ABSTRACT.-Togni M., Panziera W., Souza T.M., Oliveira Filho J.C., Mazzanti A., Barros C.S. In the last 20 years, an unknown neurological disease affected cat populations in the Western Border Region of the State of Rio Grande do Sul, Brazil. The onset of the disease was characterized by tail paralysis, followed by progressive paraparesis in the pelvic limbs, difficulty in ambulation and proprioceptive ataxia. After long prolonged clinical courses (12-24 months), when then affected cats became severely paraparetic and start to develop pressure sores do to decubitus, they were destroyed by the owners. At necropsy there were variable degrees of skeletal muscle atrophy of the pelvic muscles and some degree of reddening of the meninges at the level of T10-L7, due to the presence of a myriad of small blood vessels, as a typical varicose lesion that resembled a vascular hamartoma. Histologically, such lesions consisted of distension of the subarachnoid space due to a collection of dilated, blood-filled, tortuous blood vessels the lumina of which were occasionally partially or completely occluded by thrombi. Those varices were randomly surrounded by a lymphocytic or granulomatous inflammatory infiltrate with small foci of mature eosinophils. In the lumina of these varicose venules cross and longitudinal sections of nematode parasites could be observed. Based on the morphology of these parasites, in their anatomical localization (meningeal blood vessels) and in the species (cat) affected the nematode was identified as Gurltia paralysans. This paper describes detailed aspects of the epidemiology, clinical disease and pathology of this intriguing feline myelopathy and the definitive diagnosis of the condition: Feline crural parasitic paraplegia, a disease first described in Chile in the 1930's and now, for the first time, in Brazil. RESUMO.-Nos últimos 20 anos, uma doença neurológica desconhecida acometeu populações de gatos da Região da Campanha do RS e tornou-se um desafio diagnóstico para os veterinários locais. Os gatos afetados desenvolviam inicialmente paralisia da cauda, seguida de paraparesia progressiva nos membros pélvicos, alteração da marcha, posição plantígrada e ataxia proprioceptiva. Após longos períodos de evolução clínica (12-24 meses), quando se tornavam marcadamente paraparéticos e começavam a apresentar escaras de decúbito, eram sacrificados pelos proprietários. Na necropsia, demonstravam graus variados de atrofia dos músculos pélvicos e algum grau de avermelhamento das meninges entre T10 e L7, devido à presença de miríades