Overview of Supraorbital Nerve Block
A supraorbital nerve block is a type of procedure that is often done to numb a specific area of the head for a short amount of time. If you have suffered a complicated cut on your forehead, upper eyelid, or a severe scrape or burn on your forehead, this procedure can help manage pain. It can also be used to control pain when foreign objects need to be removed or during other medical situations such as an outbreak of acute herpes zoster.
This procedure is beneficial as it only uses a small amount of anesthetic to numb a large area, compared to other methods. This means, fewer anesthetics spread into your tissues, thus keeping the affected area’s shape and structure as normal as possible during medical treatment or procedures. This can make it easier for doctors to perform these procedures effectively.
To perform a supraorbital nerve block, the doctor only needs minimum equipment and a sound understanding of the key anatomical points in the head. This means where certain nerves, muscles, and other structures are located. By knowing exactly where to administer the anesthetic, the doctor can successfully numb the targeted area.
Anatomy and Physiology of Supraorbital Nerve Block
The anatomy associated with this particular medical procedure is very important to recognize because it is based on specific landmarks. One of these landmarks is the supraorbital nerve, which is one of the branches of the trigeminal nerve. The trigeminal nerve splits into three sections: the ophthalmic nerve, the maxillary nerve, and the mandibular nerve. The supraorbital nerve comes from the ophthalmic nerve and separates into two branches – the smaller supratrochlear nerve and the larger supraorbital nerve.
The supraorbital nerve leaves the skull through a hole above the eye socket called the supraorbital notch or supraorbital foramen. This hole is located in the inner third of the supraorbital margin, which is 2 to 3 cm from the middle line. The nerve then goes up the forehead and ends at the region of the front of the scalp. This nerve is responsible for the sensation in the tissues up to the area where the parietal and occipital bones meet in the skull. The supratrochlear nerve gives feeling to a small area close to the middle line of the forehead. You can spot the supraorbital foramen by having the patient look straight ahead and then draw line across the pupil at the level of the ridge of their eye socket. By touching this area, you can find the place where this nerve block will be performed.
The majority of supraorbital nerve exits are notches (73.8%) and the rest are foramina (26.2%). There were additional exits in 18.9% of skulls. When studying skulls, 55.1% had notches on both sides, 8.6% had foramina on both sides, and 36.3% had a notch on one side and a foramen on the other side.
The supraorbital nerve, beyond the rim of the eye socket, has two consistent divisions: (1) a superficial division that goes over the muscle in the forehead, supplying sensation to the skin of the forehead and only to the front edge of the scalp; and (2) a deep division that runs upwards across the side of the forehead as a sensory nerve to the front of the scalp.
Patients with supraorbital neuralgia experience pain, tenderness, and altered sensation in the area supplied by the affected nerve. This condition can be caused by fractures of the top of the eye socket, hits to the face, eye socket tumors, and wearing tight swimming goggles or motorcycle helmets.
Why do People Need Supraorbital Nerve Block
The supraorbital nerve block is a type of pain relief procedure that is often used for certain conditions affecting the forehead or the front side of the scalp. Here are some reasons why a doctor might suggest this type of treatment:
They may use it for when treating burns or scrapes that need to be cleaned off, a process known as debridement. This method also provides quick relief from the acute pain caused by a painful condition like herpes zoster, commonly termed shingles, and the postherpetic itch that follows.
Complex lacerations, which are deep cuts or tears in the skin, and removal of foreign bodies embedded in the skin can also be treated with a supraorbital nerve block. This procedure can also be beneficial for individuals dealing with severe headaches like migraines, cluster headaches, and hemicrania continua, a rare chronic headache.
Besides pain relief, it is also used during various surgeries near the eyes or on cranial nerves such as upper eyelid surgery, oculoplastic surgery (cosmetic or reconstructive procedures on the face, eyelids, or orbit), and awake craniotomy (a type of brain surgery where the patient is awake). The procedure has also proved useful during cranial fixation and the placement of stereotactic frames used in precise surgical navigation.
Lastly, a supraorbital nerve block can be used to control pain for supratrochlear or supraorbital neuralgia (nerve pain in forehead area), trigeminal neuralgia (a chronic pain condition affecting the trigeminal nerve in the face), and during certain dermatological or cancer-related procedures.
When a Person Should Avoid Supraorbital Nerve Block
There are several reasons why a person might not be able to have a procedure called a supraorbital nerve block:
1. The person may choose not to have the treatment.
2. The area where the procedure needs to be performed is irregular or changed, making it difficult to locate the correct spot to perform the procedure.
3. There is an infection on the skin where the injection needs to be given.
4. The person can have an allergic reaction to the anesthetic (numbing medication) used for the procedure.
Equipment used for Supraorbital Nerve Block
For a procedure known as a supraorbital nerve block, several pieces of equipment are needed:
* An anesthetic agent: What type of anesthetic is used depends on any allergies the patient has reported as well any specific duration needed for the pain relief. Examples of these include Lidocaine, which can offer relief up to 90 minutes, Bupivacaine that can last up to around 8 hours, and Tetracaine which can work for up to 3 hours. If the patient is allergic to these more common options, diphenhydramine might be used instead.
* A 25 gauge needle is used for adults, while for children, a smaller 30 gauge needle will be used to administer the anesthetic.
* A 5-10 mL syringe is used to inject the anesthetic.
* To cleanse the skin before the injection, substances like chlorhexidine or betadine are used.
* It’s important to have a lipid emulsion solution on hand. This is used in cases where the anesthetic accidentally ends up in the blood system, causing what’s known as local anesthetic systemic toxicity.
* If it’s desired to obtain a visual guide for the injection, an ultrasound machine can be used.
Preparing for Supraorbital Nerve Block
Before starting any medical procedure, it’s important to inform the patient about what the process involves, its potential risks, and expected benefits. This is the basic principle behind an ‘informed consent’, which the patient has to give. The doctor should also gather and prepare all the necessary medical tools for the procedure before getting started.
Here’s a key point for medications used in procedures like a nerve block. Lidocaine and bupivacaine are two commonly used drugs, sometimes mixed with another drug called epinephrine. The quantity of these drugs given depends on the patient’s body weight and whether they’re mixed with epinephrine.
When lidocaine is mixed with epinephrine, the typical dose is 7 mg for each kilogram of the patient’s weight. However, in total, no more than 500 mg of this mixture should be given to the patient. If lidocaine is given without epinephrine, it’s typically given in smaller doses: 4.5 mg per kg of the patient’s weight, but not more than 300 mg in total.
Bupivacaine, when mixed with epinephrine, is usually given at 3 mg per kilogram of the patient’s weight. The total dose should not exceed 225 mg for one dose, and for the whole day, a limit of 400 mg needs to be maintained. If given without epinephrine, bupivacaine is dosed at 2.5 mg per kg of the patient’s weight. No more than 175 mg should be given in one dose, but the daily limit remains the same, at 400 mg.
How is Supraorbital Nerve Block performed
The supraorbital nerve block procedure is a treatment that numbs the forehead area to provide pain relief. Let’s break this down into simpler steps:
First, the doctor determines the correct position on your forehead for the procedure, and then thoroughly cleans this area of your skin.
Next, while you lie comfortably on your back, the doctor then uses a very fine needle, which they carefully push into the lower edge of the bony ridge just above your eye. The doctor takes care not to push the needle too deep into the ridge. Before proceeding, they then make sure the needle is in the right spot.
Once the needle is in the right place, the doctor injects a small amount of a local anesthetic, which is a numbing medication. This creates a bubble under the skin, and then the doctor injects a bit more of the numbing solution. To help the medication stay in the right area, they might put a small roll of gauze above your brow.
Remember that everyone’s body is different, and sometimes the numbing medication may not reach all the nerves on the first try. This is often due to the complex structure of the ophthalmic nerve in our faces. If you still feel pain, the doctor can inject more anesthetic around the edges of your brow until all the nerves are numb.
Possible Complications of Supraorbital Nerve Block
Supraorbital nerve block is a procedure done near your forehead. Like other procedures, it has potential risks, which may include:
* The creation of a hematoma, which is a swelling of clotted blood within the tissues, or swelling of your eyelid.
* A delay in the development of periorbital ecchymosis, which is when you have bruising around your eye that happens later than expected.
* Infection, which is when harmful bacteria get into your body.
* Bleeding, which is when blood comes out of a wound.
* The accidental injection of anesthetic into a blood vessel, which is the liquid that makes you numb during the procedure.
* Nerve damage, which includes conditions known as neurapraxia, a temporary loss of nerve function, or neurolysis, a more severe nerve damage.
* Local anesthetic systemic toxicity, which is when the anesthetic used during the procedure negatively affects your entire body.
* An allergic reaction to the local anesthetic, which is when your body’s immune system fights off a substance that it misidentifies as harmful.
What Else Should I Know About Supraorbital Nerve Block?
Anesthesia, or pain relief, is extremely important for patients undergoing procedures. It not only aids in alleviating pain, but also enables doctors to perform operations smoothly, sparing the patient any further discomfort. Anesthesia can be applied by targeting the pain-sending tissues or nerves, which transfer pain signals from the tissues to the brain and parts linked with it like the brainstem.
There are two common ways to give anesthesia. One is through local infiltration, where an anaesthetic drug is directly injected into the tissue. This method is often suitable for simple injuries in a specific spot. However, it might not work as well for larger injuries, multiple separate injuries, or situations where injecting the drug might distort the area needing repair.
In these cases, a technique called nerve block can be used – it numbs a larger part of the body using a smaller amount of anesthetic. In simple terms, nerve block works by ‘switching off’ the pain signals from a nerve or set of nerves to the brain, which in turn reduces the sensation of pain in that large region. This method can be very useful for more serious or widespread injuries, ensuring the patient remains comfortable and the doctor can operate effectively.
