A Comprehensive Review of the Diagnosis, Treatment, and Management of Postmastectomy Pain Syndrome.

PURPOSE OF REVIEW: Postmastectomy pain syndrome (PMPS) remains poorly defined, although it is applied to chronic neuropathic pain following surgical procedures of the breast, including mastectomy and lumpectomy in breast-conserving surgery. It is characterized by persistent pain affecting the anterior thorax, axilla, and/or medial upper arm following mastectomy or lumpectomy. Though the onset of pain is most likely to occur after surgery, there may also be a new onset of symptoms following adjuvant therapy, including chemotherapy or radiation therapy. RECENT FINDINGS: The underlying pathophysiology is likely multifactorial, although exact mechanisms have yet to be elucidated. In this regard, neuralgia of the intercostobrachial nerve is currently implicated as the most common cause of PMPS. Numerous pharmacological options are available in the treatment of PMPS, including gabapentinoids, tricyclic antidepressants, selective serotonin reuptake inhibitors, NMDA receptor antagonists, and nefopam (a non-opioid, non-steroidal benzoxazocine analgesic). Minimally invasive interventional treatment including injection therapy, regional anesthesia, botulinum toxin, and neuromodulation has been demonstrated to have some beneficial effect. A comprehensive update highlighting current perspectives on the treatment of postmastectomy pain syndrome is presented with emphasis on treatments currently available and newer therapeutics currently being evaluated to alleviate this complex and multifactorial condition.

Stem Cell Therapies for Treatment of Discogenic Low Back Pain: a Comprehensive Review.

PURPOSE OF REVIEW: Discogenic low back pain (DLBP) stems from pathology in one or more intervertebral discs identified as the root cause of the pain. It is the most common type of chronic low back pain (LBP), representing 26-42% of attributable cases. RECENT FINDINGS: The clinical presentation of DLBP includes increased pain when sitting, coughing, or sneezing, and experiencing relief when standing or ambulating. Dermatomal radiation of pain to the lower extremity and neurological symptoms including numbness, motor weakness, and urinary or fecal incontinence are signs of advanced disease with disc prolapse, nerve root compression, or spinal stenosis. Degenerative disc disease is caused by both a decrease in disc nutrient supply causing decreased oxygen, lowered pH, and lessened ability of the intervertebral disc (IVD) to respond to increased load or injury; moreover, changes in the extracellular matrix composition cause weakening of the tissue and skewing the extracellular matrix's (ECM) harmonious balance between catabolic and anabolic factors for cell turnover in favor of catabolism. Thus, the degeneration of the disc causes a shift from type II to type I collagen expression by NP cells and a decrease in aggrecan synthesis leads to dehydrated matrix cells ultimately with loss of swelling pressure needed for mechanical support. Cell-based therapies such as autologous nucleus pulposus cell re-implantation have in animal models and human trials shown improvements in LBP score, retention of hydration in IVD, and increased disc height. Percutaneously delivered multipotent mesenchymal stem cell (MSC) therapy has been proposed as a potential means to uniquely ameliorate discogenic LBP holistically through three mechanisms: mitigation of primary nociceptive disc pain, slow or reversal of the catabolic metabolism, and restoration of disc tissue. Embryonic stem cells (ESCs) can differentiate into cells of all three germ layers in vitro, but their use is hindered related to ethical concerns, potential for immune rejection after transplantation, disease, and teratoma formation. Another similar approach to treating back pain is transplantation of the nucleus pulposus, which, like stem cell therapy, seeks to address the underlying cause of intervertebral disc degeneration by aiming to reverse the destructive inflammatory process and regenerate the proteoglycans and collagen found in healthy disc tissue. Preliminary animal models and clinical studies have shown mesenchymal stem cell implantation as a potential therapy for IVD regeneration and ECM restoration via a shift towards favorable anabolic balance and reduction of pain.