Complex Regional Pain Syndrome (CRPS) is a chronic pain condition characterized by severe regional pain, sensory disturbances, and functional impairment. Current treatment options are limited, and many patients experience substantial pain-related disability and symptom fluctuations, including flare-ups triggered by invasive procedures.
Perineural administration of botulinum toxin A has shown analgesic effects in other neuropathic pain conditions and may represent a less painful alternative to subcutaneous injection techniques. However, the feasibility, tolerability, and safety of perineural botulinum toxin administration in patients with CRPS have not been systematically evaluated.
The PINCom study is a single-center, open-label feasibility study designed to assess the safety, tolerability, and practical feasibility of ultrasound-guided perineural injection of incobotulinumtoxin-A in patients with unilateral chronic CRPS affecting an upper or lower limb. Participants receive a single perineural injection targeting major sensory nerves supplying the affected limb and are followed for 12 weeks.
Primary outcomes focus on feasibility metrics, including recruitment, retention, adherence, and data completeness, as well as safety outcomes, including serious adverse events and procedure-related complications. Tolerability is assessed through monitoring of CRPS flare-ups and a dedicated qualitative interview exploring participant experience. Exploratory outcomes include pain intensity, CRPS severity, and patient-reported measures collected to inform the design of a future randomized controlled trial.
Are over the age of 18
Have a diagnosis of CRPS type 1 or 2 in either one upper or one lower extremity which fulfils the Budapest research criteria
Have had the condition for at least 6 months
Rate CRPS as their primary pain condition
Are allergic to botulinum toxin A
Have been treated with botulinum toxin A for any indication within 3 months prior to study start
Are diagnosed with myasthenia, Lambert-Eaton syndrome, amyotrophic lateral sclerosis, or any other condition which makes differentiation of CRPS-specific pain difficult
Have an ongoing infection in the affected limb
Single group
Perineural Incobotulinumtoxin-A 200 U
DrugSingle perineural injection of 200 U iBonT-A around the brachial plexus in the case of upper limb CRPS, or 150 U iBonT-A around the distal ischial nerve and 50 U around the saphenus nerve in the case of lower limb CRPS.
Recruitment rate
Number of participants enrolled over time in the study
Screening-to-enrolment ratio
Proportion of screened patients who are enrolled in the study.
Study completion rate
Proportion of enrolled participants completing the study per protocol
Completeness of study data
Proportion of expected study data successfully collected, including completion of scheduled study visits and daily pain diary entries.
Serious Adverse Events (SAEs)
Occurrence of serious adverse events related to the perineural injection procedure or investigational medicinal product, assessed to evaluate procedural safety.
CRPS flare-ups
Incidence, severity, and duration of CRPS flare-ups following perineural incobotulinumtoxin-A injection. A flare-up is defined as an exacerbation, worsening, or new appearance of CRPS-related symptoms lasting at least 24 hours following a provoking event. Flare-ups are assessed as a tolerability outcome rather than a safety endpoint.
Participant-reported acceptability and experience
Participant experience and acceptability of the injection procedure and study participation, assessed using a semi-structured qualitative interview focusing on procedural burden, tolerability, and perceived acceptability.
Pain intensity (NRS)
Change in pain intensity measured using a daily numerical rating scale (NRS, 0-10), recorded in a pain diary.
CRPS Disease Severity
Change in CRPS Severity Score (CSS), a composite clinical measure of CRPS signs and symptoms.
Sensory symptoms and allodynia
Changes in sensory symptoms and spatial distribution of pain and allodynia assessed using standardized pain drawings and sensory mapping.
Pain quality
Change in neuropathic pain characteristics assessed using the Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2)- like questionnaire.
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Bo Biering-Soerensen
Lead sponsor
Rigshospitalet, Denmark
Sponsor institution
Merz Pharmaceuticals GmbH
Collaborator
University of Copenhagen
Collaborator
