Article Figures & Data
Figures
- Fig 1.
Insufficient infiltration and insufficient passage. A, Insufficient infiltration of the root, compressed by the herniated L4–5 disk. Contrast leakage lateral to the neural foramen (arrowheads) is observed. B, Insufficient passage of the injectate from a blockade by a huge herniated disk. A filling defect of contrast media by an inferiorly migrated huge paracentral disk herniation at L4–5 is observed (arrowheads).
- Fig 2.
Intraepineural and extraepineural injections. A, Intraepineural injection causing aggravation of the radiating pain during the procedure, resulting in a false-negative. Central feathery appearance within the tubular outline of the root (arrowheads) is observed. B, Extraepineural injection showing the root as a linear filling defect (arrowheads).
- Fig 3.
Overflow of injectate. A, Injectate from the unaffected L5 root spreads caudally to the affected S1 nerve root (arrowheads), causing a false-positive result. B, Injectate from the unaffected S1 root spreads cranially to the affected L5 root (arrowheads), causing a false-positive result.
Tables
- Table 1:
Results of receiver-operator characteristic (ROC) analysis for cutoff value for the definition of a positive result
Cutoff Value (%) Sensitivity (%) Specificity (%) Accuracy (%) Positive Predictive Value (%) Negative Predictive Value (%) ≥0 100 0 45 45 - ≥10 91 21 52 48 75 ≥20 89 26 54 49 75 ≥30 79 40 57 51 70 ≥40 72 50 60 54 69 ≥50 70 74 72 69 75 ≥60 60 78 70 68 70 ≥70 57 86 73 77 71 ≥80 36 90 66 74 63 ≥90 21 91 60 67 59 =100 4 100 57 100 56 Note:—Cutoff value indicates the cutoff value of percent decrease in radiating pain compared with the pre-injection state.
Estimate All Patients Patients Without Two Findings* on Spot Radiographs Sensitivity 57% (27/47) 71% (25/35) (42, 72)† (54, 85)† Specificity 86% (50/58) 91% (43/47) (75, 94)† (80, 98)† Accuracy 73% (77/105) 83% (68/82) (64, 81)† (73, 90)† Positive predictive value 77% (27/35) 86% (25/29) (60, 90)† (68, 96)† Negative predictive value 71% (50/70) 81% (43/53) (59, 82)† (68, 91)† * Two findings indicate inadequate blocks (including insufficient infiltration, insufficient passage, and intraepineural injection) and overflow.
† Shown in parentheses are 95% confidence intervals.
Findings Numbers False-negative Inadequate block 10 Insufficient infiltration with injectate leakage 4 Insufficient passage of injectate from a blockade by a huge herniated disk 4 Intraepineural injection 2 Not identified on spot radiographs 10 False-positive Overflow of injectate into the epidural space or into an adjacent affected level 4 From an injected upper unaffected level 2 From a injected lower unaffected level 2 Not identified on spot radiographs 4 - Table 4:
Inadequate block and false-negative rate of diagnostic selective nerve root block
Inadequate Block Results of DSNRB False-Negative Rate PValue (Fisher Exact Test) False-Negative True-Positive Present 10 2 83% (10/12) .002 Absent 10 25 29% (10/35) Note:—DSNRB indicates diagnostic selective nerve root block.
- Table 5:
Overflow of the injectate and false-positive rate of diagnostic selective nerve root block
Overflow of the Injectate Results of DSNRB False-Positive Rate PValue (Fisher Exact Test) False-Positive True-Negative Present 4 7 36% (4/11) .03 Absent 4 43 6% (4/47) Note:—DSNRB indicates diagnostic selective nerve root block.
