What is the correct technique for performing a lesser occipital nerve block?

Lesser Occipital Nerve Block Technique

The lesser occipital nerve block should be performed at the midpoint of the posterior border of the sternocleidomastoid muscle using a superficial injection technique, as the nerve is consistently located at this anatomical landmark in a superficial plane. 1

Anatomical Landmarks and Patient Positioning

The lesser occipital nerve (LON) has a predictable anatomical course that guides the injection technique:

• Primary injection site: Midpoint of the posterior margin of the sternocleidomastoid muscle 1
• The nerve wraps around the accessory nerve anteriorly before reaching the posterior edge or superficial surface of the sternocleidomastoid 1
• Distribution: Controls skin over the upper sternocleidomastoid, upper posterior cervical triangle, and middle surface behind the auricle 1

The nerve exhibits a shrub-type branching pattern without a main trunk in 82.5% of cases (predominantly three-branch type), while only 17.5% show a single branch pattern 1. This anatomical variability is clinically important but does not alter the injection site.

Step-by-Step Technique

Preparation and Antisepsis

While the provided guidelines focus on central neuraxial blockade, basic sterile technique principles apply:

• Perform hand hygiene with surgical scrub
• Use sterile gloves
• Apply skin antiseptic and allow to dry completely before needle insertion

Needle Insertion and Injection

Critical technical points:

1. Depth: The injection must be superficial - the nerve position is consistently superficial, and deep injection will miss the target 1

2. Location precision: Identify the posterior border of the sternocleidomastoid muscle by palpation, then locate the midpoint between the mastoid process superiorly and the clavicle inferiorly

3. Volume and agent:

   • Use 5 ml of 0.5% ropivacaine for effective blockade 2
   • Amide local anesthetics (like ropivacaine or bupivacaine) are preferred over ester types for peripheral nerve blocks

4. Confirmation: Paresthesia in the LON distribution (behind the ear and upper lateral neck) confirms proper placement, though this is not always achievable given the nerve's superficial and branching nature

Combined Approach Considerations

The LON block is frequently performed in combination with greater occipital nerve (GON) block for comprehensive occipital analgesia 2, 3. When performing combined blocks:

• The LON and GON can be blocked through separate injection sites
• For craniotomy patients, combined LON and great auricular nerve block (LOGAB) provides effective perioperative analgesia with reduced opioid consumption and improved hemodynamic stability 2
• Pain scores at rest and motion are significantly reduced for up to 48 hours post-procedure 2

Safety Profile and Complications

The LON block has an excellent safety profile with minimal reported adverse events:

• No serious complications reported in prospective studies 2
• Temporary numbness in the distribution area is expected and confirms successful blockade
• The superficial location minimizes risk of vascular injury or deep structure involvement

Common Pitfalls to Avoid

1. Injecting too deep: This is the most critical error - the nerve is superficial, and deep injection will fail 1
2. Wrong location along the sternocleidomastoid: Must be at the midpoint of the posterior border, not anterior or at the extremes
3. Insufficient volume: 5 ml provides adequate spread for the branching nerve pattern 2
4. Failure to allow antiseptic to dry: Premature needle insertion risks introducing antiseptic into tissues

The technique's reliability stems from the LON's consistent anatomical relationship to the sternocleidomastoid muscle, with a 100% dissection rate in anatomical studies 1, making this a reproducible and effective procedure when performed at the correct superficial depth and midpoint location.