Sensory changes and loss of intraepidermal nerve fibers in painful unilateral nerve injury.
OBJECTIVE
Dysaesthesias is a common symptom in patients with neuropathic pain after peripheral nerve injury (PNI). In contrast to neuropathies with comparable symptoms there is little knowledge of the underlying mechanisms in PNI patients.


METHODS
Quantitative sensory testing according to the German Research Network on Neuropathic Pain protocol, and changes in intraepidermal nerve fiber density were assessed in 15 patients with dysaesthesias after PNI of the lower limb. According to their small-fiber function patients were assigned into 2 subgroups.


RESULTS
The sensory profiles of PNI patients were characterized predominantly by minus symptoms (significantly increased thresholds for perception of cold, warm, touch and vibration, and significantly increased thresholds for heat and mechanical pain) on the affected compared with the unaffected side. The only plus symptom reported was a significantly reduced pressure pain threshold. The sensory profile of patients with a severe loss of small-fiber function (n=7) showed a thermal and tactile hypoaesthesia and hypoalgesia; this was in contrast to patients with a moderate loss of small-fiber function, who showed a mild thermal and tactile hypoaesthesia associated with an increased mechanical pain sensitivity. Mean intraepidermal nerve fiber density was significantly decreased in the affected compared with unaffected skin [3.50 (4.00) vs. 11.10 (7.60) fibers/mm] and correlated with warm and mechanical detection thresholds (both r=-0.60).


CONCLUSIONS
In conclusion, even though patients presented with comparable clinical symptoms, their sensory profiles differed, supporting the concept of different underlying mechanisms leading to chronic pain in PNI patients. Skin biopsies support the validity of quantitative sensory testing.
Schüning
Julia
J
Department of Pain Management, Ruhr-University Bochum, BG-Kliniken Bergmannsheil, Bochum, Germany.
Scherens
Andrea
A
Haussleiter
Ida S
IS
Schwenkreis
Peter
P
Krumova
Elena K
EK
Richter
Helmut
H
Maier
Christoph
C
D000328:Adult; D000368:Aged; D004817:Epidermis / Q000294:innervation* / Q000473:pathology*; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000293:injuries; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology* / Q000502:physiology*; D009460:Neurologic Examination; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D010292:Paresthesia / Q000453:epidemiology / Q000473:pathology; D059348:Peripheral Nerve Injuries; D010523:Peripheral Nervous System Diseases / Q000473:pathology* / Q000503:physiopathology; D010812:Physical Stimulation; D012677:Sensation / Q000502:physiology*; D055815:Young Adult