A new anatomical brachial plexus variation during interscalene block

Area of Science:

• Anesthesiology
• Anatomy
• Radiology

Background:

• Ultrasound-guided (USG) interscalene block is a standard anesthetic technique for shoulder arthroscopy.
• Anatomical variations of the brachial plexus can complicate nerve blocks.
• Accurate identification of nerve roots is essential for successful blockades.

Observation:

• An accessory muscle was identified between the anterior scalene and middle scalene muscles during a USG interscalene block.
• This accessory muscle divided the expected brachial plexus roots into two distinct groups.
• Deltoid muscle contractions were observed from both root groups upon nerve stimulation, suggesting a C5 nerve root variation.

Findings:

• A novel brachial plexus anatomical variation was identified and confirmed using magnetic resonance neurography.
• The variation involved an accessory muscle altering the typical arrangement of brachial plexus roots.
• Ultrasound guidance combined with nerve stimulation ensured successful anesthetic delivery despite the anatomical anomaly.

Implications:

• USG interscalene blocks are highly recommended for anesthetic procedures.
• Nerve stimulation is a valuable adjunct when anatomical variations of the brachial plexus are suspected.
• Confirmation of this variation via MRI advances anatomical knowledge and improves regional anesthesia practices.