. Falsini, F. Pierelli
Recent experimental evidences point out a possible involvement of retina in hypersensitivity of migraine patients to light stimuli. Our aim was to investigate the short-wavelength-sensitive and the medium/long-wavelength-sensitive cone photoreceptors of the visual pathways in migraine without aura (MO) patients between attacks and in healthy volunteers (HV) by using yellow-blue (Y-B) or red-blue (R-B) visual flicker stimuli. Square-wave focal electroretinograms (FERGs) were recorded in 22 MO patients and 20 HV. Fourier analysis allowed extracting from the FERG data the fundamental (1F) and the second harmonic (2F) components (amplitude and phase) that are related respectively to outer and inner retinal activity. Usual headache severity and photophobia during migraine were scored on a 0 to 10 visual analogue scale. When compared to HV, MO patients had an advanced 1F phase but normal amplitude in all blocks of Y-B FERG. Self-rated intensity of ictal photophobia positively correlated with attack frequency, headache severity, 1F Y-B phase, 1F R-B phase, 2F Y-B amplitude, habituation slope, and 2F R-B phase. These results suggest that an abnormal signal transduction from the outer to the inner retinal layers could contribute to the mechanisms by which light causes pain or discomfort during the migraine headache.



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Reward anticipation and trait anhedonia: An electrophysiological investigation in subjects with schizophrenia

Publication date: April 2016
Source:Clinical Neurophysiology, Volume 127, Issue 4
Author(s): A. Vignapiano, A. Mucci, J. Ford, V. Montefusco, G.M. Plescia, P. Bucci, S. Galderisi
ObjectiveInvestigate impairment of reward anticipation in subjects with schizophrenia (SCZ) and its association with negative symptom dimensions and hedonic experience.MethodsEvent-related potentials (ERPs) were recorded, in thirty SCZ and twenty-three matched healthy controls (HC), during a "Monetary Incentive Delay" task in which reward and loss cues (incentive cues of positive and negative value) of different magnitude, as well as neutral cues were presented.Assessments: anticipatory and consummatory pleasure, trait anhedonia and motivation in all subjects; avolition and expressive deficit in SCZ.ResultsSCZ had lower motivation but comparable hedonic experience with respect to HC. In HC, during reward anticipation, the early P3 was larger for large magnitude incentives, irrespective of their valence, while the late P3 was larger for large reward. In SCZ, early P3 did not discriminate the incentive magnitude and the late P3 was larger for large loss. Early P3 amplitude for large magnitude incentives was inversely related to trait social anhedonia but not to negative symptoms dimensions.ConclusionsSCZ are unable to integrate the incentive magnitude and reward value of future events in the context of their ongoing task. P3 abnormalities are associated with trait anhedonia, but not with negative symptoms dimensions.SignificanceIn line with recent studies, our findings indicate that anhedonia and avolition are partially independent constructs.



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Structural brain correlates of defective gesture performance in schizophrenia

Publication date: Available online 10 March 2016
Source:Cortex
Author(s): Katharina Stegmayer, Stephan Bohlhalter, Tim Vanbellingen, Andrea Federspiel, Jeanne Moor, Roland Wiest, René Müri, Werner Strik, Sebastian Walther
IntroductionThe neural correlates of impaired performance of gestures are currently unclear. Lesion studies showed variable involvement of the ventro-dorsal stream particularly left inferior frontal gyrus (IFG) in gesture performance on command. However, findings cannot be easily generalized as lesions may be biased by the architecture of vascular supply and involve brain areas beyond the critical region. The neuropsychiatric syndrome of schizophrenia shares apraxic-like errors and altered brain structure without macroanatomic lesions. Schizophrenia may therefore qualify as a model disorder to test neural correlates of gesture impairments.MethodsWe included 45 schizophrenia patients and 44 healthy controls in the study to investigate the structural brain correlates of defective gesturing in schizophrenia using voxel based morphometry. Gestures were tested in two domains: meaningful gestures (transitive and intransitive) on verbal command and imitation of meaningless gestures. Cut-off scores were used to separate patients with deficits, patients without deficits and controls. Group differences in GM volume were explored in an ANCOVA.ResultsPatients performed poorer than controls in each gesture category (p < 0.001). Patients with deficits in producing meaningful gestures on command had reduced gray matter (GM) predominantly in left IFG, with additional involvement of right insula and anterior cingulate cortex. Patients with deficits differed from patients without deficits in right insula, inferior parietal lobe and superior temporal gyrus.ConclusionsImpaired performance of meaningful gestures on command was linked to volume loss predominantly in the praxis network in schizophrenia. Thus, the behavioral similarities between apraxia and schizophrenia are paralleled by structural alterations. However, few associations between behavioral impairment and structural brain alterations appear specific to schizophrenia.



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