The effect of coil type and limb dominance in the assessment of lower-limb motor cortex excitability using TMS

Dharmadasa, Thanuja; Matamala, Jose M.; Howells, James; Simon, Neil G.; Vucic, Steve; Kiernan, Matthew C.

Abstract

Purpose: Clinical application of transcranial magnetic stimulation (TMS) has rapidly increased but the majority of studies have targeted upper limb muscles, with few exploring the lower-limb. Differences of coil choice have added to methodological difficulties of lower-limb studies and have challenged consistent interpretation of these parameters. The aims of this study were to determine the optimal coil choice for assessing lower-limb cortical excitability and assess laterality of normal cortical function. Methods: 69 recordings were undertaken from the tibialis anterior muscle from 48 healthy participants. Three coil types currently used in lower-limb studies (90 mm circular; 70 mm figure-of-8; and 110 mm double cone) were explored using single pulse TMS and paired-pulse threshold tracking TMS (TT-TMS) paradigms, with peripheral function also assessed. Cortical symmetry was ascertained with bilateral recordings (dominant versus non-dominant muscles). Results: The double-cone coil showed greatest efficacy, with significantly lower resting motor thresholds (49.0 +/- 2.3%, p 0.0005) and greater intracortical facilitation compared to the alternate coil choices. Using the double-cone coil, paired-pulse TT-TMS generated an averaged short interval intracortical inhibition of 11.3 +/- 1.2%, with an averaged intracortical facilitation of -6.1 +/- 1.9%. There were no differences between dominant and non-dominant hemispheres. Conclusions: The present study identified key differences in cortical parameters between the currently utilised coils for lower-limb TMS. Specifically, this indicates the importance of standardizing the lower-limb TMS protocol, particularly for accurate interpretation in disease pathology.

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Título según WOS: ID WOS:000465055200013 Not found in local WOS DB
Título de la Revista: NEUROSCIENCE LETTERS
Volumen: 699
Editorial: ELSEVIER SCI IRELAND LTD
Fecha de publicación: 2019
Página de inicio: 84
Página final: 90
DOI:

10.1016/j.neulet.2019.01.050

Notas: ISI