Scalp Block

Indications

  • Craniotomy
    Notable awake craniotomy.
  • Repair of scalp lacerations

Contraindications

Anatomy

Sensory supply to the scalp:

  • Trigeminal nerve
    Three divisions:
    • V1 (Opthalmic)
      Innervates forehead and anterior scalp via the frontal nerve, which divides in the orbit into the:
      • Supraorbital nerve
        Innervates the forehead and anterior scalp. May be blocked as it exits the supraorbital foramen.
      • Supratrochlear nerve
        Exits the supraorbital foramen and travels deep to frontalis.
    • V2 (Maxillary)
      Innervates zygomatic arch via series of cutaneous branches.
      • Zygomaticotemporal nerve
        Innervates a small area of forehead and temporal area.
    • V3 (Mandibular)
      Innervates peri-auricular scalp via series of cutaneous branches.
      • Auriculotemporal nerve
        Innervates temporal areas, lower lip and face, auricle, and scalp superior to the auricle.
  • Cervical plexus
    • Greater occipital nerve
      Innervates posterior scalp, and sometimes the top of the head and lateral scalp above the ear.
    • Lesser occipital nerve
      Ascends along posterior border of SCM, and innervates scalp posterior to the ear.
    • Greater auricular nerve
      Emerges at posterior border of SCM, and divides into an anterior and posterior branch which provide sensation of parotid, mastoid process, and auricle.

Equipment

Technique

Six or seven nerves are blocked during a scalp block:

  • Supraorbital nerve
    • Identify the supraorbital notch
      Located directly above the midpoint of the pupil.
    • Insert needle medial to the supraorbital notch, advance until bone is contacted
    • Withdraw slightly and inject 2-3ml of LA after negative aspiration
  • Supratrochlear nerve
    • Extend the supraorbital nerve block 1cm medial and inject a further 2-3ml of LA to cover this nerve as it emerges from the superomedial aspect of the orbit
  • Auriculotemporal nerve
    • Identify the superficial temporal artery
    • Insert needle 1-1.5cm superior to the tragus, posterior to the temporal artery
    • Advance through temporalis fascia, and spread 3mL of LA deep and superficial to the fascia
  • Zygomaticotemporal nerve
    • Identify the zygomatic arch, lateral to the lateral canthus
    • Insert needle through temporalis just above zygomatic arch and almost down to periosteum of the temporal bone
    • Inject 2mL of LA below the fascia
  • Greater occipital nerve
    • Infiltrate 5mL of LA along the middle third of a line between the occipital protuberance and the mastoid process
      Variable location of this nerve in this region, but lies medial to the occipital artery (may be palpated). Ensure negative aspiration to avoid occipital artery injection.
  • Lesser occipital nerve
    • Inject 5mL of LA 2.5cm lateral to the site of the greater occipital nerve block
  • Greater auricular nerve
    This nerve rarely encroaches on the surgical field for an awake craniotomy and does not usually need to be blocked.
    • Inject ~2cm posterior to the auricle at the level of the tragus; may often be blocked with the lesser occipital

At each site:

  • Inject 2-5mL of 0.25-0.5% bupivacaine

Complications

General complications of regional techniques are covered under Principles of Regional Anaesthesia

Specific complications of the scalp block include:

  • Cerebral LA toxicity
    CNS effects (including seizures) may occur with very small volumes of intra-arterial LA.

References

  1. Osborn, I., & Sebeo, J. (2010). ‘Scalp Block’ During Craniotomy: A Classic Technique Revisited. Retrieved from http://www.accessmedicine.com.
  2. Burnand C, Sebastian J. Anaesthesia for awake craniotomy. Continuing Education in Anaesthesia Critical Care & Pain, Volume 14, Issue 1, 1 February 2014, Pages 6–11.
  3. Cormack JR, Costello TG. Awake Craniotomy: Anaesthetic Guidelines and Recent Advances. 2005:7.