Effectiveness of paravertebral block in patients with herpes zoster according to the contrast spreading pattern: a retrospective cohort study

Objectives

This study aims to evaluate the treatment response to thoracic paravertebral block (PVB) in thoracic herpes zoster (HZ) pain based on the contrast spreading pattern.

Methods

Patients with HZ pain who underwent thoracic PVB under fluoroscopy were retrospectively analyzed. A comparative analysis of the treatment response was conducted between patients with epidural spread (ES group) and those without epidural spread (NES group) at the first visit after PVB. The treatment response was determined by setting the minimum clinically important difference (MCID) as a reduction of more than 1 point on the pain numerical rating scale (NRS). In addition, the treatment responses were compared according to prevertebral spread, intercostal spread, and segmented medial spread (base, foraminal, and subarticular-central spread). The NRS score was assessed at baseline and 3 days, 2 weeks, 1 and month after PVB. Generalized estimating equation (GEE) analysis was performed to identify the factors associated with the treatment response over time.

Results

In total, 48 patients were enrolled (ES, n = 21; NES, n = 27). The ES group had a higher proportion of patients with the treatment response than the NES group (p = 0.025). However, there was no significant difference in the treatment response according to prevertebral, intercostal, and segmented medial spread. In both groups, the mean NRS scores significantly decreased over time. Comparisons between groups at each time point were not significantly different. The GEE analysis showed that the duration after rash onset was the only significantly related factor in treatment response.

Conclusions

Patients with HZ pain who had epidural spread in PVB showed a better treatment response than those who did not at the first post-PVB assessment. Other spreading patterns did not have a significant effect on the treatment response. NRS decreased over time with no differences between groups. Only the duration after rash onset affected the longitudinal treatment response. Additional research is required to verify the efficacy of epidural spread in PVB.