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Topic:Central Nervous System
The central nervous system (CNS) in horses is composed of the brain and spinal cord, serving as the primary control center for processing and transmitting neural signals throughout the body. It is responsible for coordinating sensory information, motor function, and various physiological processes. The CNS plays a vital role in maintaining homeostasis and enabling the animal to interact with its environment. Research on the equine central nervous system encompasses studies on its structure, function, and response to injury or disease. This page gathers peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and pathophysiology of the central nervous system in horses, as well as its implications for equine health and behavior.
Evaluation of the bispectral index as an indicator of degree of central nervous system depression in isoflurane-anesthetized horses. To determine whether the bispectral index (BIS) can be used as an indicator of degree of CNS depression in isoflurane-anesthetized horses. Methods: 10 Standardbred and 6 Norwegian cold-blooded trotter stallions admitted for routine castration. Methods: A 2-channel referential electrode configuration was used to record EEG for calculation of BIS by the EEG monitor. The BIS was calculated before (awake) and after (sedated) administration of detomidine (0.01 mg/kg of body weight, IV) and butorphanol (0.01 mg/kg, IV). Anesthesia was induced with ketamine hydrochloride (2.5 mg/kg, IV) and diazepam ...
Clinical, pathologic, immunohistochemical, and virologic findings of eastern equine encephalomyelitis in two horses. Natural eastern equine encephalitis alphavirus (EEEV) infection was diagnosed in two adult horses with anorexia and colic, changes in sensorium, hyperexcitability, and terminal severe depression. Myocardium, tunica muscularis of stomach, intestine, urinary bladder, and spleen capsule had coagulative necrosis and perivascular lymphocytic infiltrate. Central nervous system (CNS) lesions were diffuse polioencephalomyelitis with leptomeningitis characterized by perivascular T lymphocyte cuffing, marked gliosis, neuronophagia, and multifocal microabscesses. Lesions were more prominent within cerebr...
Effects of ketamine on the equine electroencephalogram during anesthesia with halothane in oxygen. To investigate the effects of ketamine on the electroencephalogram (EEG) of the horse. Methods: Prospective experimental study. Methods: Eight Welsh mountain pony geldings weighing between 280 and 330 kg, 5 to 9 years old. Methods: During halothane anesthesia at an end-tidal halothane concentration between 0.75 and 0.85%, the EEG frequency power spectrum and the auditory evoked potential were recorded while an infusion of ketamine was given. Ketamine 200 mg was infused over 5 minutes in 8 ponies. The effects of ketamine on the EEG were recorded continuously during the infusion and for a furthe...
[Moxidectin poisoning in a foal?]. A 2 day old foal was presented with central nervous depression (coma) after moxidectin overdose. Moxidectin belongs to the milbemycin anthelmintics which elicit their working mechanism through a GABA (gamma-aminobutyric acid)-stimulatory mode of action. The foal developed profound hypothermia, bradycardia and hypoventilation. Absence of urine voiding and mild abdominal distension suggested a ruptured bladder, which was confirmed by transabdominal ultrasound and clinical-pathologic parameters. Repeat auscultation of the ventral lung parts and the occurrence of gastric reflux were suggestive of ...
[Dimethylsulfoxide (DMSO) in horses: a literature review]. The use of dimethyl sulphoxide in equine medicine is discussed with special reference to trauma of the central nervous system, chronic endometritis, trauma of the locomotor apparatus, and ischaemic bowel pathophysiology. The ability of dimethyl sulphoxide to reduce connective tissue formation might be of interest in abdominal surgery. The anti-inflammatory effect of dimethyl sulphoxide is used in the treatment of muscle trauma, tendinitis, laminitis, and arthritis. Dimethyl sulphoxide can potentiate the effects of other drugs. The most common dose is 1 g/kg body weight intravenously up to a 40...
Pediatric equestrian injuries: assessing the impact of helmet use. To assess the impact of helmet use on the pattern, and severity of pediatric equestrian injuries. Methods: A prospective observational study of all children less than 15 years of age who were brought to the University of Virginia children's Emergency Department with horse-related injuries. Results: During the two-year period of the study, 32 children were evaluated. Two children were injured when a horse stepped on them. Thirty children fell from or were thrown from a horse. Of these, 20 were wearing a helmet. Head injuries were more frequent in those patients not wearing helmets. The mean Mod...
Models for assessing the relationship between drug concentration and drug effect in performance horses. The actions of most drugs are dependent upon achieving adequate plasma concentrations. Plasma concentrations are influenced by the degree to which a drug is absorbed, distributed, metabolized and excreted. Pharmacokinetic assessment reflects changes in these variables as a function of time. Pharmacodynamics refers to specific drug effects or mechanisms of drug action. Individual drug pharmacokinetics provides information on which to base a therapeutic dose, route of administration and dosing interval. However, not all drug actions temporally correlate with plasma kinetics. To resolve this disc...
Sedatives, tranquilizers, and stimulants. Drugs of relevance to equine practice that modify the central nervous system (CNS) can be broadly classified as depressants or stimulants. The pharmacologic mechanisms of action, uses, and side effects of selected CNS depressant and stimulant drugs in horses are reviewed. Knowledge of the way these CNS-modifying drugs may affect performance is limited.
A survey of neurological diseases in horses. Case records of 450 horses with signs of neurological disease are reviewed. One hundred and nineteen horses with neurological disease due to trauma were examined, of which 60 were due to spinal cord trauma, 47 to brain or cranial nerve trauma and 12 to peripheral nerve trauma. Cervical vertebral fractures/trauma were the most common injury. Basisphenoid/basioccipital bone fractures were the most common form of cranial trauma and facial nerve paralysis the most common cranial nerve injury. Eighty-nine horses with neurological disease due to malformation were examined. Cervical vertebral malform...
[Narcolepsy in horses]. Narcolepsy is an incurable non-progressive disease of the central nervous system. In humans, narcolepsy causes excessive drowsiness during the day (sometimes a sleep-attack occurs), cataplexy (sudden loss of muscle tone), hallucinations, and sleep paralysis. In the horse and other mammals cataplexy is the most frequently observed symptom. Excessive drowsiness can occur but is harder to observe. Cataplexy is caused by a fragmentation of the REM sleep. The etiology of narcolepsy is still subject to debate, partly because normal sleeping patterns are poorly understood. In humans and certain breed...
Pharmacokinetic values of drugs frequently used in performance horses. Tables of values of pharmacokinetic variables (volume of distribution, total body clearance, and plasma elimination half-life) of drugs frequently administered to performance horses are accompanied by explanatory notes. Drugs described include the nonsteroidal anti-inflammatory drugs, corticosteroids, anabolic steroids, central nervous system-modifying drugs, respiratory system drugs, diuretics, local anesthetics, and antibacterial drugs.
Influence of yohimbine and tolazoline on the cardiovascular, respiratory, and sedative effects of xylazine in the horse. To determine the effects of yohimbine and tolazoline on the cardiovascular, respiratory and sedative effects of xylazine, four horses were sedated with xylazine and treated with either yohimbine, tolazoline or saline. Xylazine was administered as an intravenous (i.v.) bolus (1.0 mg/kg) followed by a continuous infusion at the rate of 12 micrograms/kg/min. Heart rate, respiratory rate, mean arterial pressure, arterial blood gases, and the chin-to-floor distance were recorded throughout the experiment. After 60 min, either yohimbine or tolazoline was administered i.v. in incremental doses until ...
Pathogenesis of Borna disease. Borna disease represents a unique model of a virus-induced immunological disease of the brain. Naturally occurring in horses and sheep, the mechanisms of pathogenesis have been studied in experimental animals, namely in the rat. Many investigations have revealed that the infection of the natural hosts principally follows the same pathogenic pathways as observed in rats, leading to a severe encephalomyelitis. This affliction of the central nervous system results in severe neurological disorders that again, are fully comparable in laboratory animals to those in the natural and the different expe...
Disposition of human drug preparations in the horse. II. Orally administered fencamfamine. A gas chromatographic method to measure urinary levels of the central nervous system stimulant fencamfamine and some of its metabolites is described. When 100 mg fencamfamine was given orally to four horses the parent drug could not be detected in the urine. After enzymatic hydrolysis of the urine the major human metabolite, N-desethylated fencamfamine, only accounted for 1% of the dose in 12 h. The major equine metabolites were conjugated parahydroxylated compounds representing 18% of the dose. With regard to horse doping control and analysis, the injudicious use of human doping routine metho...
Regional anesthesia. Organ toxicity from local anesthetic agents is rare. This makes these agents an attractive option in the high-risk patient. Complications associated with local anesthetics are related to overdosage. Overdosage with local anesthetic agents administered epidurally may cause motor paralysis and hind-limb weakness. Systemic signs of local anesthetic overdosage include changes in central nervous system activity (excitement or depression), muscle tremors, and hypotension. Because the dose required to produce these effects in the horse is high (12 mg/kg), this complication is uncommon. Few side effec...
Cerebrospinal fluid creatine kinase activity in horses with central nervous system disease: 69 cases (1984-1989). The CSF creatine kinase (CK) activity was determined in 70 CSF samples from 69 horses with CNS disease. Abnormal values (greater than or equal to 1 IU/L) were determined from 32 CSF samples, and normal values (less than 1 IU/L) were found in 38 samples. Increased CK activity was most frequently associated with a diagnosis of equine protozoal myelitis; CK activity was not increased in 11 horses with cervical compressive myelopathy. Other diagnoses, in which CSF CK activity was increased included trauma (n = 1), idiopathic epilepsy (n = 2), botulism (n = 2), articular facet fracture (n = 1), int...
Common injuries in horseback riding. A review. The most common location of horse-related injuries is the upper extremity (24% to 61%) with injuries to the lower extremity second in frequency (36% to 40%). The head and face sustain 20% of horse-related injuries. The most common type of injury is a soft tissue injury (92% to 1%), followed by a fracture (57% to 3%). Concussion is the third most common type of injury (63% to 2%). The most frequent cause of hospitalisation is concussion (38% to 4%) with fracture second. The most common injury which leaves residual impairment is injury to the central nervous system. The age at which most injury ...
Immune-mediated pathogenesis of Borna disease. Borna disease is an endemic progressive encephalomyelitis of horses and sheep prevalent in central Europe. A wide variety of animal species, ranging from chickens to primates can be infected experimentally with the causative virus, which is only poorly characterized. Furthermore, BD virus-specific antibodies have been detected in sera and cerebrospinal fluids of psychiatric patients. Our studies on the pathogenesis of BD have shown that-at least in rats-the disease is not caused by the infecting virus itself, but by a virus-induced immunopathological reaction. Thus, after intracerebral infecti...
Cerebrospinal fluid changes in two horses with central nervous system nematodiasis (Micronema deletrix). Two horses with cerebrospinal nematodiasis (Micronema deletrix) had signs similar to those of other neurologic diseases resulting from parasitic (fly larvae, protozoa, or other helminths) migration through the central nervous system (CNS). In one horse (horse 1), a 13-year-old Paso Fino stallion, the cerebrospinal fluid (CSF) was slightly xanthochromic (1+), with a pleocytosis (25 nucleated cells/microliter) and a normal protein level (69 mg/dl). A CSF differential cell count showed 15% neutrophils, 56% lymphocytes, 22% macrophages, 5% eosinophils, and 2% basophils. In the other horse (horse 2...
Adverse reaction to procaine penicillin G in horses. Adverse reactions to intramuscular injections of procaine penicillin G are reported in 11 horses, five of which died. The clinical findings are presented and suggest central nervous involvement in most cases. Post mortem findings in one horse were consistent with anaphylaxis whereas in other cases the clinical findings, duration of treatment, speed of onset and subsequent completion of treatment supports diagnosis of an acute procaine toxicity syndrome.
Sudden and unexpected death in horses and ponies: an analysis of 200 cases. An analysis was made of the causes of death in horses and ponies over one year of age which died suddenly (Group 1) or were found dead but were considered normal when last seen (Group 2). There were 49 animals in Group 1. Thoroughbreds were overrepresented, but there were no ponies in this group. No cause of death was found in 30.6 per cent of cases and 16.3 per cent died from each of the following causes: haemorrhage in the respiratory system, central nervous system, and adverse drug reactions. Cardiovascular lesions were the cause of death in 14.4 per cent and the remaining 3.1 per cent had ...
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...
Practical toxicologic diagnosis. Strychnine toxicosis is characterized by inducible tetanic seizures and metaldehyde poisoning by fine fasciculations progressing to generalized tremors and seizures. Intoxication with 1080 causes seizures, random running movements, vomiting, defecation, urination, acidosis and hyperglycemia. Intoxication with rodenticides causing coagulopathy is characterized by hemorrhage into body cavities but not necessarily external hemorrhage. Anticholinesterase insecticides cause salivation, urination and defecation, while chlorinated hydrocarbon insecticides cause CNS disturbances. Ethylene glycol intox...
Hyperpnea of exercise at various PIO2 in normal and carotid body-denervated ponies. We studied the effect of changes in inspired [O2] on partial pressure of CO2 in arterial blood (PaCO2) during treadmill exercise (3 mph, 3% grade) in normal, acute (+2-4 wk), and chronic (+1-2 yr) carotid body-denervated (CBD) ponies. In all studies, PaCO2 decreased (P less than 0.01) from rest during exercise, reaching a nadir usually between 15 and 30 s of exercise. During normoxia [partial pressure of O2 in arterial blood (PaO2) approximately 95 Torr], the PaCO2 nadir was 2.3 +/- 0.6 Torr below resting level in normal ponies, but the nadir was greater (P less than -0.01) in acute (delta = 6...
Myocardial necrosis secondary to neural lesions in domestic animals. Focal myocardial necrosis secondary to neural lesions was diagnosed in 2 dogs and 1 horse. In each case, the neural lesions were traumatic in origin. Spinal cord injury was evident in 1 dog; brain damage was evident in the other dog and presumably in the horse. Retrospective analysis of necropsy material showed that many species were affected, without apparent age or sex predisposition. Central nervous system injury resulting from trauma, infection or space-occupying lesions was associated with acute myocardial necrosis in all cases. The myocardial necrosis was rarely fatal; however, it did ca...
Behavioral and cardiorespiratory responses to 4-aminopyridine in healthy awake horses. 4-Aminopyridine was administered in incremental IV doses to healthy horses to evaluate cardiorespiratory and behavioral effects. Doses of 100 micrograms/kg produced apparent sensory discomfort, manifested by wiggling or curling of the lips and tongue, arching or stretching the neck, snorting, squealing, and coughing. At cumulative dosages of 300 to 500 micrograms/kg, muscle tremors, a stilted gait, and signs of excitement occurred. Once signs of excitement occurred, additional administration of 4-aminopyridine resulted in prolonged excitement consisting of severe muscle tremors and exaggerated...
Experimental poisoning of horses and cattle with Swainsona canescens var horniana. Horses and cattle fed swainsona (Swainsona canescens var horniana) over a period of 8 to 10 weeks lost condition and became incoordinated and hypersensitive. Histological examination of tissues from affected animals revealed the characteristic changes of widespread cellular vacuolation and axonal spheroids in the CNS. Cattle withdrawn from the toxic plant after being fed for varying periods up to 8 weeks returned to normal. Serum alpha-mannosidase activity declined significantly in cattle during the test period, whereas in horses that activity rose. Serum alkaline phosphatase levels increased ...
Listeriosis in an Arabian foal with combined immunodeficiency. A 1-month-old Arabian foal with signs of central nervous system disease was found to have combined (B- and T-lymphocyte) immunodeficiency. The foal died in spite of intensive antibiotic therapy. At necropsy, generalized lymphoid hypoplasia and acute necrotizing and granulomatous inflammation of the brain, heart, and adrenal glands were found. In addition, there were spinal meningitis and focal hepatic necrosis. Listeria monocytogenes was isolated on primary culture from the brain.
