Background/Purpose: Beyond classical effect on vegetative functions, the activation of the vagus nerve inhibits inflammation and reduces the pain signal. Vagus nerve stimulation (VNS) can be performed using transcutaneous VNS (tVNS) of the ascendant auricular branch of the VN that selectively innervates the cutaneous zone of cymba conchae (1). Erosive hand osteoarthritis (EHOA) is the most severe HOA subtype characterized by a higher level of pain, a higher inflammation and functional disability than its non-erosive counterpart. The aim of this open-label pilot study was to determine the tolerance and the short-term efficacy of tVNS on EHOA symptoms (NCT03919279).

Methods: Symptomatic EHOA patients, defined by at least one erosive joint (phase E or R of the Verbruggen phase score) with a pain VAS ≥40/100mm and > 1 interphalangeal swollen joint were included. The tVNS was performed using an auricular electrode applied one hour/day on the left ear, connected to a TENS device for 4 weeks (Figure 1). The TENS was set up at 25Hz frequency and 50 microseconds pulse width while the intensity was gradually increased to 15mA or below in case of ear discomfort on the stimulation zone (tingling, dysesthesia). Clinical efficacy was evaluated by hand pain VAS on a 0-100mm scale, the functional FIHOA score, the number of tender and swollen joints. Changes in EHOA symptoms between baseline and 4 weeks were evaluated using a Wilcoxon t-test.  The proportion of patients that reached the Patient Acceptable Symptom State (PASS), defined by a VAS£40mm, and the minimum clinically important improvement (MCII), defined by an absolute decreased of 15mm or a relative improvement of 20% of their hand pain VAS, were calculated. Tolerance was also reported.

Results: Twenty patients were included but the analysis was performed on eighteen patients (median age 69 years-old [IQR 66.7;73.2], 83% women), two patients being lost to follow-up after the first session. At baseline, hand pain VAS was 60mm [50;78.2] and FIHOA score 15 [10.7;20.2], median number of tender and swollen joints was 9.5 [5.7;13] and 4.5 [3;8] respectively .After 4 weeks, tVNS significantly reduced pain, with a median decrease of 23.5mm [7.7;37.2], p=0.001 and FIHOA by 2 points [0.75;5.2], p=0.01. Ten of the 18 patients (55%; CI95%: 0.33-0.75) reached the PASS and 13 the MCII (72%; CI95%: 0.49-0.87) (Figure 2). tVNS also induced a decrease of 3 [1;5.2] painful joints and 2 [1;3] swollen joints/patient. No serious adverse events were reported. One patient stopped tVNS because of an auricular discomfort.

Conclusion: This first proof-of-concept trial indicated that targeting the vagus nerve using tVNS stimulation may decrease joint inflammation and clinical symptoms in painful EHOA without major safety concern. A randomized controlled study versus sham stimulation is now necessary to confirm these results.

References:

1. Yakunina et al Neuromodulation 2017

Figure 1: tVNS device kit.

Figure 2: Effect of tVNS on EHOA symptoms. Evolution of (A) VAS hand pain on a 0-100mm scale, (B) function evaluated by FIHOA, (C) number of painful joints (0-30), (D) number of swollen joints (0-30) of the EHOA for each of the eighteen patients. Paired, non-parametric Wilcoxon t-test was used.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/effect-of-transcutaneous-vagal-nerve-stimulation-in-erosive-hand-osteoarthritis-results-from-an-open-label-non-randomized-pilot-trial/