Inter scalene block was performed by palpating groove between the anterior scalene and middle scalene muscle
[4,5,6] with 23 x 1.5G needle and locating neurovascular bundle by moving the needle anteriorly and posteriorly.
Neither approach eliminates risk of nerve injury as the dorsal scapular nerve (DSN) and the long thoracic nerve (LTN) travel through the middle scalene muscle
, while the phrenic nerve may be placed at risk of injury while traversing along the anterior scalene muscle.
The main etiology described for DSN entrapment is hypertrophy of the middle scalene muscle
causing compression of the nerve as it passes through.21 Mondelli et al.
Intramuscular haemangioma of the middle scalene muscle
. Acta Otorhinolaryngol Belg 1980; 34: 345-9.
This approach also facilitates the section of the anterior and middle scalene muscle
with perfect visualization of the artery, vein, and brachial plexus, resulting in greater safety and also improving control and preventing lesions on the sympathetic chain and the stellate ganglion.
(2, 6) At the lateral aspect of the middle scalene muscle
, the upper two roots (C5 & C6) join to form the upper trunk, the middle root (C7) continues on as the middle trunk, and the lower two roots (C8 & T1) join to form the lower trunk.
To avoid direct trauma to the plexus on initial needle placement, an insulated Tuohy needle (Contiplex Tuohy, BBraun) connected to a nerve stimulator (Pajunk Vario) was placed with real time ultrasound control within the middle scalene muscle
next to the trunks of the plexus.
The first site is the interscalene triangle, where compression can occur between the anterior scalene muscle, middle scalene muscle
and the medial surface of the first rib inferiorly.
A long axis view of the brachial plexus roots, sternocleidomastoid (SCM) muscle, levator scapula muscle, carotid artery, jugular vein, and anterior and middle scalene muscles
was identified (Figure 2).
LSA run upward and passed between anterior and middle scalene muscles
. LVA continued upward and entered deep to the transverse process at the level of the 7th cervical vertebrae.
The interscalene brachial plexus block is performed in the interscalene groove, between the anterior and middle scalene muscles
The subclavian artery emerges from between the anterior and middle scalene muscles
and becomes the axillary artery as it passes the first rib.