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Botox Adverse Events and Complications

Botulinum Toxin-A injections are very safe procedures to perform in-office and has a high safety profile. These non-invasive, non-surgical procedures though safe to perform due carry a risk aesthetically as well as medically due to incorrect needle placement.


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Botulinum Toxin-A injections are very safe procedures to perform in-office and has a high safety profile. These non-invasive, non-surgical procedures though safe to perform due carry a risk aesthetically as well as medically due to incorrect needle placement. The following summary will review possible complications associated with the most popular Botulinum Toxin-A injections.

As with any hypodermic needle injection there is always possibility of bruising associated with the procedure as well as certain patients that are more susceptible to bruising we will concentrate on the various areas for incorrect needle placement and associated adverse events.

botox complications

Botulinum Toxin-A Injections

The most common injections for Botulinum Toxin-A injections are the (3) main areas of the upper 1/3 of the face. The (3) regions are the Forehead (Frontalis Muscle), Glabella Region (Procerus and Depressor Corrugator), and the Lateral Canthal Rhytid Region (Orbicularis Oculi).

Forehead (Frontalis Muscle)

The injections should be intra-dermal which is taking a 5-10º angle at the point of needle penetration and breaking the skin. When the needle is below the skin a small amount (typically .05 – 1.0cc) is administered within the soft tissues of the epidermis or dermis (avoiding the periosteum). The areas of the injection for the Frontalis is at least (1) finger breath above the eyebrow and should not extend laterally beyond the frontal limbus. The injection may be painful due to superficial nerves throughout the forehead and visual observation should be used to avoid the (2) large veins of the forehead; supratrochlear vein and supraorbital vein. Other possible (potential) complications due to incorrect needle placement after the procedure are:

Brow Ptosis / Heaviness: This condition occurs where either the injection of the Botulinum Toxin-A was delivered too low (less than one finger breath above the eye brow) or the Glabella Region was not treated at the same time. The Frontalis Muscle is the only elevator muscle in the upper 1/3 of the face – if relaxed and the depressing muscles interacting with the frontalis are not relaxed it is possible for the eyebrow to lower and or feel heavy to the patient. Other possible reasons for this condition could be administering a too large amount (units) of the Botulinum Toxin-A in the area. This is a cosmetic condition and could last the duration of the expected treatment. 

Glabella Region (Procerus and Corrugator Muscles)

There are (3) distinct muscles that make up the Glabella Region of the face and are depressing muscles; Procerus, Corrugator, and Depressor Supercilii). Only the Procerus and Corrugator muscles are typically injected in a procedure. These injections for the Glabella area are intermuscular injections since there is a possibility of diffusion and there are fibers of the frontalis muscle that if infiltrated with the botulinum toxin-A could cause ptosis of the eyebrow or possibly the eyelid. Proper technique demands that you isolate these muscles by pinching these muscles prior and during the injection to confirm location as well as the ability to feel resistance during the needle penetration of the muscle and when infiltrating the muscle with the medication. The most common complications in this area are: 

Asymmetry: Unevenness of the eyebrow can be eliminated by ensuring that the proper dosing is administered at each injection point. Other reasons for an exaggerated asymmetry of the eyebrow would be a pre-existing asymmetry of the brow that was not addressed before treatment. 

Eyelid Ptosis: Botulinum Toxin-A cannot migrate or diffuse within the orbital rim as the medication will affect other muscles within the eye that work with acetylcholine for muscle contraction specifically the levator palpebrae superioris muscle that controls the elevating of the eyelid. If weakened or relax the eyelid will not raise correctly – this condition typically lasts (2) weeks as the histamine release within the eye will break down the botulinum toxin-A quickly. This condition is avoided by using the pinch technique when injecting the Glabella Region. 

• Eyebrow Ptosis: If the injections are not done as an intermuscular injection then there is a possibility that the injections in the area of the corrugator may affect the lower fibers of the frontalis thus allowing weakening of the elevator muscle and dropping of the eyebrow. 

Lateral Canthal Rhytids (Crows Feet Area)

The treatment for Lateral Canthal Rhytids also carry the inherent risk of eyelid ptosis due to the proximity of the injections to the orbital rim of the eye. There are techniques to eliminate the possibility of the medicine migrating within the orbital rim as primarily deals with the direction of the needle as well as a 1-2cm standoff lateral to the rim when performing the injection. The injection technique in performing these “crow’s feet” injections is intra-dermal with a small amount of the medication delivered (.05ml) with each injection as indicated. There is also a defined area of the quadrants of the orbicularis oculi muscle of the lateral eye where the medications can also be delivered. The most common possible complications associated with this injection due to improper injection technique are: 

Bruising: The orbicularis oculi muscle is highly vascularized and even the smallest gauge needle can cause bruising and is the rationale behind the intradermal injection technique. Injectors may also pinch the skin to avoid accidentally injecting a arteriole or veins within the area. Best practice is to taught the skin and look for vascular or shadows that indicate vascularity and avoid these areas with your injections. 

Ectropion: This condition can occur if you are injecting the distal portion of the orbicularis oculi muscle under the eye thus weakening the elevating status of the muscle. This condition is avoided by not making injections beneath the eye into the orbicularis oculi muscle and typically affects older patients due to muscle laxity of the orbicularis oculi muscle under the eye. Avoidance is the best measure to avoid this condition as other types of tests such as “snap tests” etc. of the lower lid are not 100% accurate. 

Diplopia: Botulinum Toxin-A can spread at larger doses and/or incorrect placement, patients suffering from diplopia after a botox treatment most likely either rubbed the injections immediately after the injection or from improper placement. Diffusion of the toxin from a periorbital muscle (orbicularis oculi) to the lateral rectus muscle is typically the reason for double vision from this injection. This condition is transient and could last as long as the expected duration of the botulinum toxin treatment (13 weeks). 

Other Specialty Injections (Lower 2/3 of the Face)

The specialty injections using Botulinum Toxin-A for other facial expressions are very safe though are off-label uses of the product. Complications and Adverse Events occur when protocols are not followed or incorrect needle placement causes the medicine to migrate or diffuse to other facial muscles. The following list are the most common lower face injections and their associated risks and complications: 

Platysmal Bands 
Hypertrophic Platysma Bands can be relaxed with the Botulinum Toxin-A and works very well in minimizing the look of these protruding bands. The injection needs to be directly into the bands at approximately .75in apart both proximal and distal of the indication of the protruded bands. Patients typically grimace which over exaggerates the bands and the physician will be able to isolate the band and enter into these bands with a slight lateral approach. Confirmation of location is achieved when the needle breaks into the band and the medicine is dispersed. However safe this injection there are complications associated with incorrect placement and they are: 

Weakened Neck Flexors/Dysphagia: Though usually associated with the side effects of using botulinum toxin for neck, tongue, and jaw dystonia there is a possibility of it occurring in a platysmal band aesthetic injection. The issue is that every patient is different and if injecting the sternocleidomastoid (SCM) muscles the botulinum toxin may diffuse to the strap muscles on the hyoid bone that may inhibit the tongue to push food back and trigger the throat to swallow. The frequency of this type of side effect are related when the bilateral injections are more frequent or if large doses are injected. The side effects are transient and last typically 4-6 weeks after the incorrect placement of the injections. 

Lips (Vertical Rhytids – Orbularis Oris) 
Vertical Lip Lines and Perioral Rhytids can be treated with Botulinum Toxin-A and are administered as an intradermal injection at small dosages (1-2u). The muscle itself covers a number of other muscles needed for facial expression so location of the injections and performing them as an intradermal injection will keep you safe from complication. Other considerations associated with the injection is that the injections need to be above the vermillion border and lateral to the philtrum as well as away from the corner commissure. Each of these areas will lead to a poor aesthetic result and complication associated with needle placement. Injections that pierce through the Orbicularis Oris also have a number of complications associated with these injections, however he most common complications for injections for vertical lip lines are: 

Asymmetric Smile: This occurs when the proper dosing is not administered equally to both sides of the muscle. This is not a strong muscle and is the reason for the smaller dosing volumes even the smallest difference in units may weaken one side of the lip compared to the other. It is possible to create asymmetry even if everything was done correctly and why it is better to use a smaller initial dose so that you have the ability to titrate to give correction to the asymmetry with no further side effects. 

Drooling | Speech Interference: Botulinum toxin injections in this area need to be conservative, there are a number of people that are sensitive to the medication where the effect is greater than in other individuals. Drooling and speech interference for these types of injection is almost always associated with excessive dosing and volumes when treating this area. 

Bunny Lines (Nasalis) 
This common injection is not without its need for proper placement of the injection or has risk associated with the injection. Most dosing charts state that the nasalis muscle injection needs to be intermuscular however it is difficult to know if you are in the muscle when it is very thin banded muscle. Therefore, the proper technique to inject this muscle is to have the patient form these lines by facial expression and inject the peaks (not valleys) of the rhytids portrayed by the patient. It is typically one injection per side and should not go lateral to the side bridge of the nose with the needle direction pointing medial due to the possibility of diffusion. Slow infiltration will limit unwanted diffusion as the botulinum toxin will stay encapsulated with soft tissue chambers rather than forcefully injecting the medication. The major complication associated with improper needle placement for the Bunny Line area is: 

Asymmetric Smile | Dropping of Upper Lip: This occurs when the injection is too far lateral in the nasalis muscle and the direction of the needle was not medial. The botulinum toxin may diffuse to the labii superioris aleque nasi muscle that controls the elevation of the facial upper lip. If weakened by the medication it would lead to relaxation of the muscle and may affect the upper lip either bilaterally (if both injections were done improperly) or unilaterally. Proper technique will avoid this complication. 

Sad Smile (Depressor Anguli Oris) 
When injecting the Depressor Anguli Oris (DAO) it is important to understand that this is not a deep muscle but is more superficial. The Depressor Anguli Oris is in proximity to and in many cases is covering another muscle, Depressor Labii Inferioris muscle that controls your lower lip movement. Either by making too deep an injection or by diffusion (injecting to hard) it may affect the lower lip. Injecting more distal within the muscle will also reduce any other complication with the various muscles associated with the corner commissure. The major complication associated with this injection is: 

Inability to Lower Bottom Lip: This complication is aesthetic and will last the duration of a normal botulinum toxin injection (13 weeks). The diffusion from the injection of the DAO muscle into the Depressor Labii Inferioris muscle is not allowing the lower bottom lip to lower further. To avoid this complication take a 15-20º angle to the injection and aim for the corner commissure but start lower in the muscle and do not go too deep – about 4-5mm in depth. 

Other Considerations

Botulinum Toxin-A Systemically: For cosmetic Botulinum Toxin treatments, the amount injected does not warrant permanent disability or nerve damage associated with an intervascular injection. However, there has been studies in rats that show that large doses of botulinum toxin systemically may affect distant muscles as they have very small bodies and diffusion would be greater. There are theories that the reason some patients suffer headaches from botulinum toxin injections is the possibility of the medication systemic after the injection. However, the majority of evidence does not support any claim that Botulinum Toxin-A cosmetically (under 100u) could cause any problems of any major significance or have much spread at all since it has never been confirmed in any patient receiving botulinum toxin.


Botulinum Toxin injections are very safe and millions of injections are delivered annually by all physician specialties. It is important as part of your standard of care to understand fully possible complications and adverse reactions that can happen from these popular easy-to-perform injections. The preceding article is a guide for you to help you further understand zones of adherence and the need for proper needle placement – this is not an all encumbering guide to these injections but should help expand your standard of care and thus enhance patient care for these popular procedures.

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