The glabellar complex consists of the two corrugator supercilii muscles and the procerus muscle. These muscles pull depresses and medially contract the eyebrows. The corrugator supercilii typically lie horizontally from medial eyebrow to near the mid-pupillary position. Some patients have long corrugator muscles that extend beyond that mid-pupillary line. The procerus stands vertically between the eyebrows. The frontalis muscle is a superficial muscle that elevates the brow. Please note that the frontalis overlaps the corrugator superficially. An injection placed superficially may cause paralysis of the inferior edges of the frontalis muscle. Orbicularis oculi is the thin, circular, “purse string” like muscle that surrounds the orbital rim. The levator palpebrae muscle lies underneath the bony orbital rim, and its function is eyelid opening.
While standing directly in front of the patient, ask your patient to look straight and frown. Visualize the corrugator and procerus muscle. Now place your noninjecting thumb and ask the patient to frown. Try to grab the corrugator with your thumb and index finger. Feel along the entire length. While the patient face is at rest, mark the mid-pupillary position on the forehead. This will serve as your marker so that your injection will not extend laterally from this mark. To steady your hand for injection, try resting your pinky on the patient’s nose or lateral hand on the patient’s cheek like a tripod.
All injections for the Glabella are intramuscular injection perpendicular to the skin. There are five injection sites: one at each medial corrugator or above the medial cantus, one at each lateral corrugator or above the mid-pupillary position and one into the procerus muscle (just above the crossing point of an imaginary X formed by drawing a line from medial eye brow contra-lateral to the medial canthus). All injections should be 1 cm above the orbital rim to minimize the risk of eyelid ptosis. Injection too high above 1cm can also cause eyebrow ptosis in patients who use their frontalis muscle to open their eyes. The 1 cm measurement is made from the palpable boney orbital rim and not from the anatomical eyebrow. The lateral corrugator injection can be at or just medial to the mid –pupillary line (this will reduce the likelihood missing the corrugator muscle if the corrugator muscle is short).
The standard dose of Dysport for the glabellar lines is 50 units total (10 units per injection site) in women and those with small to medium muscle mass. Final dosage may vary depending on the patient’s muscle strength and desired outcome. Higher doses may be required in men or those with thick corrugator muscles. Men often have straighter brow appearance as opposed to women.
To decrease the pain of the injection, we recommend the following: use ice or apply topical numbing cream, use a small gauze needle, use preservative containing normal saline for dilution and ask patient to not contract their muscle during injection.
The most common adverse events are pain at the injection site, bruising, headache, eyebrow ptosis and eyelid ptosis. Eyelid ptosis is typically caused by diffusion of botulinum toxin into the levator palpebrae muscle. This is typically from the lateral corrugator or the mid-pupillary injection. This can be minimized by ensuring that the injection is 1cm above the boney rim or protecting the orbital rim by resting the thumb of the noninjecting hand on the superior portion of the orbital rim.
Two multicenter studies show a lid ptosis rate of 5.4% and 1%. Lid ptosis can appear within 2 to 7 days. It typically resolves within 2 to 6 weeks. Iopidine 0.5%, Naphcon-A, and phenylephrine 2.5% are alpha-adrenergic agonist ophthalmic eye drops that improve the appearance of lid ptosis, as these drops stimulate the Müller’s muscle to elevate the ptotic eyelid. Typical dosage is 2 drops, BID or TID, until resolution, but no longer than 1 month. Brow ptosis can occur when the corrugators are injected superficially which causes frontalis muscle paralysis. Injection lateral to the mid-pupillary line may cause also cause brow ptosis.
Learn more about Forehead Lines.