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Keywords:

  • current perception threshold;
  • epidermal nerve fiber;
  • multiple system atrophy;
  • Parkinson's disease;
  • sensory processing

Abstract

Aim

Although peripheral deafferentation is one of the causes of abnormal sensory processing in Parkinson's disease (PD), functional assessment of different-size sensory nerve populations remains insufficient.

We assessed the characteristics of sensory perception and processing in PD patients using current perception threshold (CPT).

Methods

A total of 28 patients with PD, 20 with multiple system atrophy (MSA) and 28 healthy controls underwent CPT examination using a Neurometer device, which can selectively stimulate A-β fibers at 2000 Hz, A-δ fibers at 250 Hz and C  fibers at 5 Hz.

Results

Significant differences in CPT for all stimulus frequencies were observed among the three groups. PD patients had significantly higher CPT for all stimulus frequencies than control individuals (< 0.05). Also, PD patients had significantly higher CPT for 250 and 5 Hz than MSA patients (< 0.05). At the optimum cut-off level, the CPT distinguished PD patients from MSA patients with a high sensitivity (82% at 250 Hz, 86% at 5 Hz) and specificity (75% at 250 Hz, 80% at 5 Hz). The CPT were not affected by clinical profile, cardiac sympathetic denervation or cardiovascular autonomic dysfunction.

Conclusion

Significantly increased CPT in PD indicate altered processing of sensory information involving A-β, A-δ and C fibers. The clear distinction of CPT between PD and MSA might reflect the involvement in small fiber dysfunction in PD, but not in MSA. These findings suggest that CPT testing might contribute to diagnosis of PD, as well as the understanding of sensory processing involving peripheral deafferentation.