title: Intracortical inhibitory and excitatory circuits in subjects with minimal hepatic encephalopathy: a TMS study.
abstract: Minimal hepatic encephalopathy (MHE) is the earliest form of hepatic encephalopathy (HE) and affects up to 80 % of patients with liver cirrhosis. By definition, MHE is characterized by psychomotor slowing and subtle cognitive deficits,  but obvious clinical manifestations are lacking. Given its covert nature, MHE is often underdiagnosed. This study was aimed at detecting neurophysiological changes, as assessed by means of transcranial magnetic stimulation (TMS), involved in the early pathogenesis of the HE. We investigated motor cortex excitability in 15 patients with MHE and in 15 age-matched age-matched cirrhotic patients without MHE; the resting motor threshold, the short-interval intracortical inhibition (SICI) and the intracortical facilitation (ICF) were examined. Paired-pulse TMS revealed significant increased SICI and reduced ICF in the patients with MHE. These findings may reflect abnormalities in intrinsic brain activity and altered organization of functional connectivity networks. In particular, the results suggest a shift in the balance between intracortical inhibitory and excitatory mechanisms towards a net increase of inhibitory neurotransmission. Together with other neurophysiological (in particular EEG) and neuroimaging techniques, TMS may thus provide early markers of cerebral dysfunction in cirrhotic patients with MHE.
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria. raffaele.nardone@asbmeran-o.it.|Department of Neurology, Franz Tappeiner Hospital, Via Rossini, 5, 39012, Merano, BZ, Italy. raffaele.nardone@asbmeran-o.it.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Nardone
authors.affiliation: University of Torino and Collegio Carlo Alberto, Torino, Italy.
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: De Blasi
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Höller
authors.affiliation: Department of Neurology, Franz Tappeiner Hospital, Via Rossini, 5, 39012, Merano, BZ, Italy.|Department of Neurological and Movement Sciences, Section of Clinical Neurology, University of Verona, Verona, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Brigo
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Golaszewski
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Vanessa N
authors.initials: VN
authors.lastname: Frey
authors.affiliation: Department of Neurology, Franz Tappeiner Hospital, Via Rossini, 5, 39012, Merano, BZ, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Orioli
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Eugen
authors.initials: E
authors.lastname: Trinka
mesh_terms: D000368:Aged; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006501:Hepatic Encephalopathy / Q000503:physiopathology / Q000523:psychology* / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
keywords: Electroencephalography; Intracortical facilitation; Magnetic resonance imaging; Minimal hepatic encephalopathy; Short-latency intracortical inhibition; Transcranial magnetic stimulation