Chronic pain

Pain that has lasted longer than three to six months, though some theorists and researchers have placed the transition from acute to chronic pain at 12 months.

Others apply acute to pain that lasts less than 30 days, chronic to pain of more than six months duration, and subacute to pain that lasts from one to six months.

A popular alternative definition of chronic pain, involving no arbitrarily fixed duration, is “pain that extends beyond the expected period of healing”.

Chronic pain remains a serious public health problem. A survey estimates that almost one in five (19%) adults in Europe suffer from chronic pain with almost two-thirds of chronic pain patients reporting inadequate pain control at times 1).

Around 20% of patients undergoing surgery for lumbar radiculopathy develop chronic pain after surgery, leading to high socio-economic burden. Current perioperative interventions, including education and rehabilitation, are not always effective in preventing prolonged or chronic postoperative pain and disability.

Goudman et al.,proposed a shift in educational intervention from a biomedical towards a biopsychosocial approach for people scheduled for lumbar surgery. Pain neuroscience education (PNE) is such a biopsychosocial approach which aims at decreasing the threat value of pain by reconceptualizing pain and increasing the patient's knowledge about pain.

In a a paper they provides a clinical perspective for the provision of perioperative PNE, specifically developed for patients undergoing surgery for lumbar radiculopathy. Besides the general goals of PNE, perioperative PNE aims to prepare the patient for post-surgical pain and how to cope with it 2).

The corpus callosum substructure region has extensive damage in chronic pain, and the selective microstructural integrity damage was particularly manifested by changes in axons and myelin sheath in the genu and body of corpus callosum 3).

A randomized double-blinded clinical trial with a crossover research design. Patients with an already implanted Dorsal Root Ganglion Stimulation Therapy DRG-S system was included and randomly tested with 4 Hz, 20 Hz, 60 Hz, and sham stimulation. Amplitude was adjusted to subthreshold values for each frequency. Each frequency was tested for 5 days, followed by a 2-day washout period. Patients were assessed using VAS, McGill Pain Questionnaire, EQ-5D-5L, and Beck Depression Inventory.

Seventeen patients were included. The time between inclusion in this study and the primary implant was 32.8 months. The baseline stimulation frequency was 20 Hz in all patients. The mean baseline pain intensity was VAS 3.2 (SD 2.2). With 4-Hz stimulation, VAS was 3.8 (SD 1.9), with 20 Hz VAS 4.2 (SD 2.0), and with 60 Hz VAS 4.6 (SD 2.7). Worst pain control was seen with sham stimulation with a VAS of 5.3 (SD 3.0). Stimulation with 4 Hz achieved lower VAS scores, but this was only statistically significant when compared to sham (p = 0.001). A similar trend favoring 4-Hz stimulation was seen using the Beck Depression Inventory, but in this case, no statistical significance was found. Outcomes of McGill Pain Questionnaire and EQ-5D-5L favored 20 Hz stimulation, but again without statistical significance.

Low-frequency stimulation was not significantly better than classic 20-Hz stimulation in relieving pain intensity; the study might however be underpowered. Longer washout and observational periods might also be necessary to show clear differences in frequency response 4).

Soloukey S, de Rooij JD, Drenthen J, De Zeeuw CI, Huygen FJPM, Harhangi BS. Unilateral L2-Level DRG-stimulation Evokes Bilateral CPG-Like Motor Response in a Patient with Chronic Pain. Brain Stimul. 2020 Oct 7:S1935-861X(20)30260-6. doi: 10.1016/j.brs.2020.09.021. Epub ahead of print. PMID: 33038598 5).

Lawson McLean et al. from the Division of Functional and Restorative Neurosurgery, Department of Neurosurgery, Jena University Hospital, present the case of a chronic pain patient treated surgically for degenerative cervical myelopathy secondary to cervical spinal stenosis. Following this surgery, the patient experienced an intractable postoperative pain syndrome that had anatomical borders, an intensity and a character that was different to the background chronic pain from which they suffered.

They successfully implanted a cervical spinal cord stimulation (SCS) lead in the period following their stenosis surgery, which had good therapeutic effect on the postoperative-onset pain. To the best of the knowledge, this is the first description of SCS having a strong positive effect on an acute exacerbation of neuropathic pain. At follow-up 12 months later, assessment of the patient's pain diary revealed a modal pain intensity of NRS 3/10 over the preceding three months. The Brief Pain Inventory (Short Form) scores at this point in time were 10/40 in the pain severity domain and 18/70 in the interference with function domain, demonstrating the long-term effectiveness of this SCS strategy. While SCS has hitherto been untested as a therapy for acute-onset pain, this report demonstrates its utility as a salvage treatment in select cases of uncontrollable postoperative pain 6).

Breivik H, Eisenberg E, O'Brien T. Openminds. The individual and societal burden of chronic pain in Europe: the case for strategic prioritisation and action to improve knowledge and availability of appropriate care. BMC Public Health. 2013;13:1229.
Goudman L, Huysmans E, Ickmans K, Nijs J, Moens M, Putman K, Buyl R, Louw A, Logghe T, Coppieters I. A Modern Pain Neuroscience Approach in Patients Undergoing Surgery for Lumbar Radiculopathy: A Clinical Perspective. Phys Ther. 2019 Mar 28. pii: pzz053. doi: 10.1093/ptj/pzz053. [Epub ahead of print] PubMed PMID: 30921465.
Li R, Chang N, Liu Y, Zhang Y, Luo Y, Zhang T, Zhao Q, Qi X. The Integrity of the Substructure of the Corpus Callosum in Patients with Right Classic Trigeminal Neuralgia-A Diffusion Tensor Imaging Study. J Craniofac Surg. 2020 Sep 22. doi: 10.1097/SCS.0000000000007082. Epub ahead of print. PMID: 32969923.
Piedade GS, Gillner S, McPhillips PS, Vesper J, Slotty PJ. Effect of low-frequency dorsal root ganglion stimulation in the treatment of chronic pain. Acta Neurochir (Wien). 2023 Jan 27. doi: 10.1007/s00701-023-05500-1. Epub ahead of print. PMID: 36705762.
Soloukey S, de Rooij JD, Drenthen J, De Zeeuw CI, Huygen FJPM, Harhangi BS. Unilateral L2-Level DRG-stimulation Evokes Bilateral CPG-Like Motor Response in a Patient with Chronic Pain. Brain Stimul. 2020 Oct 7:S1935-861X(20)30260-6. doi: 10.1016/j.brs.2020.09.021. Epub ahead of print. PMID: 33038598.
Lawson McLean A, Kalff R, Reichart R. Spinal Cord Stimulation for Acute Pain Following Surgery for Cervical Myelopathy: A Novel Treatment Strategy. Pain Pract. 2018 Oct 27. doi: 10.1111/papr.12742. [Epub ahead of print] PubMed PMID: 30369016.
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