Respectfully, your question is more appropriate posted in Landlord/Tenant law than family law. But if what you are asking is whether there is a Nevada law explicitly permitting the breaking of leases to care for family members, I am familiar with no such statute and would be very surprised if any such existed.
I suggest you first read your lease carefully about how and when you can terminate it, and then consider having a chat with a landlord/tenant attorney.
Although I am not a NV lawyer, and can not give you legal advise, I can give an informed opinion based upon my experience in landlord-tenant matters.
Your rights as a tenant will be governed by the law of your state and the terms and provisions of the lease agreement itself. The NV attorney has already addressed the issue of NV law, and neither he nor I have the lease before us, so he and I have to depend upon your reading the provisions.
If there is no provision in the lease allowing you terminate the lease after giving 30-days' notice, then if you leave and do not pay rent for the remaining months you will be in breach of the lease. The landlord will be able to bring suit if he/she/it chooses. I understand very well needing to take care of a sick family member, but this is not about whether you are or are not a good human being. You are a son or daughter of a mom who needs help. Trying to do the right thing by way of your family. But, none of those factors you mentioned--the giving of notice, the medical statements, etc.--provide you with a defense to the breach of the lease.
You may want to discuss the matter with the landlord, perhaps agree to pay a few extra months in a lump sum as consideration for the mutual agreement that the lease be terminated, but first and foremost, consult with a lawyer with your lease present.
Good luck to you working out this problem with the landlord, and I hope your mother does better.
The response given is not intended to create, nor does it create an ongoing duty to respond to questions. The response does not form an attorney-client relationship, nor is it intended to be anything other than the educated opinion of the author. It should not be relied upon as legal advice. The response given is based upon the limited facts provided by the person asking the question. To the extent additional or different facts exist, the response might possibly change.
I agree with the prior answers, but wish to add that you may be able to sublet or make another arrangement, but you should talk to your landlord. Landlords are human beings, too and they have been known to have mothers. You may be able to work out an arrangement that both of you can live with.