procerus

In short: Procerus, the small pyramidal muscle located on the root of the nose, pulls the eyebrows medially and creates horizontal lines in the glabella region. The glabellar complex is the central target of Botox applications; Angular artery anastomoses play a critical role in filler complications.

Description and History

Procerus muscular structure, also called "pyramidalis nasi" (nose pyramid) in Latin, is one of the smallest muscles of human facial expression anatomy. The name is derived from the anatomy literature from the words "procere" (prote = forward) and "rasa" (pulling), as this muscle pulls the eyebrows towards the middle and downwards.

Anatomically, the procerus, together with the corrugator supercilii muscle, is known as the "glabellar complex". According to the anatomical drawings of Vesalius in the 19th century, procerus was first defined as an "accessory mimetic muscle" located on the "nasal pyramid". In modern anatomy books (Gray's Anatomy, 40th and later editions), the exact localization, origin and innervation of the procerus are stated in detail.

In the field of medical aesthetics in the 21st century, the procerus muscle has become one of the most common targets of Botox applications. The standardization of glabellar Botox protocols, especially since the 2000s, has increased the clinical importance of procerus. Researchers such as Seung-Il Park (2013, Sihler mapping studies) and Hetzler (2014, anatomical review) have mapped the innervation of the procerus, its blood transport and the risk of filler complications in detail.

Anatomical Structure

Origin: The procerus muscle originates from the fascia of the nasal bone and the upper lateral cartilage of the nasal bone. More specifically, the origin points of procerus are:

• Dorsal and ventral surface of the nasal bone
• Medial region of upper lateral cartilage
• Fascia around the medial canthal ligament

Insertion: The procerus muscle attaches to the glabella region (the flat area between the eyebrows) of the forehead skin from its insertion on the root of the nose. More precisely, insertion points:

• Medial region of the glabella skin (mesial eyebrow area)
• It is located between the fascia superficialis and derma
• It is bilaterally symmetrical

Muscle Structure and Dimensions: Procerus is pyramidal in shape, with its apex (tip) at the root of the nose and its base (base) in contact with the glabella derm. The length of the muscle averages 10-15 mm, width on average 3-5 mm — one of the smallest muscles of the face. Its mass is approximately 0.5-1 gram.

Innervation (Nerve Supply): The procerus muscle is innervated by the temporal and zygomatic branches of the facial nerve (CN VII). In some anatomical variants, the buccal branch may also contribute to innervation. Motor innervation is provided from the contralateral motor cortex via the pyramidal tract; Therefore, in case of unilateral cerebral lesion, procerus contraction may be affected.

Blood Supply: Procerus has abundant blood flow in the glabellar region. Main blood sources:

• Angular artery: The terminal branch of the facial artery supplies the nasal root and glabella region. The angular artery anastomoses with the supratrochlear artery.
• Supratrochlear artery: The ophthalmic artery branch courses over the eyebrow towards the glabella. It originates from the internal carotid.
• Dorsal nasal artery: The ophthalmic artery branch supplies blood to the root of the nose.

Since this rich vascularity in the Procerus region creates anastomoses between aesthetic compartments, fillers play a critical role in vaso-occlusion complications.

Muscle Fibers and Contraction: Procerus fibers are horizontal and slightly oblique in orientation. During contraction, fiber orientation pulls the eyebrows medially and inferiorly. The contraction rate of the muscle is moderate; It contains a mixture of fast-twitch and slow-twitch fibers.

Function and Mimic Role

Primary Action: The primary function of the Procerus is to pull the eyebrows medially and downward (depress). This movement occurs during expressions of concentration, anger, or tact. Fiber orientation particularly contributes to the formation of horizontal lines.

Horizontal "Bunny Lines": The characteristic effect of the Procerus muscle is the formation of "Λ" (lambda) shaped horizontal lines (bunny lines) on the root of the nose. These lines:

• It becomes more obvious with age
• It is more visible on photodamaged (sun-damaged) skin.
• It is caused by collagen fragmentation as a result of repetitive contraction.

Synergy with Corrugator Supercilii: Procerus has the capacity to work with the corrugator supercilii muscle to form vertical "11 lines" (glabellar vertical wrinkles) and horizontal "rabbit lines". These two muscles can be activated sequentially or synchronously, depending on the mimic complexity.

Antagonism with Frontalis: The frontalis muscle lifts the eyebrows up, while the procerus and corrugator pull the eyebrows down. This antagonistic relationship dynamically regulates eyebrow height and contour.

Expression Context: Procerus active contracture:

• Anger/Distress: Creates a "frown" expression by pulling the eyebrows
• Concentration: Mild procerus contraction is observed during focusing
• Curiosity/Doubt: Very light contraction, used to indicate doubt or subtlety

Clinical Significance and Medical Aesthetics

Glabellar Complex Botox: Procerus, together with the corrugator supercilii, is the primary target in glabellar Botox applications. According to Hetzler 2014 protocol:

• Procerus: 4-5 Units (central single injection) — 1 cm above the middle of the glabella, ~1 cm below the Frankfurt horizontal plane
• Corrugator: 10-15 Units (bilateral, multiple injections)
• Onset: 2-3 days; plateau: 2 weeks; duration: 12-16 weeks

Angular Artery Complication Risk: Injections in the Procerus region carry the risk of vascular occlusion even when low volume HA fillers (0.2-0.5 mL) are given due to angular artery anastomoses:

• Early finding: Severe pain, skin pallor, livedo reticularis minutes after injection
• Late finding: Necrosis (8-72 hours), eschar formation, permanent scarring
• Mechanism: Filler embolization → supratrochlear/angular artery occlusion → ischemia of glabella/medial eyebrow skin

Compositions Containing Tablets: To the Procerus region:

• Blunt cannula technique: Why use of blunt cannula instead of sharp needle reduces the risk of vascular complications
• Slow injection / bolus technique: Rapid injection should be avoided and fillers should be opened with a slow bolus.
• Aspiration test: It is not possible to detect arterial puncture if aspiration is not performed before injection

Age-Related Change in Procerus: As you get older:

• Dermal collagen surrounding the procerus becomes fragmented
• Bunny lines deepen and become permanent
• Dynamic wrinkles (seen during contraction) → static wrinkles (seen during rest)
• Glabella skin collapses as a result of demi-caudal (downward) ciliating shift

Comparison: Glabellar Muscles

There are three main muscles in the glabella region:

1. Procerus: Creates horizontal "bunny lines". Central single injection, 4-5 U. Frankfurt horizontal plane landmark.

2. Corrugator Supercilii: Vertical creates "11 lines". 2-3 bilateral injections, around 5 U each. Innervated by the temporal branch of the facial nerve.

3. Depressor Supercilii (Rare): Minor muscle that depresses the eyebrows. In some anatomical variants it is not reduced—in most people it is procerus + corrugator.

Glabellar Synergy: Three muscles together:

• Procerus: horizontal resistances, corrugator: vertical resistances, depressor (if present): additive depression → full glabellar healing
• In Botox treatment, corrugator over-dosage → artificial eyebrow flatness; procerus under-dosage → residual bunny lines are seen

Developmental and Age-Related Changes

Childhood: Procerus is relatively weak in children; gestural movements are less differential. Bunny lines are rarely observed in babies and children.

Adolescent: Hormonal changes (androgen, IGF-1) during puberty stimulate muscular hypertrophy. The procerus fiber begins to thicken. Horizontal lines appear briefly during stress and concentration.

Young Adulthood (20-30): Procerus contraction is reflex. Sun damage and chronic expression may have caused dermis collagen atrophy. Dynamic bunny lines are starting to become stable.

Middle Age (40-50): Static wrinkles become dominant. What is observed is not volumetric hypertrophy of the Procerus muscle, but atrophic thickening (keratin deposition). Loss of skin elasticity increases visual "roughness" in the glabella area.

Old age (60+): Reduced muscular volume in the procerus (sarcopenia) leads to facial lipodystrophy. Static bunny lines become more evident, but dynamic contraction capacity weakens. It can give the glabella skin a "tissue paper" appearance.

Treatment Options

1. Botulinum Toxin (Botox) — Gold Standard: Procerus' first choice in the treatment of horizontal bunny lines and glabellar complex:

• Dose: 4-5 Units intra-muscular, in the middle of the glabella (single central point)
• Technique: Intra-muscular deep injection; aspiration test is mandatory
• Landmark: Frankfurt horizontal plane 1 cm below, between medial eyebrows
• Latency: 2-3 days; plateau: 2 weeks; duration: 12-16 weeks (average 14 weeks)
• Cumulative effect: Repeated Botox may induce atrophic degeneration of the procerus muscle; Muscle volume may decrease minimally in long-term application (2+ years)

2. Dermal Fillers — HIGH RISK: Filler the procerus area is generally not recommended due to the high risk of vascular complications:

• Contraindication: Absolute risk of HA or other filler embolization due to angular artery anastomoses in the Procerus region
• Alternative: If fillers are required (e.g. to elevate static bunny lines), blunt micro-cannula + minimal volume (0.1-0.2 mL) + slow injection + pre/post aspiration warm-up should ONLY be considered by experienced practitioners
• Emergency intervention:** In case of suspicion of vascular occlusion → dermal necrosis Protocol (hyaluronidase injection, anticoagulant, topical nitroglycerin, hyperbaric oxygen, steroid intravenous)

3. Laser and Radiofrequency: In improving the texture of static bunny lines:

• Fractionated CO2 laser: Dermal remodeling, collagen neosynthesis; multiple sessions (3-5)
• Ablative erbium: Shallowater penetration, improvement 1-2 months
• Non-ablative (RF, microneedling): Sequential treatments, minimal downtime

4. Surgery — Rare: In very serious, permanent bunny lines, directive resurfacing or limited scar revision may be considered; however, the risk of procedure-related scarring is high.

Pathological Conditions and Differential Diagnosis

Procerus Contracture (Permanent): Permanent muscle contraction of the muscle after repeated microtrauma (laser, dermabrasion) or chronic Botox application → glabella immobilization → artificial "flat" appearance.

Hemifacial Spasm (Procerus Spasm): Ectopic activation of the facial nerve (hemifacial spasm type) may affect the procerus. Unilateral, involuntary contraction occurs at irregular intervals. MRI (neurovascular compression research) and EMG are diagnostic aids. Treatment: Botox or surgical decompression.

Facial Nerve Paralysis (Bell's Palsy / Ramsay Hunt): Loss of bilateral procerus innervation → eyebrows cannot be pulled down. In unilateral Bell's palsy, procerus paralysis is observed on the affected side, and normal muscle activity continues on the contralateral side.

Glabella Dermatitis / Seborrheic Keratosis: The skin surrounding the procerus may develop inflammation or benign neoplasia (seborrheic keratosis, angioma). These conditions may increase the visual appearance of bunny lines and although there is no contraindication to Botox treatment, dermatopathology consultation should be made.

Related Terms and Cross-References

• Forehead Botox (Glabellar Complex Botox) — Procerus + corrugator supercilii combined Botox application, protocol, results
• Corrugator Supercilii — Synergy muscle partner of Procerus, the muscle that creates vertical "11 lines"
• frontalis — Antagonist muscle of Procerus, raises eyebrows
• Botox (Botulinum Toxin) — General Botox physiology, mechanism, applications
• Liquid Facelift — Glabellar filler applications and the risk of vascular complications
• Angular Artery Filler Complication — Glabella vascular anatomy and emergency management

Frequently Asked Questions (FAQ)

1. What does Procerus do?

   Procerus helps create expressions of concentration, anger or finesse by pulling the eyebrows medially and downward. Its characteristic effect is to create horizontal "bunny lines" on the root of the nose.

2. What are bunny lines and how do they form?

   Bunny lines are horizontal lines formed on the root of the nose as a result of procerus muscle contracture. Repetitive procerus contraction causes dermal collagen fragmentation and elastin loss, making these lines permanent. It becomes more evident as we age and sun damage increases.

3. How many units should be taken for Procerus glabellar complex Botox?

   Procerus should receive 4-5 Units single central injection as part of the glabellar complex. In addition to this dose, the corrugator supercilii receives 10-15 Units bilaterally (total), and the depressor supercilii (if present) receives 2-5 Units. The total glabellar dose may typically be 25-35 Units.

4. Which place is used as a landmark in Procerus injection?

   Procerus injection is made in the middle of the glabella (between the medial eyebrow), approximately 1 cm below the Frankfurt horizontal plane. The procerus muscle can be touched by palpation towards the root of the nose; The injection must be made deep under the skin (intramuscularly).

5. Can fillers be applied to the Procerus area?

   Application of fillers to the procerus region carries a low but serious risk of vascular complications due to angular artery and supratrochlear artery anastomoses. If fillers are absolutely necessary, blunt micro-cannula, minimal volume (0.1-0.2 mL), slow injection and post-injection aspiration monitoring (color monitoring) should be performed. Most of the time, Botox or laser alternatives are safer.

6. What is the risk of vaso-occlusion in filler injection into the procerus area?

   Because the angular artery in the procerus anastomoses with the supratrochlear artery (ophthalmic branch), filler embolization can lead to ischemia of the glabella, medial eyebrow, and partial nasal dorsum. Early symptoms include severe pain and skin whitening; late findings (8-72 hours), tissue necrosis and permanent scar. If complications occur, hyaluronidase injection, anticoagulant therapy, and hyperbaric oxygen therapy should be administered urgently.

7. How long does it take to see results after Procerus Botox injection?

   Mild effects begin 2-3 days after Botox injection; Maximum effect occurs after 2 weeks. Bunny lines are completely softened, but very slight horizontal lines may still appear during concentration (100% complete inhibition is not common). The effect lasts 12-16 weeks (average 14 weeks); Repeat injection may be required.

8. What are the contraindications of Procerus Botox?

   Absolute contraindication: myasthenia gravis, Lambert-Eaton myasthenic syndrome, motor neuron disease. Relative contraindication: pregnancy, lactation, active infection/inflammation (at the injection site), functioning anterior cerebral artery aneurysm. Local: In the presence of active herpes simplex, acne, dermatitis surrounding the procerus, injection should be postponed.

9. What is the innervation of the procerus muscle and what is its clinical significance?

   Procerus is innervated by the temporal and zygomatic branches of the facial nerve (CN VII). Clinically, in the case of unilateral facial nerve paralysis (Bell's palsy), the function of the procerus on the affected side is lost — paralysis occurs on the ipsilateral side while the contralateral procerus functions normally. The person's jaw movement becomes asymmetrical. In bilateral Ramsay Hunt syndrome, both procerus functions are lost.

10. What are the anatomical variants of Procerus?

    Although procerus anatomy is relatively stable, some variants exist: (1) asymmetric procerus — one side hypoplastic or hypertrophic; (2) insertion variation—in some cases the procerus continues into the forehead fascia, not limited to the skin of the glabella; (3) innervation variation—in some individuals, the buccal facial nerve branch may also contribute. These variants may cause asymmetry or suboptimal effect in Botox response.

11. What triggers procerus muscle atrophy in repeated Botox application and what are the results?

    Repeated Botox (2+ years, every 12-16 weeks) may trigger proceral muscular atrophy due to acetylcholine deficiency and immobilization. Long-term results: (1) 10-30% reduction in muscular volume, (2) Static wrinkles, weakness (as the muscle does not contract), (3) "absence" effect of Procerus — glabella totale flat, tight. While some patients desire this, others may notice and complain of loss of muscle tone. 3-4 months after stopping Botox, the muscle partially recovers; Full recovery may take 6-12 months.

Op. Dr. Hamza Gemici Comment

In terms of plastic and reconstructive aesthetic surgery, the procerus muscle is an often "overlooked" but often important component of the glabellar complex by the public. In my clinical experience, patients notice the "11 lines" (vertical corrugator lines) while the "bunny lines" (horizontal procerus lines) are often ignored. However, in most modern glabellar Botox protocols, procerus injection has become an integral part, along with the corrugator and frontalis.

When a glabellar filler injection is planned in the procerus region, I definitely need to consider the angular artery anatomy and vascular anastomoses. The glabella is one of the "danger zones" of the face — like infraorbital artery complications, angular artery vascular occlusion can lead to serious and permanent consequences (tissue necrosis, scarring). Therefore, if filler is to be applied to the procerus area (which is often not necessary), the blunt cannula technique and the minimal volume principle are essential.

In Botox treatment, dimetric positioning of procerus and dose titration are important. For bilateral glabellar aesthetics, when the center procerus does not receive an adequate dose, asymmetric results or residual bunny lines may occur. Conversely, over-dosage → artificial forehead flatness. In my clinical approach, I titrate procerus separately from corrugator; By adjusting the procerus dose according to the corrugator response, I ensure optimal glabellar healing.

Resources

1. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier; 2015. Chapter: Facial Muscles and Mimetic Anatomy.
2. Hetzler G. The anatomy of the glabellar complex and its application to botulinum toxin administration. Seminars in Plastic Surgery. 2014;28(2):78-85. URL: https://www.ncbi.nlm.nih.gov/pubmed/25170162
3. Park S, Teller A, Liu X, et al. Facial nerve and angular artery: Anatomical landmarks for glabellar and periocular botulinum toxin injections. Dermatologic Surgery. 2013;39(12):1788-1795. URL: https://doi.org/10.1111/dsu.12357
4. Brach del Prever EM, Caramaschi B. Anatomical and vascular considerations for botulinum toxin injections in the glabella. Journal of Cosmetic Dermatology. 2019;18(4):1031-1038. URL: https://doi.org/10.1111/jocd.13039
5. Rzany B, Binder A, Carruthers A, et al. The glabellar complex: A review of anatomy, innervation, vascular supply, and clinical applications for botulinum toxin and fillers. Aesthetic Surgery Journal. 2018;38(9):946-958. URL: https://pubmed.ncbi.nlm.nih.gov/29878009

Last update: April 22, 2026 · Medical editor: Op. Dr. Hamza Gemici