Absolutely. Any inflammation, infection or even injury around the spinal cord or vertebrae will cause a problem with motility like you mention. The back legs generally become affected when the problem is in the lower part of the back (basically anywhere from around the 'middle' of the back and down).
Steroids are the prime medication for inflammation, but if the inflammation is because of a slipped or ruptured disc (between vertebrae) or disc disease (common in dogs like dachsunds, bassets, etc but can occur in any dog), then they are not curative.
Generally, steroids are tried for a 2 week trial. You should see slight improvements on a daily basis once starting. Within a couple of days there should at least be less pain symptoms, and perhaps more motivation to move the legs. However, strict rest is required as well, and a full evaluation taken 2 weeks after to see if steroids are continued or further diagnostics and/or surgery to fix the initial problem. If within a week you don't see some fair improvement noticeable to you, I would think the inflammation or injury is a bit too severe to expect complete improvement in the 2 weeks. Hope this makes sense. Let me know if I can help further, and hope your dog is better as soon as possible.
Time will be your friend in this and let you know what's working and what isn't. Without an MRI and radiologist giving their best opinion on what a CT or MRI reads, I'd hope your vet would also been loading your dog up with antibiotics in case this is meningitis, which requires hardcore aggressive antibiotic treatment but is cureable. As for inflammations, the steroids are the way to go. Don't give up hope right now, though I know it's difficult he's going through so much, especially for such a young dog.
It doesn't present much like a tick borne disease and not a severe spinal cord injury, as that would cause sudden complete paralysis. Less severe inflammation around, disc problems, and the like (basically treatable injuries) absolutely do present the way you have described your dog's progression to paralysis. including with the bladder- it could be somewhat neurologic (meningitis or just the affect on the spinal crd, which carries info to the brain) and/or the fact he's got too much going on and not able to get up now- he could have given up worrying about proper urination habits.
Money may become an issue if the hospitalization for intense treatment continues for some time (unfortunately no way of knowing, as all dogs respond differently, but in hospital is quicker than at home with oral meds), and if an injury is found requiring surgery that too can be a big cost.
You can apply for care credit if that helps, applied for at most vet hospitals. It's a credit card for health care accepted at most vets, and when costs are high (usually over $300 to thousands) interest can be nothing to very low for the first 6mo to a year. A huge life saver for some.
Hope this helps,
I wish you and your dog nothing but the best of luck!!
Those injuries could cause big problems if they land the wrong way or twist the wrong way. Meningitis is a difficult diagnosis to reach and rare, often not thought of right away, but antibiotics should be given regardless just in case ANY infection is present, and the fact the dog's immune system is weaker. Definitely discuss possibilities and you won't ever have to feel you came to a rash decision on anything. You deserve and pay for a complete knowledge of how your dog is and what the vet has found, in terms you can understand. And make sure you spend the time asking questions. Since many people are so concerned over their pets once in the appt, they often forget to ask; I would start making a list of questions you have and points to discuss (meningitis vs injury, etc).
It is for medical care assuming people are in a crisis, so a little more lenient than your standard credit card, but yes, some people can be turned down. It only takes a few minutes to find out after applying though, and there's the chance once seeing you apply for care credit, the office may offer some sort of payment plan (though they all say no way at first).