Pituitary Tumors
The second most common type of tumor in female rats 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%.
As the tumor grows it presses on the brain and eventually causes neurological impairment. Symptoms may appear slowly, over a period of a few days or a few weeks, or quickly. These tumors are highly vascular and in some cases they can hemorrhage, which can cause acute severe symptoms, such as paralysis, seizures and death. It also seems that a slight hemorrhage from the tumor can cause symptoms that later clear up.
For a typical pituitary tumor causing a slow onset of symptoms, the usual first symptom is a loss of coordination, followed by some loss of function of the arms and legs and mouth. Sometimes the rat is hyperactive, and she may walk in circles and run into objects. Some rats with pituitary tumors become very infant-like and cuddly and must be hand-fed.
One symptom that is common with a pituitary tumor is a quite distinctive posture: first the front, then the hind legs are held out stiffly forward and cannot be flexed by the rat. When you pick the rat up, the arms and legs will often be held forward, although sometimes the hands are curled. Another behavior that is common is when a rat butts her head up against your hand when you pet her.
Neurological symptoms, including seizures, a head tilt, circling, and lethargy, can also have other causes, such as a stroke, toxins, encephalitis, or an inner ear infection (head tilt). Fortunately, the recommended treatment for neurological impairment from any cause is with prednisone at 1 mg/lb twice a day and an antibiotic. These can reduce the size of a pituitary tumor and temporarily relieve the symptoms, but the treatment doesnât always help. In one case, prednisone did not help but dexamethasone did help.
If the treatment is going to help, you should see improvement in the symptoms within a week. The treatment then needs to be continued for the rest of the ratâs life. I know of a few cases where this treatment was able to give a good quality life to the rat for 3 to 10 months. If despite treatment the rat is no longer able to eat, she should be euthanized.
