STATIC MECHANICAL ALLODYNIA IS A PAINFUL TOUCH-EVOKED TACTILE HYPO-AESTHESIA: A COHORT STUDY FROM 86 PATIENTS WITH CRPS

S. De Andrade Melo Knaut¹, V. Ribeiro Chiquito¹, M.E. Mazepa¹, L.A. Portela¹, M.V. Zene¹, T.L. Packham², J.-O. Dyer³, N. Mermet-Joret^4,5, J.-M. Annoni⁶, C.J. Spicher^6,7,8

¹Universidade Estadual do Centro-Oeste do Paraná, Physiotherapy, Guarapuava, Brazil, ²McMaster University, School of Rehabilitation Sciences, Hamilton, Canada, ³Université de Montreal, School of Physical and Occupational Therapy, Faculty of Medicine, Montreal, Canada, ⁴Århus University, DANDRITE, The Danish Research Institute of Translational Neuroscience, Århus, Denmark, ⁵Århus University, Department of Molecular Biology and Genetics, Århus, Denmark, ⁶University of Fribourg, Department of Neurosciences and Movement Sciences, Faculty of Medicine and Sciences, Fribourg, Switzerland, ⁷Clinique Générale, Somatosensory Rehabilitation Centre, Fribourg, Switzerland, ⁸McGill University, School of Physical and Occupational Therapy, Faculty of Medicine and Health Sciences, Montreal, Canada

Background: Complex Regional Pain Syndrome (CRPS) is a chronic pain condition often involving neuropathic pain with allodynia and hyperalgesia. Mechanical allodynia is a frequent feature of neuropathic pain associated with a specific nerve branch lesion and/or the result of spinal, supra-spinal and/or cortical sensitization. It is commonly found in pain conditions such as CRPS. It is hypothesized that Static Mechanical Allodynia (SMA) is the consequence of damage to large-diameter Aß neurofibers. However, SMA is, paradoxically, a painful touch-evoked tactile hypoaesthesia. According to the Atlas of Cutaneous Branch Territories, when a patient describes neuropathic pain symptoms, they presents with axonal lesions of at least one cutaneous nerve branch, including Aβ neurofibers. The method of Somatosensory Pain Rehabilitation (SPR) was developed to diagnose and treat neuropathic pain, based on current knowledge about the functioning of the somatosensory nervous system, adaptative neuroplasticity and the phenomenon of pain. Recent studies show favorable results using SPR to decrease neuropathic pain.

Purpose: To analyse the presence of underlying tactile hypoaesthesia after the disappearance of SMA in patients treated for CRPS of the foot.

Methods: This is a retrospective analysis of prospectively collected data from a clinical database of patients presenting with CRPS of the foot who were treated with the Somatosensory Pain Rehabilitation (SPR) method. In the presence of an allodynic territory, the SPR method comprises two treatment phases: (1) distant vibrotactile counter-stimulation and then (2) rehabilitation of the underlying hyposensitivity. To be included in the study, patients had to have achieved resolution of their SMA with SPR. The pre-treatment allodynic territory was mapped by using allodynography and then by using the Rainbow Pain Scale (RPS). The intensity and quality of the pain were assessed using the McGill Pain Questionnaire (MPQ). The pressure and the vibration perception thresholds and two-point discrimination tests were used to assess the somatosensory disorder.

Results: Eighty-six patients with a CRPS of the foot fulfilled the inclusion criteria. On admission, 43 patients had a discrete, 26 patients a consequential and 17 patients a serious severity of SMA on the RPS. Significant improvements were noted for the MPQ, Pressure Perception Threshold and 2-Point Discrimination Test (p ˂ 0.001), with an effect size of 1.49, 0.31 and 1.04, respectively.

Conclusions: This study confirms that SMA is a painful touch-evoked tactile HYPO-aesthesia for patients with CRPS. Moreover, results support the efficacy of the method of SPR to improve neuropathic pain in this population.

Implications: Static mechanical allodynia is a painful touch-evoked tactile HYPO-aesthesia even in persons with CRPS condition. The underlying tactile HYPO-aesthesia is related to the spontaneous neuropathic pain in patients with CRPS of the foot. Distant vibrotactile counter-stimulation, respecting the cutaneous nerve branch, is an important therapeutic management opportunity in patients with CRPS of the foot.

Keywords:
Complex regional pain syndrome
Allodynia
Somatosensory pain rehabilitation

Topics:
Pain & pain management
Neurology
Disability & rehabilitation

Did this work require ethics approval? Yes

Institution: Université de Montréal

Committee: Comithé d'Éthique de la Recherche en Sciences et en Santé (CERSES)

Ethics number: 2016-566