Seizures in horses are neurological events characterized by sudden, uncontrolled electrical disturbances in the brain. These episodes can manifest as changes in behavior, motor activity, or consciousness and may vary in duration and severity. The underlying causes of seizures in horses can include genetic predispositions, metabolic disorders, infections, or traumatic brain injuries. Diagnosis often involves a combination of clinical examination, neurological assessment, and diagnostic imaging. This topic encompasses peer-reviewed research studies and scholarly articles that explore the etiology, pathophysiology, diagnostic approaches, and management strategies for seizures in equine patients.
Hubbell JA, Kelly EM, Aarnes TK, Bednarski RM, Lerche P, Liu Z, Lakritz J.Midazolam is used to control seizures in horses and to enhance muscle relaxation, but its pharmacokinetics are unknown. Objective: To determine the pharmacokinetics and sedative effects of midazolam in horses. Methods: Blinded, randomised, crossover design. Methods: Midazolam was administered i.v. at either 0.05 or 0.1 mg/kg bwt to 6 horses on 2 occasions at least 7 days apart using a crossover design. Blood samples were collected before and at predetermined times through 24 h after administration. Serum midazolam concentrations were determined by a liquid chromatography tandem-mass spectromet...
Spissu N, Panichi G, Montisci A, Fiore F.West Nile Virus (WNV) is an enveloped, positive-sense RNA virus belonging to the genus Flavivirus, antigenically related to the Japanese encephalitis complex in the family Flaviviridae. The principal vectors are mosquitoes, in particular Culex spp, and virus amplification seems to occur in susceptible birds that are the principal vertebrate reservoir hosts, whereas humans, horses and other vertebrates are considered incidental or dead-end hosts. The first Italian equine outbreak was reported in late summer of 1998 in Tuscany, in the area surrounding the Fucecchio marshes, where 14 clinical cas...
Lichter-Peled A, Polani S, Stanyon R, Rocchi M, Kahila Bar-Gal G.Juvenile idiopathic epilepsy (JIE) in Arabian foals resembles benign-familial neonatal convulsion (BFNC) syndrome, a rare idiopathic epilepsy of new-born humans. BFNC syndrome exhibits genetic heterogeneity, as has been hypothesised to occur in Arabian foals, and is known to be caused by mutations in the voltage-gated potassium channel subunit KCNQ2 and KCNQ3 genes. The close phenotypic characteristics of both Arabian foals and children suggest these epileptic syndromes are caused by the same genetic disorder. In horses, the KCNQ2 and KCNQ3 genes are located on the terminal region of chromosom...
van der Ree M, Wijnberg I.Epilepsy in the horse is diagnosed based on clinical signs, but diagnosing can be difficult if a grand mal is not present. The future prospects of the horse and potentially the safety of the owner depend on an accurate diagnosis. This review presents information on epilepsy and focuses on the diagnostic potential of (Ambulatory) electroencephalography ((A) EEG). An epileptic seizure is a brain disorder, which expresses itself as a recurrent episode of involuntary abnormal behaviour. The aetiology can originate from inside or outside the brain or is idiopathic. Besides those categories, seizure...
Lacombe VA, Mayes M, Mosseri S, Reed SM, Fenner WR, Ou HT.In contrast with reports in man and small animals, a systematic classification of seizures in horses is lacking. Objective: The purpose of this study was to classify seizures based on their aetiology and to characterise epilepsy in 104 horses presented for seizures at the Ohio State University Veterinary Medical Center between 1988 and 2009. Methods: In a retrospective observational study, seizures were classified by aetiology based on history, clinical observations, diagnostic investigations (e.g. electroencephalograms, cerebrospinal fluid and computed tomography imaging of the head) and post...
Wong D, Wilkins PA, Bain FT, Brockus C.Neonatal encephalopathy is a common central nervous system disorder of neonatal foals and human infants, resulting in clinical signs such as lethargy, inappropriate behavior, seizures, and other neurologic deficits. Although neonatal encephalopathy is frequently seen in equine practice, a paucity of veterinary clinical and basic science research data is available. Therefore, the pathophysiologic mechanisms of this disorder in equids, such as energy deprivation, excess excitatory amino acids, and free radical injury, have been extrapolated from human medicine. Equine veterinarians have used var...
Easterwood L, Chaffin MK, Marsh PS, Porter B, Barr C.66 horses were potentially exposed to phosphine (a gas) 14 hours after being fed a pelleted ration treated with aluminum phosphide. Results: 28 horses had clinical signs of profuse sweating, tachycardia, tachypnea, pyrexia, ataxia, seizures, and widespread muscle tremors. Clinically relevant laboratory findings included hypoglycemia and high plasma concentrations of lactate and ammonia and activities of gamma-glutamyl transpeptidase, aspartate aminotransferase, and alkaline phosphatase. At least 4 horses had signs consistent with hepatic encephalopathy. Necropsy findings included petechial and...
Sogaro-Robinson C, Lacombe VA, Reed SM, Balkrishnan R.To determine neurologic indications associated with abnormal results for computed tomography (CT) imaging of the head of horses affected by neurologic disorders. Methods: Retrospective case series. Methods: 57 horses. Methods: Signalment, history, clinical abnormalities, and clinicopathologic findings were obtained from medical records of horses examined because of neurologic disorders, and precontrast and postcontrast CT images of the head were reviewed. Data were analyzed by use of univariate and multivariate logistic regression. Results: For a horse with abnormal mentation, odds of having a...
Wilcox AL, Calise DV, Chapman SE, Edwards JF, Storts RW.Hypoxic/ischemic encephalopathy in a cloned American Quarter horse foal was initially associated with placental insufficiency and exacerbated by protracted hypotension during anesthesia for a surgical procedure. The foal, born at the Texas A&M Veterinary Medical Center, was diagnosed at birth with neonatal maladjustment syndrome that was accompanied by dysmaturity, muscle contracture of the front limbs, and a blood clot within the lumen of the urinary bladder. Seizures that developed after anesthesia were attributed to hypoxia/ischemia during anesthesia and culminated in death. Macroscopically...
Raidal SL, Edwards S.To determine the pharmacokinetics of potassium bromide (KBr) in horses after a single and multiple oral doses. Methods: Twelve adult Standardbred and Thoroughbred mares. Methods: Horses were randomly assigned into two treatment groups. In Part 1 of the study, horses were given a single oral dose of 120 mg/kg KBr. Part 2 of the study evaluated a loading dose of 120 mg/kg KBr daily by stomach tube for 5 days, followed by 40 mg/kg daily in feed for 7 days. Serum concentrations of bromide were determined by colorimetric spectrophotometry following drug administration to permit determination of con...
Dickinson CE, Gould DH, Davidson AH, Avery PR, Legare ME, Hyatt DR, DebRoy C.A postpartum mare and foal were presented for evaluation of fever and lethargy in the mare. The mare was diagnosed with endometritis and initially responded well to treatment. On the second day of hospitalization, the mare developed renal insufficiency characterized by oliguria, azotemia, hemolysis, and thrombocytopenia. Concurrently, the foal developed rapidly progressive central nervous system signs culminating in refractory seizures. Both animals failed to respond to treatment and were euthanized. Thrombotic microangiopathy involving glomeruli was evident on microscopic examination of the m...
Lehner AF, Stewart J, Dafalla A, Ely KJ, Connerly AL, Jones CN, ElkHoly H, Thompson K, Tobin T, Dirikolu L.Gabapentin [1-(aminomethyl)cyclohexaneacetic acid, Neurontin], is a new anticonvulsant used as adjunctive therapy in the treatment of partial seizures in humans not controlled with standard antiseizure drugs, and it has also been used in veterinary medicine. In performance horses, gabapentin is listed as a class 3 performance-enhancing substance by the Association of Racing Commissioners International, and thus is considered to have the potential to influence the outcome of races. Therefore, we developed and validated a sensitive gas chromatographic-mass spectrometric (GC-MS) method for gabape...
Loynachan AT, Williams NM, Freestone JF.A 5-day-old Thoroughbred foal was submitted to the necropsy service at the University of Kentucky Livestock Disease Diagnostic Center. The foal had a clinical history of seizure activity and severe icterus. A complete blood count and serum chemistry analysis indicated that the foal was anemic (hematocrit, 16%), hyperbilirubinemic (45 mg/dl), and hypoglycemic. At necropsy, all tissues were discolored various shades of yellow. Microscopically, there was degeneration and necrosis of cerebral neurons and cerebellar Purkinje cells; severe hepatocellular degeneration and necrosis; and deposition of ...
Bryant UK, Lyons ET, Bain FT, Hong CB.A 13-week-old Thoroughbred colt from central Kentucky was euthanized after an acute onset of ataxia, blindness, head tremors, leaning to the right, recumbency, and seizures. Microscopically, there was a verminous meningoencephalitis characterized by an eosinophilic and granulomatous inflammatory reaction primarily affecting the cerebellum. Dispersed within regions of inflammation were numerous cross and longitudinal sections of intact and degenerative small nematodes. The nematodes had dorsoflexed ovaries and ventroflexed vulvas, which are distinguishing features of Halicephalobus gingivalis. ...
Raidal SL, Edwards S.To determine the pharmacokinetics of potassium bromide (KBr) in horses after single and multiple oral doses. Methods: Twelve adult Standardbred and Thoroughbred mares. Methods: Horses were randomly assigned to two treatment groups. Group 1 horses were given a single oral dose of 120 mg/kg potassium bromide. Part 2 of the study evaluated a loading dose of 120 mg/kg KBr daily by stomach tube for 5 days, followed by 40 mg/kg daily in feed for 7 days. Serum concentrations of KBr were measured to construct concentration versus time curves and to calculate pharmacokinetic parameters. Treated horses ...
Pellegrini-Masini A, Bentz AI, Johns IC, Parsons CS, Beech J, Whitlock RH, Flaminio MJ.Three adult horses were evaluated for signs of musculoskeletal pain, dullness, ataxia, and seizures. A diagnosis of bacterial meningitis was made on the basis of results of CSF analysis. Because primary bacterial meningitis is so rare in adult horses without any history of generalized sepsis or trauma, immune function testing was pursued. Flow cytometric phenotyping of peripheral blood lymphocytes was performed, and proliferation of peripheral blood lymphocytes in response to concanavalin A, phytohemagglutinin, pokeweed mitogen, and lipopolysaccharide was determined. Serum IgA, IgM, and IgG co...
Galvin N, Collins D.: This report presented a brief overview of the literature on the perinatal asphyxia syndrome (PAS) in foals as a prelude to a description of the investigation and treatment of acute onset seizures in a 24-hour-old Thoroughbred colt foal.PAS can cause a wide variety of clinical abnormalities, of which seizures due to encephalopathy are the most significant. The structural and biochemical components of CNS neurones are disrupted by the shift from oxidative to anaerobic metabolism, with a resultant deficit in cellular energy. The cells succumb to the combined effects of acidosis, neurotoxic acti...
Fitzgerald SD, Braselton WE.Diagnostic evaluation of a mildly ataxic young gelding Quarterhorse included a contrast myelogram. Unfortunately, sodium diatrizoate was inappropriately administered by intrathecal injection resulting in severe unrelenting seizure activity and necessitated the destruction of the animal. The contrast agent was identified by analyzing cerebrospinal fluid by high-performance liquid chromatography and confirmed with probe mass spectrometric analysis. This contrast agent is highly ionic, has high osmolarity, and also blocks neurotransmission at specific receptors; for these reasons it is contraindi...
Khan SA, Kuster DA, Hansen SR.Moxidectin is a macrolide endectocide available as a 2% equine oral gel in the US. This report presents clinical signs of moxidectin toxicosis and its treatment in equines as reported to the ASPCA Animal Poison Control Center (APCC) from January 1998 to December 2000. Nine cases of moxidectin overdose in equines occurred: 5 had signs of toxicosis such as coma, dyspnea, depression, ataxia, tremors, seizures, or weakness. The approximate dose of moxidectin at which these signs were observed ranged from 1.0 to 5.1 mg/kg. The 4 equines that ingested moxidectin between 0.9 mg/kg to 1.7 mg/kg did no...
Lacombe VA, Podell M, Furr M, Reed SM, Oglesbee MJ, Hinchcliff KW, Kohn CW.Electroencephalography (EEG) is a valuable diagnostic test to identify functional disturbances in brain activity. The purpose of this study was to assess the validity of EEG as a diagnostic indicator of intracranial diseases in horses. The validity of EEG was estimated by comparing clinical, clinicopathologic, and histopathologic findings to EEG findings in 20 horses examined for seizures. collapse, or abnormal behavior between 1984 and 1997. A bipolar left-to-right, back-to-front montage and a bipolar circular montage were recorded from sedated (4) and anesthetized (16) horses. Visual and sem...
Kinde H, Mathews M, Ash L, St Leger J.Two horses, a 16-year-old male Holsteiner and a 5-year-old male miniature horse, were diagnosed with halicephalobiasis at the California Veterinary Diagnostic Laboratory System, San Bernardino Branch, in April and June of 1998. Over a period of 4 weeks, the Holsteiner horse developed renal dysfunction, blepharospasm, and blindness in the right eye. A 15-cm-diameter mass was detected on ultrasound examination in the right kidney. Terminally, the animal developed seizures and was euthanized. The miniature horse had a 6-week-long illness characterized by testicular enlargement and uveitis. This a...
Feige K, Eser MW, Geissbühler U, Balestra E, Metzler K.Hirsutism was the most often observed symptom in horses with a pituitary gland tumor and was present in all 13 examined horses. Other symptoms were atrophy of muscles (n = 10), hyperhidrosis (n = 8), polyuria/polydipsia (n = 5), bulging or supraorbital fat (n = 3), polyphagia (n = 2), apathy (n = 2) and seizures (n = 2). Laminitis was the most frequently observed concurrent disease (n = 8). Hyperglycaemia (mean, 9.9 +/- 3.71 mmol/l) in 13 horses and glucosuria (median, 55 [range, 2-55] mmol/l) in 7 horses were the most important laboratory results. The dexamethasone suppression test was positi...
Couëtil LL, Hoffman AM.A 3-day-old female Pinto was admitted with profuse watery diarrhea and severe hypovolemic shock. After 1 week of intensive care, the foal developed seizures associated with profound serum electrolyte abnormalities suggestive of hypoadrenocorticism. Treatment with prednisone and isotonic saline (0.9% NaCl) solution led to prompt clinical response. Premature withdrawal of prednisone resulted in relapse of clinical signs. A diagnosis of adrenal insufficiency was made on the basis of clinical signs, electrolyte abnormalities, low baseline cortisol concentration, and lack of response to administrat...
Beyer MJ, Freestone JF, Reimer JM, Bernard WV, Rueve ER.Five thoroughbred foals (4 fillies and 1 colt), all in good to excellent body condition, ranging in age from 4 days to 5 weeks at the time of onset of signs, were presented to 2 Kentucky equine hospitals from 1992 through 1996. All 5 foals presented with tachycardia, hyperhidrosis, diarrhea or a recent history of diarrhea, and muscle rigidity or stiff gait. Four of the 5 foals presented for recumbency, seizure-like activity with opisthotonos, or pronounced extensor muscle rigidity. All 5 foals were hypocalcemic. All foals either died or had euthanasia performed. None responded to oral calcium ...
Rees WA, Harkins JD, Woods WE, Blouin RA, Lu M, Fenger C, Holland RE, Chambers TM, Tobin T.Amantadine is an antiviral agent effective against influenza A viruses. We investigated 1) the antiviral efficacy, 2) analytical detection, 3) bioavailability and disposition, 4) pharmacokinetic modelling and 5) adverse reactions of amantadine in the horse. In vitro, amantadine and its derivative rimantadine suppressed the replication of recent isolates of equine-2 influenza virus with effective doses (EDs) of less than 30 ng/ml. Rimantadine was more effective than amantadine against most viral isolates; we suggest a minimum plasma concentration of 300 ng/ml of amantadine for therapeutic effic...
van der Kolk JH, Wisse H, van Dijk S.A 20-year-old Arab crossbred gelding was examined because it had apparently suffered an overstimulation of the parasympathetic nervous system for three hours. The clinical signs consisted of hypersalivation, profuse sweating, maximal miosis, fasciculation of the muscles and lateral recumbency in combination with continuous convulsions without diarrhoea. The horse's plasma pseudocholinesterase activity was approximately 10 per cent of normal. It responded well to 10 mg atropine and 50 mg diazepam administered intravenously.
Lavy E, Ziv G, Glickman A.An aqueous solution of norfloxacin nicotinate (NFN) was administered to donkeys (Aquus asinus) intravenously (once at 10 mg/kg), intramuscularly and orally (both routes once at 10 and 20 mg/kg, and for 5 days at 20 mg/kg/day). Blood samples were collected at predetermined times after each treatment and urine was sampled after intravenous drug administration. Serum NFN concentrations were determined by microbiological assay. Intravenous injection of NFN over 45-60 s resulted in seizures, profuse sweating and tachycardia. The intravenous half-life (t1/2 beta) was 209 +/- 36 min, the apparent vol...
Jackson CA, deLahunta A, Dykes NL, Divers TJ.Cholesterinic granulomas have been previously reported as an incidental post mortem in horses. Three adult horses with diencephalic dysfunction due to cholesterinic granulomas are described. All the horses exhibited profound depression, somnolence and reluctance to move. One horse experienced generalised seizures. Cerebrosinal fluid was xanthochromic with an elevated total protein in two of the cases evaluated. The large cholesterinic granulomas caused expansion of the lateral ventricle and secondary hydrocephalus due to the build up of cerebrospinal fluid behind the mass. Cholesterinic granul...
Khan SA, Kuster DA, Hansen SR.Moxidectin is a macrolide endectocide available as a 2% equine oral gel in the US. This report presents clinical signs of moxidectin toxicosis and its treatment in equines as reported to the ASPCA Animal Poison Control Center (APCC) from January 1998 to December 2000. Nine cases of moxidectin overdose in equines occurred: 5 had signs of toxicosis such as coma, dyspnea, depression, ataxia, tremors, seizures, or weakness. The approximate dose of moxidectin at which these signs were observed ranged from 1.0 to 5.1 mg/kg. The 4 equines that ingested moxidectin between 0.9 mg/kg to 1.7 mg/kg did no...
Wijnberg ID, van der Ree M, van Someren P.Short-duration electroencephalography (EEG) recordings in horses are helpful in diagnosing intracranial disorders. Potentially, long-duration ambulatory EEG (AEEG) recordings in horses will enhance the chance of detecting abnormal brain activity independent of the presence of an insult. Objective: The objective of this study was to test if AEEG recordings in unsedated horses can be acquired and benefit diagnosing abnormal brain activity. Methods: Recordings were taken from 8 adult control horses and 10 patients suspected of intracranial abnormalities. Self-adhesive electrodes and the 'Porti-5'...
Raidal SL, Edwards S.To determine the pharmacokinetics of potassium bromide (KBr) in horses after single and multiple oral doses. Methods: Twelve adult Standardbred and Thoroughbred mares. Methods: Horses were randomly assigned to two treatment groups. Group 1 horses were given a single oral dose of 120 mg/kg potassium bromide. Part 2 of the study evaluated a loading dose of 120 mg/kg KBr daily by stomach tube for 5 days, followed by 40 mg/kg daily in feed for 7 days. Serum concentrations of KBr were measured to construct concentration versus time curves and to calculate pharmacokinetic parameters. Treated horses ...
Sogaro-Robinson C, Lacombe VA, Reed SM, Balkrishnan R.To determine neurologic indications associated with abnormal results for computed tomography (CT) imaging of the head of horses affected by neurologic disorders. Methods: Retrospective case series. Methods: 57 horses. Methods: Signalment, history, clinical abnormalities, and clinicopathologic findings were obtained from medical records of horses examined because of neurologic disorders, and precontrast and postcontrast CT images of the head were reviewed. Data were analyzed by use of univariate and multivariate logistic regression. Results: For a horse with abnormal mentation, odds of having a...
Lacombe VA, Mayes M, Mosseri S, Reed SM, Fenner WR, Ou HT.In contrast with reports in man and small animals, a systematic classification of seizures in horses is lacking. Objective: The purpose of this study was to classify seizures based on their aetiology and to characterise epilepsy in 104 horses presented for seizures at the Ohio State University Veterinary Medical Center between 1988 and 2009. Methods: In a retrospective observational study, seizures were classified by aetiology based on history, clinical observations, diagnostic investigations (e.g. electroencephalograms, cerebrospinal fluid and computed tomography imaging of the head) and post...
Rivas VN, Magdesian KG, Fagan S, Slovis NM, Luethy D, Javsicas LH, Caserto BG, Miller AD, Dahlgren AR, Peterson J, Hales EN, Peng S, Watson KD....Idiopathic hypocalcemia in Thoroughbred (TB) foals causes tetany and seizures and is invariably fatal. Based upon the similarity of this disease with human familial hypoparathyroidism and occurrence only in the TB breed, we conducted a genetic investigation on two affected TB foals. Familial hypoparathyroidism was identified, and pedigree analysis suggested an autosomal recessive (AR) mode of inheritance. We performed whole-genome sequencing of the two foals, their unaffected dams and four unaffected, unrelated TB horses. Both homozygosity mapping and an association analysis were used to prior...
Episodic collapse in horses has equine welfare and human safety implications. There are, however, no published case series describing this syndrome. Objective: To characterize the cause and outcomes for horses referred for investigation of episodic collapse. Methods: Twenty-five horses referred for investigation of single or multiple episodes of collapse. Methods: Retrospective study. Clinical records from the Dick Vet Equine Hospital, University of Edinburgh from November 1995 to July 2009 were searched using the following keywords: collapse, collapsing, fall, syncope. Collapse was defined as...
Aleman M, Finno CJ, Weich K, Penedo MCT.The carrier status of lavender foal syndrome (LFS), cerebellar abiotrophy (CA), severe combined immunodeficiency (SCID), and occipitoatlantoaxial malformation (OAAM1) in foals with juvenile idiopathic epilepsy (JIE) is unknown. Objective: To determine the carrier status of LFS, CA, SCID, and OAAM1 in foals with JIE. Methods: Ten foals with JIE. Methods: Archived DNA samples were tested for known genetic mutations causing LFS, CA, SCID, and OAAM1. The inclusion criteria consisted of having been diagnosed with JIE by ruling out other causes of seizures in foals and supported by electroencephalog...
Sakurai M, Isshiki S, Sasaki N, Sakai Y, Yamada Y, Morimoto M.A 7-year-old male Thoroughbred horse exhibited recurrent falls followed by convulsive seizures. The horse was clinically diagnosed with epilepsy and phenobarbital treatment was initiated. However, as seizure control was unsuccessful, the animal was euthanized. At necropsy, yellow-brown linear lesions were found extensively at the U-fibres and cingulate gyrus within the cerebral white matter. Histopathologically, linear demyelination and occasional cavitation were observed. Glial cells with yellow-brown pigment granules, which were autofluorescent, positive to the periodic acid-Schiff reaction ...
Cesar FB, Stewart AJ, Boothe DM, Ravis WR, Duran SH, Wooldridge AA.Nine horses received 20 mg/kg of intravenous (LEV ); 30 mg/kg of intragastric, crushed immediate release (LEV ); and 30 mg/kg of intragastric, crushed extended release (LEV ) levetiracetam, in a three-way randomized crossover design. Crushed tablets were dissolved in water and administered by nasogastric tube. Serum samples were collected over 48 hr, and levetiracetam concentrations were determined by immunoassay. Mean ± SD peak concentrations for LEV and LEV were 50.72 ± 10.60 and 53.58 ± 15.94 μg/ml, respectively. The y-intercept for IV administration was 64.54 ± 24.99 μg...
Bak EJ, Jean YH, Woo GH.Four thoroughbred horses showing lameness, ataxia, circling, depression, recumbency, and seizures, were examined. The horses had gross, pale- to dark-red manifestations and foci in the central nervous system (CNS). Multifocal to coalescing eosinophilic necrotizing encephalomyelitis was observed histologically in the CNS along with intact or degenerated nematodes. Nematodes had polymyarian-coelomyarian musculature, a smooth thin cuticle, and intestines lined by multinucleated cells with microvilli. These traits suggested the nematodes belonged to the family Protostrongylidae, which includes Par...
McEntee M, Summers BA, de Lahunta A, Cummings J.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...
Wong D, Hepworth K, Yaeger M, Miles K, Wilgenbusch C.An 8-year-old Thoroughbred mare presented for decreased appetite, ataxia, and weakness. Abdominal ultrasound revealed a large volume of anechoic fluid along with multiple masses involving the spleen, liver, and diaphragm. Pleural fluid was identified via ultrasonography and thoracic radiography. Thoracic radiographs also identified pulmonary interstitial nodules, an undulant dorsal diaphragmatic margin and enlargement of tracheobronchial lymph nodes. Clinical signs of weakness and mild seizures were concurrent with hypoglycemic episodes. The final diagnosis was cholangiocarcinoma with extensiv...
Lichter-Peled A, Polani S, Stanyon R, Rocchi M, Kahila Bar-Gal G.Juvenile idiopathic epilepsy (JIE) in Arabian foals resembles benign-familial neonatal convulsion (BFNC) syndrome, a rare idiopathic epilepsy of new-born humans. BFNC syndrome exhibits genetic heterogeneity, as has been hypothesised to occur in Arabian foals, and is known to be caused by mutations in the voltage-gated potassium channel subunit KCNQ2 and KCNQ3 genes. The close phenotypic characteristics of both Arabian foals and children suggest these epileptic syndromes are caused by the same genetic disorder. In horses, the KCNQ2 and KCNQ3 genes are located on the terminal region of chromosom...
Beyer MJ, Freestone JF, Reimer JM, Bernard WV, Rueve ER.Five thoroughbred foals (4 fillies and 1 colt), all in good to excellent body condition, ranging in age from 4 days to 5 weeks at the time of onset of signs, were presented to 2 Kentucky equine hospitals from 1992 through 1996. All 5 foals presented with tachycardia, hyperhidrosis, diarrhea or a recent history of diarrhea, and muscle rigidity or stiff gait. Four of the 5 foals presented for recumbency, seizure-like activity with opisthotonos, or pronounced extensor muscle rigidity. All 5 foals were hypocalcemic. All foals either died or had euthanasia performed. None responded to oral calcium ...
Ciosek J, Kimes A, Vinardell T, Miller DC, Antczak DF, Brooks S.Valued for their temperament, beauty, athletic ability, and exhibition in the show ring, Arabian horses are an important component of the horse industry. Juvenile idiopathic epilepsy (JIE), a seizure disorder, is most often reported in Arabian foals from birth to 6 months of age. Affected foals exhibit tonic-clonic seizures lasting as long as 5 min and risking secondary complications like temporary blindness and disorientation. Some foals outgrow this condition, while others die or suffer lifelong complications if not treated. Previous work suggested a strong genetic component to JIE and propo...
Lakritz J, Madigan J, Carlson GP.Hypovolemic hyponatremia attributable to severe fluid and electrolyte alterations was diagnosed in a foal with diarrhea. Subsequent consumption of water resulted in rapid reduction of serum sodium concentration and serum osmolar depression. Clinical signs of neurologic disease developed including blindness, loss of menace response, and seizures. Treatment of this condition with IV administered fluids included hypertonic saline solution (7.2%; 2 ml/kg of body weight), and frequent monitoring of serum electrolyte concentrations and osmolality resulted in gradual correction of the fluid and elect...
MacDonald KD, Hart KA, Davis JL, Berghaus LJ, Giguère S.Seizures are a common manifestation of neurological disease in the neonatal foal and are an important cause of morbidity and mortality in this population. Current antiepileptic options are effective, but often have undesirable adverse effects, short duration of action and high cost. Levetiracetam has an ideal safety and pharmacokinetic profile in multiple species, including the adult horse, and may be a safe and cost-effective alternative anticonvulsant in neonatal foals. Due to differences in drug disposition and clearance dosages in neonates, dosing recommendations in other species or adult ...
Rees WA, Harkins JD, Woods WE, Blouin RA, Lu M, Fenger C, Holland RE, Chambers TM, Tobin T.Amantadine is an antiviral agent effective against influenza A viruses. We investigated 1) the antiviral efficacy, 2) analytical detection, 3) bioavailability and disposition, 4) pharmacokinetic modelling and 5) adverse reactions of amantadine in the horse. In vitro, amantadine and its derivative rimantadine suppressed the replication of recent isolates of equine-2 influenza virus with effective doses (EDs) of less than 30 ng/ml. Rimantadine was more effective than amantadine against most viral isolates; we suggest a minimum plasma concentration of 300 ng/ml of amantadine for therapeutic effic...
Ross MW, Lowe JE, Cooper BJ, Reimers TJ, Froscher BA.A 12-year-old, 195 kg Shetland pony broodmare had eight seizures between May 29 and August 7, 1979. Plasma glucose levels during three of these seizures were markedly depressed (16, 18 and 19 mg/100 ml). Serum insulin levels were elevated during two of the seizures (86.0 and 97.7 microU/ml). Although a fasting hypoglycemia was not demonstrated, plasma glucose values during a normal day were abnormal; a plasma glucose level of 42 mg/100 ml was noted eight hours post-feeding. Serum insulin values obtained during an oral glucose tolerance test and intravenous glucagon tolerance test were consiste...
van der Ree M, Wijnberg I.Epilepsy in the horse is diagnosed based on clinical signs, but diagnosing can be difficult if a grand mal is not present. The future prospects of the horse and potentially the safety of the owner depend on an accurate diagnosis. This review presents information on epilepsy and focuses on the diagnostic potential of (Ambulatory) electroencephalography ((A) EEG). An epileptic seizure is a brain disorder, which expresses itself as a recurrent episode of involuntary abnormal behaviour. The aetiology can originate from inside or outside the brain or is idiopathic. Besides those categories, seizure...
Fitzgerald SD, Braselton WE.Diagnostic evaluation of a mildly ataxic young gelding Quarterhorse included a contrast myelogram. Unfortunately, sodium diatrizoate was inappropriately administered by intrathecal injection resulting in severe unrelenting seizure activity and necessitated the destruction of the animal. The contrast agent was identified by analyzing cerebrospinal fluid by high-performance liquid chromatography and confirmed with probe mass spectrometric analysis. This contrast agent is highly ionic, has high osmolarity, and also blocks neurotransmission at specific receptors; for these reasons it is contraindi...
Collins NM, Axon JE, Carrick JB, Russell CM, Palmer JE.To evaluate severe hyponatraemia in foals presenting as medical emergencies to an intensive care unit (ICU) in order to determine the prevalence, clinical findings, primary diagnosis and outcome. Methods: Retrospective case study of records from Thoroughbred foals aged less than 3 months presenting to an ICU as medical emergencies in 2002-12; foals with severe hyponatraemia (serum sodium <122 mmol/L) on admission laboratory data were identified. Data retrieved included signalment, clinical findings, laboratory results, primary diagnosis, treatment and outcome. Results: Severe hyponatraemia w...
Bingham J, Payne J, Harper J, Frazer L, Eastwood S, Wilson S, Lowther S, Lunt R, Warner S, Carr M, Hall RA, Durr PA.West Nile virus (WNV; family Flaviviridae; genus Flavivirus) group members are an important cause of viral meningoencephalitis in some areas of the world. They exhibit marked variation in pathogenicity, with some viral lineages (such as those from North America) causing high prevalence of severe neurological disease, whilst others (such as Australian Kunjin virus) rarely cause disease. The aim of this study was to characterize WNV disease in a mouse model and to elucidate the pathogenetic features that distinguish disease variation. Tenfold dilutions of five WNV strains (New York 1999, MRM16 a...
Mello GW, Riet-Correa F, Batista MC, Carvalho CJ, Dias AC, Franklin FL, Silva SM, Dias A.Farmers in the State of Piauí in northeastern Brazil reported nervous signs in ruminants and donkeys after ingestion of Brunfelsia uniflora at the start of the rainy season when the plant is flowering. Leaves of the plant, collected at the start or at the end of the rainy season, were administered in single doses of 5-20 g/kg body weight to 8 sheep and 3 donkeys. Two sheep and 1 donkey that ingested 10 g/kg of the plant in November at the start of the rainy season, when the plant was flowering, developed severe convulsions and diarrhea. One sheep was euthanized and autopsied, and no significa...
Di Cesare F, Negro V, Ravasio G, Villa R, Draghi S, Cagnardi P.Gabapentin is an anticonvulsant drug, which presents an established clinical efficacy in human patients for the management of refractory partial seizures, secondarily generalized tonic-clonic seizures, and for the control of chronic neuropathic pain. Gabapentin was synthesized as a structural analogue of the inhibitory neurotransmitter GABA, with GABA-mimetic effects, able to cross the blood-brain barrier. In veterinary medicine, is extra-label used in combination with other treatments to control seizures when other drugs are no longer effective or become toxic or for neuropathic pain treatmen...
Raidal SL, Edwards S.To determine the pharmacokinetics of potassium bromide (KBr) in horses after a single and multiple oral doses. Methods: Twelve adult Standardbred and Thoroughbred mares. Methods: Horses were randomly assigned into two treatment groups. In Part 1 of the study, horses were given a single oral dose of 120 mg/kg KBr. Part 2 of the study evaluated a loading dose of 120 mg/kg KBr daily by stomach tube for 5 days, followed by 40 mg/kg daily in feed for 7 days. Serum concentrations of bromide were determined by colorimetric spectrophotometry following drug administration to permit determination of con...
Wilson JW.Creatine phosphokinase activity was determined in cerebrospinal fluid samples submitted for analysis from 126 animals suspected of having central nervous system disease. Values less than 1 sigma unit/ml were obtained on 32 samples and values less than or equal to 1 sigma unit/ml were obtained on 94 samples. The creatine phosphokinase values were increased in all cases of feline toxoplasmosis and feline infectious peritonitis. From other cases, especially seizure disorders and suspected poisonings, and apparent aid in prognosis for future cases was identified.
Wong D, Wilkins PA, Bain FT, Brockus C.Neonatal encephalopathy is a common central nervous system disorder of neonatal foals and human infants, resulting in clinical signs such as lethargy, inappropriate behavior, seizures, and other neurologic deficits. Although neonatal encephalopathy is frequently seen in equine practice, a paucity of veterinary clinical and basic science research data is available. Therefore, the pathophysiologic mechanisms of this disorder in equids, such as energy deprivation, excess excitatory amino acids, and free radical injury, have been extrapolated from human medicine. Equine veterinarians have used var...
Spehar AM, Hill MR, Mayhew IG, Hendeles L.Pharmacokinetic characteristics of the anticonvulsant phenobarbital were studied in seven pony and two Thoroughbred foals aged between four and 10 days. A single, 20 mg/kg bodyweight (bwt) dose of phenobarbital was given intravenously over 25 mins and the serum concentrations of the drug were measured using an EMIT AED assay (coefficient of variation 1.37 per cent at 30 micrograms/ml, n = 7). Phenobarbital elimination was found to follow first order kinetics. The mean (+/- sd) peak phenobarbital serum concentration was 18.6 +/- 2.1 micrograms/ml at 1 h after initiation of infusion with a mean ...
