There is a 3% risk of droopy eyelids after a Botox injection into the forehead area. How can a simple procedure that is supposed to elevate the forehead, remove wrinkles and give you a “lift” turn out to cause more problems than expected? Well, it’s all to do with our individual forehead anatomy.

Anatomy of the forehead

There are two types of muscles in the forehead area:

Brow elevators

The main brow and forehead elevator is the Frontalis muscle. The action of this muscle is to elevate the eyebrows. As it does so, it contracts and can cause skin folds of the forehead, which are commonly known as “worry lines.” Its lowermost portion is about one fingerbreadth above the eyebrows.

Brow depressors

There are three main brow depressors. These are the muscles whose function is to bring down the eyebrows.

  • Procerus: the muscles that cause “bunny lines”; horizontal lines at the top of the nose
  • Corrugator supercilli: the muscles in between the eyebrows; responsible for two lines between brows, the ones you get when you look angry—“number 11s”
  • Orbicularis Oculi: the muscles around the eyes, both under and above the eyelids; responsible in part for eye closure, such as when you squint; these are the ones that cause crow’s feet on either side of your eyes when you squint hard (see below—part of this muscle also closes the eyelids)

Anatomy of eyelid muscles

facial muscles

There are two main types of eyelid muscles:

Eyelid elevators

  • Levator Oculi Superioris: This thin muscle lifts up the eyelid. Close your eyes. Now open them. You just used your levators!
  • Muller’s muscle: This is the superior tarsal muscle and also lifts the eyelid via the “sympathetic nervous system,” a system of involuntary nerves. This muscle elevates the lids when you are startled. That open-eyed look of surprise or fear is mainly due to elevation of the eyelids via the action of this muscle.

Eyelid depressors

  • The eyelid portion (Palpebral portion) of the Orbicularis Oculi closes the lids gently, as when we go to sleep or blink.

Muscles always work in pairs, a depressor muscle being balanced by an elevator muscle. The fact that one group may be a little stronger and have more effect leads to facial lines being more noticeable. If the muscles were in perfect balance, there would be no lines!

The effect of Botox is to selectively stop the function of the muscle it is injected into. The balance of forces is thus affected, and the opposing muscle’s action becomes more prominent as it is now unopposed. For example, say you injected Botox into the corrugator muscles between the eyebrows. Normally, these muscles pull the middle of the eyebrows in. After Botox, it is knocked out so that the opposing forehead elevator, the Frontalis muscle, pulls the forehead up!

Lots more on this topic in the next post. Raise your brows and stay alert!

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