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Transcranial magnetic stimulation distinguishes patients with behavioral variant fronto‐temporal dementia from primary progressive aphasia patients
Author(s) -
Lorenzo Francesco Di,
Motta Caterina,
Bonnì Sonia,
Assogna Martina,
Caltagirone Carlo,
Martorana Alessandro,
Koch Giacomo
Publication year - 2020
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1002/alz.044111
Subject(s) - transcranial magnetic stimulation , primary progressive aphasia , neuroscience , frontotemporal dementia , disinhibition , psychology , dementia , aphasia , medicine , audiology , stimulation , disease
Background In the recent years the use of neurophysiological techniques, combined with other clinical and neuroimaging biomarkers, allowed to further deepen physiopathological mechanisms of neurodegeneration. Fronto‐temporal Dementia (FTD) patients showed an impairment of intracortical circuits investigated with SICI/ICF and LICI protocols, while there is a normal activity of central cholinergic circuitry (investigated with SAI protocol), reflecting the relative sparing of cholinergic system in this disease. In the current work we aimed to determine whether a transcranial magnetic stimulation (TMS) multiparadigm approach can be used to distinguish the behavioral variant of frontotemporal dementia (bvFTD) from non fluent variant of Primary Progressive Aphasia (nfPPA) Method 30 patients with bvFTD and 30 nfAPP patients have been enrolled for this study. Paired‐pulse TMS was used to investigate short‐interval intracortical inhibition (SICI) and facilitation (ICF), long‐interval intracortical inhibition (LICI) , and short‐latency afferent inhibition (SAI) to measure the activity of different intracortical circuits in all the participants to the study. We also tested Long‐term Potentiation (LTP) cortical plasticity with iTBS protocol. All the patients underwent an extensive neuropsychological evaluation, MRI and CSF sampling. Result bvFTD patients exhibited a deficit of SICI, consisting in a disinhibition, while on the other hand nfPPA patients had a weakened ICF resulting in a weakened facilitation. No difference was observed for SAI, reflecting the sparing of cholinergic neurons for both nfPPA and bvFTD patients. bvFTD patients showed a deficit of LICI evident at 100 msec, expression of an impairment of GABA‐B receptors, resulting in a disinhibition of the MEP compared to nf‐PPA. bvFTD patients had a weakened iTBS after effects, oppositely to nfPPA patients that showed the expected LTP‐like cortical plasticity. Conclusion Intracortical circuitry investigation and iTBS protocol showed clear differences among bvFTD patients and PPA, probably reflecting distinct phisiopathological mechanisms. TMS is a noninvasive procedure able to distinguishes between different variants of FTD. These preliminary findings pave to way for a more spread use of neurophysiological techniques in the study and management of neurodegenerative disease such as FTD, not just for better understanding of phisiopathological mechanisms of disease but also in case of monitoring of therapeutical efficiency.