On the origin of epileptic High Frequency Oscillations observed on clinical electrodes

Publication date: Available online 11 February 2018
Source:Clinical Neurophysiology
Author(s): Mohamad Shamas, Pascal Benquet, Isabelle Merlet, Mohamad Khalil, Wassim El Falou, Anca NICA, Fabrice Wendling
ObjectiveIn this study we aim to identify the key (patho)physiological mechanisms and biophysical factors which impact the observability and spectral features of High Frequency Oscillations (HFOs).MethodsIn order to accurately replicate HFOs we developed virtual-brain / virtual-electrode simulation environment combining novel neurophysiological models of neuronal populations with biophysical models for the source/sensor relationship. Both (patho)physiological mechanisms (synaptic transmission, depolarizing GABAA effect, hyperexcitability) and physical factors (geometry of extended cortical sources, size and position of electrodes) were taken into account. Simulated HFOs were compared to real HFOs extracted from intracerebral recordings of 2 patients.ResultsOur results revealed that HFO pathological activity is being generated by feed-forward activation of cortical interneurons that produce fast depolarizing GABAergic post-synaptic potentials (PSPs) onto pyramidal cells. Out of phase patterns of depolarizing GABAergic PSPs explained the shape, entropy and spatiotemporal features of real human HFOs.ConclusionsThe terminology "high-frequency oscillation" (HFO) might be misleading as the fast ripple component (200-600Hz) is more likely a "high-frequency activity" (HFA), the origin of which is independent from any oscillatory process.SignificanceNew insights regarding the origins and observability of HFOs along depth-EEG electrodes were gained in terms of spatial extent and 3D geometry of neuronal sources.



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10-10 Electrode Placement System

Publication date: Available online 11 February 2018
Source:Clinical Neurophysiology
Author(s): Marc R. Nuwer




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To warn or not to warn: A reappraisal of brainstem auditory evoked potential warning criteria during surgery

Publication date: Available online 11 February 2018
Source:Clinical Neurophysiology
Author(s): Aatif M. Husain




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Functional capacity in adults with cerebral palsy: Lower limb muscle strength matters.

Publication date: Available online 10 February 2018
Source:Archives of Physical Medicine and Rehabilitation
Author(s): Jarred G. Gillett, Glen A. Lichtwark, Roslyn N. Boyd, Lee A. Barber
ObjectiveTo investigate the relationship between lower limb muscle strength, passive muscle properties and functional capacity outcomes in adults with cerebral palsy (CP).DesignCross-sectional study.SettingTertiary institution biomechanics laboratory.ParticipantsSample of 33 adults with spastic-type CP with a mean age of 25 (range, 15-51) years; mean ± SD body mass 70.15 ± 21.35 kg; Gross Motor Function Classification System (GMFCS) level I n=20, level II n=13.InterventionsNot applicable.Main Outcome MeasuresSix-minute walk test (6MWT) distance (m); lateral step-up (LSU) test performance (total repetitions); timed up-stairs (TUS) performance (s); maximum voluntary isometric strength of plantar flexors (PF) and dorsiflexors (DF) (Nm.kg^-1); and passive ankle joint and muscle stiffness.ResultsMaximum isometric PF strength independently explained 61% of variance in 6MWT performance; 57% of variance in LSU test performance; and 50% of variance in TUS test performance. GMFCS level was significantly and independently related to all three functional capacity outcomes, and age was retained as a significant independent predictor of LSU, and TUS test performance. Passive medial gastrocnemius muscle fascicle stiffness and ankle joint stiffness were not significantly related to functional capacity measures in any of the multiple regression models.ConclusionsLow isometric PF strength was the most important independent variable related to distance walked on the 6MWT, fewer repetitions on the LSU test, and slower TUS test performance. These findings suggest lower isometric muscle strength contributes to the decline in functional capacity in adults with CP.



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What factors are associated with the recovery of autonomy after a hip fracture? A prospective multicentric cohort study

Publication date: Available online 10 February 2018
Source:Archives of Physical Medicine and Rehabilitation
Author(s): Mattia Morri, Paolo Chiari, Cristiana Forni, Antonella Orlandi Magli, Domenica Gazineo, Natalia Franchini, Lorenzo Marconato, Tiziana Giamboi, Andrea Cotti
Objectiveto identify the factors associated with recovering autonomy in the activities of daily livingDesignA prospective cohort studySettingThe orthopedic and orthogeriatric departments of 2 regional hospitalsParticipantsPatients 65 years of age or older with a diagnosis of fragility hip fracture. There were 840 eligible patients. Forty-three patients were excluded and 55 were lost. Seven hundred and forty-two consecutive patients was enrolled at the time of hospitalization and 727 at follow-up.Main Outcome MeasuresThe level of autonomy at 4 months was assessed using the ADL scale.ResultsThe score of the ADL scale at 4 months had a median equal to 3 (IQR=5). Half of the population was unable to recover their prefracture autonomy levels. The following were found to be risk factors: increasing age (B= 0.02; p<0.001), an elevated number of comorbidities (B=0.044; p=0.005); a lower level of prefracture autonomy (B=0.087; p<0.001); more frequent use of an anti-decubitus mattress (B=0.211; p<0.001), an increased number of days with disorientation (B=0.002; p=0.012); failure to recover deambulation (B=0.199; p<0.001); an increased number of days with diapers (B=0.003; p<0.001), with a urinary catheter (B=0.03; p<0.001) and with bed rails (B=0.001; p=0.014), and a non-intensive care pathway (B=0,199; p=0,014).ConclusionIn the initial phase, treatment of patients with hip fractures is significantly associated with the functional recovery of autonomy and should be activated starting from those factors which have the possibility of being modified in clinical practice: recovery of deambulation, treatment for disorientation and management of incontinence.



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Reply to “10-10 Electrode System for EEG Recording”

We thank Prof. Nuwer for providing additional information on the 10-10-system (Nuwer, 2018) which helps to put the development of the current EEG-nomenclature and related discussions in the correct historical context to which Prof Nuwer contributed significantly. We, as the international clinical neurophysiological community, continue to try to improve not only the nomenclature, but our clinical tools and their implementation to improve the patient care – which would have not been possible without the commitment of colleagues active in the field like Prof Nuwer.

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Ectopic impulse generation in peripheral nerve hyperexcitability syndromes and amyotrophic lateral sclerosis

Publication date: Available online 10 February 2018
Source:Clinical Neurophysiology
Author(s): Yu-ichi Noto, Neil G. Simon, Alexis Selby, Nidhi Garg, Kazumoto Shibuya, Nortina Shahrizaila, William Huynh, José M. Matamala, Thanuja Dharmadasa, Susanna B. Park, Steve Vucic, Matthew C. Kiernan
ObjectiveTo elucidate differences in the distribution and firing frequency of fasciculations between peripheral nerve hyperexcitability syndromes and amyotrophic lateral sclerosis (ALS) and to explore the generator site of fasciculations.MethodsUltrasound of 14 preselected muscles was performed in patients with peripheral hyperexcitability and ALS. The distribution and firing frequency of fasciculations were calculated. Cortical excitability assessment was also done by threshold tracking transcranial magnetic stimulation.ResultsIn total, 518 muscles from 37 peripheral hyperexcitability patients and 756 muscles from 54 ALS patients were examined. Regarding the detection rate, 74% of muscles in ALS patients demonstrated fasciculations, compared with 34% of muscles in peripheral hyperexcitability patients (P <0.001). The number of unique repeating focal muscle fasciculation movements per muscle and firing frequency of individual fasciculations in ALS were both significantly higher than those in peripheral hyperexcitability (P <0.001). Furthermore, cortical silent period duration negatively correlated with the number and firing frequency of fasciculations in ALS (P <0.05). A similar relationship was not evident in peripheral hyperexcitability.ConclusionsALS patients exhibited a widespread distribution of fasciculations, whereas peripheral hyperexcitability patients had a lower limb-dominant pattern.SignificanceA significant proportion of fasciculations in ALS may be influenced by changes in central excitability.



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