Frontiers in Human Neuroscience (May 2020)
Cortical Inhibitory Imbalance in Functional Paralysis
Abstract
BackgroundFunctional neurological disorders are characterized by neurological symptoms that have no identifiable pathology and little is known about their underlying pathophysiology.ObjectivesTo analyze motor cortex excitability and intracortical inhibitory and excitatory circuits’ imbalance in patients with flaccid functional weakness.MethodsTwenty-one consecutive patients with acute onset of flaccid functional weakness were recruited. Single and paired-pulse transcranial magnetic stimulation (TMS) protocols were used to analyze resting motor thresholds (RMT) and intracortical inhibitory (short interval intracortical inhibition – SICI) and excitatory (intracortical facilitation – ICF) circuits’ imbalance between the affected and non-affected motor cortices.ResultsWe observed a significant increase in RMT and SICI in the affected motor cortex (p < 0.001), but not for ICF, compared to the contralateral unaffected side.ConclusionThis study extends current knowledge of functional weakness, arguing for a specific central nervous system abnormality which may be involved in the symptoms’ pathophysiology.
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