Managing Frontalis & Brow Depressor Asymmetry
[Asymmetry Series: Part 2B]

By Jude Harford

BNurs (Hons), PgDip (Adv Practice), NMIP

Nurse Practitioner, skinByJude

Jude is a prescribing aesthetics nurse practitioner with a strong interest in menopausal skin health and regenerative treatments. Her focus is on achieving natural results through evidence-based practice using the highest quality product

• Website: https://skinbyjude.co.uk/
• Instagram: https://www.instagram.com/skin_by_jude/

Building on our foundational guide, Treating Facial Muscle Asymmetry with Botulinum Toxin: Clinical Approach, this article explores the biomechanical relationships governing the upper face. See also Upper Facial Muscle Balance: Frontalis & Brow Depressors [Asymmetry Series: Part 2A].

Frontalis Asymmetry

The frontalis is unique among the muscles of facial expression because it has no bony origin. Instead, it arises from the galea aponeurotica and inserts into the dermis of the forehead and eyebrows, elevating the brows and creating horizontal forehead rhytides.

In many patients, the two halves of the frontalis do not contract equally. One side may produce greater brow elevation, deeper forehead lines or more extensive recruitment during facial expression.

Clinical Presentation

Patients may report:

• “One eyebrow is always higher.”
• “One side of my forehead wrinkles more.”
• “One eye looks more open.”
• “One eyebrow arches much more in photographs.”

On examination, asymmetry is often most apparent when the patient raises the eyebrows. One brow may elevate earlier, travel further or remain elevated for longer. Careful observation also reveals whether forehead rhytides are deeper or more numerous on one side.

Why Does This Happen?

Frontalis asymmetry may reflect:

• normal anatomical variation
• habitual unilateral eyebrow elevation
• compensation for brow ptosis
• compensation for upper eyelid hooding
• previous botulinum toxin treatment
• previous facial nerve injury

Compensatory recruitment deserves particular attention. Patients with dermatochalasis or a relatively heavy upper eyelid often subconsciously increase frontalis activity in an attempt to improve their visual field. This may occur asymmetrically if one eyelid is more hooded than the other.

Injecting the apparently “stronger” frontalis without recognising this compensatory mechanism may worsen brow descent and leave the patient feeling that the eye is smaller or heavier.

Assessment

Observe the patient at rest before asking them to elevate the brows.

Assess:

• brow height
• brow shape
• upper eyelid show
• forehead rhytides at rest
• forehead movement during conversation
• eyebrow elevation during maximal contraction
• symmetry of forehead recruitment

Ask the patient whether the asymmetry has always been present and whether one eyelid feels heavier than the other.

Photography in both the relaxed and animated state is invaluable.

Treatment Philosophy

Treatment planning should focus on restoring muscular balance rather than equalising wrinkle severity.

Where genuine unilateral frontalis overactivity is present, carefully reducing excessive contraction may improve symmetry while preserving brow support.

However, if asymmetrical frontalis recruitment is compensatory, reducing activity may unmask the underlying brow ptosis or eyelid hooding. In such cases, addressing brow depressor overactivity—or recognising that treatment is not appropriate—may produce a better functional and aesthetic outcome.

A conservative approach is particularly important in patients with naturally low brows, pre-existing dermatochalasis or reduced levator function.

Clinical Pearl: A highly active frontalis is not always the problem. Sometimes it is the patient’s solution.

Brow Depressor Asymmetry

This is one of the most frequently misunderstood areas of upper facial assessment.

The brow depressor complex comprises the corrugator supercilii, procerus, orbicularis oculi and, variably, the depressor supercilii. Together, these muscles pull the brows medially and inferiorly.

Asymmetry within this group can produce:

• one brow sitting lower
• asymmetrical glabellar lines
• unequal frowning
• one eye appearing more hooded

A patient may therefore present complaining of an asymmetric brow when the underlying issue is excessive depressor activity rather than inadequate frontalis function.

Assessment

Observe:

• brow position at rest
• frown strength
• glabellar wrinkle pattern
• medial brow movement
• lateral brow position

Palpation during active frowning often helps identify differences in muscle bulk and contraction.

Treatment Philosophy

Rather than treating the elevated brow, practitioners should determine whether one side demonstrates disproportionately stronger brow depression.

Selective reduction of excessive depressor activity may allow the ipsilateral frontalis to elevate the brow more effectively, restoring symmetry without directly targeting the frontalis itself.

This principle often produces a more natural result than attempting to lower the opposite brow.

Clinical Pearl: Not every high brow needs lowering. Sometimes the lower brow simply needs to be allowed to rise.

Orbicularis Oculi Asymmetry

The orbicularis oculi is often thought of simply as the muscle responsible for crow’s feet. In reality, it performs a far more complex role, contributing to blinking, forceful eyelid closure, lacrimal pump function, lower eyelid support and lateral brow position. Consequently, asymmetry of the orbicularis oculi may present in a variety of ways, some of which are easily mistaken for asymmetry arising from other muscle groups.

Unlike the frontalis, whose primary action is brow elevation, the orbicularis oculi functions as a sphincter muscle surrounding the palpebral fissure. It comprises orbital, preseptal and pretarsal components, each contributing differently to eyelid function and facial expression. The orbital fibres are principally responsible for forceful eye closure and also contribute to lateral brow depression, whilst the pretarsal fibres are essential for involuntary blinking and maintenance of the tear film.

From an aesthetic perspective, asymmetrical orbicularis activity most commonly presents as:

• unequal lateral canthal rhytides
• narrowing of one palpebral fissure during smiling
• apparent differences in eye size
• asymmetrical brow tail position
• unequal lower eyelid movement

It is important to recognise that these findings do not necessarily indicate pathology. Mild asymmetry of blinking and smiling is common in healthy individuals and often reflects normal variation in muscle recruitment.

Assessment

Assessment should always begin at rest before observing movement.

Evaluate:

• palpebral fissure height
• scleral show
• brow tail position
• eyelid symmetry
• lower eyelid support
• static periocular rhytides

The patient should then be observed during:

• spontaneous smiling
• maximal smiling
• gentle eye closure
• forceful eye closure
• conversation
• laughter

Many asymmetries become apparent only during genuine facial expression rather than instructed movements.

Particular attention should be paid to whether one eye narrows disproportionately during smiling. This may reflect increased orbicularis recruitment, compensatory movement following previous facial nerve dysfunction or synkinetic activity after recovery from Bell’s palsy.

Treatment Philosophy

The aim is rarely to create identical crow’s feet on both sides of the face.

Instead, treatment should seek to restore harmony between periocular movement, brow position and overall facial expression.

Before considering treatment, practitioners should determine whether the apparent asymmetry reflects:

• true muscular imbalance
• brow position
• eyelid anatomy
• dermatochalasis
• facial nerve dysfunction
• previous treatment effects

Reducing orbicularis activity may influence brow position by reducing its depressor effect on the lateral brow. Appreciating this interaction is essential when planning treatment of patients presenting with both crow’s feet and brow asymmetry.

Treatment should always preserve adequate eyelid closure and blink function. Excessive weakening risks lagophthalmos, exposure symptoms and patient dissatisfaction.

Note:

This article was written by a guest contributor from our community. The views and clinical opinions expressed here belong to the author and do not necessarily reflect the opinions or endorsements of Dr Tim Ltd.