Central post-stroke pain (CPP) is extremely difficult to relieve and responds very poorly to analgesics targeting neuropathic pain, probably because the mechanisms underlying this pain remain poorly understood.
Stroke pain is traditionally considered to be of central origin and related to changes in the spinal cord and/or brain nociceptive systems. However, a recent study in a small cohort of patients has suggested that the peripheral nervous system (PNS) may have a role in the initiation and persistence of APD.
The main objective of this prospective randomised controlled bicentric study (Raymond Poincaré and Ambroise Paré) in double blind and parallel groups against placebo (3 arms) will be to evaluate the efficacy of two peripheral nerve blocks performed 14 days apart on spontaneous neuropathic pain after stroke. The active treatments used for the blocks will be either lidocaine 20 mg/ml or levobupivacaine 1.25 mg/ml or placebo (saline)
Patients aged 18 years and over with no maximum age (blocks are generally very well tolerated in the very elderly)
Pain in the upper or lower limb distal enough to be completely covered by a peripheral nerve block
Chronic pain for at least 6 months
Ischaemic or haemorrhagic stroke for at least 6 months documented clinically and by appropriate imaging (MRI)
Inability or unwillingness to sign an informed consent
Person subject to a legal protection measure (safeguard of justice, curatorship, guardianship)
Patients with ongoing psychiatric pathology (major depression, psychosis) or cognitive disorders that prevent a good understanding of the protocol and questionnaires
Pain that is too widespread in one hemicycle or limb and cannot be adequately covered by blocks
Parallel
Lidocaine 20mg/ml
Drug2 bolus administrations at 14 day intervals Route of administration: Peri-Nervous Dosage for administration: 20ml
Levobupivacaine Hydrochloride 1.25 MG/ML
Drug2 bolus administrations at 14 day intervals Route of administration: Peri-Nervous Dosage for administration: 20ml
Sodium Chloride 0.9% Inj
Drug2 bolus administrations at 14 day intervals Route of administration: Peri-Nervous Dosage for administration: 20ml
To evaluate the efficacy of two peripheral nerve blocks performed 14 days apart on spontaneous neuropathic pain after stroke. The active treatments used for the blocks will be either lidocaine 20mg/ml or levobupivacaine 1.25mg/ml or placebo (saline)
The evolution in neuropathic pain intensity assessed on an 11-point pain intensity scale (0 = no pain: 10: maximum imaginable pain), expressed as a difference in pain intensity between the value obtained before each block and that obtained 45 minutes after, corresponding to the maximum expected effect. The values obtained before and after each block will first be analysed individually and then combined for the two successive blocks for each patient and the comparison will be between the three treatment arms, lidocaine 20mg/ml, levobupivacaine 1.25mg/ml or placebo Rationale for the choice of the main criterion : Pain intensity will be assessed on a numerical scale that corresponds to the usual validated measurement criterion and the choice of 45 minutes corresponds to the maximum effect of local anaesthetics
- To evaluate the time course and duration of the effectiveness of the nerve blocks on spontaneous pain on a pain intensity scale completed daily by the patient on a self-evaluation booklet up to 14 days after each block.
\- Comparison of the duration (in days) of efficacy of lidocaine 20 mg/ml levobupivacaine 1.25 mg/ml and placebo blocks on spontaneous and exertional pain assessed by an 11-point pain intensity scale (0 to 10) completed daily by the patient on a self-report diary, up to 14 days after each block.
- Evaluate the effectiveness of blocks on exercise pain
\- Comparison of the efficacy of levobupicacaine 1.25 mg/ml, lidocaine 20 mg/ml and placebo on spontaneous and exertional pain assessed by an 11-point pain intensity scale (0 to 10) at 45 minutes and then at 5 hours after the block and then daily on a self-evaluation booklet, up to 14 days after each block
- Directly compare the efficacy of active blocks, i.e. lidocaine and levobupivacaine, on spontaneous and provoked pain (allodynia)
* Comparison of the efficacy of lidocaine, levobupivacaine and placebo blocks on the intensity of rubbing pain if present (dynamic mechanical allodynia) assessed before treatment with a brush and then at 45 minutes and at 5 hours after each block. * Comparison of the efficacy of lidocaine, levobupivacaine and placebo blocks on spontaneous and provoked pain area (mechanical allodynia if present) assessed by a tracing (and then plotted on a graph allowing measurement of area in cm2) before treatment and then at 45 minutes and at 5 hours after each block using a method used in our previous studies
- Evaluate the effectiveness of each block on provoked pain (mechanical allodynia), mechanical, hot and cold pain thresholds and pain area
\- Comparison of the efficacy of lidocaine, levobupivacaine and placebo blocks on mechanical pain and detection thresholds assessed by Semmes Weinstein monofilaments (calibrated from 0.057 g to 300 g) as well as on thermal pain and detection thresholds assessed by a thermotest before the treatment and at 45 minutes and at 5 hours after each block
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