579441

research-article2015

MSJ0010.1177/1352458515579441Multiple Sclerosis JournalManogaran

MULTIPLE SCLEROSIS MSJ JOURNAL

Original Research Paper

Corticospinal tract integrity measured using transcranial magnetic stimulation and magnetic resonance imaging in neuromyelitis optica and multiple sclerosis

Multiple Sclerosis Journal 1­–8 DOI: 10.1177/ 1352458515579441 © The Author(s), 2015. Reprints and permissions: http://www.sagepub.co.uk/ journalsPermissions.nav

Praveena Manogaran, Irene Vavasour, Michael Borich, Shannon H Kolind, Alex P Lange, Alexander Rauscher, Lara Boyd, David KB Li and Anthony Traboulsee

Abstract Background: Both multiple sclerosis (MS) and neuromyelitis optica (NMO) can present with transverse myelitis; however, NMO symptoms are usually more severe and may present with more extensive axonal loss. Transcranial magnetic stimulation (TMS)-based input–output recruitment curves can quantitatively assess the excitability of corticospinal tract pathways and myelin water imaging can quantify the amount of myelin within this same pathway. Objective: To compare differential effects of MS and NMO on TMS recruitment curves and myelin water imaging. Methods: Ten healthy controls, 10 individuals with MS and 10 individuals with NMO completed clinical assessments, a TMS assessment and magnetic resonance imaging scan to measure recruitment curves and myelin water fraction in the corticospinal tract. Results: Individuals with NMO had lower recruitment curve slopes (mean 13.6±6 μV/%) than MS (23.6±11 μV/%) and controls (21.9±9 μV/%, analysis of variance (ANOVA) P=0.05). Corticospinal tract myelin water fraction was lower in individuals with NMO (mean 0.17±0.02) compared to MS (0.19±0.02) and controls (0.20±0.02, ANOVA P=0.0006). Conclusion: Corticospinal pathway damage in individuals with NMO was evident by reduced recruitment curve slope and lower myelin water fraction. These specific measures of corticospinal function and structure may be used to obtain a better understanding and monitor brain injury caused by inflammatory central nervous system disorders.

Keywords:  Multiple sclerosis, neuromyelitis optica, transcranial magnetic stimulation, magnetic resonance imaging, corticospinal tract, recruitment curve Date received 1 November 2014; revised 12 January 2015 and 23 February 2015; accepted 7 March 2015 Introduction Neuromyelitis optica (NMO) is a rare, autoimmune disorder of the central nervous system (CNS), which has overlapping clinical features with multiple sclerosis (MS) including optic neuritis and transverse myelitis.1 NMO is characterized by episodes of inflammation and damage to astrocytes with secondary injury to myelin and axons.2 NMO relapses are typically more severe than MS and may lead to more extensive axonal loss.3

Transcranial magnetic stimulation (TMS) is a noninvasive method to investigate cortical excitability and functional integrity of central motor pathways in the corticospinal tract (CST).4 TMS has been studied in numerous disease models such as stroke, movement disorders and spinal cord injury, demonstrating a high sensitivity in quantifying dysfunction in the CST.5,6 In particular, TMS can be used to obtain a recruitment curve that evaluates the cortical physiology and detects changes in cortical output maps.4,7 Motor evoked

Correspondence to: Anthony Traboulsee Department of Medicine, University of British Columbia, S-221A UBC Hospital, 2211 Wesbrook Mall, Vancouver, BC V6T2B5, Canada. [email protected] Praveena Manogaran Shannon H Kolind Alex P Lange Anthony Traboulsee Department of Medicine, University of British Columbia, Canada Irene Vavasour Alexander Rauscher David KB Li Department of Radiology, University of British Columbia, Canada Michael Borich Department of Rehabilitation Medicine, Division of Physical Therapy, Emory University, USA/Department of Pediatrics, University of British Columbia, Canada Lara Boyd Department of Physical Therapy, Brain Behaviour Laboratory, Canada The first two authors contributed equally to this paper.

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Multiple Sclerosis Journal  Table 1.  Subject characteristics and results. Technique

Measurement

Control

MS

NMO

TMS     MRI Clinical      

RMT (%) AMT (%) Recruitment curve slope (μV/%) †* MWF CST †‡ EDSS Disease duration (years) Age (years) Sex (M:F)

42.00 (8.27) 33.75 (5.08) 21.93 (8.52) 0.199 (0.017) – – 42.3 (10.3) 2:8

47.80 (9.24) 40.55 (8.27) 23.61 (11.06) 0.193 (0.016) 2.0 (1.2) 8.65 (4.9) 42.4 (8.9) 3:7

49.75 (8.89) 39.85 (9.08) 13.60 (5.68) 0.165 (0.022) 3.0 (1.4) 7.4 (4.1) 43.2 (11.2) 3:7

MRI: magnetic resonance imaging; MS: multiple sclerosis; NMO: neuromyelitis optica; TMS: transcranial magnetic stimulation; RMT: resting motor threshold; AMT: active motor threshold; CST: corticospinal tract; MWF: myelin water fraction; EDSS: Expanded Disability Status Scale. The mean of each measure is presented except for sex (ratio of male to female). Standard deviation is in parentheses. Significant measurements indicated as such: †P

Corticospinal tract integrity measured using transcranial magnetic stimulation and magnetic resonance imaging in neuromyelitis optica and multiple sclerosis.

Both multiple sclerosis (MS) and neuromyelitis optica (NMO) can present with transverse myelitis; however, NMO symptoms are usually more severe and ma...
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