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Supraorbital Nerve Block


The supraorbital nerve (SON) is a branch of the ophthalmic division of the trigeminal nerve (V1). This nerve travels through the supraorbital foramen or notch to provide sensory innervation to the upper eyelid and forehead. After leaving the orbit, the SON lies deep to (or within) the periorbital muscles (orbicularis oculi, corrugator supercilii and frontalis). The SON does not emerge from the foramen/notch as a single discrete nerve, but rather as a collection of branches that are bundled together.

The dividing line between the SON territory and the greater occipital nerve territory is typically at the vertex of the head. In some cases, SON innervation can extend as far posteriorly as the lambdoid suture. The medial and lateral extent of the SON distribution is limited by the supratrochlear and zygomaticotemporal nerve territories, respectively.

SON blocks are used to provide local anesthesia of the forehead or treat supraorbital neuralgia manifest as frontal headaches. These blocks can be used for a variety of neurosurgical procedures. In cases of supraorbital neuralgia, a Tinel sign can sometimes be elicited over the SON at the supraorbital notch.

Potential advantages of ultrasound guidance for SON block include less local anesthetic volume, fewer arterial punctures, and less periorbital swelling. If lower volumes are used, it may be possible to reduce block of adjacent nerves (such as the temporal branch of the facial nerve). More complete blocks (i.e., more extensive medial and lateral coverage, and deeper periosteal fibers of the frontal bone) also are possible. Because the exit point of the SON is not constant, ultrasound imaging is a useful tool to guide these regional blocks. Ultrasound is a highly effective tool for identifying features of supraorbital foramen morphology and associated pathology.

Suggested Technique

The supraorbital foramen/notch is approximately 2.5 cm from the midline (range 2 to 3.5 cm), slightly medial to the midpupillary line. This exit point is usually 1 to 2 mm superior to the orbital rim but may be as much as 2 cm for accessory foramina. The supraorbital foramen/notch is located at the lower border of the corrugator supercilii muscle, where medial and lateral branches of the SON diverge from each other. The supraorbital artery and nerve run together into the frontalis muscle, the artery superficial to the nerve.

  • SON block can be done awake or asleep (there is a low risk of paresthesia and nerve injury).

  • The operator and machine remain in one location for bilateral SON block.

  • Povidone-iodine is typically used for skin prep before SON block (avoid chlorhexidine contamination of the eyes).

  • Light touch with the transducer is necessary because the supraorbital artery is superficial and therefore easily compressed against the adjacent bone.

  • For supraorbital block, use an in-plane approach from either side.

  • Limit the injection volume to less than 3 mL per side to reduce periorbital swelling.

  • The block can be performed either above or below the eyebrow (which can be pushed up or down with the transducer).

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