The following is a summary of “Cutaneous nerve fiber and peripheral Nav1.7 assessment in a large cohort of patients with postherpetic neuralgia,” published in the November 2023 issue of Pain by Fetell et al.
Postherpetic neuralgia (PHN) pain mechanisms are unclear, but nerve fiber loss may correlate with pain level. Researchers performed a retrospective study to assess the correlation between skin biopsy results, pain scores, mechanical hyperalgesia, and Neuropathic Pain Symptom Inventory (NPSI) in PHN patients treated with TV-45070- a topical semi-selective sodium 1.7 channel (Nav1.7).
The study quantified intraepidermal nerve fibers and subepidermal Nav1.7 immunolabeled fibers from skin punch biopsies taken from the site of maximal PHN pain, as well as from the contralateral, homologous (mirror image) region.
The result demonstrated a 20% reduction in nerve fibers on the PHN-affected side compared to the contralateral side, with a greater reduction of nearly 40% in individuals aged 70 or older. Contralateral fiber counts also decreased, though the reason for this decline remains unclear. Nav1.7-positive immunolabeling was present in about one-third of subepidermal nerve fibers and did not differ between the PHN-affected and contralateral sides. Using cluster analysis, two groups were identified, with the first group having higher baseline pain, NPSI scores for squeezing and cold-induced pain, nerve fiber density, and Nav1.7 expression. Nav1.7 does not appear to be a key driver of PHN pain, as it varies among patients.
The study found that Nav1.7 expression levels may determine the intensity and sensory aspects of pain, even though people vary in their expression of this protein.
