Ultrasonographic Evidence of Trapezius Fascia Thickening in Patients Undergoing Trigger Site Deactivation Surgery Compared With Healthy Control (2020)

PURPOSE: Trigger site deactivation surgery at the occipital site involves release of the greater occipital nerve (GON) from surrounding structures such as muscle, fascia, and occipital vessels. Recent intraoperative anatomic data at this site found that the trapezius fascia was macroscopically thickened in the majority of patients (94%) undergoing surgery.1 This structural anomaly has resemblance to the thickened transverse carpal ligament (TCL) seen in carpal tunnel syndrome (CTS). Ultrasonographic examination has been used to show transverse carpal ligament thickening as part of the screening and diagnosis of CTS. We hypothesized that similar to CTS, trapezius fascia would be significantly thicker in patients with migraine/headache/occipital neuralgia than in healthy controls when measured with ultrasound. METHODS: Ten patients undergoing screening for trigger site deactivation surgery at the occipital site were enrolled in this study prospectively. Ten subjects with no history of migraine, headache, occipital/ trigeminal neuralgia, or trauma to the head and neck region were matched by gender/age/body mass index and included as controls. All participants underwent an ultrasound examination of the occipital region by the same examiner using standardized settings (frequency 10.0 MHz, depth 2.5 cm) and standardized pressure. Trapezius fascia thickness was measured bilaterally 3 cm inferior and 1.5 cm lateral to the occiput, at the exit point of the GON from the semispinalis capitis muscle. The resulting data were analyzed by unpaired t test. RESULTS: Twenty participants were enrolled in the study with equal gender distribution between groups (12 females and 8 males). There was no statistically significant difference in age (49.1 versus 47.3; P = 0.09) or body mass index (27.5 versus 26.8; P = 0.21) between groups. Trapezius fascia was significantly thicker in patients presenting with migraine (mean ± SD, 2.0 ± 0.88 mm) than control (mean ± SD, 0.9 ± 0.23 mm) (P < 0.01). Maximum thicknesses among migraineurs was 4.1 versus 1.2 mm in healthy controls. CONCLUSION: As previously seen in observational intraoperative studies, trapezius fascia appears grossly abnormal and thickened in patients undergoing trigger site deactivation surgery at the occipital site. This is the first study to quantify trapezius fascia thickness at the exit site of the GON from the semispinalis capitis muscle using ultrasound. It is also the first evidence that trapezius fascia is thickened in occipital migraine/headache/neuralgia patients versus control. As we continue to analyze the pathomechanism of headaches, it is critical to understand the origin of pain. We hypothesize that the structural anomalies seen at this site could be related to microtrauma/overuse or actual trauma in the head and neck region. Understanding the pathomechanism could lead to better diagnostic and screening methods for headaches, accelerated diagnosis and more effective treatment. REFERENCE: 1. Gfrerer L, Hansdorfer MA, Ortiz R, et al. WG. Occipital neuralgia/migraine: intra-operative evidence for extracranial pathology. American Society for Reconstructive Microsurgery Meeting 2019, Palm Desert, CA, USA.