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Dharmadasa T, Pavey N, Tu S, Menon P, Huynh W, Mahoney CJ, Timmins HC, Higashihara M, van den Bos M, Shibuya K, Kuwabara S, Grosskreutz J, Kiernan MC, Vucic S. Novel approaches to assessing upper motor neuron dysfunction in motor neuron disease/amyotrophic lateral sclerosis: IFCN handbook chapter. Clin Neurophysiol 2024; 163:68-89. [PMID: 38705104 DOI: 10.1016/j.clinph.2024.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 02/08/2024] [Accepted: 04/14/2024] [Indexed: 05/07/2024]
Abstract
Identifying upper motor neuron (UMN) dysfunction is fundamental to the diagnosis and understanding of disease pathogenesis in motor neuron disease (MND). The clinical assessment of UMN dysfunction may be difficult, particularly in the setting of severe muscle weakness. From a physiological perspective, transcranial magnetic stimulation (TMS) techniques provide objective biomarkers of UMN dysfunction in MND and may also be useful to interrogate cortical and network function. Single, paired- and triple pulse TMS techniques have yielded novel diagnostic and prognostic biomarkers in MND, and have provided important pathogenic insights, particularly pertaining to site of disease onset. Cortical hyperexcitability, as heralded by reduced short interval intracortical inhibition (SICI) and increased short interval intracortical facilitation, has been associated with the onset of lower motor neuron degeneration, along with patterns of disease spread, development of specific clinical features such as the split hand phenomenon, and may provide an indication about the rate of disease progression. Additionally, reduction of SICI has emerged as a potential diagnostic aid in MND. The triple stimulation technique (TST) was shown to enhance the diagnostic utility of conventional TMS measures in detecting UMN dysfunction in MND. Separately, sophisticated brain imaging techniques have uncovered novel biomarkers of neurodegeneration that have bene associated with progression. The present review will discuss the utility of TMS and brain neuroimaging derived biomarkers of UMN dysfunction in MND, focusing on recently developed TMS techniques and advanced neuroimaging modalities that interrogate structural and functional integrity of the corticomotoneuronal system, with an emphasis on pathogenic, diagnostic, and prognostic utility.
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Affiliation(s)
- Thanuja Dharmadasa
- Department of Neurology, The Royal Melbourne Hospital City Campus, Parkville, Victoria, Australia
| | - Nathan Pavey
- Brain and Nerve Research Center, The University of Sydney, Sydney, Australia
| | - Sicong Tu
- Brain and Mind Centre, The University of Sydney, and Department of Neurology, Royal Prince Alfred Hospital, Australia
| | - Parvathi Menon
- Brain and Nerve Research Center, The University of Sydney, Sydney, Australia
| | - William Huynh
- Brain and Mind Centre, The University of Sydney, and Department of Neurology, Royal Prince Alfred Hospital, Australia
| | - Colin J Mahoney
- Brain and Mind Centre, The University of Sydney, and Department of Neurology, Royal Prince Alfred Hospital, Australia
| | - Hannah C Timmins
- Brain and Mind Centre, The University of Sydney, and Department of Neurology, Royal Prince Alfred Hospital, Australia
| | - Mana Higashihara
- Department of Neurology, Tokyo Metropolitan Institute for Geriatrics and Gerontology, Tokyo, Japan
| | - Mehdi van den Bos
- Brain and Nerve Research Center, The University of Sydney, Sydney, Australia
| | - Kazumoto Shibuya
- Neurology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Satoshi Kuwabara
- Neurology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Julian Grosskreutz
- Precision Neurology, Excellence Cluster Precision Medicine in Inflammation, University of Lübeck, University Hospital Schleswig-Holstein Campus, Lübeck, Germany
| | - Matthew C Kiernan
- Brain and Mind Centre, The University of Sydney, and Department of Neurology, Royal Prince Alfred Hospital, Australia
| | - Steve Vucic
- Brain and Nerve Research Center, The University of Sydney, Sydney, Australia.
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Qasem H, Fujiyama H, Rurak BK, Vallence AM. Good test–retest reliability of a paired-pulse transcranial magnetic stimulation protocol to measure short-interval intracortical facilitation. Exp Brain Res 2020; 238:2711-2723. [DOI: 10.1007/s00221-020-05926-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 09/15/2020] [Indexed: 12/21/2022]
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Gunes ZI, Kan VWY, Ye X, Liebscher S. Exciting Complexity: The Role of Motor Circuit Elements in ALS Pathophysiology. Front Neurosci 2020; 14:573. [PMID: 32625051 PMCID: PMC7311855 DOI: 10.3389/fnins.2020.00573] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 05/11/2020] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal disease, characterized by the degeneration of both upper and lower motor neurons. Despite decades of research, we still to date lack a cure or disease modifying treatment, emphasizing the need for a much-improved insight into disease mechanisms and cell type vulnerability. Altered neuronal excitability is a common phenomenon reported in ALS patients, as well as in animal models of the disease, but the cellular and circuit processes involved, as well as the causal relevance of those observations to molecular alterations and final cell death, remain poorly understood. Here, we review evidence from clinical studies, cell type-specific electrophysiology, genetic manipulations and molecular characterizations in animal models and culture experiments, which argue for a causal involvement of complex alterations of structure, function and connectivity of different neuronal subtypes within the cortical and spinal cord motor circuitries. We also summarize the current knowledge regarding the detrimental role of astrocytes and reassess the frequently proposed hypothesis of glutamate-mediated excitotoxicity with respect to changes in neuronal excitability. Together, these findings suggest multifaceted cell type-, brain area- and disease stage- specific disturbances of the excitation/inhibition balance as a cardinal aspect of ALS pathophysiology.
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Affiliation(s)
- Zeynep I Gunes
- Institute of Clinical Neuroimmunology, Klinikum der Universität München, Ludwig Maximilians University Munich, Munich, Germany.,Graduate School of Systemic Neurosciences, Ludwig Maximilians University Munich, Munich, Germany.,Biomedical Center, Ludwig Maximilians University Munich, Munich, Germany
| | - Vanessa W Y Kan
- Institute of Clinical Neuroimmunology, Klinikum der Universität München, Ludwig Maximilians University Munich, Munich, Germany.,Graduate School of Systemic Neurosciences, Ludwig Maximilians University Munich, Munich, Germany.,Biomedical Center, Ludwig Maximilians University Munich, Munich, Germany
| | - XiaoQian Ye
- Institute of Clinical Neuroimmunology, Klinikum der Universität München, Ludwig Maximilians University Munich, Munich, Germany.,Biomedical Center, Ludwig Maximilians University Munich, Munich, Germany
| | - Sabine Liebscher
- Institute of Clinical Neuroimmunology, Klinikum der Universität München, Ludwig Maximilians University Munich, Munich, Germany.,Biomedical Center, Ludwig Maximilians University Munich, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
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