One eye squinting when you smile can often be attributed to a condition called facial synkinesis.
What is Facial Synkinesis?
Facial synkinesis refers to involuntary muscle movements that occur alongside voluntary movements in the face. The reference text defines it as undesirable facial movements (aka “simultaneous movement”) associated with voluntary facial movements. In simpler terms, it means that when you try to perform one facial expression, like smiling, another unintended movement happens at the same time, such as your eye squinting or closing.
The Link to Bell's Palsy
Facial synkinesis often develops in people who have previously experienced Bell's palsy.
- Bell's Palsy: This condition causes temporary weakness or paralysis of the facial muscles. During the recovery process, nerve fibers can sometimes regenerate incorrectly. This incorrect regeneration can lead to the nerve that controls your smile also stimulating the muscle that closes your eye, causing the squint.
How Synkinesis Affects Smiling
When you smile, you're intentionally contracting specific muscles around your mouth. However, if you have synkinesis, the nerve signals intended for those muscles might inadvertently activate other muscles as well. This can lead to:
- Eye Closure/Squinting: The most common symptom related to your question is the involuntary closure or squinting of one eye when smiling.
- Other Involuntary Movements: Synkinesis can manifest in other ways, such as neck muscle contractions or pulling of the corner of the mouth in an unexpected direction.
Summary Table
| Feature | Description |
|---|---|
| Facial Synkinesis | Involuntary facial movements occurring with voluntary ones. |
| Common Example | Eye squinting when smiling. |
| Frequent Cause | Previous Bell's palsy and aberrant nerve regeneration. |
| Underlying Issue | Nerve signals intended for one muscle group inadvertently activating another. |
