Terminology

Short definitions grouped by what they belong to. Each term links to its own page, where the same idea is set out properly with the published work behind it. The full A–Z index follows underneath.

Anatomy: layers and structures

Injection anatomy — facial anatomy read for the purpose of deciding where a needle can go and what lies beneath if that judgement is wrong. Organised around three ideas: layers, compartments and danger zones.

Facial retaining ligaments — fibrous structures tethering soft tissue to bone or deep fascia. They are why the ageing face folds along particular lines rather than descending evenly. Named ones include the zygomatic, mandibular, masseteric, orbital retaining and tear trough ligaments.

Midface — orbital rim to mouth. Ages by three processes at once: bone resorption, uneven fat compartment deflation, and tissue descending against fixed tethers.

Upper face — forehead, glabella, periorbital. Predictable for toxin, dangerous for filler, because the arteries here belong to the internal carotid supply.

Perioral region — lips and the muscular complex around them. Dense arterial supply, thin mucosa, constant functional load.

Tear trough — the groove running inferomedially from the inner canthus, marking the tear trough ligament. The least forgiving area on the face.

Hand rejuvenation — dorsal volume loss exposing tendons, veins and metacarpals. Thin skin, mobile tissue, low tolerance for overcorrection.

Anatomy: vessels and nerves

Vascular supply of the face — facial artery from the external carotid, ophthalmic artery from the internal carotid, and the anastomoses that connect them.

External and internal carotid arteries — the two systems, and the medial canthal junction between them. The anatomical basis of filler-induced blindness.

Trigeminal nerve — cranial nerve V, sensory to the face through V1, V2 and V3, motor to the muscles of mastication. Exits at three foramina roughly aligned in the mid-pupillary plane.

Cervical plexus — C1–C4. Its superficial branches supply the neck and the skin over the mandibular angle, which is therefore not trigeminal territory.

Neurosensory innervation — the sensory map and the foramina where nerves emerge and can be compressed by injected volume.

Lymphatics — facial drainage, sparse in the infraorbital region, which is why malar oedema after tear trough treatment can persist for months.

Products and their behaviour

Dermal fillers — injectable materials adding volume or support. Grouped most usefully by whether they can be removed.

Injectable fillers — the class as a whole: reversible (hyaluronic acid), biodegradable but not reversible (calcium hydroxylapatite, poly-L-lactic acid), and permanent.

Hyaluronic acid — the glycosaminoglycan behind most modern fillers. Crosslinked to slow breakdown; reversible with hyaluronidase, which is why it displaced the alternatives.

Hyaluronidase — the enzyme that degrades hyaluronic acid. Two distinct jobs: elective dissolution, and emergency reversal of vascular occlusion.

Dilution — reconstitution volume, which sets concentration and therefore how far a product spreads through tissue. For toxin preparations the licensed figures belong to the manufacturer — see Preparations.

Advanced botulinum toxin — treatment beyond the licensed upper-face areas, where technique rests on anatomical reasoning rather than a product label.

Technique

Percutaneous injection — getting product through skin into a plane. Needle versus cannula is one of the few technique variables with a consistent safety signal behind it.

Myomodulation — the proposition that filler placed at specific points changes how muscles act, not only how the face looks at rest.

Aesthetic facial procedures — the umbrella term, usefully grouped by mechanism: relaxation, volume, stimulation, resurfacing.

Complications

Complications — sorted by onset, because timing narrows the mechanism faster than appearance does.

Intravascular injection — product entering a vessel lumen. The mechanism behind everything catastrophic.

Vascular occlusion — obstruction of a vessel by injected material, producing ischaemia downstream. (The original site spelled this “occulsion”; the address is preserved, the term is not.)

Loss of vision — embolic occlusion of the retinal or ophthalmic circulation. Largely irreversible, with a window measured in tens of minutes.

Ischaemic stroke — rare but documented, when embolised material reaches the intracranial circulation.

Palsy — weakness of a muscle group, almost always toxin diffusion into a muscle that was not the target. Appears over days, which is the diagnostic clue.

Impairment — loss of function rather than appearance: motor, sensory or visual. The three have different urgencies.

Where the authoritative sources live

For UK product information — licensed indications, reconstitution, dose, storage — the electronic medicines compendium carries the current Summary of Product Characteristics for every licensed preparation. Nothing on this site restates those figures.

For complication management, the published guidelines on vascular occlusion and on hyaluronidase use are the reference points, and both are linked below.

For anatomy, the danger-zone and safe-zone literature is where the mapping actually comes from, rather than from technique diagrams passed between courses.

Full A–Z