One can suspect the presence of a brain tumour as cause for neurological abnormalities through the characteristics of the dog, his anamnesis and neurological signs. However, other causes can also lead to a similar presentation (inflammations, degenerative disease). To be sure of the cause, it is necessary to visualize it.
Clinical and neurological examination
During the neurological examination the dog can be checked for neck pain and abnormalities in the way the paws are repositioned.
Blood and urine analysis
The analysis of blood and urine give information about (problems with) the general state of the dog.
In 23% of dogs with a brain tumour there are concomitant tumours that are not related to the brain tumour. To find these, it is advised to do an ultrasound of the abdomen.
One can visualize metastases (when the tumour is large enough) in the lungs or a second tumour when taking radiographs from different angles. It is rare that the tumour (meningioma) causes a local enlargement of the bone or even bone destruction.
Radiographs of the skull do not provide useful information in case of brain tumours.
MRI is the preferred visualization technique for brain tumours. On these images it is possible to make the distinction between a meningioma and a glioma (the meningioma will rather displace the brain tissue, absorbs contrast die in a uniform way, and has a clear delineation, whereas a glioma is more likely to penetrate the neighboring brain tissue, absorbs the contrast die in a non-uniform way, and often does not have a clear delineation). This being said, there are exceptions to the rule. In a study with MRI, in about 70% of cases the tumour type could be predicted via MRI. The definitive diagnosis is possible via a tissue sample (that can only be taken after the possible biopsy location has been carefully determined).
It is not yet clear what the importance or the need is to examine cerebrospinal fluid in dogs with a brain tumour. The cerebrospinal fluid is often abnormal, but does not provide specific information regarding the tumour. If a tumour of the brain blood vessels (choroid plexus tumour) is present, the cerebrospinal fluid can indicate whether it’s benign or malignant. Tumour visualization (via MRI) is always advised before performing a punction of the cerebrospinal fluid as this can represent a risk. When the pressure within the skull is elevated, punction of the cerebrospinal fluid can lead to a sudden loss of pressure which can cause a shift in the location of a part of the tumour and even lead to death.