Quantitative sensory testing predicts histological small fiber neuropathy in postural tachycardia syndrome

Abstract

Background: Retrospective investigation of the somatosensory profile and prediction of histologic small fiber neuropathy (SFN) in postural orthostatic tachycardia syndrome (POTS) was performed using quantitative sensory testing (QST) as a standardized noninvasive test.

Methods: In this investigation, full data sets from 30 patients (age: 34.03 ± 10.82 years, n = 6 males), including results of autonomic function testing, norepinephrine values, skin biopsy, and QST, were retrospectively analyzed. The QST data were compared with healthy controls (HCs) (age: 34.20 ± 10.5 years, n = 6 males, t test: 0.95).

Results: The evaluation of all QST parameters in POTS compared with HCs yielded differences in all thermal parameters (cold detection threshold: p < 0.05, warm detection threshold: p < 0.001, thermal sensory limen: p < 0.001, cold pain threshold: p < 0.05, and heat pain threshold: p < 0.001) and in paradoxical heat sensations (p < 0.05). Differences in nonpainful stimuli (mechanical detection threshold: p < 0.05 and vibration detection threshold: p < 0.001) were also detected. All patients who had clinical signs of SFN in combination with impairment of small fibers in QST also had SFN on skin biopsy.

Conclusion: These results suggest that a non-region-specific SFN in POTS compared with controls can be detected by noninvasive QST that predicts histologic small fiber pathology.

Figure. QST in POTS (n = 30, except for CDT, WDT, TSL, CPT, HPT n = 29)

At the hand and foot, the z-profile in QST shows a generalized and combined large fiber neuropathy and small fiber neuropathy for nonpainful thermal and mechanical stimuli (CDT, WDT, TSL, and MDT) and thermal pain thresholds, which were transmitted by combined C- and Aδ-fibers. CDT = cold detection threshold; CPT = cold pain threshold; DMA = dynamic mechanical allodynia; HPT = heat pain threshold; MDT = mechanical detection threshold; MPS = mechanical pain sensitivity; MPT = mechanical pain threshold; PHS = paradoxical heat sensation; POTS = postural orthostatic tachycardia syndrome; PPT = pressure pain threshold; QST = quantitative sensory testing; TSL = thermal sensory limen; VDT = vibration detection threshold; WDT = warm detection threshold; WUR = wind-up ratio.