Preoperative Erector Spinae Plane Block Versus Paravertebral Plane Block in Decreasing Post Mastectomy Pain Syndrome

Breast cancer is considered the commonest malignancy affecting women with an incidence exceeding one million cases per year. Although it has a favorable prognosis with improved lines of treatment, some complications may still disturb the patient's life quality. One of these complications is post-mastectomy pain syndrome (PMPS) ¹. The International Association for Study of Pain (IASP) defines PMPS as chronic pain that persists more than 3 months in the anterior thorax, axilla \&/or upper arm ². It is usually neuropathic in nature includes altered sensations such as dysesthesia, hypo or hyperesthesia, allodynia or particular qualities of dysesthesia e.g burning, dull aching sensations. It is usually of at least moderate intensity and may be either continuous or intermittent pain ³. The etiology and mechanism of PMPS remain incompletely clear yet. Some risk factors are believed to be associated with PMPS, including the presence and intensity of postoperative pain, the type of surgery, younger women, prior history of other types of pain and adjuvant therapies like chemo or radiotherapy ⁴. Regional Anaesthesia (RA) is considered one of the most effective methods in reducing acute pain after breast surgeries, these include pectoral nerves block (PECS), serratus anterior plane block (SAPB), paravertebral plane block (PVPB) and erector spinae plane block (ESPB) ⁵. Theoretically RA can minimize the development of PMPS by decreasing the afferent nociceptive input and central sensitization during the perioperative period, However clinically the role of RA in preventing PMPS is still under investigations ⁶. PVPB includes injecting local anesthetic in the paravertebral space where the spinal nerves exit from the intervertebral foraminae. Paravertebral space is bounded by the parietal pleura, superior costotransverse ligament, vertebrae, intervertebral foraminae and the heads of the ribs ⁷. While ESPB includes injection of the local anesthetic in the fascial plane between the vertebral transverse processes and the erector spinae muscle ⁸. Many studies were done in order to evaluate the efficacy of either ESPB or PVB in controlling acute postoperative pain after breast surgeries, some studies compared between them in controlling acute postoperative pain after breast surgeries ⁹. Also there are some studies that evaluate the effect of either ESPB or PVPB in the prevention of PMPS after breast surgeries ¹⁰, but still the comparison between the effect of preoperative ESPB versus the effect of preoperative PVPB in the prevention of PMPS in patients undergoing breast surgeries is still under investigated. Our study is aiming for comparing the effect of preoperative PVPB versus preoperative ESPB in the prevention of PMPS in patients undergoing unilateral breast surgeries.