Perhaps I was too hasty; if your new vet is truly interested in treating exotics then he may deserve more chances...so long as he proves open to learning.
Of course he's right that rats can get brain tumours other than PT - but If he had more experience with rats, he would probably weigh the fact that PTs are by far the most common brain tumour found in female rats. And some of Snowy's specific symptoms (e.g. the rigid forearms) are highly indicative of PT. Success with cabergoline is far from assured in any event. But it may offer the best prospect of extending Snowy's life beyond a few weeks. (Remember that steroids alone usually buy very limited time where any fast-growing tumour is involved.)
Your vet might understandably not know about the use of cabergoline in treating rat PTs; and while it's unfortunate that he didn't glance at the Rat Guide info you presented, he might have felt pressed for time. Can you send short emails to this vet? He might be more inclined to digest short blurbs selected from the Rat Guide, such as the following bit from the PT article
http://ratguide.com/health/neoplasia/pituitary_tumor.php:
Recommended treatment is geared for comfort and the reduction of clinical signs, and may include the following:
- Cabergoline or bromocriptine, a dopamine receptor agonist, that inhibits prolactin secretion; thereby reducing circulating prolactin in the blood stream and reducing tumor size. Depending on when initiated in the disease process may extend life/quality time from 3- 6 months.
- Since it has been shown that significant shrinkage of the tumor may take a number of weeks following the initiation of a dopamine receptor agonist; vets may wish to treat with a corticosteroid (e.g.,dexamethasone or prednisone or prednisolone) on a more extended reduction schedule to address brain swelling, until tumor reduction is significant enough to alleviate clinical signs.
- In the event long-term corticosteroid (e.g. prednisone, prednisolone,or dexamethasone) therapy is instituted, given the commonality of chronic mycoplasma infections in the pet rat population, it is advised to consider including broad-spectrum antibiotics such as Baytril and doxycycline.
You might also quote an article by the much-respected rat expert Debbie Ducommun to help demonstrate the high incidence of PT tumours in female rats. From
http://www.ratfanclub.org/tumors.html :
The second most common type of tumor in female rats (next to mammary tumours)
is an adenoma (benign tumor) of the pituitary gland, which lies beneath the brain. In fact, this is probably the third most common cause of death in female rats. The incidence in my unspayed female rats has been 20% and in my male rats 7%.
By all means start Snowy on the prednisolone as recommended, but do keep a watchful eye for signs of respiratory infection as the days pass. Your doctor's chosen dosage (0.5 mg/day) seems well within the Rat Guide's recommended range of 0.25-1.0 mg/lb per day, given that Snowy weighs close to one pound. Meanwhile, I hope you can find a way to access cabergoline and a good antibiotic in order to give Snowy the best shot possible.