The perception of affective touch in Parkinson's disease and its relation to small fibre neuropathy

Kass-Iliyya, L, Leung, M, Marshall, A, Trotter, P, Kobylecki, C, Walker, S, Gosal, D, Jeziorska, M, Malik, RA, McGlone, F and Silverdale, MA (2017) The perception of affective touch in Parkinson's disease and its relation to small fibre neuropathy. European Journal of Neuroscience, 45 (2). pp. 232-237. ISSN 0953-816X

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Abstract

Affective touch sensation is conducted by a sub-class of C-fibres in hairy skin known as C-Tactile (CT) afferents. CT afferents respond maximally to gentle skin stroking at velocities between 1 and 10 cm/s. Parkinson’s disease (PD) is characterised by markedly reduced cutaneous C-fibres. It is not known if affective touch perception is influenced by C-fibre density and if affective touch is impaired in PD compared to healthy controls. We predicted that perceived pleasantness to gentle stroking in PD would correlate with C-afferent density and that affective touch perception would be impaired in PD compared to healthy controls. Twenty-four PD patients and 27 control subjects rated the pleasantness of brush stroking at an optimum CT stimulation velocity (3 cm/s) and two sub-optimal velocities (0.3 and 30 cm/s). PD patients underwent quantification of C-fibre density using skin biopsies and corneal confocal microscopy. All participants rated a stroking velocity of 3 cm/s as the most pleasant with significantly lower ratings for 0.3 and 30 cm/s. There was a significant positive correlation between C-fibre density and pleasantness ratings at 3 and 30 cm/s but not 0.3 cm/s. Mean pleasantness ratings were consistently higher in PD patients compared to control subjects across all three velocities. This study shows that perceived pleasantness to gentle touch correlates significantly with C-fibre density in PD. The higher perceived pleasantness in PD patients compared to controls suggests central sensitisation to peripheral inputs, which may have been enhanced by dopamine therapy.