Unfortunately, at his 3-month postoperative MRI follow-up exam, a small residual tumor was detected in the scalenus medius muscle (Figure 4a).
However, unfortunately, the excision margins adjacent to the scalenus medius muscle were positive.
nerve roots interdigitating within the anterior scalenus muscle or scalenus medius muscle
The posterolateral boundaries of Sibson fascia are the vertebral column, first rib, levator scapulae muscle, and scalenus medius muscle
; the medial boundary is formed by the superior mediastinal structures; and the anterior boundary is formed by the scalenus anterior and sternocleidomastoid muscles.
The scalenus anterior muscle pulls the lateral portion of the first rib proximally and posteriorly and the scalenus medius muscle
pulls the medial portion of the first rib proximally and medially.
It has been regarded as the posterior part of the scalenus medius muscle and often it is difficult to separate these two muscles from each other.
An accessory muscular fasciculus measuring 6.2cm in length and 1.3cm in width was seen to be arising from the middle of the anterior surface of scalenus medius muscle .
There have been reports of anomalous muscular slips between scalenus anterior and scalenus medius muscles. These anomalous muscular slips sometimes arose from scalenus medius muscle and ran into scalenus anterior muscle or vice-versa (Yamamoto, 1992).
In one subject, a vein was identified between the scalenus anterior and scalenus medius muscles
amongst the trunks (see Figure 5).