Cortical function and corticomotoneuronal adaptation in monomelic amyotrophy

José Manuel Matamala; Nimeshan Geevasinga; William Huynh; Thanuja Dharmadasa; James Howells; Neil G Simon; Parvathi Menon; Steve Vucic; Matthew C Kiernan

doi:10.1016/j.clinph.2017.05.005

Cortical function and corticomotoneuronal adaptation in monomelic amyotrophy

Clin Neurophysiol. 2017 Aug;128(8):1488-1495. doi: 10.1016/j.clinph.2017.05.005. Epub 2017 May 17.

Authors

José Manuel Matamala¹, Nimeshan Geevasinga², William Huynh³, Thanuja Dharmadasa⁴, James Howells⁴, Neil G Simon⁵, Parvathi Menon², Steve Vucic⁶, Matthew C Kiernan⁴

Affiliations

¹ Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW 2050, Australia. Electronic address: jose.matamalacapponi@sydney.edu.au.
² Western Clinical School, University of Sydney, Sydney, NSW 2145, Australia.
³ Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW 2050, Australia; Prince of Wales Clinical School, The University of New South Wales, Sydney, NSW 2052, Australia.
⁴ Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW 2050, Australia.
⁵ Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW 2050, Australia; St Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW 2010, Australia.
⁶ Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW 2050, Australia; Western Clinical School, University of Sydney, Sydney, NSW 2145, Australia.

PMID: 28624492
DOI: 10.1016/j.clinph.2017.05.005

Abstract

Objective: To evaluate corticomotoneuronal integrity in monomelic amyotrophy using threshold tracking transcranial magnetic stimulation (TT-TMS).

Methods: Cortical excitability studies were prospectively performed in 8 monomelic amyotrophy patients and compared to 21 early-onset amyotrophic lateral sclerosis (ALS) patients and 40 healthy controls. Motor evoked potentials responses were recorded over abductor pollicis brevis.

Results: Maximal motor evoked potential (MEP/CMAP ratio) was significantly increased in monomelic amyotrophy compared with controls (monomelic amyotrophy 51.2±12.4%; control 22.7±2.1%, p=0.04). Averaged short-interval intracortical inhibition (SICI, ISI 1-7ms) in monomelic amyotrophy patients was similar to controls (monomelic amyotrophy 9.6±2.1%; control 10.0±0.9%, p=0.98). However, it was significantly reduced in early-onset ALS in comparison with monomelic amyotrophy patients (monomelic amyotrophy 9.6±2.1%; ALS 2.3±1.7%, p<0.001). Averaged SICI is a good parameter (area under the curve 0.79, p=0.02) to discriminate between monomelic amyotrophy and early-onset ALS patients.

Conclusions: TT-TMS technique has identified normal cortical function in monomelic amyotrophy, a feature that distinguishes it from early-onset ALS. The greater corticomotoneuronal projections to spinal motoneurons may represent central nervous system adaptive change in monomelic amyotrophy.

Significance: Corticomotoneuronal dysfunction does not drive the lower motor neurone loss presented in monomelic amyotrophy.

Keywords: Amyotrophic lateral sclerosis; Corticomotoneuronal plasticity; Monomelic amyotrophy; Motor evoked potentials; Short-interval intracortical inhibition; Threshold tracking transcranial magnetic stimulation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adaptation, Physiological / physiology*
Adult
Cohort Studies
Evoked Potentials, Motor / physiology*
Female
Humans
Male
Middle Aged
Motor Cortex / physiopathology*
Motor Neurons / physiology*
Prospective Studies
Spinal Muscular Atrophies of Childhood / diagnosis
Spinal Muscular Atrophies of Childhood / physiopathology*
Transcranial Magnetic Stimulation / methods*
Young Adult

Supplementary concepts

Amyotrophy, monomelic