23 de jul de 2009

Paraplegia aguda com perda da percepção de dor profunda em cães: revisão de literatura

Autores: Bruno Martins Araújo, Mônica Vicky Bahr Arias, Eduardo Alberto Tudury
Revista Clínica Veterinária, n.81, 2009
Resumo: A paraplegia aguda com perda da percepção de dor profunda indica lesão medular grave, capaz de lesionar fibras bastante resistentes à lesão e localizadas profundamente na medula espinhal. Várias enfermidades são consideradas no diagnóstico diferencial de cães com essa alteração, em que na maioria dos casos, a lesão ocorre por extrusão de disco intervertebral, fraturas/luxações vertebrais e embolismo fibrocartilaginoso. O diagnóstico baseia-se na resenha clínica, na anamnese, na evolução aguda dos sinais clínicos e nos resultados do exame neurológico e de exames complementares, como imagens da coluna vertebral e da medula espinhal. O tratamento deve ser direcionado na prevenção da destruição neuronal bioquímica, na descompressão da medula espinhal e/ou na estabilização da coluna vertebral. O prognóstico varia de reservado a desfavorável, dependendo da etiologia da lesão e das opções de tratamento disponíveis.
Abstract: Acute paraplegia with loss of deep pain perception (DPP) indicates severe spinal injury, capable of damaging resistant fibers that are deeply situated in the spinal cord. Several conditions are considered for the differential diagnosis of dogs with this alteration. In most cases, the lesion occurs by intervertebral disk extrusion, vertebral fractures/luxations and fibrocartilaginous embolism. The initial mechanisms of acute spinal lesion correspond to the primary injury. They occur at the moment of injury, with the partial or complete rupture of nervous tissue and the loss of medullary tissue, which are considered untreatable lesions. Afterwards, a series of vascular and metabolic alterations take place, which constitute the events referred to as secondary lesions. The diagnosis is based on patient signalment, history, on the acute evolution of clinical signs and on the results of the neurological exam and complementary exams, such as imaging of the vertebral column and the spinal cord. The treatment must be directed towards preventing biochemical neuronal destruction, with the use of neuroprotectors (substances which prevent or limit the mechanisms of secondary injury to the spinal cord). Corticosteroids have been the most frequently employed drugs in trauma and decompression of the spinal cord, both in animals and human beings. They are frequently associated with gastrointestinal complications like hemorrhage, pancreatitis, ulcers and/or gastric perforations. The medical management of the intervertebral disk disease (IVDD) with loss of DPP still consists, for some authors, in the administration of methylprednisolone sodium succinate (MPSS) during the eight hours following trauma, and in the referral for emergency decompression. Surgical treatment of these animals must be readily arranged, as it is considered a neurological emergency, and must entail: decompression of the spinal cord (hemilaminectomy or laminectomy), removal of the disk material extruded into the vertebral canal, decrease of medullary edema and ischemia, macroscopic evaluation and intraoperatory irrigation of the spinal cord. Animals that present with spinal trauma and suspected vertebral instability must be placed in a firm surface to avoid movement and additional injury to the spinal cord, while proper treatment is initiated. Hypotension must be controlled through the use of fluids, and followed by treatment with MPSS as soon as possible, within the first eight hours after trauma. Surgery is indicated for cases presenting with vertebral instability, in which animals must be evaluated through mielography or magnetic ressonance to detect evidence of spinal cord transection or extensive necrosis. If none of these alterations are present, the surgeon may perform a hemilaminectomy, to decompress (in cases where there is extradural compression) and identify a possible progressive hemorrhagic myelomalacia (PHM). If the spinal cord is intact, surgical fixation takes place. There is no specific treatment for FCE, nor is there evidence that any treatment possesses more value than the general nursing care for patients that remain recumbent. The prognosis varies from guarded to unfavorable, depending on the etiology of the lesion and on the available treatment options. In IVDD, the main factor to be considered is the presence or absence of DPP. Among dogs without DPP, the main parameters to be evaluated are speed of occurrence and duration of analgesia, and the recovery time frame to pain perception. Animals which have lost deep pain perception after suffering exogenous vertebral trauma usually present an unfavorable prognosis for recovery, because in this type of injury, the lack of nociception is frequently associated with the transection of the spinal cord or to the rapid onset of PHM. For dogs suffering medullary infarction due to FCE, prognosis in terms of recovery of function is very unpredictable, reflecting the varying severity of the characteristic lesion of this disease. It is important to point out that some animals manage to regain the ability to walk without recovering DPP. In these animals, the occurrence of involuntary motor activity may indicate the development of spinal cord reflex walk, which originates from the mechanism of neural plasticity and the formation of local circuits 53. Paraplegic animals need intensive nursing care during their recovery period or during their entire life (in cases where there isirreparable spinal cord injury). Attention must be given to the emptying of the bladder and intestines, by means of abdominal massage or urinary catheter, and the use of an appropriate diet; to the prevention of skin sores and decubitus ulcers, by constantly cleaning the skin of urine and feces and changing position every four hours; to the treatment of trauma related wounds (usually in case of car accidents) and to the use of passive and active physical therapy, to avoid muscle atrophy and contracture and loss of articular and neuromuscular function.
Resumen: La paraplejia aguda con pérdida de la percepción del dolor profundo indica lesión medular severa, capaz de lesionar fibras muy resistentes a lesiones y situadas profundamente en la médula espinal. Varias enfermedades deben ser consideradas en el diagnóstico diferencial de esta alteración, que en la mayoría de los casos, tienen lesiones por extrusión del disco intervertebral, fracturas / dislocaciones vertebrales o embolismo fibrocartilaginoso. El diagnóstico se basa en la reseña, la anamnesis, los signos clínicos agudos, los resultados del examen neurológico y pruebas adicionales como la obtención de imágenes de la columna vertebral y médula espinal. El tratamiento debe ser dirigido a la prevención de la destrucción neuronal bioquímica, la descompresión de la médula espinal y/o en la estabilización de la columna vertebral. El pronóstico varía de reservado a desfavorable, dependiendo de la etiología de las lesiones y las opciones de los tratamientos disponibles.
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