Botox works on the terminal end of the motor nerve, where it stimulates
the muscle to contract. The junction between the motor nerve ending and the
striated muscle is referred to as the “neuromuscular junction”. With normal
muscle movement, a nerve impulse travels down the motor nerve and causes the
release of a chemical (the neurotransmitter, acetylcholine) from the end of the
nerve. This chemical travels across the neuromuscular junction, and stimulates
the muscle to contract. Botox paralyzes/relaxes muscles by blocking the release
of this chemical (acetylcholine) from the motor nerve ending; if the chemical
neurotransmitter is not released, the muscle does not contract.
Botox does not affect sensory nerves. The infraorbital nerve
is a sensory nerve, and is not affected by Botox. The infraorbital nerve
supplies sensation to the medial portion of the cheek, the upper lip, the side
of the nose, and the lower eyelid.
Zygomaticus major and zygomaticus minor muscles are
responsible for elevating the corner of the mouth / lip when you smile. The
weakness in your smile is related to Botox affecting the motor nerve function
to the zygomaticus major and minor muscles. Experienced Botox injectors know to
avoid this area, for the reasons you have experienced.
I am confused why your doctor chose to inject a local
anesthetic into this area as well. Most local anesthetics last only a few
hours, so I would suspect that your numbness has subsided. If your numbness has
not subsided, then further evaluation is warranted.
The effects of Botox are not permanent. The muscle weakness/
relaxation caused by Botox typically ranges from 3 to 6 months, with the
average relaxation being about 4 months duration. How long your weakness will last
depends upon how much Botox was injected into this area, and how much of the
muscle was affected. It is possible that after about a month you may start to
see some gradual improvements on a week to week basis. I suspect that by about
four months or so you should see relatively reasonable return of muscle
My advice moving forward would be to find an experienced
Botox injector for your next treatment. Best wishes.
This doctor doesn't appear to know how to inject Botox. This is an area to stay away from. Cut you losses and go to someone else in the future and for follow up. All Botox effects should be temporary, but can last up to 4 months. Numbness should resolve, it's difficult to permanently affect the nerve with just injecting Botox.
Unfortunately this happened but luckily the effects on the muscle will wear off in 3-4 months and you will have no permanent long term issue. It is rare for the nerve to be damaged from needle injection into that area. This is likely a result of poor injection technique. Best, Dr. Emer.
Not to worry! Although I know you're distressed and worried, results from Botox (and all the other cosmetic neurotoxins) are completely transient. You'll see results reversing as early as the end of April (soon!). It's best not to have them inject the other side to "even-it-out" because you'll be asymmetric when the initial side starts to wear off. Be patient- and make sure in the future they never inject that same area.. Stay higher up on the face when injecting to avoid those sensitive nerve areas. Ultimately - be reassured that your results are only temporary.
The good news is that the effects of Botox are completely temporary, and you should start to see normalization of your smile around six weeks following your injection. Thank you for sharing.
Very sorry for your difficulties. More than likely, the left zygomaticus major and minor muscles were inadvertently injected with Botox leading to the irregularity with smiling. There is no aesthetic indication for injecting a major sensory nerve or the area in its vicinity with Botox. This is one of those complications that is relatively "hard to do" and suggestive of lack of experience in injecting toxins. Luckily, this effect will resolve spontaneously in 3-4 months.
It is clear that you've had a complication. But let's clear up a few things about the infraorbital nerve and Botox:
- the infraorbital nerve is a sensory nerve, providing sensation to the lower eyelid, the side of the nose, the cheek and upper lip. It doesn't move any muscles. If the numbness has worn off, then you don't have any damage to the infraorbital nerve. If numbness is still present then further investigation is warranted.
- the asymmetry with your smile is due to injection of Botox into the muscles involved in smile -- zygomaticus major & minor. Botox works where the nerve meets the muscle, so the nerves that move these muscles are also okay, it's just that their muscles have been Botox'ed. Why Botox was injected around those muscles, and why your surgeon followed up with a numbing agent, is a mystery to me.
Botox lasts 3-5 months with an average of 4. Unfortunately there is nothing that can speed the recovery of the muscle function, but they will return.
Harry V. Wright MD