Dear Sooyong

I am afraid it is not a matter of guessing the answer, but a matter of knowing. So you should autopsy your dead mice to really find out what is going on.

You should consider the fact that stroke can lead to death; hence, its induction in animals carries a significant risk of mortality.

Hi Sooyong  

This is a fairly standard and usually ow morbidity/mortality procedure by which to induce a focal cortical stroke. I agree with Tomas that a necropsy is the best investigation to determine if there are any obvious lesions / haemorrhages that may account for the death. But if there is nothing to be seen (and I suspect there won't) I would look very carefully at your anaesthetic choice and depth of anaesthesia during the procedure. Are they recovering well immediately post op?  Are you using gas or injectables? If the latter, do you use an effective reversal agent such as anti sedan for a a ketamine/metomidine mix? (your local vet should be able to help here). Also, minimise the amount of handling and degree of trauma under anaesthesia. 

Hope this helps.

Regards

John Reynolds

To JohnReynolds,

I appreciate you answer.

I used 2% isoflurane Inhalant for anesthesia. The mouse was awake after surgery, but he didn't move well.

According to Tomas Koltai and your suggestion, which part do I have to check by  necropsy to figure out death in this case? 

I would suggest lungs (for pulmonary oedema) and heart for infarction, abdomen for bleeding as well as brain for bleeding extra or sub durally that could possibly be related to excess pressure applied to the skull with the fibre optic.  And check for sites of ear bar insertion and ip / Iv injection puncture sites into the abdomen and vein where you injected the rose bengal for haemorrhage. It is good to have a vet or someone else experienced on hand to help you with the first necropsy and interpreting the findings. 

Regards 

John Reynolds