Introduction:
The frontal nerve block is performed to accomplish regional anesthesia of the face. Nerve block requires less anesthesia than local infiltration and provides anesthesia without causing tissue distortion of normal anatomy during the procedure. A facial nerve block provides immediate localized anesthesia for various types of injuries, such as facial lacerations, debridement of abrasions, burns to the forehead, upper eyelid laceration repair, removal of foreign bodies, pain relief from migraines, and acute herpes zoster. While performing the procedure, good knowledge of appropriate anatomical landmarks is required.
What Is the Anatomy of the Frontal Nerve?
A frontal nerve block is a procedure requiring appropriate knowledge about the anatomy, as it is landmark-based. The frontal nerve gets into the orbit through the uppermost part of the superior orbital fissure, then divides into the supraorbital and supratrochlear branches. The frontal nerve is the largest of the sensory components of the ophthalmic nerve, an extension of the trigeminal nerve.
The trigeminal nerve splits into the ophthalmic nerve, the maxillary nerve, and the mandibular nerve. The frontal nerve, an extension of the ophthalmic nerve, is divided into terminal branches, such as larger supraorbital and smaller supratrochlear branches. The supraorbital nerve leaves the cranium through the supraorbital notch or supraorbital foramen (a small opening), which is situated within the medial one-third of the supraorbital margin.
The nerve then ascends to the forehead and ends in the region of the anterior scalp. It provides sensory input for tissues surrounding the lambdoidal suture. The supratrochlear nerve supplies sensory information for a small area closer to the midline. These two branches supply sensation to the frontal scalp and forehead, the upper eyelid's middle part, and the nose's root. The supraorbital foramen can be identified by making the patient sit and look straight and palpating along the supraorbital ridge until feeling a subtle notch.
This is the area for performing this nerve block. Most supraorbital nerve exits existed as notches, and the rest as foramina. After exiting the orbital rim, the supraorbital nerve again has two divisions: a superficial division and a deep division. These branches provide sensory supply to the forehead skin and anterior margin of the scalp.
What Are the Indications for Frontal Nerve Block?
The facial nerve block is done to anesthetize the part of the face innervated by the frontal nerve. This block is indicated for procedures such as:
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Closing wounds or lacerations.
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Debridement of burns or abrasions.
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Relief of acute pain from herpes zoster and migraine headaches.
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Relief from neuralgic pain such as supratrochlear or supraorbital.
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Relief from hemicrania continua.
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Removal of foreign bodies.
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For dermatologic procedures.
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Oculoplastic surgery (surgical procedures that deal with the orbit, tear ducts, eyelids, and the face.
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Trabeculectomy surgery (a surgical procedure for glaucoma).
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Contraindications to general anesthesia.
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Awake craniotomy.
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Pain management after a surgical procedure.
What Are the Contraindications for Frontal Nerve Block?
Contraindications to the frontal nerve block include:
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Refusal of the patient.
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Any allergy or sensitivity to local anesthesia.
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Distortion of anatomical landmarks.
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Infection at the site of injection.
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Uncooperative patient.
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Patients with bleeding disorders or coagulopathy.
What Is the Procedure for Frontal Nerve Block?
A supraorbital nerve block can be performed by injecting local anesthesia under real-time ultrasound guidance. The healthcare professional may use one to three milliliters of any anesthetic agent, such as Lidocaine, Tetracaine, and Bupivacaine. During the procedure, the patient is made to sit or lie down flat, and the injection site is sterilized with an antiseptic solution such as a povidone-iodine solution.
The supraorbital nerve exits through the supraorbital foramen at the inferior margin of the supraorbital ridge. The supraorbital foramen can be located by palpating along the supraorbital ridge until feeling a subtle notch; this is the supraorbital foramen. The physician inserts the needle and injects a small amount of the anesthetic agent to raise a wheel in the area.
To prevent the anesthetic from swelling the eyelid, gently press a roll of gauze over the eyelid. Insert the needle into the wheel; care should be taken not to enter the foramen. Aspirate the syringe to check that the needle is not inside a blood vessel, then slowly inject the anesthetic agent and withdraw the needle. The pain during the procedure can be reduced by the correct needle position and by injecting the anesthetic agent slowly. To feel the anesthetic effect, it may take 10 minutes. In the event of unsuccessful anesthesia, the doctor may administer another injection along the supraorbital rim.
What Is the Duration of Action of a Frontal Nerve Block?
Predicting the duration of the action of the frontal nerve block is quite complicated. In some individuals, the frontal nerve block will yield immediate pain relief from migraine or herpes zoster virus, lasting up to six weeks, while others may find no benefit. The duration of the action of the frontal nerve block used to perform a procedure depends on the type of anesthetic agent used. The patient may experience pain, discomfort, or tingling sensation in the area as the action of the nerve block fades. Post-procedure pain may be managed with painkillers.
The approximate duration of the anesthetic effect is as follows:
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Lidocaine - The duration of action will last approximately 75 minutes.
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Bupivacaine - The duration of action will last approximately up to eight hours.
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Tetracaine - The duration of action will last approximately up to three hours.
What Are the Complications of a Frontal Nerve Block?
Complications occurring due to a frontal nerve block are very rare. But in some cases, the following complications have been reported:
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Hematoma (collection of blood outside blood vessels).
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Bleeding.
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Infection.
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Eye globe damage.
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Intravascular injection.
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Unintentional injection into vein or artery.
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Nerve damage or injury.
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Swelling of the eyelid.
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Hypersensitivity, allergy, or systemic reaction to local anesthesia.
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Post-procedural pain flare-up mainly occurs when steroids are used in the injection.
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Post-block ecchymosis (discoloration of the skin due to blood leak under the skin).
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Failure to anesthetize.
Conclusion:
Frontal nerve is a branch of the ophthalmic nerve that divides into the supraorbital and supratrochlear branches. The frontal nerve block provides regional anesthesia of the face without causing tissue distortion of the normal anatomy of the face. It offers immediate localized anesthesia for multiple injuries to the face. However, good knowledge of anatomy is needed to get good results.
