Heterogeneous sensory processing in persistent postherniotomy pain.
Previous studies on sensory function in persistent postherniotomy pain (PPP) have only identified pressure pain threshold to be significantly different from pain-free patients despite several patients reporting cutaneous pain and wind-up phenomena. However the limited number of patients studied hinders evaluation of potential subgroups for further investigation and/or treatment allocation. Thus we used a standardized QST protocol to evaluate sensory functions in PPP and pain-free control patients, to allow individual sensory characterization of pain patients from calculated Z-values. Seventy PPP patients with pain related impairment of everyday activities were compared with normative data from 40 pain-free postherniotomy patients operated>1 year previously. Z-values showed a large variation in sensory disturbances ranging from pronounced detection hypoesthesia (Z=6, cold) to pain hyperalgesia (Z=-8, pressure). Hyperalgesia for various modalities were found in 80% of patients, with pressure hyperalgesia in approximately 65%, and cutaneous (mechanical or thermal) hyperalgesia in approximately 35% of patients. The paradoxical combination of tactile hypoesthesia and hyperalgesia was seen in approximately 25% of patients. Increased pain from repetitive tactile and/or brush stimulation was found in 51%, suggesting a role of altered central nociceptive function in this subpopulation. A high incidence (26%) of pressure hyperalgesia was found in the contralateral groin, with a significant correlation (rho=0.58, p=0.002) to the hyperalgesic level on the painful side, again suggesting central nervous mechanisms in PPP. In conclusion, this study shows that a standardized trauma results in heterogeneous combinations of hypo- and hyperalgesia. Z-score evaluation of sensory function identifies subpopulations in PPP, which may be used in selecting surgical and/or pharmacological treatment strategies.
Aasvang
Eske Kvanner
EK
Section of Surgical Pathophysiology, Rigshospitalet, Copenhagen University, Denmark Danish Pain Research Center, Aarhus University Hospital, Aarhus, Denmark Department of Neurology, Aarhus University Hospital, Aarhus, Denmark.
Brandsborg
Birgitte
B
Jensen
Troels Staehelin
TS
Kehlet
Henrik
H
D000328:Adult; D006119:Groin / Q000503:physiopathology / Q000601:surgery; D006552:Hernia, Inguinal / Q000601:surgery*; D006801:Humans; D006930:Hyperalgesia / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D010149:Postoperative Pain / Q000175:diagnosis* / Q000503:physiopathology; D010812:Physical Stimulation; D018709:Statistics, Nonparametric
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