The overarching aim of this study is to investigate the contribution of peripheral afferent input to spontaneous and evoked central neuropathic pain after a spinal cord lesion or disease.
A key question that has been subject to longstanding debates in the field relates to the sites and mechanisms within the peripheral or central nervous system that potentially perpetuate chronic spontaneous and evoked central neuropathic pain. The investigators hypothesize that spontaneous central neuropathic pain depends on continuous, "physiological" somatosensory input from the painful body region in the periphery. Thus, spontaneous central neuropathic pain results from pathological gain control in central somatosensory networks with decreased activation thresholds for thermo- and mechanosensitive peripheral afferents.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
DIAGNOSTIC
Masking
DOUBLE
Enrollment
20
Lidocaine (10 mg/ml) will be injected according to established protocols using ultrasound guidance and an aseptic technique by an experienced anesthesiologist.
Isotonic saline will be injected according to established protocols using ultrasound guidance and an aseptic technique by an experienced anesthesiologist.
Indication of most pain relief
Limb with most pain relief on Numerical Rating Scale (NRS) \[0-10, 0=no pain 10=worst pain imaginable\] 40 minutes after nerve block
Time frame: 40 minutes
Intensity on Numerical Rating Scale (NRS) [0-10, 0=no pain 10=worst pain imaginable] of spontaneous pain
Intensity on Numerical Rating Scale (NRS) \[0-10, 0=no pain 10=worst pain imaginable\] of spontaneous pain in the pre-specified region covered by the block 40, 60 and 90 min after the nerve block compared to baseline
Time frame: 90 minutes
Pain relief 45 min after the nerve block
Pain relief 45 min after the nerve block using a 6-point verbal scale ranging from worse pain to no, little, moderate, good and complete pain relief (-1 to 4)
Time frame: 45 minutes
Pain extent [% of body surface on standardized pain drawings] 50 minutes after the nerve block
Pain extent will be mapped on standardized pain drawings 50 minutes after the nerve block compared to baseline
Time frame: 50 minutes
Pain descriptors 50 minutes after the nerve block
Pain descriptors (burning, squeezing, pins and needles, tingling, stabbing, electrical shocks) are captured 50 minutes after the nerve block compared to baseline
Time frame: 50 minutes
Area [% of pain extent] of hypersensitivity to thermal and nociceptive stimuli
Area of hypersensitivity \[% of pain extent\] to warm (40°C) and cold (20°C) thermo rollers (Somedic AB, Hörby, Sweden), pinprick (Semmes-Weinstein monofilament no 5.88 (bending force 75.9 g/745 mN)), and brush (SENSELab Brush-05; Somedic AB, Hörby, Sweden), if any, 55 and 95 min after nerve block compared to baseline
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Time frame: 95 minutes
Intensity of hypersensitivity on Numerical Rating Scale (NRS) [0-10, 0=no pain 10=worst pain imaginable] to thermal and nociceptive stimuli
Intensity of hypersensitivity on Numerical Rating Scale (NRS) \[0-10, 0=no pain 10=worst pain imaginable\] to warm (40°C) and cold (20°C) thermo rollers (Somedic AB, Hörby, Sweden), pinprick (Semmes-Weinstein monofilament no 5.88 (bending force 75.9 g/745 mN)), and brush (SENSELab Brush-05; Somedic AB, Hörby, Sweden), if any, 55 and 95 min after nerve block compared to baseline
Time frame: 95 minutes