Sukenaga N, Matsuki Y, Maeda L, et al. - Researchers performed a multi-institutional retrospective study in order to examine neuropathic characteristics in patients with persistent idiopathic facial pain (PIFP) using the Douleur Neuropathique 4 (DN4) questionnaire. From 205 consecutive patients with adult chronic pain, the following clinical data were obtained: gender, age, BMI, diseases causing chronic pain, disease duration, visual analog scale score of pain strength, and DN4 score. Patients with PIFP (n = 19) and patients with postherpetic neuralgia (PHN) (n = 33) were selected to compare neuropathic characteristics between PIFP and PHN and Each of these patients was matched by age and gender (n = 16 in each group) to perform a case-control study. The PIFP group had significantly lower DN4 score than the PHN group before and after matching. In the PIFP group, the incidence was 10.5% before matching and 12.5% after matching when DN4 was ≥ 4, both of which were significantly lower than those in the PHN group before and after matching (66.7% and 75.0%). Neuropathic pain characteristics were thus likely in 10% of the PIFP patients.