FNIRS a new tool for assessment of central sensitization in fibromyalgia

Abstract

Fibromyalgia (FM) is a multi-symptomatic disorder with a varying degree of widespread pain in the body. With emerging evidences pathophysiological concept shifted from peripheral damage or inflammation to central neural mechanism. Fibromyalgia is characterised by dysfunction in central pain processing, “central sensitivity”. In this cross-sectional study central sensitization was recorded in patients with fibromyalgia by observing cortical oxygenation in prefrontal cortex using Functional Near Infrared Spectroscopy (fNIRS). fNIRS 300B (BIOPAC), a wearable continuous fNIRS system with 4 optode and 16 detectors was used to assess changes in oxy-haemoglobin concentration (μM) from Brodmann areas 9, 10, 45 and 46. Number of activation (max and 60% max signals) was compared in time series of Oxygenated Haemoglobin level with Rt foot immersed in ice cold water. For comparison of categorical variable, sex Chi 2 test was used. For non-parametric data, i.e. age and fNIRS data Mann–Whitney U test was used. Both of the test was done in SPSS Statistics 23 by IBM, Chicago, IL with a confidence interval of 95% and a significance level lower than 5%. Fifty FM patients diagnosed according to ACR 2010 fibromyalgia criteria and equal number of age and sex matched controls were enrolled in the study. There was increased oxygenation in FM compared to control in prefrontal cortex. This increased oxygenation in prefrontal cortex in FM group objectively demonstrates alteration in central activity in FM group. Changes in central activity along with pain hypersensitivity in FM points towards central sensitisation. Lack of 3D digitiser restrict us to comment on localisation of activation. fNIRS can be used as tool to evaluate central sensitization.