HISTORY

A 8-months-old, male, Bernese mountain dog was referred due to previous seizures at six months of age. Clinical signs, results of ancillary tests, and pathological findings are described. The owner reported pain manifestation on head movements. Previously, at four and five months of age, unilateral epistaxis episodes were presented. The dog suffered two generalized seizures (tonic-clonic convulsions with autonomic disturbances) at six months of age. Physical examination was normal. At neurological examination low proprioceptive deficit on right hindlimb and mild cervical pain were detected. Differential diagnostic included inflammatory-infectious disease, congenital abnormality, degenerative disorder and neoplasia. Complete blood count, biochemistry profile, serum bile acids, ammonia levels, TT4/TSH levels, urinalysis, and coagulation profile were normal. Brain magnetic resonance imaging was performed. On T1-weighted images, there was a 5 cm heterogeneous hyperintensity mass, and hydrocephalus (obstructive hydrocephalus). The mass was located between left olfactory bulb, basal nuclei and diencephalon. There was a vasogenic edema in left hemisphere evident on T2-weighted images. After gadolinium intravenous administration there was a slight enhancement of the mass. A presumptive diagnosis of neoplasia or congenital abnormality was made, and the dog was euthanized due to poor prognosis. Histologically the lesion was classified as a meningioangiomatosis.

DISCUSSION

Meningioangiomatosis (MA) is a rare vascular malformation of the central nervous system. It is a benign, focal proliferation of blood vessels and meningothelial cells in brain and leptomeninges. There are only a few reports of MA in dogs. Most of them described the lesion as a congenital vascular malformation, but in some cases neoplastic cells are present. In this dog there was a benign proliferation of spindle-shaped cells arranged in whorls around small blood vessels. Proliferating meningothelial cells infiltrated the brain and formed perivascular cuffs, those cells stained positively for vimentin and S-100. Necrotic areas were observed but any neoplastic cells or mitotic figures were detected.

The pathogenesis is uncertain but probably MA is a vascular malformation that is later accompanied by meningioendothelial cell proliferation without evidence of malignancy. Other hypothesis refers to a congenital hamartomatous malformation. In human medicine there are two populations of patients with MA: symptomatic children and young adults who present headaches or seizures, and asymptomatic individuals. In symptomatic patients, complete or partial resection can be curative.