Topic:Neurological Diseases
Neurological diseases in horses encompass a range of disorders affecting the central and peripheral nervous systems. These conditions can arise from various etiologies, including infectious agents, genetic predispositions, trauma, or metabolic imbalances. Common neurological diseases in horses include equine protozoal myeloencephalitis (EPM), equine herpesvirus myeloencephalopathy (EHM), and cervical vertebral stenotic myelopathy (CVSM), also known as wobbler syndrome. Clinical signs associated with these diseases may include ataxia, weakness, altered gait, and changes in behavior or mental status. Diagnosis typically involves a combination of clinical evaluation, imaging techniques, and laboratory testing. This page compiles peer-reviewed research studies and scholarly articles that investigate the pathophysiology, diagnostic approaches, and treatment options for neurological diseases in equine populations.
Equine degenerative myeloencephalopathy. This article discusses the history and signalment, clinical signs, differential diagnosis, pathology, etiology and pathogenesis, and treatment and prevention of equine degenerative myeloencephalopathy.
Indication and use of electrodiagnostic aids in neurologic disease. Electrodiagnostic aids, electromyography, auditory brainstem response testing, and electroencephalography are extensions of the neurologic examination and provide valuable information about the nervous system. This article discusses the use and interpretation of electrodiagnostic aids in equine neurology as well as the equipment that is employed. It is hoped that with a better understanding of the available electrodiagnostic aids, they will come into greater use.
Neurologic examination of the horse. Methodology for the neurologic examination in the equine species is described. Information is organized to assist the reader in defining neurologic deficits and in localizing lesions to the major subdivisions within the central or peripheral nervous system. Numerous examples of deficits are presented to assist the reader in recognition of common neurologic disease states.
Head tilt in horses. Head tilt in the horse is commonly a sign of either central or peripheral vestibular disease. The confirmation of vestibular disease is based on physical findings, including results of cranial-nerve function evaluation and observation of stance, posture, and gait. Further localization is made by ancillary tests such as cerebral spinal fluid analysis, electrodiagnostic testing, and radiography. The normal anatomy and physiology of the vestibular system, the abnormal clinical signs demonstrated during physical examination, and the various etiologies are discussed.
Equine protozoal myeloencephalitis. Equine protozoal myeloencephalitis (EPM) is a disease that produces neurologic signs of brain or spinal cord dysfunction. The causative organism is believed to be a Sarcocystis species of protozoa. A definitive diagnosis can only be made on histopathology of affected spinal cord or brain. No preventive measures or documented treatment is available at this time for suspected cases of EPM.
Central nervous system trauma. Traumatic injury to the central nervous system causes immediate damage and sets in motion a complex series of pathophysiologic events that result in further neuronal injury. This secondary damage seems to be related to changes in blood flow and pressure on a systemic, regional, and microvascular level. Currently, there is evidence that these changes are, in part, mediated by endogenous opioids and arachidonic acid metabolites, namely thromboxane A2. Medical management is generally designed to intervene at one or more stages in this secondary cascade of events. Further research should lead us t...
Cerebellar abiotrophy. Cerebellar abiotrophy is a degenerative condition of Arabian horses that produces signs of head tremors and ataxia. Affected foals demonstrate clinical signs between the time of birth and 6 months of age. The condition is untreatable, although some animals have reportedly improved to varying degrees. The disease is believed to be inherited; however, definitive evidence is lacking at this time.
Convulsive and allied syndromes of the neonatal foal. This article discusses the clinical signs, etiology, management, and prognosis for the neonatal foal afflicted with a convulsive or allied syndrome.
Seizures in the horse. This article discusses the diagnosis and treatment of extracranial, intracranial, and idiopathic seizures.
Cervical vertebral malformations. Cervical vertebral malformations are recognized clinically when they result in spinal cord compression causing neurologic deficits. Confirmation of diagnosis is based on radiographic and myelographic evidence of cord compression. Medical therapy is not usually successful. Several successful surgical treatments are described.
Medical management of spinal cord disease. In spinal cord disease of horses, a complete history, neurologic examination, and adjunctive diagnostic procedures are very helpful in establishing a tentative diagnosis; however, a definitive diagnosis may be difficult or impossible to establish antemortem. Medical management should be initiated with full consideration of possible etiologies and knowledge of the effects and consequences of medical therapies. This article discusses the drugs commonly used in the management of spinal cord disease and the rationale for their use.
Equine herpes myeloencephalopathy. The neurologic form of EHV-1 infection appears to be the result of central nervous system infarction caused by vasculitis, which is initiated in endothelial cells of small blood vessels. The etiologic agent is equine herpesvirus-1, subtype 1. There is some evidence to suggest that the neurologic form of the disease actually results from reactivation of a previous infection. Whether the vasculitis that causes the central nervous system injury is the direct result of the infection or an immune response to the infection has not been determined. The clinical signs are rapid in onset, nonprogressiv...
Examination of cerebrospinal fluid in the horse. The examination of cerebrospinal fluid (CSF) is often part of the diagnostic work-up of a patient exhibiting signs of disease involving the central nervous system. Awareness of the capabilities and limitations of these laboratory tests is important in assessing the benefit-to-risk ratio of performing such procedures. Collection of CSF is a relatively simple procedure, and together with a thorough history, physical examination, and other diagnostic tests, may be a valuable aid in arriving at a diagnosis or prognosis.
Equine viral encephalomyelitis in Canada: a review of known and potential causes. Rabies, equine herpesvirus type I, and eastern and western encephalomyelitis viruses, known causes of equine neurological disease, are reviewed with emphasis on epidemiology, pathogenesis, clinical signs, and diagnosis.Several arboviruses known to be active in Canada and capable of producing neurological disease in humans (Powassan, St. Louis encephalitis, snowshoe hare, and Jamestown Canyon viruses) are discussed as potential causes of encephalomyelitis in horses.
Carcinoma of the mammary gland in a mare. A 17-year-old Quarter Horse mare developed rapidly progressive, bilateral, firm enlargements of both mammary glands, ventral abdominal edema, dyspnea, and neurologic signs. The horse was euthanatized, and a carcinoma of the mammary gland was diagnosed at necropsy. Microscopically, normal glandular parenchyma was replaced by neoplastic nodules, and the tumor had metastasized to most visceral organs and throughout the musculoskeletal and central nervous systems. The tumor had a solid pattern, with microglandular differentiation, and numerous syncytial sheets.
The pathogenesis of equine laryngeal hemiplegia–a review. Recent research on the muscular and nervous changes which occur in idiopathic equine laryngeal hemiplegia has indicated that many of the traditional concepts of the aetiology of this disease are erroneous. In light of the new knowledge gained, the various predispositions and possible causes of laryngeal hemiplegia are discussed, and it is suggested that the underlying mechanism of axonal damage in this neuropathy of horses may be related to abnormal energy metabolism in the axon.
Neurological disease and lipofuscinosis in horses and sheep grazing Trachyandra divaricata (branched onion weed) in south Western Australia. A severe paretic syndrome accompanied by intense neuronal lipofuscinosis is described in sheep and horses exposed to Trachyandra divaricata. This is a newly recognised toxic hazard for grazing livestock in the coastal region of the south west of Western Australia. Animals appear to become affected over a period of weeks when summer conditions induce a scarcity of alternative feed. The disease is discussed in relation to its recent documentation in South Africa where the plant is indigenous.
Equine degenerative myeloencephalopathy: a vitamin E deficiency that may be familial. Two horse farms, on which there was a high incidence of proven and suspected equine degenerative myeloencephalopathy (EDM), were studied. Symmetric ataxia and paresis, along with laryngeal adductor, cervicofacial, local cervical, and cutaneous trunci hyporeflexia, characterized the syndrome. Serum vitamin E concentration reflected a deficient state in affected and unaffected horses on both farms when compared with selected reference groups and with published values. A high incidence of the disease was evident in offspring of two particular sires on one farm. Vitamin E supplementation resulted ...
[Neurological examination of the horse]. Neurological examination in equine practice, physiological findings and pathological disturbances are described. Because of the sizes of the horse the neurological examination is more difficult than in small animals. The examination of cerebrospinal fluid is a worthful completion and is able to refer to the etiology of a certain disease. The technique of the puncture of cerebrospinal fluid is described.
Use of an ELISA in the differential diagnosis of cauda equina neuritis and other equine neuropathies. In 27 potential neuropathies an enzyme-linked immunosorbent assay, using P2 preparations from either bovine or equine myelin, detected all cases of cauda equina neuritis in which there was caudal involvement. The test was of limited value in differentiating neuropathies involving only cranial or other peripheral nerves.
Meningocerebral hemangiomatosis resembling Sturge-Weber disease in a horse. A 3-year-old horse presented with intermittent generalized seizures of 2-month duration. During interictal periods, the horse appeared normal and a cause for the seizures could not be identified. Necropsy revealed opacity of the leptomeninges, covering most of one cerebral hemisphere along with thinning and collapse of the cortex in the ipsilateral pyriform lobe. Histopathology demonstrated leptomeningeal vascular proliferation and meningothelial hyperplasia. Prominent tortuous vessels of the gyri and sulci extended into some regions of the subjacent cortex, where there was neuronal loss, ecto...
Genetic studies of neuraxonal dystrophy in the Morgan. A naturally occurring disease condition, neuraxonal dystrophy, was identified in 27 male and 15 female Morgans, many of which were closely related. Five-generation pedigrees were constructed for 33 of these horses and were compared with those for 29 randomly selected age- and sex-matched Morgans. Their mean coefficient of inbreeding was not statistically different (P greater than 0.1, 1 tailed t test; P less than 0.001, median test). Breeding of 2 severely affected and 2 normal stallions to 2 severely affected, 3 mildly affected, and 6 normal mares produced 10 mildly affected, 8 suspect affect...
Dysplastic disease of the cerebellum of an adult horse. A 4-year-old horse was evaluated at the Colorado State University Veterinary Teaching Hospital for rapidly progressing cerebellar disease. Euthanasia was elected and at postmortem examination a proliferative mass encompassing the right side of the cerebellum was discovered. The lesion was characterized by large, convoluted, vascular folia and absence of the core of central white matter. Histologically, there was a diminution or loss of the internal granule cell layer, cavitation of the central white matter, and absence of Purkinje cells. The molecular layer was thickened with myelinated axons ...
Parasitic laryngeal papillomatosis in a horse. Papillomatous lesions intruding into the laryngeal airway were identified in an imported polo pony during a routine neurological examination for partial quadriplegia. Histological examination established a diagnosis of laryngeal besnoitiosis but it is unlikely that the laryngeal parasitism was associated with the cerebellar neuropathy which was also present.
Equine laryngeal hemiplegia. Part V. Central nervous system pathology. Evidence of long central nerve fibre degeneration (axonal spheroids) in the lateral cuneate nuclei was found in all eight Thoroughbreds affected clinically and subclinically with equine laryngeal hemiplegia, but in only one of six control animals. It was considered that these spheroids may signify a central nervous component of the disease process of laryngeal hemiplegia although until further investigations are performed no firm conclusions regarding the relationship of these findings with laryngeal hemiplegia could be made. Examination of the left and right nucleus ambiguus of clinical and s...
Equine laryngeal hemiplegia. Part IV. Muscle pathology. This study confirmed that neurogenic muscle pathology exists in intrinsic laryngeal muscles supplied by the recurrent laryngeal nerves in horses subclinically and clinically affected with laryngeal hemiplegia. An important additional observation was the occurrence in three out of four laryngeal hemiplegic horses of neurogenic muscle changes in a hindlimb muscle, the extensor digitorum longus, a muscle supplied by another long peripheral nerve. This finding suggests that a polynenropathy exists in laryngeal hemiplegic horses, and supports the classification of this disease as a distal axonopath...