Thermal QST Phenotypes Associated with Response to Lumbar Epidural Steroid Injections: A Pilot Study.
OBJECTIVE
Response to lumbar epidural steroid injection in lumbar radicular pain varies. The purpose of this study is to characterize the changes in quantitative sensory testing (QST) phenotypes of subjects and compare the QST characteristics in patients who do respond to treatment of radicular pain with a lumbar epidural steroid injection (ESI).


METHODS
Prospective, observational pilot study.


METHODS
Outpatient pain center.


METHODS
Twenty subjects with a lower extremity (LE) radicular pain who were scheduled to have an ESI were recruited. At the visit prior to and four weeks following an ESI, subjects underwent QST measurements of both the affected LE and the contralateral unaffected UE.


RESULTS
Following an ESI, nine subjects reported a greater than 30% reduction in radicular pain and 11 reported a less than 30% reduction in radicular pain. Subjects who had less than 30% pain reduction response (nonresponders) to an ESI had increased pre-injection warm sensation threshold (37.30 °C, SD = 2.51 vs 40.39, SD = 3.36, P = 0.03) and heat pain threshold (47.22 °C, SD = 1.38, vs 48.83 °C, SD = 2.10, P = 0.04). Further, the nonresponders also showed increased pre-injection warm sensation threshold as measured in the difference of warm sensation detection threshold difference in the affected limb and the unaffected arm (2.68 °C, SD = 2.92 vs 5.67 °C, SD = 3.22, P  = 0.045). Other QST parameters were not affected.


CONCLUSIONS
The results show that the nonresponders to ESIs have increased detection threshold to heat pain and warm sensation, suggesting that a preexisting dysfunction in the C fibers in this group of subjects who can be detected by QST. Such altered QST characteristics may prognosticate the response to ESIs.
Department of Anesthesia, Massachusetts General Hospital, Boston, Massachusetts.|Department of Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland.
Dermot P
DP
Maher
Department of Anesthesia, Massachusetts General Hospital, Boston, Massachusetts.
Weihua
W
Ding
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland.
Sarabdeep
S
Singh
Department of Anesthesia, Massachusetts General Hospital, Boston, Massachusetts.
Arissa
A
Opalacz
Department of Anesthesia, Massachusetts General Hospital, Boston, Massachusetts.
Claire
C
Fishman
Department of Anesthesia, Massachusetts General Hospital, Boston, Massachusetts.
Mary
M
Houghton
MGH Center for Translational Pain Research.
Shihab
S
Ahmed
Department of Anesthesia, Massachusetts General Hospital, Boston, Massachusetts.
Lucy
L
Chen
Department of Anesthesia, Massachusetts General Hospital, Boston, Massachusetts.
Jianren
J
Mao
Division of Pain Medicine, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts, USA.
Yi
Y
Zhang
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007268:Injections, Epidural; D017116:Low Back Pain / Q000188:drug therapy*; D008161:Lumbosacral Region; D008297:Male; D008875:Middle Aged; D017288:Pain Threshold / Q000502:physiology*; D010641:Phenotype; D010865:Pilot Projects; D011446:Prospective Studies; D011843:Radiculopathy / Q000188:drug therapy*; D012684:Sensory Thresholds / Q000502:physiology*; D016896:Treatment Outcome