Cortical Inhibitory Imbalance in Functional Paralysis

Alberto Benussi; Enrico Premi; Valentina Cantoni; Silvia Compostella; Eugenio Magni; Nicola Gilberti; Veronica Vergani; Ilenia Delrio; Massimo Gamba; Raffaella Spezi; Angelo Costa; Michele Tinazzi; Alessandro Padovani; Barbara Borroni; Mauro Magoni

doi:10.3389/fnhum.2020.00153

Cortical Inhibitory Imbalance in Functional Paralysis

Front Hum Neurosci. 2020 May 7:14:153. doi: 10.3389/fnhum.2020.00153. eCollection 2020.

Authors

Affiliations

¹ Neurology Unit, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.
² Stroke Unit, Azienda Socio Sanitaria Territoriale Spedali Civili, Brescia, Italy.
³ U.O. Neurologia, Fondazione Poliambulanza Hospital, Brescia, Italy.
⁴ Neurology Unit, Movement Disorders Division, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.

Abstract

Background: Functional neurological disorders are characterized by neurological symptoms that have no identifiable pathology and little is known about their underlying pathophysiology.

Objectives: To analyze motor cortex excitability and intracortical inhibitory and excitatory circuits' imbalance in patients with flaccid functional weakness.

Methods: Twenty-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.

Results: We 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.

Conclusion: This study extends current knowledge of functional weakness, arguing for a specific central nervous system abnormality which may be involved in the symptoms' pathophysiology.

Keywords: functional neurological disorders; functional paralysis; motor threshold; short interval intracortical inhibition; transcranial magnetic stimulation.