How Long Does A Supratrochlear Nerve Block Last?

A supratrochlear nerve block in an injection of anesthetic below the eyebrow to numb the face.

A supratrochlear nerve block is a procedure to anesthetize the lower middle portion of the forehead and the bridge of the nose. An anesthetic injection is administered below the eyebrow on the edge close to the nasal bridge, where the supratrochlear nerve comes out of the skull and runs up the forehead. The anesthetic agent blocks transmission of pain signals from the supratrochlear nerve to the brain.

The supratrochlear nerve is a terminal branch of the ophthalmic nerve, which is one of the three main divisions of the trigeminal nerve. The trigeminal nerves provide motor and sensory function to the face and the front part of the scalp.

The supratrochlear nerve provides sensation to the lower middle part of the forehead, the bridge of the nose, the membrane (conjunctiva) over the whites of the eyes and the inner lining of the upper eyelids. The supraorbital nerve provides sensation to the rest of the forehead and frontal scalp up to the top of the head.

A supratrochlear nerve block is mostly performed along with a supraorbital nerve block to anesthetize the entire forehead, during treatment procedures that include:

• Repair of injuries in the forehead
• Removal of damaged tissue (debridement) from burns or abrasions
• Removal of cysts or benign growths
• Removal of foreign bodies
• Tissue removal for biopsy
• Scalp incisions for surgeries in the frontal head such as fluid drainage for hydrocephalus (ventriculoperitoneal shunt)
• Pain management after a surgical procedure in the forehead
• Along with steroids for pain relief from painful conditions such as:
  • postherpetic neuralgia after shingles (Herpes zoster)
  • trigeminal neuralgia
  • migraines

Supratrochlear nerve block is avoided in the following situations:

• Patient’s inability to tolerate the procedure
• Infection at the injection site
• Allergy to local anesthetics
• Distortion of anatomy

A supratrochlear nerve block is superior to a local tissue infiltration anesthesia in the forehead because it provides:

• Rapid anesthetic effect with immediate pain relief
• Anesthesia of a larger area with minimal quantity of anesthetic agent
• Anesthesia without tissue distortion

A supratrochlear nerve block is usually performed as an outpatient procedure, unless it is part of a major surgery involving the forehead. The nerve block may be performed with just an anesthetic agent or combined with steroids for long-term pain relief for neuralgia.

Anesthesia

Depending on the required duration of anesthesia, the doctor may use one of the following anesthetic agents:

• Lidocaine
• Tetracaine
• Bupivacaine

Preparation

• The patient may be seated or lying flat for the procedure.
• The injection site is sterilized with antiseptic solution.
• The doctor may administer a mild sedative if necessary.

Procedure

The doctor

• Feels the bony ridge of the eyebrow to locate the hole in the bone through which the supraorbital nerve naturally emerges from the eye socket.
• Marks the injection site between the supraorbital foramen and the nasal bridge.
• Inserts the needle into the tissue under the skin pointing towards the nasal bridge.
• Presses a roll of gauze over the eyelid to prevent the anesthetic swelling into the eyelid.
• Aspirates the syringe to ensure that the needle is not inside a blood vessel.
• Injects the anesthetic agent around the supratrachlear nerve slowly in a fanlike distribution and withdraws the needle.

The anesthetic in the supratrochlear nerve block provides pain relief within 10 to 20 minutes depending on the anesthetic agent. The effect of the supratrochlear nerve block lasts for hours. The long-term pain relief, if steroid is also injected for inflammation,  may take two or three days to take effect. The long-term benefit of steroid injection varies from individual to individual. Some people find pain relief from the nerve block with steroids lasting several weeks to years, while some may find no benefit.

The approximate durations of anesthesia from the supratrochlear nerve block are as follows:

• Lidocaine: up to 75 minutes
• Tetracaine: up to three hours
• Bupivacaine: up to eight hours

The patient may experience tingling, discomfort or pain as sensation returns. Post-procedure pain may be relieved with oral painkillers.

The complications of a supratrochlear nerve block include:

• Bleeding
• Hematoma
• Infection
• Discoloration of skin due to bleeding under the skin (ecchymosis)
• Allergic reaction to the anesthetic agent
• Injection into a blood vessel resulting in systemic toxicity
• Nerve damage
• Swelling of the eyelid
• Failure to anesthetize