Plantar cutaneous function in Parkinson’s disease patients ON and OFF L-dopa

• It is unclear if plantar cutaneous function is disrupted in Parkinson’s disease (PD).
• Sensitivity and lower-limb reflexes were assessed in PD patients ON/OFF L-dopa.
• Plantar cutaneous function was similar to healthy age-matched control groups.
• Intact function in PD supports the use of therapeutics (e.g., vibrating insoles).

While Parkinson’s disease (PD) is traditionally viewed as a motor disorder, there is mounting evidence that somatosensory function becomes affected as well. However, conflicting reports exist regarding whether plantar sensitivity is reduced in early-onset PD patients. Plantar sensitivity was assessed using monofilaments and a gold-standard, two-interval two-alternative forced choice vibrotactile detection task at both 30 and 250 Hz. Lower-limb cutaneous reflexes were assessed by delivering continuous, sinusoidal vibration at 30 and 250 Hz while recording muscle activity in Tibialis Anterior. We found no evidence of elevated plantar thresholds or dysfunctional lower-limb cutaneous reflexes in PD patients ON medication. We also found no acute effect of ceasing L-dopa intake on either plantar sensitivity or cutaneous reflexes. Our finding of intact cutaneous function in PD supports the further exploration of therapeutics that enhance plantar sensitivity to minimize postural instability, a source of considerable morbidity in this clinical population.