Anatomy & Filler Complications

ANATOMICAL REGIONS CONCERNED BY THE RISK OF INJURY DURING INJECTION

Arterial Vasculature

Facial artery

The facial artery, which originates in the external carotid, provides the main blood supply to the face.

The facial artery enters the face from the submaxillary region, running along the lower edge of the mandible and curving upwards to its lateral aspect just in front of the antero-inferior angle of the masseter muscle and under the platysma muscle.

The facial artery has a very sinuous course. According to certain authors it continues its tortuous course between the modiolus and the nasal ala, travelling up from the medial side of the nasolabial fold (NLF) in 42.9% of cases, arising from the lateral side of the NLF in 23.2% of cases, crossing the NLF laterally in 19.6% of cases, and crossing the NLF medially in 14.3% of cases.

In most cases, the subalar or inferior alar artery arises from the facial artery but sometimes from the superior labial artery.

Some authors consider the angular artery to most often be a small branch rather than a main continuation of the facial artery.

Variations of the facial artery: The rule rather than the exception.

The standard description of the termination of the facial artery in the angular artery at the medial canthus and its anastomosis with the dorsal nasal branch of the ophthalmic artery does not always represent the most frequently found model.

Some authors have reported that the facial artery most often ends near the base of the nasal ala, after giving off the superior labial artery, where it may divide into the subalar artery (or inferior alar artery) and the lateral nasal artery (or superior alar artery).

Although some studies have reported that the most common distribution model is the classic course for the facial artery, which becomes the angular artery at the medial canthus of the eye in 68% of dissections, other publications have described a much lower frequency, with percentages of 12%, 22%, 24%, and 36% in their series.

The maxillary Artery

The maxillary artery is one of two terminal branches of the external carotid artery and its diameter is approximately 2.75mm at its origin.

The Superficial Temporal Artery

The superficial temporal artery is the most external and superficial terminal branch of the external carotid artery, reported by some authors to have approximately a diameter of 2mm, or 2.52mm by others.

The Ophthalmic Artery

The ophthalmic artery, which originates in the internal carotid, enters the orbital cavity through the optic canal, accompanied by the optic nerve. It gives off numerous collateral branches: central retinal, muscular, ciliary, lacrimal, supraorbital, posterior ethmoidal, anterior ethmoidal, meningeal, superior and inferior medial palpebral, and ends at the medial angle of the upper eyelid as the supratrochlear and dorsal nasal arteries.

The periorbital and nasal regions constitute zones with a high risk of embolic complicationsduring aesthetic filler injections.

Venous vasculature

Description of the veins that concern the face and that might represent an anatomical danger zone for aesthetic injections to the face.

Internal jugular vein

The internal jugular vein is the continuation of the sigmoid sinus. It is contained in the carotid sheath, initially with the vagal nerve and internal carotid artery, and then with the common carotid artery. It receives many tributaries draining the brain and certain superficial parts of the face and neck.

The supratrochlear vein arises from a network of veins communicating with the frontal branch of the superficial temporal vein.

The existence of anastomoses between the facial vein and cavernous sinus via the ophthalmic veins is of great importance since they may facilitate the spread of a thrombophlebitis due to infection of an area of the face.

The angular vein is formed from the anastomosis between the supratrochlear and supraorbital veins at the inner angle of the eye. It then becomes the facial vein.

The existence of communications between the facial and endocranial venous networks plays a key role in the etiopathogenesis of craniofacial thrombophlebitis.

External jugular vein

The external jugular vein is formed in the thickness of the parotid gland by the junction of the posterior branch of the retromandibular vein (which is in turn formed by the confluence of the superficial temporal and maxillary veins) and the posterior auricular vein.

The external jugular vein provides drainage for most of the scalp, and for certain superficial and deep lateral parts of the face and neck.

Anterior jugular vein

The anterior jugular vein originates in the suprahyoid region from the superficial submental veins.

The anterior jugular vein drains part of the anterior region of the neck and submental region. It retains large anastomoses with the internal and external jugular veins.

Nervous system

The nerves involved in the sensory and motor innervation of the face are mainly the trigeminal nerve (Cranial Nerve V) and the facial nerve (Cranial Nerve VII).

Trigeminal nerve

The sensory innervation of the face is provided mainly by the trigeminal nerve (CN V). It divides into three branches that innervate all the integuments of the face and other deep structures.

The ophthalmic nerve – The maxillary nerve – The mandibular nerve

Facial nerve

The facial nerve is a mixed nerve, since it has motor, sensory, and vegetative function. It innervates all the muscles of the face and neck except for the levator palpebrae superiorismuscle.

It provides sensitivity to part of the concha of the ear, and to the external auditory canal and tympanum. It provides taste sensation to the anterior two-thirds of the tongue via the chorda tympani, and controls secretion by the lacrimal and submaxillary and sublingual salivary glands.

The trajectory of the facial nerve includes two terminal trunks, the temporofacial and cervicofacial, which end in five terminal branches: the temporal, zygomatic, buccal, marginal mandibular and cervical

1-DANGEROUS ANATOMICAL ZONES

Despite the variability of precise locations of blood vessels in the face, it is very useful to have in mind an image of the approximate boundaries of the major vessels.

The regions that are most commonly involved in serious adverse events following injection of dermal fillers include the glabella and brow region, the nose, the periorbital areas of the cheeks, and the nasolabial fold.

It is useful to consider three main vascular regions in the face: The internal carotid region, the external carotid region, the combined region.

Small branches supplying the dermis can also have anastomoses to the deeper vessels, and so even when treating relatively safe superficial rhytids, the risk if distant injury is not zero.

The glabella and forehead region

The entire glabellar region between the eyebrows should be considered a high-risk zone at all needle depths, whereas the forehead area, lateral to the glabellar region, is low risk in the subgaleal plane from approximately 15mm above the supraorbital rim to the hairline.

Any color change in the glabella should be considered dangerous as it means there is a vascular obstruction of the nasal area. The author has named this the “Pope Hat Sign”.

The entire nasal area, and in particular the dorsum and radix are high-risk areas. Filler treatments of the nasal dorsum should be done exceptionally slowly with tiny aliquots, and deposition directly upon bone or cartilage in the midline.

The labial area is usually divided into the upper and lower labial areas but we shall consider them as one region since they each show similar patterns of injury. The labial arteries travel in the region of the red lip posterior to the wet-dry line. Small amounts of filler typically only affect the lip itself. Larger volumes can cause serious degrees of obstruction because of retrograde flow to the facial artery.

2-PATHOPHYSIOLOGY OF THE VASCULAR ADVERSE EVENTS: EXTERNAL PRESSURE HYPOTHESIS VS EMBOLISM

The failure of laboratory confirmation of the external pressure hypothesis in conjunction with pathological evidence of intra-arterial filler, confirms the clinical opinion that accidental intra-arterial injection of dermal filler is responsible for the pathology in the vast majority of cases.

All preventive strategies involve reducing the risk of intravascular injection of filler material.

With the tiny amount of dermal fillers typically used, intravenous injection will likely not have any serious effect, partly because of the extreme redundancy of the venous system, and secondly because of the amount of filler injected.

However, even a small amount of filler has the potential to cause serious ischaemia of the dermis, or worse.

It must be remembered that most regions of the human face have very extensive collateral blood vessels, with significant anastomoses between regions. On the one hand, this may provide a pathway for filler to travel distant areas and cause unexpected problems. On the other, anastomoses will provide alternative pathways for blood to reach tissues that would otherwise be completely obstructed.

Low-volume versus high-volume embolism

There is a qualitative difference in high-volume embolism (HVE) versus the much more common (but still rare) low-volume embolism (LVE).

The author readily admits that almost all of the vascular events observed consist of the LVE type (probably more than 95%), and so LVE is the prevalent form and the one that the reader is most likely to encounter.

HVE events are basically preventable when following best practices, however, and are most unlikely. The main problem with treatment of HVE resulting from use of HA fillers is that treatment with Hyaluronidase (HYAL) product is typically not immediately effective when embolic events involve a large volume of tissue.

The non-zero risk assessment is the main take-away message of this chapter.

Avoiding embolism

An injector must have intimate knowledge of the detailed vascular anatomy of the face in three dimensions, especially the surface anatomy. He must know the depths of the vessels from the surface, however it is practically speaking impossible to know in every specific case which arterial pattern is present. We can only estimate the areas that are higher risk, and those that are lower risk.

For example, blunt cannulas are less likely to penetrate a vessel. Because there is less bruising and less discomfort with a cannula than a needle of equivalent diameter, some doctors may preferentially use cannulas.

Injection techniques: There are several methods of injecting fillers that can be used to some benefit. This part will examine each injection technique and discuss the risks and benefits of each.

3- CLINICAL SIGNS

Almost all cases of acute vascular ischaemia resulting from filler injection occur within moments after the treatment. However, there have been cases reported of a delayed onset of ischaemia, when the signs of vascular compromise happened several minutes after the end of the treatment.

Visual loss is possibly the single most dramatic and feared complication of filler embolism. The possible causes of loss vision may be grouped according to the presumed location of the obstruction.

4- TREATMENT PROTOCOL FOR VASCULAR ADVERSE EVENTS

Diagnosis of vascular compromise, once established, should take priority over all other activities at the clinic.

Pain is almost never currently reported in acute events. Note the colour of the skin, and in particular, note the presence of livedo reticularis.

A small dose of lidocaine missed with HYAL greatly improves the patient experience and if, anything, lidocaine will act as a vasodilator.

The filler “crash cart” consists of only HYAL and knowledge, as all the peripheral techniques previously described are no longer needed.

Overcorrections/asymmetries

Unwanted results after the injection of filler are usually due to overcorrection and/or erroneous placement.

What is defined as overcorrection depends on the cultural environment. An aesthetically preferred result in one part of the world might be considered an overcorrection in other parts of the world.

Photographs might be helpful to assess and discuss the treatment strategies for asymmetries and overcorrections.

Common adverse reactions vs rare adverse reactions and treatment strategies

Patients and physicians are aware of common adverse reactions (oedema/swelling, haematoma). Their frequency and severity are usually assessed in clinical trials.

Rare adverse reactions can be categorized as abscess-like reactions, ulcers and nodules which appear in most cases in a delayed manner.

In the case of an unclear medical history, it is recommended to identify the relevant filler first.

It might avoid erroneous reports to the regulatory agencies and help decide on the best possible treatment strategies.

It should be clear that all the general rules for cleanliness should be followed when injecting fillers.