Ultrasound-Guided Supraorbital Nerve Block
CLINICAL CONSIDERATIONS
Ultrasound-guided supraorbital nerve block is useful in the diagnosis and treatment of a variety of painful conditions in areas subserved by the supraorbital nerve, including supraorbital neuralgia, supraorbital nerve entrapment, swimmer’s headache, and pain secondary to herpes zoster (Fig. 11.1). This technique is also useful in providing surgical anesthesia in the distribution of the supraorbital nerve for lesion removal, cosmetic procedures, and laceration repair.
CLINICALLY RELEVANT ANATOMY
The supraorbital nerve is a pure sensory nerve. It arises from fibers of the frontal nerve, which is the largest branch of the ophthalmic nerve. The frontal nerve enters the orbit via the superior orbital fissure and passes anteriorly beneath the periosteum of the roof of the orbit. The frontal nerve gives off a larger lateral branch, the supraorbital nerve, and a smaller medial branch, the supratrochlear nerve. Both nerves exit the orbit anteriorly along with the supraorbital artery via the supraorbital foramen (Fig. 11.2). The supraorbital nerve provides sensory innervation to the forehead, upper eyelid, and anterior scalp all the way to the vertex of the skull (Fig. 11.3).
ULTRASOUND-GUIDED TECHNIQUE
The patient is placed in a supine position. A total of 2 mL of local anesthetic is drawn up in a 5-mL sterile syringe. When treating conditions involving the supraorbital nerve thought to have an inflammatory component such as supraorbital neuralgia, acute herpes zoster, neuritis, and postherpetic neuralgia, 40 to 80 mg of depot steroid may be added to the local anesthetic.
The basis for the use of ultrasound when performing supraorbital nerve block is its ability to easily identify the discontinuity of the hyperechoic image associated with the supraorbital foramen when imaging the supraorbital ridge. To perform ultrasound-guided supraorbital nerve block, the supraorbital foramen on the affected side is identified by palpation (Fig. 11.4). The foramen can usually be found 2.5 to 2.8 cm laterally from the midline. The skin overlying the supraorbital foramen is then prepped with antiseptic solution. Care must be taken to avoid allowing the antiseptic solution to flow into the eye. A high-frequency small linear or hockey stick transducer is then placed in a transverse plane over the previously identified supraorbital notch and slowly moved from a cephalad to caudad direction until a discontinuity in the supraorbital ridge is identified (Figs. 11.5 and 11.6). In most patients, color Doppler can be utilized to identify the supraorbital artery, which exits the supraorbital foramen along with the supraorbital nerve (Fig. 11.7).