Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology
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Ketamine is an N-methyl-d-aspartate (NMDA) receptor antagonist commonly administered as a general anesthetic. However, neural circuit mechanisms to explain ketamine anesthesia-induced unconsciousness in humans are yet to be clearly defined. Disruption of frontal-parietal network connectivity has been proposed as a mechanism to explain this brain state. However, this mechanism was recently demonstrated at subanesthetic doses of ketamine in awake-patients. Therefore, we investigated whether there is an electroencephalogram (EEG) signature specific for ketamine anesthesia-induced unconsciousness. ⋯ The EEG signature of ketamine anesthesia-induced unconsciousness may offer new insights into NMDA circuit mechanisms for unconsciousness.
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Observational Study
GABAA circuit mechanisms are associated with ether anesthesia-induced unconsciousness.
An emerging paradigm for understanding how anesthetics induce altered arousal is relating receptor targeting in specific neural circuits to electroencephalogram (EEG) activity. Enhanced gamma amino-butyric acid A (GABAA) inhibitory post-synaptic currents (IPSCs) manifest with large-amplitude slow (0.1-1Hz) and frontally coherent alpha (8-12Hz) EEG oscillations during general anesthesia. Therefore, we investigated the EEG signatures of modern day derivatives of ether (MDDE) anesthesia to assess the extent to which we could obtain insights into MDDE anesthetic mechanisms. ⋯ These observations are consistent with the notion that GABAA circuit-level mechanisms are associated with MDDE anesthesia-induced unconsciousness.
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Transthyretin familial amyloid polyneuropathy (TTR-FAP) is an axonal sensory-motor and autonomic neuropathy. Reliable quantification of sudomotor function could prove essential in the diagnosis and early treatment management. We aim to assess the diagnostic value of a new sudomotor test (Sudoscan) in TTR-FAP. ⋯ Abnormal feet responses on Sudoscan support early diagnosis in TTR-FAP.
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In amyotrophic lateral sclerosis (ALS), fasciculations are believed to become less frequent during disease progression, associated with the loss of motor units. To address this issue, we studied the variation of fasciculation potential (FPs) frequency as evaluated by surface electromyography of the first dorsal interosseous muscle (1st DI) in patients with ALS and other related disorders, and to relate this change with the neurophysiological index (NI), a surrogate measure of functional motor units. ⋯ In ALS, the FP firing frequency does not decline significantly over several months, in spite of a marked reduction in the number of functional motor units.
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To explore ocular vestibular evoked myogenic potentials (oVEMP) to low-frequency vertex vibration (125 Hz) as a diagnostic test for superior canal dehiscence (SCD) syndrome. ⋯ Amplitude analysis of oVEMP evoked by low-frequency vertex bone vibration stimulation is an additional indicator of SCD syndrome and might serve for diagnosing SCD patients with coexistent conductive middle ear problems.