Q: I am a middle-aged woman with asymmetrical eyebrows.

Since I was young, my left eyebrow has been higher than the right eyebrow. It is as if there is a muscle pulling the left eyebrow upwards.

I have heard that Botox can help with this issue.

In particular, I would like to know the effectiveness, duration of the effect and possible side effects of the treatment.

If Botox is the answer, then what should I take note of when searching for the appropriate doctor or surgeon to administer this treatment?

Besides Botox, are there any other non-invasive procedures I can consider?

A: Minor eyebrow asymmetry is a fairly common problem.

However, significant disparity in eyebrow heights could be a result of an imbalance in the muscles that elevate and depress the brow.

Unrecognised ptosis (droopy eyelid) of the left upper eyelid can be an underlying cause.

In this instance, the left forehead muscle exerts a greater pull on the eyebrow to compensate for the droopy eyelid and to elevate it.

When this happens, opening of the eyes becomes more symmetrical - but at the expense of the eyebrows, which end up at different heights.

Damage to the frontal branch of the right facial nerve, which controls the muscles of facial expression, can also cause uneven eyebrows.

This condition causes the right eyebrow to droop, making the left eyebrow appear relatively higher.

Botox is effective in managing this problem. It temporarily weakens the targeted muscle by preventing the release of neurotransmitters at the junction between the nerve endings and the muscle.

In your case, Botox can be used to weaken the left eyebrow elevator (frontalis muscle of the left forehead) to lower the brow position.

The amount and number of sites injected depends on the severity of the brow asymmetry. Ultra-fine needles are used for the injections, so any discomfort is minimised.

The effects of treatment is expected within a few days to a week and is most apparent by two weeks.

TOUCH-UP INJECTIONS

Meanwhile, the effects can last between two and six months.

The side effects of Botox injections are generally mild and manageable. Bruising, if any, is minimal and usually resolves within one to two weeks. Such bruising can be worsened by taking aspirin, warfarin and non-steroidal anti-inflammatory drugs, which can thin the blood.

If the left eyebrow is not lowered enough, touch-up injections can be given about two weeks later.

If the left eyebrow becomes too depressed, the right eye brow elevator muscle can be injected with Botox to achieve symmetry.

Occasionally, ptosis may occur on the treated side with two possible explanations. This is most likely due to pre-existing mild ptosis of the left upper eyelid that went undiagnosed, as the overactive left forehead muscle can conceal this condition. When Botox is injected, this muscle is weakened, revealing the underlying ptosis.

In this case, surgical correction of the weak left eyelid elevator is required.

Another cause of the ptosis, although less likely, is the diffusion of Botox when it is accidentally massaged into the proximity of the left eyelid after it is injected near the eyebrow. Medicated eyedrops can alleviate this to some extent.

Some users have also reported an allergy to Botox - a risk that applies to the use of any kind of medication.

Botox remains the least invasive procedure to manage asymmetrical eyebrows. Other non-invasive procedures such as radiofrequency treatment and phototherapy are unlikely to be as effective.

Invasive procedures, on the other hand, can have long-lasting results.

Depending on the underlying cause of your condition, a right-sided browlift or a left-sided ptosis correction surgery can be done.

Browlifts can be carried out in a minimally invasive manner (with small scars hidden behind the hairline), or via an incision at the suprabrow or upper eyelid.

Ptosis correction can be combined with the removal of excessive skin on the upper eyelid.

Your surgeon may also suggest bilateral eyelid correction to achieve better symmetry.

The Ministry of Health provides a list of qualified plastic surgeons who can help you to determine the underlying problem and discuss the entire spectrum of treatment options with you.

DR NG SIEW WENG, consultant at the department of plastic, reconstructive and aesthetic surgery at Singapore General Hospital

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