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Topic:Nervous System
The nervous system in horses is a complex network responsible for transmitting signals between different parts of the body. It consists of the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which comprises nerves that extend throughout the body. The nervous system regulates various physiological processes, including movement, sensation, and the coordination of bodily functions. It plays a critical role in processing sensory information and initiating appropriate responses. This page compiles peer-reviewed research studies and scholarly articles that explore the structure, function, and clinical implications of the equine nervous system, including its role in behavior, response to stimuli, and neurological disorders.
Neuroaxonal dystrophy associated with vitamin E deficiency in two Haflinger horses. Neuroaxonal dystrophy and minimal diffuse degenerative myelopathy was diagnosed in two female full sibling, 1- and 2-year-old, Haflinger horses. Both animals developed slowly progressive ataxia from the age of 4 months. Clinical signs, which were more prominent in the hind legs, included hypermetria and dysmetria. Histological examination revealed neuroaxonal dystrophy characterized by spheroid formation, vacuolation, astrogliosis and lipofuscin pigment deposition in macrophages and neuronal perikarya. These changes were restricted to the gracilis and cuneate nuclei, nucleus of the solitary tr...
Quantitative and qualitative morphology of equine peripheral nerve: teased fibre studies. Single teased fibre studies were made on samples of the lateral palmar nerve from 16 horses of mixed age and size which had no evidence of neuromuscular disease. Significant proportions of abnormal fibres indicative of axonal degeneration/regeneration and demyelination/remyelination were identified. Measurements of internodal length and fibre diameter were made. Internodal length was shown to be related to fibre diameter, changes in this relationship being mainly influenced by the incidence of abnormal fibres rather than by the age of the horse. Information about the incidence of abnormal fibr...
Melanotic hamartoma of the hind brain in a riding horse. A 3 1/2-year-old bay gelding of the cob type showed nervous signs and coughing associated with breaking-in and exercise. At post-mortem examination, heavy melanin pigmentation of the meninges of the hind brain and the medulla was identified and, on histological examination, melanin-containing cells were found within connective tissue extending into the medulla. The lesion was considered to be a melanotic hamartoma.
Effects of indomethacin on neural and myogenic components in equine airway smooth muscle. Equine airway smooth muscle is innervated by vagal efferents and, in addition, displays spontaneous mechanical activity. The preparation thus appears to contain at least two discrete excitable components, the cholinergic neural elements and the smooth muscle membrane. Indomethacin (INDO), a cyclooxygenase (CO) inhibitor, exerts a considerable potentiation of function in this preparation. The latter may be effected indirectly, through loss of the inhibitory effect of endogenous prostaglandin E2 (PGE2) on neural acetylcholine release and through direct effects on smooth muscle of the generally a...
Dopamine in the cerebrospinal fluid of prepubertal and adult horses. Catecholamine concentrations (pg/ml) in the cerebrospinal fluid (CSF) of prepubertal (n = 9) and adult (n = 18) horses were determined by radioenzymatic assay. Norepinephrine was low or non detectable in all CSF samples. In contrast, measurable CSF dopamine concentrations were effected by age, reproductive status and exogenous steroid treatments. The concentration of dopamine in the CSF of prepubertal females (733 +/- 92) was greater (p less than 0.05) than the concentration in the CSF of prepubertal males (117 +/- 67). Prepubertal male horses which were treated with testosterone for 5 days (5...
A retrospective study of nineteen ataxic horses. A retrospective study of 19 ataxic horses admitted to the College of Veterinary Medicine of the University of Montreal during the period of January 1985 to December 1988 is presented. There were 11 cases of cervical vertebral malformation, four of equine degenerative myeloencephalopathy, two of equine protozoal myeloencephalitis, one each of vertebral osteomyelitis and intervertebral disc protrusion. The clinical diagnosis of ataxia in horses requires neurological, radiographic, myelographic, and laboratory examinations.
Further evidence for a central nervous system component in equine laryngeal hemiplegia. Evidence for a central nervous system component of the distal axonopathy associated with equine laryngeal hemiplegia was found in this survey of 33 horses (control, 15; subclinical, 8; clinical, 10). Significantly higher numbers of axonal spheroids were present in sections of the lateral cuneate nuclei in layngeal hemiplegic horses than in those unaffected by the disease.
Australian Stringhalt–epidemiological, clinical and neurological investigations. An investigation of 78 cases of typical Australian Stringhalt from 52 properties in Victoria was carried out from 1985 to 1987. Horses were either examined in the field (n = 52), referred to the Veterinary Clinical Centre (n = 13) or clinical details were obtained verbally (n = 13). In addition 10 cases of false or atypical stringhalt were examined. Detailed soil and pasture analysis was carried out on 14 properties where Australian Stringhalt had occurred. Information was also obtained on epidemiology of the condition from a survey of practitioners. Fifty of the 52 cases examined in the field...
Distribution and density of neuropeptide Y-immunoreactive nerve fibres and cells in the horse urinary bladder. The distribution and density of neuropeptide Y (NPY)-immunoreactive nerve fibres and cells were determined in the urinary bladder of the horse by using the peroxidase-antiperoxidase (PAP) immunohistochemical method. Numerous undulating NPY-immunoreactive nerve fibres were found throughout the vesical wall, sometimes forming nerve bundles which ramified repeatedly as they coursed through the connective tissue septa to give rise to smaller bundles or single fibres which projected into the muscle fascicles forming muscular nerve plexuses, mainly in the bladder base. In the submucosa of this regio...
Cortical somatosensory-evoked potentials in the horse. Cortical somatosensory-evoked potentials (SEP) were recorded from thoracic and pelvic limbs in 15 horses (13 Thoroughbreds and 2 Quarter Horses). Ulnar nerve SEP were evoked by electrical stimulation of the lateral palmar branch of the ulnar nerve at the level of the metacarpophalangeal joint. Recordings were taken between electrodes at 2 cm lateral to the vertex (contralateral to the stimulated limb) and the midpoint of the interorbital line. Four peaks were found in all recordings: N1, P1, N2, and P2. Latencies to the peaks were 39.0 +/- 2.7, 45.5 +/- 5.3, 50.4 +/- 5.2, and 62.3 +/- 3.7 ms (...
Attempts to prevent equine post neurectomy neuroma formation through retrograde transport of two neurotoxins, doxorubicin and ricin. Digital neurectomies, performed to relieve pain and lameness, are often complicated postoperatively by formation of painful neuromas. In this study attempts were made to deliver lethal doses of neurotoxin to the cell bodies of the transected digital nerve fibres via long-distance retrograde axon transport and, thereby, prevent the regenerative changes that lead to neuroma formation. After applying doxorubicin in various ways to the digital nerve stumps of ponies, degenerating or necrotic neurones appeared only sporadically in the spinal ganglia. Although doxorubicin was largely ineffective in ...
Influence of the autonomic nervous system in the horse urinary bladder. alpha and beta-adrenergic receptors in detrusor muscle and bladder base of horses were investigated by in vitro responses of smooth muscle strips to exogenous agonist and antagonist drugs. Noradrenaline, isoprenaline and salbutamol induced relaxation of detrusor muscle strips which was significantly inhibited by propranolol and butoxamine suggesting that the response is mediated by beta-2 adrenergic receptors. In the urinary bladder base noradrenaline, phenylephrine and B-HT 920 induced strong contractile effects. These contractile responses were inhibited by the alpha antagonist phenoxybenzam...
[Infection with equine herpesvirus and its manifestation in the central nervous system of the horse]. Infections with EHV1 can lead to manifestation at the CNS of horses followed by encephalomyelitis and "equine stroke". Horse experiments could confirm the clinical picture and gave links to the potential pathogenesis of the disease. We also have been in the position to isolate and characterize an EHV4 virus out of the brain of a horse with CNS disorders. The two viruses carry different biological properties which obviously dominate the pathogenesis. These properties as well as experimental and field cases are described and different diagnostic tests are discussed.
Neuritis of the cauda equina in the horse. Ultrastructural lesions of the cranial nerves and their ganglia and the autonomic nervous system from 5 cases of neuritis of the cauda equina in the horse are described. They include lysosomal inclusions within the semilunar, geniculate and sympathetic chain ganglia, granulomatous involvement of the coeliaco-mesenteric ganglion and accumulation of axonal organelles in unmyelinated fibres of the great splanchnic nerve, sympathetic chain and oesophageal vagus.
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...
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...
Observations on headshaking in the horse. The clinical records of 100 cases of headshaking in horses were reviewed. Possible causes of the abnormal behaviour were identified in 11 animals; these included ear mite infestation, otitis interna, cranial nerve dysfunction, cervical injury, ocular disease, guttural pouch mycosis, dental periapical osteitis and suspected vasomotor rhinitis. However, in only two of these could it be shown that correction of the abnormality led to elimination of the headshaking. The additional clinical signs exhibited by the other idiopathic cases of headshaking included evidence of nasal irritation, sneezing ...
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.
Ultrastructural observations of organelle accumulation in the equine recurrent laryngeal nerve. The left recurrent laryngeal nerves from five horses with sub-clinical neuropathy were examined by light and electron microscopy in a study designed to examine accumulation of axonal organelles at paranodal and internodal locations. Transverse sections of the nerve showed scattered fibres with split myelin sheaths and axonal accumulation of organelles. On longitudinal sections these collections were seen to result from an axonal outpouching in which dense lamellar bodies and mitochondria had accumulated. These paranodal collections, which could be found on both sides of the node, were often as...
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 ...
Subclinical entrapment neuropathy of the equine suprascapular nerve. The suprascapular nerve from 14 horses, which had no clinical evidence of spinatus muscle atrophy, were obtained to determine whether the nerve was sub-clinically compressed at the scapular edge. The nerves were divided into three portions, proximal and distal to the scapular edge and as it reflected around it. In nine horses there was evidence of a chronic neuropathy which varied in severity and which was most severe at the site of reflection, where the nerve appeared constricted by a tendinous band. At this site the predominant change was that of chronic demyelination and remyelination, with...
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 I. A light microscopic study of peripheral nerves. This light microscopic investigation of 15 Thoroughbred horses provided substantial evidence for the classification of equine laryngeal hemiplegia as a distal axonopathy. Morphologic and morphometric examinations were performed on resin embedded recurrent laryngeal nerves from control, subclinical and clinical laryngeal hemiplegic animals. In the latter group of animals some distal hindlimb nerves were also examined. A distally graded loss of myelinated fibres selectively affecting those of large diameter was demonstrated in both left and right recurrent laryngeal nerves. Morphologic evidence ...
