Neuromodulator Threading Revisiting an Approach to Neurotoxin Delivery

H. William Higgins II, MD, MBE; Kachiu C. Lee, MD, MPH; Yoash Enzer, MD
Department of Dermatology, Brown University, Providence, Rhode Island;
Department of Surgery (Ophthalmology), Brown University, Providence Rhode Island

Disclosure: The authors report no relevant conflicts of interest.

Neuromodulator toxins are traditionally delivered to facial muscles via a depot technique using a 32g needle. This article revisits the threading technique, which was used more commonly in the 1990s and early 2000s prior to the introduction of the 32g x ½” gamma ray sterilized needle. A description of the threading technique, illustrated by diagrams and patient photos, is presented for the orbicularis oris and corrugator supercilii injection sites. In contrast to the depot technique in which the needle enters the skin at a 90-degree angle, the threading technique enters the skin at a 20- to 30-degree angle. Specifically, for the orbicularis oris, onabotulinum toxin A injections are performed 2 to 5mm beyond the “white roll” of the vermillion border. After the needle punctures the skin, the toxin is injected while withdrawing in a threading manner parallel to the vermillion border. This method is repeated along the entire length of the orbicularis oris muscle. For the corrugator supercilii muscles, the injection technique differs slightly. A depot injection is given at the most medial point of the muscle, targeting the body of the muscle. The tail of the corrugator supercilii is injected using the threading technique as described for the orbicularis oris, in which the needle inserts at a 20- to 30-degree angle. This paper revisits the threading injection technique for neurotoxin treatment of the orbicularis and corrugator supercilii sites.  (J Clin Aesthet Dermatol. 2014;7(6):38–41.)

Onabotulinum toxin A is well-documented as a useful therapy to reduce the appearance of facial rhytides. Precise localization of the neurotoxin is essential to produce the desired clinical effects. Undesirable effects can occur if the neurotoxin spreads into untargeted muscles or if inadequate amounts are injected into the targeted muscle. Prior studies have examined whether the dilution, dose, and type of botulinum toxin A used has implications on the spread of toxin and desired effect.[1–11] The plane of injection and its impact on treatment outcomes in certain locations has also been evaluated (i.e., two-plane injection into glabellar frown lines).[12]
More recently, the microdroplet technique has been introduced for neuromodulator injections of the brow region.[13] This article revisits the threading technique for the orbicularis oris and corrugator supercilii muscles, facilitating precise neurotoxin delivery to the targeted musculature. This technique was widely used in the 1990s and early 2000s when injections were commonly performed with the 30g x 1″ needle, allowing for treatment of large areas with one skin puncture. With the advent of the 32g x ½” gamma ray sterilized needle, the currently used method of depot injections quickly gained favor. Therefore, younger physicians may not be aware of the threading technique, which provides an alternative to the commonly taught depot method. This article concisely reviews how to perform the threading technique using several illustrations and photographs.

In this threading technique, the patient is treated in a semi-reclined position. Prior to injection of onabotulinum A toxin, disposable ice-packs are placed on injection sites for 3 to 5 minutes to reduce edema and bruising. Onabotulinum toxin A is used for the procedure at a dilution of 2.5mL of unpreserved normal saline per 100 units of neurotoxin.
For the orbicularis oris of the upper and lower lips, onabotulinum toxin A injections are placed 2 to 5mm beyond the “white roll” of the vermillion border. Typical injection sites of the traditional depot technique are illustrated  ( “href=””>Figure 1A), as are injection sites of the threading technique ( “href=””>Figure 1B). In contrast to the traditional depot technique, which injects at an angle perpendicular to the skin, the threading technique injects toxin at 20 to 30 degrees, entering the skin at a location just lateral to the targeted rhytid. Typically, 1.25 to 1.75 units of onabotulinum toxin A (Botox®) is used to infiltrate each lip quadrant (5–7 units total to treat the upper and lower lips). The toxin is also dispensed while withdrawing the needle, essentially “threading” the injection along the length of the orbicularis oris ( “href=””>Figure 2A and 2B).
This method is then repeated along the area of muscle contraction adjacent to the creases at the vermilion border on either side of the “cupid’s bow” until the entire length of the orbicularis oris along the upper lip is infiltrated. This results in a pseudo-eversion of the lip and reduces the undesirable “smoker’s” lip lines.
For the glabellar lines, the action of corrugator supercilii is easily visualized and palpated by asking the patient to contract these muscles (frown). Four injection points were symmetrically chosen, with two points targeting each corrugator ( “href=””>Figure 3A and “href=””>Figure 3B). The more medial points are administered directly above the inner canthus, with intramuscular injections of 3 to 7 units of onabotulinumtoxin A performed perpendicularly to the skin in the traditional “depot” manner. The lateral points of the corrugator supercilii are injected using the threading technique as described above for the orbicularis oris. However, this technique differs from the conventional manner. When treating the two lateral injection points, the needle is inserted just medial to the mid-pupillary lines, targeting the second third of the corrugators. Similar to the approach to the orbicularis oris, rather than injecting at an angle more perpendicular to the skin, injections are performed at an angle of roughly 20 to 30 degrees, entering the skin at a location just medial to the dimple created by the terminal insertion of the corrugator muscle ( “href=””>Figure 3B). The needle is then directed laterally and slightly superiorly in order to follow the anatomy of the corrugators supercilii, threading the injection along the muscle’s length while withdrawing. Typically, 1.25 to 1.75 units of onabotulinumtoxin A (Botox) is infiltrated into the lateral most area of corrugator activity. The authors usually utilize 9 to 19 units total to treat all four sites on bilateral corrugators, with larger amounts reserved for stronger-acting muscles, especially in men.
Injections at all sites are placed just under the dermis in all locations using 32g x ½” needles on a 1cc syringe (Norm Ject). Before and after treatment photographs illustrate patient improvement ( “href=””>Figure 4, “href=””>Figures 5 and 6).

It has been shown that botulinum toxin A results in amelioration of glabellar and perioral rhytides.[14–16] The current method of injecting these areas requires placing subepidermal blebs to produce localized paresis of the targeted muscle. However, treatment in the perioral area is known to result in inadequate responses, as compared to forehead and glabellar lines, therefore requiring more frequent touch-up injections.[16] In the forehead, spreading of the toxin beyond the target muscles sometimes involves muscles necessary for other facial movements, such as the levator palpebrae, the inactivation of which causes upper eyelid ptosis. One of the main problems in treating both facial locations may be failure to address the pertinent anatomy. The orbicularis oris essentially functions as a sphincter and consists of numerous muscle fibers in strata surrounding the orifice of the mouth. The corrugators supercilii are attached to the periosteum in the glabellar region under the frontalis muscle deep in the medial aspect. The muscles then course laterally and superficially to insert in the skin superior to the eyebrows.
The threading technique revisited in this manuscript was popular in the 1990s and early 2000s and provides an alternative to traditional methods of neuromodulator injections. The threading technique has the advantage of injecting the entire muscle along its normal anatomic course compared to the traditional technique, which only targets discrete points along the muscle. Furthermore, the threading technique has the advantage of fewer needle sticks, likely resulting in less pain and a smaller chance of bruising (especially when compared to the microdroplet technique, which requires far more injections).[13] The threading technique also allows more molecules of neurotoxin to come in direct contact with motor plate musculatures and myoneural junctions.
Even with conservative dosing, neuromodulator treatment of perioral rhytides may affect mouth function by weakening the lip sphincter function.[14] Similarly, brow ptosis can occur with overinjection of the corrugator supercilii, or more likely the spreading effect to the interdigitated frontalis muscle. A controlled study of the depot versus threading technique is necessary to determine whether similar side effects would be seen with the threading technique.
For future considerations, this method could possibly be improved and require even fewer injections by utilizing a longer 1 or 1.5-inch needle. The threading technique could also be tried for injections in other areas of the face, beyond the perioral and glabellar areas mentioned in this manuscript. Additional studies are also needed to compare this technique to the depot injection and microdroplet techniques.

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