Will Botox help to shrink my temporalis muscles? (Photo)

Great question. The answer is yes probably. Whilst it's not the main reason for injecting this site (usually one of the areas injected in migraine sufferers), it does tend to occur. 
I would also rate you that none of my patients have noted loss of strength of bite. The muscle is one used in eating. 

Good luck. 

Yes Botox can temporally decrease the prominence of your temporalis muscles. However it would require repeated injections. Botox is not designed to permenantly fix the sides of your head however there are some procedures that could possibly address your concerns. There is a possibility to get what you are looking done. Every patient has different results.

Good afternoon, 
A neuromodulator works by interrupting the pathway from the nerve to the muscle, this will then decrease the size of the muscle. You would require a face to face review to ensure that this is a appropriate treatment for you. The temporalis muscle is responsible for chewing so you should see an expert injector to ensure you have a thorough assessment as to the dose required. Good luck.

Botox can be used to slim the masseter. It will take 1-2 weeks for final results with Botox. Hope this helps.

Botox can be injected into these areas to create a softer look. The botox will essentially relax the muscles creating the appearance of atrophic muscles. The results will last up to 3-4 months hence you will have to re-inject roughly 3x per year. When administered by an expert injector you shouldn't have an issue with too much laxity. The biggest issue will be muscle weakness if you inject too large doses, which will be required in larger muscles (as compared to cosmetic forehead/face injections) See an expert. Best, Dr. Emer.