I got on the phone with a nearby board-certified veterinary neurologist and said to her, "I'm pretty sure I have a dog with either meningitis or an acute disc prolapse."
"She probably too young for a disc," she told me, "she has meningitis." After discussing with the owner the likely diagnosis and quote for a referral for a CSF-tap (an important analysis of the fluid surrounding the brain and spinal cord), the owner elected to have me treat the dog and declined the referral due to its high cost. The neurologist gave specific doses for steroids (dexamethasone) and antibiotics should the owner not be able to make the referral.
The dog responded within four hours of treatment, and walked out of the clinic with much more ease than when she was presented to me. She continues to improve.
The dog likely has steroid-responsive meningitis, or auto-immune meningitis, where the body produces antibodies against its own tissues and this produces a massive inflammatory response. It is unknown why this occurs. Antibiotics were used in this case because a CSF-tap was not performed, making bacterial meningitis a possibility as well.
Meningitis can occur because of viruses, bacteria, fungi, and parasites, as well as different types of steroid-responsive meningitides (the plural of meningitis), as discussed above. Pugs get their own type of meningitis, called granulomatous meningo-encephalitis (or GME), for which steroids are used in its treatment. There are other breed-specific types of the disease.
Interesting case, but I'd rather treat an ear infection than meningitis given the much better prognosis with the former.

Collecting cerebrospinal fluid from a dog requires practice and technical skill.