Sonographic measurement of the normal suprascapular nerve and omohyoid muscle

Abstract

The aim of this study was to obtain normative ultrasonography (US) data on the suprascapular nerve (SSN) and omohyoid muscle (OM) in the lateral cervical region. The SSN and OM are known to be related throughout the nerve's course, yet little imaging data exists on these structures at areas more proximal than the suprascapular foramen. US data from a convenience sample of 33 asymptomatic subjects between 21 and 42 years of age were collected. Cross sectional area (CSA) of the SSN, distances from the OM to the SSN, and long-axis diameter of the OM at three reference points were obtained. The mean CSA of the SSN at both its origin and over the first rib was 1.9 mm2 and at the distal clavicle was 2.0 mm2. The mean distance of the OM to the SSN at these locations was 7.6 mm, 4.2 mm and 2.8 mm respectively. The mean long axis diameter of the OM was 2.4 mm at the SSN origin, 3.4 mm at the first rib, and 4.1 mm at the distal clavicle. We present US data from asymptomatic subjects on the SSN and OM. Our results show that the SSN nerve CSA is consistent throughout the nerves proximal course. Furthermore, the OM and SSN tend to approximate as they course distally. Future studies with larger samples will better characterize the normal sonoanatomy of these structures between genders and across different ages.