assess electrophysiological changes in some facial muscle dynamics following hyaluronic acid filler injection in superficial versus deep level of injection.

Participants will be subjected to injection of cross-linked hyaluronic acid fillers on both sides of the face in 3 different regions: temples, cheeks and chins.

Each female will undergo:

1. Before injection:

   1. Aesthetic facial clinical analysis.
   2. Baseline quantitative surface electromyography.
   3. Baseline digital photography.

2. Injection:

   Each female will receive the injection in the particular facial region at superficial level to the muscle (subcutaneous) on one side and the same amount at deep level to the muscle (supraperiosteal) on the other side.

3. One week after injection:

   1. Follow up quantitative surface electromyography.
   2. Follow up digital photography.

Inclusion Criteria:

1. Age: 20-60 years.
2. Sex: females.
3. Areas eligible for injection: temples, cheeks and chin.

Exclusion Criteria:

1. Active infection near the site of injection.
2. Pregnant or lactating women.
3. Patients suffering from any neuromuscular disorders.
4. Known allergy/hypersensitivity to hyaluronic acid fillers.
5. History of botulinum toxin injection in the last 4 months.
6. History of injection of fillers in the last 2 years.
7. Patients receiving any muscle relaxants.
8. Coagulation disorder or anticoagulants therapy.