title: Abnormal cortical synaptic plasticity in minimal hepatic encephalopathy.
abstract: Minimal hepatic encephalopathy (MHE) represents the earliest stage of hepatic encephalopathy (HE). MHE is characterized by cognitive function impairment in the domains of attention, vigilance and integrative function, while obvious clinical manifestations are lacking. In the present study, we aimed at assessing whether subjects with MHE showed alterations in synaptic plasticity within the motor cortex. Previous findings suggest that learning in human motor cortex occurs through long-term potentiation (LTP)-like mechanisms. We employed therefore the paired associative stimulation (PAS) protocol by transcranial magnetic stimulation (TMS), which is able to induce LTP-like effects in the motor cortex of normal subjects. Fifteen patients with MHE and 15 age- and sex-matched cirrhotic patients without MHE were recruited. PAS consisted of 180 electrical stimuli of the right median nerve paired with a single TMS over the hotspot of right abductor pollicis brevis (APB) at an ISI of 25ms (PAS25). We measured motor evoked potentials (MEPs) before and after each intervention for up to 30min. In healthy subjects the PAS25 protocol was followed by a significant increase of the MEP amplitude. On the contrary, in patients with MHE the MEP amplitude was slightly reduced after PAS. These findings demonstrated that associative sensorimotor plasticity, an indirect probe for motor learning, is impaired in MHE patients.
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: Patrick B
authors.initials: PB
authors.lastname: Langthaler
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Schwenker
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Cristina
authors.initials: C
authors.lastname: Florea
authors.affiliation: Department of Physiology, Medical University of Graz, Graz, Austria.
authors.forename: Monica
authors.initials: M
authors.lastname: Christova
authors.affiliation: Department of Neurology, Franz Tappeiner Hospital, Merano, 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: Eugen
authors.initials: E
authors.lastname: Trinka
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Department of Neurology, Franz Tappeiner Hospital, Merano, Italy. Electronic address: raffaele.nardone@asbmeran-o.it.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Nardone
mesh_terms: D000704:Analysis of Variance; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006501:Hepatic Encephalopathy / Q000473:pathology*; D006801:Humans; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009483:Neuropsychological Tests; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation
keywords: Minimal hepatic encephalopathy; Paired associative stimulation; Synaptic plasticity; Transcranial magnetic stimulation