Topic:Neurology
Neurology in horses encompasses the study of the equine nervous system, including its structure, function, and associated disorders. The equine nervous system is divided into the central nervous system (CNS), consisting of the brain and spinal cord, and the peripheral nervous system (PNS), which includes nerves extending throughout the body. Neurological conditions in horses can manifest as gait abnormalities, behavioral changes, or sensory deficits. Common neurological disorders include equine protozoal myeloencephalitis (EPM), cervical vertebral stenotic myelopathy (CVSM), and equine herpesvirus myeloencephalopathy (EHM). Diagnostic approaches may involve clinical evaluation, imaging techniques, and laboratory tests. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, pathophysiology, diagnosis, and management of neurological disorders in horses.
Magnetic resonance imaging of two normal equine brains and their associated structures. Magnetic resonance images were obtained from two isolated horses' heads. Ten mm thick, T1-weighted images were taken with a 1.5 Tesla magnet and a body coil, and compared with the corresponding frozen cross-sections of the heads, relevant structures being identified and labelled at each level. The images should provide reference material for clinical magnetic imaging studies of horses' heads.
The effect of the NMDA receptor blocker, dextromethorphan, on cribbing in horses. Stereotypic cribbing in horses is thought to involve excess dopaminergic activity within the striatum. Various models of stress-induced stereotypies including cribbing in horses postulate that stress stimulates the release of endorphins, triggering the release of striatal dopamine. Dopamine in turn activates basal ganglia motor programs, reinforcing behavior via a reward mechanism. Furthermore, the release of dopamine by endorphins has been shown to depend on activation of NMDA receptors. In the present study, horses identified as cribbers and volunteered by their owners were treated with the ...
Equine herpesvirus myeloencephalopathy in a 14-year-old quarter horse stallion. A 14-year-old, quarter horse stallion was presented in lateral recumbency, unable to rise. Equine herpesvirus myeloencephalopathy was diagnosed, based on presentation, clinical signs, and the ruling out of other possibilities. After initial rapid improvements, ataxia remained, as did chronic cystitis secondary to bladder paralysis. He was euthanized after 2 months.
Expression of vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, and intermediate neurofilaments in nasal mucosal nerve fibers of horses without nasal disease. To determine the distribution of nerve fibers containing calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP), and intermediate neurofilaments in nasal mucosa of horses. Methods: 6 horses without evidence of nasal disease. Methods: Full-thickness nasal tissue specimens were obtained from the rostral portion of the nasal septum at necropsy, and fluorescence immunohistochemistry was performed to assess mucosal distribution of nerve fibers. Results: Nerve fibers with CGRP-like immunoreactivity (CGRP-Li) formed a dense subepithelial network, and a large num...
Studies on the experimental induction of ptosis in horses. The precise appearance of ptosis due to lesions at different sites was investigated in experimental ponies. The angles of the eyelashes to the head was used as an objective measurement of ptosis after local anaesthesia of the sympathetic trunk or the palpebral nerve and the administration of an ocular alpha agonist or antagonist. It was shown that ptosis is not an inevitable consequence of palpebral nerve pathology, that ocular alpha antagonists can induce ptosis, and that alpha agonist eyedrops have an inconsistent effect on the equine pupil, but are consistent at reversing ptosis induced by ...
Evaluation of substance P as a neurotransmitter in equine jejunum. To determine whether substance P (SP) functions as a neurotransmitter in equine jejunum. Methods: Samples of jejunum obtained from horses that did not have lesions in the gastrointestinal tract. Methods: Jejunal smooth muscle strips, oriented in the plane of the circular or longitudinal muscle, were suspended isometrically in muscle baths. Neurotransmitter release was induced by electrical field stimulation (EFS) delivered at 2 intensities (30 and 70 V) and various frequencies on muscle strips that were maintained at low tension or were under contraction. A neurokinin-1 receptor blocker (CP-96...
Functional morphology of the equine pelvic flexure and its role in disease. A review. The hindgut is the major site in the horse for nutrient digestion and absorption. Most of this activity occurs in the large intestinal compartments, i.e., cecum, right and left ventral colon and left and right dorsal colon. The colonic pelvic flexure is a short and narrow loop connecting the left ventral and left dorsal colon. It is not significant directly in digestive and absorptive processes but plays an important functional role in regulating colonic aboral and retropropulsive transit of digesta through its motility pacemaker activity. The pelvic flexure also contributes to the pathophysio...
Halicephalobus gingivalis encephalomyelitis in a horse. An 8-year-old, Arabian mare presented with acute progressive ataxia and a firm swelling over the right mandible. Radiographs revealed multiple radiolucent areas on the mandibles. The mare's neurological signs progressed, she was consequently euthanized. Postmortem examination revealed mandibular granulomatous reactions and meningoencephalitis due to the nematode Halicephalobus gingivalis.
Tissue culture of the enteric nervous system from equine ileum. Ileal samples were harvested fresh from euthanized adult horses. The tissues were microdissected to prepare wholemount preparations for immunohistochemistry and for either explant or dissociated culture systems of the enteric nervous system. Explant culture systems were established using whole-mounts of either the submucous plexus or the muscularis externa (including the myenteric plexus). Dissociated cell cultures could only be obtained from the submucous plexus. Culture systems were maintained for up to 5 days. Immunoreactivity for a neuronal marker (Pan-N) and for glial cell markers (GFAP a...
Neurocalcin-immunoreactive neurons in the mammalian dorsal root ganglia, including humans. Neurocalcin (NC) is a recently characterized EF-hand calcium-binding protein present in a discrete population of sensory neurons and their peripheral mechanoreceptors, but its presence in peripheral nervous system neurons other than in the rat is still unknown. The present study was designed to investigate the occurrence of NC in the dorsal root ganglia (DRG) of several mammalian species (horse, buffalo, cow, sheep, pig, dog, and rat), including humans. DRG were fixed, embedded in paraffin, and processed for immunohistochemistry using a polyclonal antibody against NC. The size of the immunorea...
Imaging diagnosis–occipitoatlantoaxial malformation in a miniature horse foal. This research article presents a case study of a one-month-old Miniature Horse colt that was diagnosed with a rare congenital condition called occipitoatlantoaxial malformation (OAAM). Case Presentation The foal was […]
Cerebello-olivary and lateral (accessory) cuneate degeneration in a juvenile American Miniature horse. A 12-month-old American Miniature horse colt was presented to the Virginia Tech Veterinary Teaching Hospital with a 7-month history of progressive ataxia. Physical examination revealed a head intention tremor, base-wide stance, and ataxia. Necropsy findings were confined to the brain. There were bilateral areas of liquefactive necrosis and cavitation corresponding to the dorsal accessory olivary and lateral (accessory) cuneate nuclei. Cerebellar folia of the dorsal vermis were thin. Microscopically, the cerebellar cortex was characterized by patchy areas of Purkinje cell loss with associated v...
Electrically elicited blink reflex in horses with trigeminal and facial nerve blocks. To reassess reference values for the components of the electrically induced blink reflex, document reference values for facial motor nerve conduction velocity, and demonstrate usefulness of the blink reflex as a diagnostic tool in peripheral facial and trigeminal nerve dysfunction in horses. Methods: 10 healthy adult horses (8 males, 2 females) without neurologic abnormalities. Methods: Blink reflex tests were performed by electrical stimulation of the supraorbital nerve and facial (auriculopalpebral) nerve. Reflex and direct muscle-evoked potentials of the orbicularis oculi muscles were recor...
Cross-species and intraspecies morphometric analysis of the corpus callosum. A cross-species morphometric study of the corpus callosum was performed in the rat, rabbit, cat, dog, horse, cow and human. Across species, the results indicate a strong, although less than linear, dependency of callosal size on brain weight. This relation tends to lose significance within species. This is consistent with other morphometric studies indicating a tendency to decrease the correlations between morphometric variables in within-species analyses as compared to between-species analyses. There are species differences in the relative size of some callosal segments particularly in the po...
Intracellular microelectrode recording to characterize inhibitory neuromuscular transmission in jejunum of horses. To evaluate electrical activity of jejunal circular muscle in horses and characterize electrical responses to stimulation by intrinsic inhibitory neurons. Methods: Portions of jejunum obtained from horses euthanatized for reasons other than gastrointestinal tract disease. Methods: Isolated circular muscle preparations were perfused with oxygenated modified Krebs solution. Glass microelectrodes were used for intracellular recording of membrane potentials from single smooth muscle cells. Electrical activity and responses to electrical field stimulation (EFS) of intrinsic neurons in the presence ...
Effect of nervous excitation on acid secretion in horses. Nervous excitation was induced by various means in horses provided with a gastric cannula. Insulin hypoglycaemia profoundly inhibited the basal acid output and volume secreted from the stomach. No clear effect on acid secretion was noted after administration of bethanechol, as the acid output was covered by the copious secretion of saliva. Atropine almost abolished the basal acid output. Sensoric stimulation by teasing caused a slight but not significant increase in the total acid output. These data suggest that cholinergic excitation might play a role in the stimulation of both volume and aci...
Pathophysiology of dorsal displacement of the soft palate in horses. Dorsal displacement of the soft palate (DDSP) is an intermittent obstructive upper airway condition that occurs in athletic horses during high-intensity exercise. The pathogenesis of this condition is unknown, but may involve epiglottic hypoplasia, malformation, or neuromuscular dysfunction. In this paper, we report on investigations into the pathophysiology of DDSP. In 3 separate experiments, Standardbred horses were exercised on a high-speed treadmill at speeds corresponding to 50, 75 and 100% of maximum heart rate. The upper airway was evaluated by videoendoscopy and measurement of tracheal...
Evaluation of nitric oxide as an inhibitory neurotransmitter in the equine ventral colon. To determine the role of nitric oxide and an apamin-sensitive nonadrenergic noncholingeric inhibitory transmitter on contractility of the ventral colon of horses. Methods: Strips of the circular and longitudinal muscle layers and taenia of the ventral colon from 14 horses. Methods: Muscle strips were suspended in tissue baths and attached to force transducers. Contractile activity of circular, longitudinal, and taenia muscle strips in response to electrical field stimulation was measured after addition of apamin and a nitric oxide inhibitor, N-nitro-L-arginine methyl ester (L-NAME). Results: E...
The distribution of nerve fibres immunoreactive for vasoactive intestinal peptide, calcitonin gene-related peptide, substance P and dopamine beta-hydroxylase in the normal equine larynx. The autonomic innervation of the mammalian respiratory system is complex, and involves a wide variety of peptide and non-peptide neurotransmitters which will have an important role in normal laryngeal function and the response to disease. This innervation has been partially described in the horse airway and lung, but there is no information on the equine larynx. This paper describes the expression and distribution of nerve fibres immunoreactive for vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), substance P (SP) and the adrenergic enzymatic marker dopamine beta-hyd...
Influence of artificial saddle riding on postural stability in children with cerebral palsy. Stability of quiet upright stance was investigated in 25 children with cerebral palsy at the beginning and the end of a 3-month period of therapy involving 20 min microprocessor-controlled saddle riding, performed twice a week. The traditional parameters of postural sway based on the centre-of-pressure analysis (range, standard deviation, mean speed and mean radius) dropped significantly over time confirming advantageous influence of this treatment. As a complementary tool, an autoregressive modelling technique was used allowing us to establish after each single ride considerable decreases in ...
Latency-associated transcripts of equine herpesvirus type 4 in trigeminal ganglia of naturally infected horses. Equine herpesvirus type 4 (EHV-4) is a major respiratory pathogen of horses. Unlike most other members of the Alphaherpesvirinae, EHV-4 was regarded as non-neurotropic. Here, neural and lymphoid tissues of 17 horses have been analysed post-mortem. EHV-4 DNA was detected in 11 cases (65%) by PCR, exclusively in the trigeminal ganglia. In order to define the transcriptional activity, RNA preparations of 10 EHV-4 DNA-positive ganglia were investigated by nested RT-PCR. EHV-4-specific transcripts derived from genes 63 [herpes simplex virus type 1 (HSV-1) ICPO gene homologue] and 64 (HSV-1 ICP4 gen...
Distribution of substance P binding sites in equine airways. Autoradiography with [125I]-Bolton Hunter substance P ([I]-BHSP) was used to detect substance P binding sites in the equine lung. Specific [I]-BHSP binding sites were very dense over small bronchial vessels, tracheobronchial glands and airway epithelium in large and small airways. The density of [I]-BHSP binding sites over airway smooth muscle was much lower than in the preceding tissues. Competition with an excess of either a specific neurokinin 1 receptor agonist, or a specific neurokinin 2 receptor agonist indicated that most specific [I]-BHSP binding sites in the equine lung represent neur...
The neurology and enterology of equine grass sickness: a review of basic mechanisms. Autonomic dysfunction constitutes a prominent clinical feature of equine grass sickness (EGS). Significant injury to the nervous control of the alimentary system is life threatening, partly because of dysphagia but also because of the failure of the unique regulatory mechanisms in equine digestion involving water and electrolyte balance. The neuropathology also indicates the presence of a somatic polyneuropathy. The morphological features of EGS are similar to those of excitotoxic neuronal degeneration, which resembles neuronal apoptosis. It is difficult to ascertain from published accounts th...
[Hypothesis concerning the anatomical basis of cauda equina syndrome and transient nerve root irritation after spinal anesthesia]. Cauda equine syndrome is a rare neurological complication associated with subarachnoid anesthesia, and particularly with the use of 5% hyperbaric lidocaine and small gauge catheters. Our aim was to study a possible anatomical factor that might impede adequate dilution of local anesthetic and explain the development of cauda equine syndrome and transitory radicular irritation. Methods: The spinal dura matters and their contents from two male human cadavers were examined after organs had been extracted for transplantation. Both men had recently died at ages 56 and 65 years of age. Samples were f...
Anatomy of the thoracolumbar vertebral region. A thorough understanding of the structure and function of the equine vertebral column can provide a clearer understanding of thoracolumbar spinal disorders. Three primary functions of the vertebral column include protection of the spinal cord, support for weight bearing, and flexibility for locomotion. Osseous structures provide structural support and vary from one vertebral region to another as functional requirements change. The spinal musculature produces complex vertebral movements while the spinal ligaments provide stability to the vertebral column. Proprioception and nociception are two ...
Back problems. Neuroanatomy and neurological examination. Components of the equine nervous system are described including classical anatomy and newer sensory innervation maps that are useful for localizing lesions to and within the nervous system. The key components in a neurological examination that help differentiate primary neurologic disease from musculoskeletal disorders are explained. Gait deficits associated with neurologic dysfunction are listed as well as diagnostic aids and an overview of differential diagnoses.
Spinal muscle pathology. Clinical signs that are easily referred to spinal muscle pathology include atrophy of epaxial muscles, focal swelling and palpable tenderness, as well as enlarged muscles with increased tone. Less easily recognized signs include rigidity of the spine, shortened stride, hindlimb lameness, and indicators of poor performance. Muscle biopsy is one option in evaluating sore backs and is best used when physical examination and imaging procedures do not reveal a likely diagnosis or when conventional treatments are unsuccessful. Rhabdomyolysis of spinal muscles may be due to nutritional myodegeneratio...
Exercise in the heat: thermoregulatory limitations to performance in humans and horses. This paper reviews the limits to exercise imposed by increases in ambient, hypothalamic, and contracting skeletal muscle temperature in humans and horses. Like humans, horses frequently compete in hot environments, yet their high mass-specific rate of heat production and low mass-specific surface area for heat dissipation places them at a great disadvantage compared to humans. Exercise in hot conditions increases the rate of body heat storage and reduces the time required to reach a critical hypothalamic temperature that results in voluntary fatigue. This critical temperature appears to be ass...
Comparison of the effects of halothane, isoflurane and methoxyflurane on the electroencephalogram of the horse. We have investigated in eight ponies the effects of three different end-tidal concentrations of halothane, isoflurane and methoxyflurane on median (F50) and 95% spectral edge (F95) frequencies of the EEG and the second differential (DD) of the middle latency auditory evoked potential (MLAEP). The three concentrations of each agent were chosen to represent approximately the minimum alveolar concentration (MAC), 1.25 MAC and 1.5 MAC for each agent. During halothane anaesthesia, F95 decreased progressively as halothane concentration increased, from mean 13.9 (SD 2.6) at 0.8% to 11.9 (1.1) at 1.2%...