Sono-anatomy Glide-View ©

The section below presents the essential sono-anatomy required for performing the block.

Interactive Image: Move the slider bar left and right to explore the image with and without colourised anatomical landmarks.

Simplified Complexity: The interactive design helps you visualise and understand complex sono-anatomy, enhancing the safety and precision of nerve blocks.Sono-anatomy Glide-View © - Interscalene Brachial Plexus Block

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Interscalene Brachial Plexus Block

Brachial Plexus (Roots/Trunks):

Appearance: The brachial plexus appears as a collection of hypoechoic (dark) structures surrounded by hyperechoic (bright) connective tissue. In the interscalene region, the roots or trunks of the brachial plexus typically have a round or oval appearance, often described as a “string of pearls” sign.

Location: These nerve structures are located between the anterior and middle scalene muscles, typically found at the level of the C5 to C7 vertebrae. The plexus is usually positioned lateral to the carotid artery and jugular vein.

Optimisation: A high-frequency linear probe should be used to provide the best resolution of these nerves. Position the probe transversely across the neck at the level of the cricoid cartilage (C6 level) and scan laterally until the brachial plexus is visualised between the scalene muscles. Adjust the depth and focus to centre the plexus within the image, ensuring the entire cluster of nerves is visible.

Anterior Scalene Muscle:

Appearance: The anterior scalene muscle is seen as a hypoechoic (dark) triangular structure, positioned anteriorly to the brachial plexus. It is usually more superficial compared to the middle scalene muscle.

Location: This muscle is located anterior to the brachial plexus and separates it from the carotid artery and jugular vein.

Optimisation: To enhance the visibility of the anterior scalene muscle, ensure the probe is placed slightly lateral to the midline, scanning from medial to lateral across the neck. Identifying this muscle is key to locating the brachial plexus beneath or adjacent to it. Adjust the probe angle to clearly delineate the muscle from the adjacent vascular structures.

Middle Scalene Muscle:

Appearance: The middle scalene muscle appears as a hypoechoic structure with a triangular shape, similar to the anterior scalene muscle but located more posteriorly.

Location: It lies posterior to the brachial plexus, forming the posterior boundary of the interscalene groove where the plexus resides.

Optimisation: Position the probe to include both the anterior and middle scalene muscles in the field of view. This ensures the brachial plexus is adequately framed between these two muscles. Slight adjustments in probe tilt can help differentiate the middle scalene from other surrounding musculature.

Sternocleidomastoid Muscle:

Appearance: The sternocleidomastoid muscle (SCM) is seen as a superficial, hypoechoic, elongated structure running obliquely across the neck.

Location: The SCM is positioned more anteriorly and superficially, above the anterior scalene muscle. While not directly involved in the block, it serves as an important landmark.

Optimisation: Position the probe to visualise the SCM alongside the anterior scalene muscle to provide orientation. The SCM helps in guiding the placement of the probe, ensuring correct identification of the deeper structures like the brachial plexus.

Vertebral Artery:

Appearance: The vertebral artery appears as an anechoic (black) circular structure, often identified near the transverse processes of the cervical vertebrae.

Location: It runs medially to the brachial plexus, within the transverse foramina of the cervical vertebrae.

Optimisation: Doppler mode should be used to identify the vertebral artery and distinguish it from other vascular structures. It’s important to identify and avoid this artery during the block to prevent complications.

Transverse Processes of Cervical Vertebrae:

Appearance: The transverse processes are visualised as hyperechoic (bright) linear structures with acoustic shadows beneath them.

Location: These bony structures lie deeper in the neck and serve as important landmarks for the brachial plexus, which is located just superficial to these processes.

Optimisation: Adjust the depth and angle of the probe to visualise the transverse processes clearly. Recognising these structures helps in orienting the probe to locate the brachial plexus more accurately.

Tips for Success:

Use a High-Frequency Linear Probe: This is essential for visualising the superficial structures of the neck, including the brachial plexus and surrounding muscles.

Optimal Patient Positioning: Have the patient lie supine with the head turned slightly away from the side being blocked. This opens up the interscalene space, making it easier to visualise the brachial plexus.

Apply Gentle Probe Pressure: To improve the visibility of the brachial plexus, gently press the probe against the neck to displace superficial tissue without compressing the underlying nerves.

Hydrodissection: Injecting a small amount of saline into the plane where the brachial plexus is located can help confirm the correct plane and facilitate the spread of local anaesthetic. This also assists in needle placement by separating the nerves from surrounding tissues.

Real-Time Visualisation: Continuously visualise the needle tip as it advances towards the brachial plexus to ensure accurate placement and avoid injury to surrounding structures, such as the vertebral artery or pleura.