Prevalence and Discordance of the “Startle Response” with True Discogenic Pain According to Spine Intervention Society Guidelines for Provocation Discography: A Cohort Study

Summary of Background Data The literature on cervical provocation discography (C-PD) is sparse. A “Startle Response” during C-PD is a known phenomenon that might be mistaken as an indicator of discogenic pain at the provoked disc level, but this has not been quantitatively described. Objectives To determine the incidence of the Startle Response and its concordance/discordance with true-positive C-PD in patients referred for surgical planning or evaluation after ruling out other axial pain generators. Methods Retrospective cohort study of consecutive patients who received C-PD at an outpatient spine center. The primary outcome was the rate of discordance of the Startle Response with true-positive C-PD according to the operational criteria of the Spine Intervention Society (SIS) guidelines. Results One hundred five discs were provoked in 36 individuals (19 female, mean age [SD] = 45.7 [10.9] years). C-PD was performed at a median of three levels (range = 1–5) with C4/5 (N = 30), C5/6 (N = 30), and C6/7 (N = 31) the most commonly evaluated. Twenty-six of 36 patients reported responses consistent with true-positive C-PD. A Startle Response was observed in 14 patients (39%, 95% confidence interval [CI] = 23–57%), and 22 of 105 (21%, 95% CI = 14–30%) provoked discs. Of the 14 patients who exhibited a Startle Response, four had negative C-PD results (29%, 95% CI = 8–58%). As assessed per disc, C-PD results were positive in 12 of the 22 (55%, 95% CI = 32–76%) provoked discs that generated a Startle Response. Conclusions The present data demonstrate high discordance, 45% (95% CI = 24–68%), between the Startle Response and true-positive C-PD. Clinicians should be aware of this phenomenon and take care to distinguish it from a true-positive response during C-PD, as defined by the SIS guidelines. Misinterpretation of the Startle Response as a positive C-PD result may lead to inappropriate future care decisions in a substantial proportion of patients.