A Review of Fibrocartilaginous Embolic Myelopathy and Different Types of Peracute Non-Compressive Intervertebral Disk Extrusions in Dogs and Cats

Abstract

This review discusses terminology, pathological, clinical, and magnetic resonance imaging (MRI) findings, treatment, outcome, and prognostic factors of fibrocartilaginous embolic myelopathy (FCEM), acute non-compressive nucleus pulposus extrusion (ANNPE), and intradural/intramedullary intervertebral disk extrusion (IIVDE). FCEM, ANNPE, and IIVDE have a similar clinical presentation characterized by peracute onset of neurological dysfunction that is generally non-progressive after the initial 24–48 h. Differentiating between these conditions can be challenging, however, certain clinical and imaging findings can help. FCEM can occur in both adult and immature animals, whereas ANNPE or IIVDE have been reported only in animals older than 1 year. In dogs, ANNPE and IIVDE most commonly occur in the intervertebral disk spaces between T12 and L2, whereas FCEM has not such site predilection. In cats, FCEM occurs more frequently in the cervical spinal cord than in other locations. Data on cats with ANNPE and IIVDE are limited. Optimal MRI definition and experience in neuroimaging can help identify the findings that allow differentiation between FCEM, ANNPE, and IIVDE. In animals with ANNPE and IIVDE, the affected intervertebral disk space is often narrowed and the focal area of intramedullary hyperintensity on T2-weighted images is located above the affected intervertebral disk space. In dogs with ANNPE signal changes associated with the extruded nucleus pulposus and epidural fat disruption can be identified in the epidural space dorsal to the affected intervertebral disk. Identification of a linear tract (predominantly hyperintense on T2-weighted images, iso to hypointense on T1-weighted images and hypointense on T2*-weighted gradient recall echo images) extending from the intervertebral disk into the spinal cord parenchyma is highly suggestive of IIVDE. Treatment of FCEM and ANNPE is conservative. Dogs reported with IIVDE have been managed either conservatively or surgically. Prognostic factors include degree of neurological dysfunction (particularly loss of nociception) and disease-specific MRI variables.

Diagnóstico e tratamento do embolismo fibrocartilaginoso em um cão de pequeno porte: Relato de caso

“…Em cães, esta doença acomete principalmente animais adultos e de grande porte; contudo, assim como no presente caso, também tem sido encontrada em cães de raças de pequeno e médio porte com freqência relativa na raça schnauzer e em cães condrodistróficos. Quanto a fisiopatologia do embolismo fibrocartilaginoso (EFC) ainda é incerto como o êmbolo histologicamente compatível com o núcleo pulposo do disco intervertebral chega nos vasos da medula espinhal (De Risio and Platt, 2010, De Risio, 2015, Garavito-Bernal and León-Torres, 2015. As seguintes terorias são propostas:…”

“… Hérnia do núcleo pulposo com exposição da vasculatura do corpo vertebral, por meio de manipulação direta durante procedimentos cirúrgicos ou traumatismos dentro da porção esponjosa do corpo cervical, e se observa somente em humanos (De Risio and Platt, 2010, De Risio 2015, Garavito-Bernal and León-Torres, 2015.…”

“…Um aumento repentino da pressão intradiscal que exceda a pressão arterial pode facilitar a penetração de fibrocartilagem do núcleo pulposo dentro dos vasos sanguíneos do disco degenerado, chegando à medula espinhal (De Risio and Platt, 2010, De Risio, 2015, Garavito-Bernal and León-Torres, 2015.…”

“… Persistência de vasos remanescentes embrionários dentro do núcleo pulposo (De Risio and Platt, 2010, De Risio, 2015, Garavito-Bernal and León-Torres, 2015, De Risio, 2014.…”

“… Desenvolvimento de uma metaplasia fibróide do núcleo pulposo, onde ocorre a perda da viscoelasticidade do anel intervertebral em cães adultos e condrodistróficos com possível ruptura parcial do anel fibroso e uma neovascularização que comunica o núcleo pulposo com a artéria espinhal ou artérias radiculares (De Risio and Platt, 2010, De Risio, 2015, Garavito-Bernal and León-Torres, 2015 Risio and Platt, 2010, De Risio, 2015, GaravitoBernal and León-Torres, 2015.…”