Increased Intracranial Pressure
History. You examine a 9-year-old female boxer dog. The owner states that recently the dog has seemed more drowsy than usual and had what you recognize to be a generalized tonic-clonic seizure the preceding night.
Clinical Examination. Physical examination of the dog reveals a hard, nodular mass of the mammary gland. Other deficits are referable to the nervous system and are characterized by apparent drowsiness and confusion and by a deficit of the proprioceptive positioning reaction of the right front and right rear legs. Lateral radiographs of the chest reveal metastatic, neoplastic lesions in the lungs. The CSF pressure, as measured with a manometer through a needle placed in the cisterna magna, is 310 mm CSE ( The normal CSF pressure in dogs is less than 180 mm CSF.)
Comment. This is a typical case of a dog with a neoplasm of the mammary gland that has spread first to the lungs, which contain the first capillary bed filter encountered by tumor cells as they invade the venous system, and then to the brain. As the tumor mass increases within the fixed encasement of the cranial vault, CSF and other fluid volumes are displaced. Some loss of myelin may compensate temporarily for the expanding intracranial mass, but eventually the expanding tumor, encased in the skull, causes an increase in intra-