I am in the process of writing a report on clinical findings. Studies are ongoing, but I am happy to help the bearded dragon community; obviously this has become my specialty and we are aggressively looking for veterinarians and biologists to join the battle.
I will post my personal blog and start a thread for meningitis, as well as posting here to tell you I have done that.
There are so many things that bearded dragons can become ill with.
http://c.ymcdn.com/sites/members.arav.org/resource/resmgr/Files/Proceedings_2011/2011_007.pdf
As for this little dragon, I can only recommend what is known, low dosages of systemic antibiotics with a low dosage of corticosteroid may give you positive results if you are willing to go that direction.
Naturopathically I refer to this table
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC88925/table/T1/
There are so many contributing factors that without knowing the cause it is impossible for me to help treat.
The most common cause thus far is listeria, which is usually the result of something they actually ate.
For example Dole lettuce had a recall a few years ago due to a particular outbreak with listeriosis I know of one entire bearded dragon collection that was effected.
https://en.wikipedia.org/wiki/Listeria
Listeria affects those already immunocompromised and I hypothesize that most of these dragons have endured a past fracture, some sort of neurological stress, a respiratory infection, etc.
Including within the egg, before they are even born. Some forms of hybrid are more vulnerable to meningitis, specifically vittikins, and any hybrid of barbata, nullarbor or minor. Mitchells (yes a minor species) has been the lowest percentage after Vitticeps.
Drysdale river dragon unknown.
It has been difficult to study this particular issue with any species, but due to blood testing and microscopy we are finally beginning to understand bearded dragons. A lot of these things were found in the past through necropsy.
As a note ADV presents almost identically to Hepatitis, both visually and microscopically.
Cancer Is extremely common in middle aged to older bearded and has NOT been an identified cause of meningitis in the species pogona.