Any dog presenting with seizures, sudden vision problems or other signs of abnormal mentation or behavior will be given a thorough physical examination and a complete neurological work-up. Of course, a complete history of the dog’s symptoms and progression of the behavioral abnormalities will be taken from the owner. Most general veterinary practitioners can skillfully perform a basic neurological examination. In many cases, how the dog presents to the veterinarian, together with the history and results of the physical and neurological examinations, will enable the veterinarian to localizer the problem to the brain, and maybe even to a particular location within the brain. A urinalysis and routine blood work, including a complete blood count and serum biochemistry profile, can be extremely useful to rule out causes of the dog’s symptoms that may not be neurological in nature. Survey radiographs (X-rays) and ultrasound of the chest and abdomen may help to identify any primary masses in those areas that may have metastasized to the brain. Skull X-rays are usually not very helpful in identifying primary brain tumors, but they may disclose masses in adjacent areas, such as the nasal cavities or nearby bone that possibly metastasized into brain tissue.
More advanced diagnostics include computed tomography (CT scan) and magnetic resonance imaging (MRI). These procedures are only offered at certain specialized veterinary facilities and at veterinary teaching hospitals. They can provide extremely accurate identification of the presence, location and size of masses in the brain and elsewhere. The attending veterinarian can also take a tap (sample) of the dog’s cerebrospinal fluid (CSF), which is the fluid that coats the brain, spinal cord and associated tissues. The results of laboratory analysis of CSF can identify inflammation, infection and sometimes the presence of tumor cells. The CSF tap must be done very carefully – usually only after advanced radiographic imaging such as a CT scan and/or MRI is performed – to avoid any adverse consequences associated with rapid changes in the pressure inside the brain (intracranial pressure) that may result from withdrawing a sample of cerebral spinal fluid.
The most (and perhaps only) definitive way to diagnose the type of tumor in the brain is by doing a biopsy. This is not commonly done, due to the cost and invasiveness of the procedure. However, it is considered to be the gold standard and probably should be done or at least considered before any therapy is considered.