Photo Credit: Axel Kock

The following is a summary of “Idiopathic Distal Sensory Polyneuropathy and Fibromyalgia Syndrome: A Comparative Phenotyping Study,” published in the September 2024 issue of Pain by Burgess et al.

Painful idiopathic distal sensory polyneuropathy (IDSP) and fibromyalgia syndrome (FMS) are chronic pain conditions with the role of small fiber pathology (SFP) in FMS being debated.

Researchers conducted a retrospective study to quantify SFP in participants with IDSP and FMS and to identify associations between SFP and sensory phenotypes.

They assessed 73 individuals (FMS: 25, IDSP: 23, healthy volunteers: 25) who underwent comprehensive assessment, including neurological exams, questionnaires, sensory tests, and corneal confocal microscopy.

The results showed participants with IDSP had a lower wind-up ratio (WUR) compared to FMS (P< 0.001), along with more significant loss of function to thermal and mechanical stimuli and higher neuropathy disability scores than FMS and healthy volunteers (all P<0.001). FMS participants experienced increased sensitivity to heat and blunt pressure compared to IDSP and healthy volunteers (heat: P=0.002 and P=0.003; pressure: both P<0.001) and had a higher WUR (both P<0.001). Participants with FMS had reduced corneal nerve fiber density (P=0.02), while participants with IDSP showed lower global corneal nerve measures (density, branch density, and length) compared to healthy volunteers (all P<0.001). SFP was identified in 66.6% of participants using corneal nerve fiber length (FMS: 13/25; IDSP: 22/23).

They concluded participants with SFP in both FMS and IDSP reported symptoms indicative of SFP, with over 50% showing both loss and gain of thermal and mechanical function, suggesting shared mechanisms. However, sensory phenotypes were linked to SFP in IDSP only.

Source: link.springer.com/article/10.1007/s40122-024-00646-x