Do diagnostic segmental nerve root blocks in chronic low back pain patients with radiation to the leg lack distinct sensory effects? A preliminary study.
BACKGROUND
The present preliminary study documents the effects of a selective nerve root block (SNB) with short or long acting local anaesthetic compared with baseline measurements in patients with chronic low back pain radiating to the leg with maximum pain in one dermatome (L4).


METHODS
Ten consecutive patients underwent 20 controlled SNBs at L4 with ropivacaine 0.25% and lidocaine 1% in a prospective, randomized, double blind, crossover fashion. Baseline measurements included sensory function (assessed by pinprick on both unaffected and painful leg) and pain (Verbal Numeric Rating Scale; VNRS, 0-10). A change in size of areas with altered sensory function >10% and a VNRS change of 2 points were considered clinically significant. P-values<0.05 were considered statistically significant.


RESULTS
Asymptomatic hypoaesthesia, variable in extent and non-dermatomal in distribution, was present in seven patients at baseline. It appeared to be more extensive and distal with longer duration of pre-existing pain. SNB produced no consistent changes in extent and distribution of hypoaesthetic areas. Change in VNRS did not correlate with the extent of pre-block or post-block hypoaesthesia. No differences in effects were found between lidocaine and ropivacaine.


CONCLUSIONS
Pre-block assessment of sensory function is essential to assess the net effect of SNBs. In this small study group, SNBs failed to demonstrate uniform or distinct effects on sensory function.
Wolff
A P
AP
Pain Centre, Institute for Anaesthesia, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands. a.wolff@anes.umcn.nl
Groen
G J
GJ
Wilder-Smith
O H G
OH
Richardson
J
J
van Egmond
J
J
Crul
B J P
BJ
D000328:Adult; D000577:Amides; D000779:Anesthetics, Local; D002908:Chronic Disease; D004558:Electric Stimulation; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D006987:Hypesthesia / Q000503:physiopathology; D007866:Leg / Q000294:innervation; D008012:Lidocaine; D017116:Low Back Pain / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009407:Nerve Block; D010147:Pain Measurement / Q000379:methods; D000077212:Ropivacaine; D012677:Sensation; D013126:Spinal Nerve Roots / Q000503:physiopathology*; D013997:Time Factors
D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine; D008012:Lidocaine