Figure 1: 6-years-old, female Boxer dog. 3D reconstruction on an intracranial meningioma compressing the cerebellar bulb. A: intracranial meningioma (arrow) presenting a well-delimited mass with peritumoral edema. B: intracranial meningioma (arrow) compressing the cerebellar bulb.
On ophthalmologic examination of the remaining eye, it was observed slight opacity of the lens, no blink to threat reflex and presence of photopupillary reflex without evidence of any change on the fundus examination by direct ophthalmoscopy. Complete blood count(CBC), hepatic and renal biochemical profile (ALT, AST, FA, urea and creatinine), electrocardiography and CT scan of the orbits and skull were tests requested. Both CTs were performed in helical device ESLCINT SELECT SP, with axial and coronal slices with 2 mm thick, using intravenous non-ionic contrast.
The subjects were sedated for the CT, using an association of pethidine (2mg/kg) and acepromazine (0.05 mg/kg) intramuscular (IM) injection and 10 mL of iodinated contrast injected intravenously (IV). The subject 1 showed a significant increase of the cerebrospinal fluid (CSF) within the left and right lateral ventricles. The cortical sulci and basal cisterns were compressed due to the increase of CSF within the lateral ventricles. The images were suggestive of hypercaptant mass (Figure 2) in the cerebellum evidenced by intravenous contrast, affecting and compressing the cerebellar bulb, the peribulbar cistern, the amygdala, pons, the cerebellar peduncle, rostral lunate lobule, the simple lobe and right quadrangular lobe, also involving the cerebellar tonsil and fourth ventricle. It was noted protrusion of the cerebellum in consequence of the increase in volume caused by the neoplasia.
Due the difficulty of performing intracranial biopsy to establish the histological classification of the tumor, it was decided to use lomustine in the chemotherapy protocol because of the drug’s ability to pass the blood-brain barrier. Chemotherapy protocol was established, consisting of lomustine (60 mg/m2) every 21 days, orally and 1 mg/kg of prednisone every 24 hours throughout the treatment. The subject showed no clinical alterations by the use of chemotherapy drugs and survival of 180 days. During necropsy, we could verify the presence of 2x2x2xcm node located in the cerebellum base, causing compression of adjacent structures. Histopathology was compatible with meningioma.The subject 2 revealed a neoplastic mass in the right orbital region, invading the orbital fissure and optic nerve, following visual tract through the intracranial portion of the optic nerve, with invasion of the optic chiasm. The tumor was compressing the encephalic mass. After diagnosis, a chemotherapy protocol was established, consisting of lomustine at a dose of 60 mg/m2 every 28 days, orally prednisone at 1 mg/kg, every 24 hours. Laboratory tests were repeated every 28 days, and it was observed a decrease in leukocytes and platelets lineage, three weeks after the first dose of lomustine, and significant increase in ALT after the third dose. A CT performed after four months of the initiation of chemotherapy, showed an increase of the intracranial tumor and also a process of invasion of the left optic tract. After 240 days of treatment, the animal died and her owner chose not to conduct necropsies.