Case presentation
An 18 month old female neutered Great Dane presented with an acute history of generalised seizures. She had been off colour for the previous two weeks. Physical examination revealed a palpable mass over the left caudal ribs. Neurological examination was initally unremarkable, but after a second seizure, she was temporarily blind and disoriented.

Question: What is your neurolocalisation?
Question: What are your most likely differentials?

For further investigations, imaging and the answers to these questions, please scroll down the page.
















Further investigations
Routine haematology showed a marked neutrophilia. Ultrasonography of the rib mass revealed the mass extended some way internally. MRI was performed of the brain to attempt to identify the cause of the seizures. This revealed a mass with a ring pattern of contrast enhancement in the right forebrain, with associated oedema (fig 1). CSF analysis showed a mild pleocytosis. MRI of the thorax also helped identify the size and invasiveness of the mass (fig 2). Trucut biopsies were taken of the thoracic mass, which revealed an undifferentiated sarcoma, thought possibly to be a rhabdomyosarcoma. The brain mass was presumed to be a metastasis of this tumour. Palliation with phenobarbitone was commenced, but unfortunately the outlook for this dog was poor.

Fig 1: T1 + gadolinium transverse MRI scan showing a ring enhancing mass in the right forebrain

Fig 2: T1 weighted MRI of soft tissue mass over the lateral thorax

Most dogs that experience their first seizure aged between 6 months and 6 years, which are neurologically normal interictally, do not have abnormalities diagnosed on further investigations and are diagnosed with idiopathic epilepsy. One paper looking at MRI findings in dogs with epilepsy found significant MRI abnormalities in only 1/46 dogs under 6 years of age, compared with 8/30 dogs over the age of 6 (Smith, Talbot & Jeffery 2007). It was somewhat surprising to find a brain tumour in a dog this young. This tumour was presumed to be secondary to the mass in the thoracic wall.  In one paper looking at secondary intracranial neoplasia in dogs, 29% were haemangiosarcomas, 25% were pituitary tumours, 12% were lymphomas and 12% were metastatic carcinomas (Snyder et al 2008).

Smith, Talbot & Jeffery (2007) Veterinary Journal 176, 320
Synder et al (2008) JVIM. 22, 172

Question. What is your neurolocalistion?
Answer. Seizures suggest forebrain disease. Blindness can be caused by ophthalmological disease, and by lesions in various areas of the nervous system, but in this case is likely a post-ictal change as it was temporary.

Question. What are your most likely differentials?
Answer. A dog of this age with seizures is most likely to be suffering from idiopathic epilepsy. Other possibilities include metabolic disease such as hepatic encephalopathy, immune-mediated and infectious disease, and less likely, neoplasia.

First published: Tue, Mar 15 2011