Transversus Abdominis Plane (TAP) Peripheral Nerve Stimulation (PNS) for Abdominal Wall Myofascial Pain Syndrome: A Case Report

Case Diagnosis: Abdominal Wall Myofascial Pain Syndrome

Case Description or Program Description: A 21-year-old female with no past medical history presented with a two-year history of constant, achy, burning left lower quadrant abdominal pain. The pain worsened with walking, standing, and climbing stairs but improved with lying down, heat, and gabapentin. Examination revealed tenderness over the left rectus abdominis and abdominal wall, without tenderness over the thoracic spine or paraspinal muscles. Extensive evaluations by gastrointestinal (GI), obstetrics and gynecology (OBGYN), neurology, and pain specialists—including colonoscopy, magnetic resonance imaging (MRI) of the abdomen, pelvis, and spine, diagnostic laparoscopy, cervical biopsy, and electromyography—ruled out inflammatory bowel disease (IBD), malignancy, endometriosis, multiple sclerosis (MS), and spinal pathology. Prior treatments, including nonsteroidal anti-inflammatory drugs (NSAIDs), transversus abdominis plane (TAP) block, botulinum toxin, trigger point injections, and physical therapy, provided only moderate relief.

Setting: Outpatient pain management clinic

Assessment/Results: Given persistent symptoms, a TAP PNS trial was pursued. Under ultrasound guidance, a stimulating probe reproduced her pain, confirming the target nerve. A four-contact electrode array was placed in the TAP at 1499 Hz, 30 μs pulse width, and 2.5 mA amplitude. A one-month trial of a left TAP PNS improved symptoms by over 80%, marking her greatest relief in over 2.5 years.

Discussion (relevance): Abdominal myofascial pain syndrome is a rare diagnosis of exclusion. It can be especially challenging to diagnose in younger, menstruating women as the differential includes GI, OBGYN, neurologic, and other pain-related etiologies. While TAP PNS has been studied and shown to be effective in post-surgical abdominal pain, neuromodulation in this case effectively alleviated non-surgically related abdominal pain. This indicates a broader potential for TAP PNS.

Conclusions: Abdominal myofascial pain syndrome is a rare diagnosis of exclusion, challenging both to diagnose and treat. This case exemplifies the role of TAP PNS in management.