Brainstem auditory evoked responses and bone conduction assessment in alpacas

Auditory loss has been reported in camelids using brainstem auditory evoked responses (BAER). Differentiation between conductive versus sensorineural dysfunction has not been investigated. Therefore, the objective of the study was to investigate auditory function using BAER and bone conduction (BC). Twenty-four alpacas: 15 females, 9 intact males (2-16 years of age) were included in a randomized clinical trial. BAER and BC were recorded using two derivations (vertex to mastoid and vertex to cranial aspect of second cervical vertebra). All alpacas underwent complete physical examinations and were sedated with xylazine hydrochloride at 0.6 mg/kg IM. Peaks, when present, were identified and latencies, amplitudes, and amplitude ratios were determined. Eleven alpacas had normal responses and 13 had auditory loss based on BAER. The latter consisted of complete absence of peaks bilaterally (n = 3), absence of peaks unilaterally (n = 1), delayed latencies bilaterally (n = 4), and delayed latencies unilaterally (n = 5). Distinct peaks on BC supported conductive auditory loss in 6 alpacas, difficult to interpret due to stimulus artifact and additional undefined peaks in 4, and absent peaks in 3 alpacas. The cause of auditory loss was presumed to be due to otitis in 6, aging in 4 (10-16 years old), and congenital sensorineural (absent peaks on BAER and BC) in 3 alpacas with unpigmented fiber and irises. BAER and BC are useful and non-invasive to perform techniques for the investigation of auditory loss in alpacas, and further characterization as conductive or sensorineural.

Presumed Neuroglycopenia Caused by Severe Hypoglycemia in Horses

BACKGROUND

Neuroglycopenia refers to a shortage of glucose in the brain resulting in neuronal dysfunction and death if left untreated. Presumed neuroglycopenia has not been described in horses.

OBJECTIVE

To report neurological signs in horses with presumed neuroglycopenia as the result of severe hypoglycemia.

ANIMALS

Ninety horses (hours to 28 years of age) diagnosed with hypoglycemia (blood glucose concentration < 75 mg/dL [< 4.2 mmol/L]).

METHODS

Retrospective study. Electronic medical records were searched. Signalment, history, complaint, clinical signs, laboratory findings including CSF analysis, electroencephalogram, clinical or definitive diagnosis, and outcome were recorded. Kruskal-Wallis analysis of variance and logistic regression were used to investigate association between blood glucose concentration and data extracted. Statistical significance was set at P < 0.05.

RESULTS

Thirty-eight and 52 horses had mild (50-74 mg/dL [2.8-4.1 mmol/L]), and severe hypoglycemia (< 50 mg/dL [< 2.8 mmol/L]), respectively. Most common causes of hypoglycemia included liver and gastrointestinal (40%) disease, sepsis (33%), neoplasia (7%), and insulin-induced (4%). Most common neurologic deficits included obtundation (100%), seizures (42%), and disorientation (22%). CSF-glucose was severely low (mean 2.5 mg/dL [0.1 mmol/L], median 0 mg/dL). Paroxysmal discharges in support of seizures were identified in the occipital (visual) and parietal (closest to temporal-auditory) cortical regions upon EEG examination (8/8 horses).

CONCLUSIONS AND CLINICAL IMPORTANCE

Neuroglycopenia is presumed to occur in horses as the result of severe hypoglycemia. Subclinical seizures, and intermittent blindness and deafness of cortical origin can occur. Severe altered state of consciousness and seizures can be observed at a blood glucose cut-off value of < 42 mg/dL (< 2.3 mmol/L).

Investigation of Known Genetic Mutations of Arabian Horses in Egyptian Arabian Foals with Juvenile Idiopathic Epilepsy

Background

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.

Hypothesis/Objectives

To determine the carrier status of LFS, CA, SCID, and OAAM1 in foals with JIE.

Animals

Ten foals with JIE.

Materials and 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 electroencephalographic examination.

Results

Ten Egyptian Arabian horses (5 females and 5 males) were phenotyped as foals with JIE by electroencephalography (EEG). All foals were negative for the genetic mutations that cause LFS, CA, SCID, and OAAM1 except for 1 foal that was a carrier of CA.

Conclusions and Clinical Importance

Juvenile idiopathic epilepsy of Egyptian Arabian foals and LFS appear to be phenotypically and genetically distinct disorders. There was no apparent association between JIE and LFS, CA, SCID, and OAAM1.

Nitrogen doped carbon dots derived from Sargassum fluitans as fluorophore for DNA detection

This work focused on the use of waste seaweed Sargassum fluitans (S. fluitans) as carbon source precursor to prepare nitrogen doped carbon dots (NCDs) by hydrothermal method. High resolution transmission electron microscopic (HR-TEM) studies revealed that the synthesized water soluble NCDs are in the size range of 2-8nm and exhibits excellent fluorescent properties with a quantum yield of 18.2%. Elemental nitrogen in NCDs was evidenced by X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectrum (FT-IR). The phytochemical analysis of S. fluitans using 1H NMR and 13C NMR revealed the presence of few amino acids which act as nitrogen source in the preparation of NCDs. Application of NCDs as fluorophore for double stranded DNA, single stranded DNA and RNA detection was highlighted in this study. Excellent fluorescent tagging abilities of NCDs with the biological nucleic acids were evidenced using gel electrophoresis. Significant increase in fluorescence was observed upon tagging of NCDs with nucleic acids and this particular phenomenon helps better in visualizing the nucleic acids. All three nucleic acids i.e. double stranded DNA, single stranded DNA and RNA showed similar phenomenon upon tagging with NCDs. Thus synthesized NCDs may be used as an alternate fluorophore for commercial toxic organic staining agents to visualize nucleic acids.

Skin-to-skin contact after birth and the natural course of neurosteroid levels in healthy term newborns

OBJECTIVE

To determine the postnatal course of neurosteroid levels in relation to gender, mode of delivery and the extent of skin-to-skin (STS) contact during the first days of life in healthy term newborns.

STUDY DESIGN

Prospective observational study of 39 neonates in which parents recorded total duration of STS in the first 2 days and nine neurosteroids (dehydroepiandrosterone-sulfate, progesterone, pregnenolone, pregnenolone-sulfate, allopregnanolone, isopregnanolone, epipregnanolone, pregnanolone and pregnanolone-sulfate) were assayed from blood samples at birth and at 1-2 days of age.

RESULTS

All nine neurosteroid levels declined significantly during the first 2 days of life. Gender did not significantly affect the change in neurosteroid levels. The decline in neurosteroid levels was generally more pronounced in vaginal deliveries, and there was a trend toward a larger decline with more exposure to STS.

CONCLUSION

Ongoing studies may better characterize the role of neurosteroids and the influence of STS in more critically ill and premature neonates.

Deletion of 2.7 kb near HOXD3 in an Arabian horse with occipitoatlantoaxial malformation

In the horse, the term occipitoatlantoaxial malformation (OAAM) is used to describe a developmental defect in which the first cervical vertebra (atlas) resembles the base of the skull (occiput) and the second cervical vertebra (axis) resembles the atlas. Affected individuals demonstrate an abnormal posture and varying degrees of ataxia. The homeobox (HOX) gene cluster is involved in the development of both the axial and appendicular skeleton. Hoxd3-null mice demonstrate a strikingly similar phenotype to Arabian foals with OAAM. Whole-genome sequencing was performed in an OAAM-affected horse (OAAM1) and seven unaffected Arabian horses. Visual inspection of the raw reads within the region of HOXD3 identified a 2.7-kb deletion located 4.4 kb downstream of the end of HOXD4 and 8.2 kb upstream of the start of HOXD3. A genotyping assay revealed that both parents of OAAM1 were heterozygous for the deletion. Additional genotyping identified two of 162 heterozygote Arabians, and the deletion was not present in 371 horses of other breeds. Comparative genomics studies have revealed that this region is highly conserved across species and that the entire genomic region between Hoxd4 and Hoxd3 is transcribed in mice. Two additional Arabian foals diagnosed with OAAM (OAAM 2 and 3) were genotyped and did not have the 2.7-kb deletion. Closer examination of the phenotype in these cases revealed notable variation. OAAM3 also had facial malformations and a patent ductus arteriosus, and the actual malformation at the craniocervical junction differed. Genetic heterogeneity may exist across the HOXD locus in Arabian foals with OAAM.

Clinical Implications and Hospital Outcome of Immune-Mediated Myositis in Horses

BACKGROUND

Immune-mediated myositis (IMM) is a cause of rhabdomyolysis, stiffness, and muscle atrophy predominantly affecting Quarter horses. Limited information is available with regard to outcome, prognostic indicators, and associations with concurrent diseases.

HYPOTHESIS/OBJECTIVES

To report outcomes and associations between outcome and clinical and laboratory parameters, and presence of concurrent illness.

ANIMALS

Sixty-eight horses; 52 Quarter horses and related breeds and 16 other breeds.

METHODS

Retrospective cohort study (1991-2014). Medical records of horses with histological diagnosis of IMM were reviewed. Data recovery included signalment, laboratory variables, therapy, and outcome. Logistic regression was used to quantify the association between potential prognostic factors and survival to discharge.

RESULTS

Quarter horses were younger (mean < 4 years, range 3 months-21 years) than other breeds (mean < 10 years, range 1-23 years). Pathogens causing concurrent or recent infection included S. equi equi, S. equi zooepidemicus, C. pseudotuberculosis, Anaplasma phagocytophilum, herpes virus-1, and influenza. The most common clinical signs consisted of rapidly progressive diffuse symmetrical muscle atrophy (80%), stiff gait (74%), and fever (44%). All horses that received medical therapy immediately upon admission survived to discharge (survival proportion = 87%). Leucocytosis was a common finding (60%). Horses with concurrent fever and other illness had a poor prognosis for hospital discharge.

CONCLUSIONS AND CLINICAL IMPORTANCE

Horses with IMM can have a favorable outcome. Horses with concurrent fever and another illness had decreased probability of survival to discharge.

Seizure Disorders in Goats and Sheep

Background

Goats and sheep are more likely to be presented for examination for seizures than are cattle, possibly as a consequence of their relatively smaller body size. Currently, no reports describing seizure disorders in goats and sheep are available.

Objectives

To describe clinical features and treatment outcomes of sheep and goats presented for seizures.

Animals

A total of 59 goats and 21 sheep presented for seizures.

Methods

Retrospective study. Medical records from 1994 to 2014 at the Veterinary Medical Teaching Hospital, University of California, Davis, were reviewed. Descriptive statistics were used to summarize data. Logistic regression was performed to determine whether variables were associated with mortality.

Results

The majority of seizures in goats and sheep had structural or metabolic causes. Polioencephalomalacia (PEM) secondary to ruminal lactic acidosis or PEM of undetermined cause was the most frequently diagnosed cause of seizures in goats and sheep. The proportions of mortality in goats and sheep were 49.2 and 42.9%, respectively. Age increased the odds mortality (odds ratio [OR], 1.51; 95% confidence interval [CI], 1.07, 2.14) in goats. Goats with structural or metabolic causes of seizures had higher odds for mortality (OR, 37.48; 95% CI, 1.12, 99.10) than those with unknown causes. Age and etiological diagnosis were not significant (P > .05) predictors of mortality in affected sheep.

Conclusions and Clinical Relevance

Seizure disorders in goats and sheep are associated with high mortality, despite treatment. Current treatment in goats and sheep with seizures warrants further investigation to determine whether treatments are beneficial or detrimental to survival.

Drug Residues after Intravenous Anesthesia and Intrathecal Lidocaine Hydrochloride Euthanasia in Horses

Background

Intrathecal lidocaine hydrochloride under general anesthesia has been used as an alternative method of euthanasia in equids. Carnivore, scavenger, and even human consumption of horse meat from carcasses have been anecdotally reported in rural areas after this method of euthanasia. The presence of drug residues in horse meat has not been investigated.

Hypothesis/Objectives

To investigate if drug residues are found in horse tissues and determine their concentrations.

Animals

Of 11 horses requiring euthanasia for medical reasons.

Methods

Prospective descriptive study. Horses were anesthetized with total IV dose of xylazine (mean, 2.5 mg/kg), midazolam (0.1 mg/kg), and ketamine hydrochloride (mean, 5.8 mg/kg). An atlanto‐occipital cisterna centesis for the collection of cerebrospinal fluid (CSF) and administration of lidocaine hydrochloride (4 mg/kg) was performed. Blood samples for both serum and plasma, skeletal muscle (triceps brachii, gluteus medius), and CSF were collected for the determination of drug residues. Frozen skeletal muscle available from 5 additional horses that received standard dosages of drugs for short‐term anesthesia (xylazine 1.1 mg/kg, midazolam 0.1 mg/kg, and ketamine 2.2 mg/kg) also were analyzed.

Results

Drug residues were found in the tissues of all horses, but at extremely low concentrations.

Conclusions and Clinical Importance

Euthanasia by administration of lidocaine intrathecally to horses under IV anesthesia poses a low risk of toxicity to carnivores and scavengers that might consume muscle tissue from a carcass in which this protocol has been used.

Qualitative and Quantitative Characteristics of the Electroencephalogram in Normal Horses during Administration of Inhaled Anesthesia

BACKGROUND

The effects of anesthesia on the equine electroencephalogram (EEG) after administration of various drugs for sedation, induction, and maintenance are known, but not that the effect of inhaled anesthetics alone for EEG recording.

OBJECTIVE

To determine the effects of isoflurane and halothane, administered as single agents at multiple levels, on the EEG and quantitative EEG (qEEG) of normal horses.

ANIMALS

Six healthy horses.

METHODS

Prospective study. Digital EEG with video and quantitative EEG (qEEG) were recorded after the administration of one of the 2 anesthetics, isoflurane or halothane, at 3 alveolar doses (1.2, 1.4 and 1.6 MAC). Segments of EEG during controlled ventilation (CV), spontaneous ventilation (SV), and with peroneal nerve stimulation (ST) at each MAC multiple for each anesthetic were selected, analyzed, and compared. Multiple non-EEG measurements were also recorded.

RESULTS

Specific raw EEG findings were indicative of changes in the depth of anesthesia. However, there was considerable variability in EEG between horses at identical MAC multiples/conditions and within individual horses over segments of a given epoch. Statistical significance for qEEG variables differed between anesthetics with bispectral index (BIS) CV MAC and 95% spectral edge frequency (SEF95) SV MAC differences in isoflurane only and median frequency (MED) differences in SV MAC with halothane only.

CONCLUSIONS AND CLINICAL IMPORTANCE

Unprocessed EEG features (background and transients) appear to be beneficial for monitoring the depth of a particular anesthetic, but offer little advantage over the use of changes in mean arterial pressure for this purpose.

Neurologic Deficits Including Auditory Loss and Recovery of Function in Horses with Temporohyoid Osteoarthropathy

BACKGROUND

Auditory loss is a common deficit in horses with temporohyoid osteoarthropathy (THO), however, recovery of function is unknown.

HYPOTHESIS/OBJECTIVES

To investigate neurologic function with emphasis in audition in horses with THO after treatment. To describe anatomical alterations of the petrous temporal bone that might result in auditory loss.

ANIMALS

Twenty-four horses with a clinical diagnosis of THO.

METHODS

Prospective study. A brainstem auditory evoked response (BAER) study was done as part of the criteria for inclusion in horses with a clinical diagnosis of THO from the years of 2005 to 2014. Physical and neurologic status and BAER findings were recorded. Brainstem auditory evoked response variables were compared by using Wilcoxon sign test. Fisher's exact test was also used. Significance was set at P < 0.05.

RESULTS

The most common signs included auditory loss (100% of horses), vestibular and facial nerve dysfunction (83%), and exposure ulcerative keratitis (71%). Concurrent left laryngeal hemiparesis was observed in 61% of horses through endoscopy. Auditory dysfunction was bilateral in 50% of the cases (complete and partial), and unilateral affecting more commonly the right ear (R = 8, L = 4). Short- and long-term follow-up revealed persistent auditory loss in all horses based on abnormal response to sound, and further confirmed through a BAER in 8 horses.

CONCLUSIONS AND CLINICAL IMPORTANCE

Auditory dysfunction appears to be a permanent neurologic deficit in horses diagnosed with THO despite overall neurologic improvement.

Pneumonia Caused by Klebsiella spp. in 46 Horses

BACKGROUND

Klebsiella spp. are implicated as a common cause of bacterial pneumonia in horses, but few reports describe clinical presentation and disease progression.

HYPOTHESIS/OBJECTIVES

To describe the signalment, clinicopathologic data, radiographic and ultrasonographic findings, antimicrobial susceptibility, outcome, and pathologic lesions associated with Klebsiella spp. pneumonia in horses.

ANIMALS

Forty-six horses from which Klebsiella spp. was isolated from the lower respiratory tract.

METHODS

Retrospective study. Medical records from 1993 to 2013 at the William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis were reviewed. Exact logistic regression was performed to determine if any variables were associated with survival to hospital discharge.

RESULTS

Survival in horses <1 year old was 73%. Overall survival in adults was 63%. For adults in which Klebsiella pneumoniae was the primary isolate, survival was 52%. Mechanical ventilation preceded development of pneumonia in 11 horses. Complications occurred in 25/46 horses, with thrombophlebitis and laminitis occurring most frequently. Multi-drug resistance was found in 47% of bacterial isolates. Variables that significantly impacted survival included hemorrhagic nasal discharge, laminitis, and thoracic radiographs with a sharp demarcation between marked caudal pulmonary alveolar infiltration and more normal-appearing caudodorsal lung.

CONCLUSIONS AND CLINICAL IMPORTANCE

Klebsiella spp. should be considered as a differential diagnosis for horses presenting with hemorrhagic pneumonia and for horses developing pneumonia after mechanical ventilation. Multi-drug resistance is common. Prognosis for survival generally is fair, but is guarded for adult horses in which K. pneumoniae is isolated as the primary organism.

Electrophysiologic Study of a Method of Euthanasia Using Intrathecal Lidocaine Hydrochloride Administered during Intravenous Anesthesia in Horses

Background

An intravenous (IV) overdose of pentobarbital sodium is the most commonly used method of euthanasia in veterinary medicine. However, this compound is not available in many countries or rural areas resulting in usage of alternative methods such as intrathecal lidocaine administration after IV anesthesia. Its safety and efficacy as a method of euthanasia have not been investigated in the horse.

Hypothesis/Objectives

To investigate changes in mean arterial blood pressure and electrical activity of the cerebral cortex, brainstem, and heart during intrathecal administration of lidocaine. Our hypothesis was that intrathecal lidocaine affects the cerebral cortex and brainstem before affecting cardiovascular function.

Animals

Eleven horses requiring euthanasia for medical reasons.

Methods

Prospective observational study. Horses were anesthetized with xylazine, midazolam, and ketamine; and instrumented for recording of electroencephalogram (EEG), electrooculogram (EOG), brainstem auditory evoked response (BAER), and electrocardiogram (ECG). Physical and neurological (brainstem reflexes) variables were monitored. Mean arterial blood pressure was recorded throughout the study.

Results

Loss of cerebro‐cortical electrical activity occurred up to 226 seconds after the end of the infusion of lidocaine solution. Cessation of brainstem function as evidenced by a lack of brainstem reflexes and disappearance of BAER occurred subsequently. Undetectable heart sounds, nonpalpable arterial pulse, and extremely low mean arterial blood pressure supported cardiac death; a recordable ECG was the last variable to disappear after the infusion (300–1,279 seconds).

Conclusions and Clinical Importance

Intrathecal administration of lidocaine is an effective alternative method of euthanasia in anesthetized horses, during which brain death occurs before cardiac death.

Endoscopic Balloon Dilation of Esophageal Strictures in 9 Horses

Background

Medical treatment of esophageal strictures in horses is limited and the use of balloon dilatation is described in few cases. Long‐term follow up after balloon dilatation and the use of intralesional corticosteroids has not been evaluated.

Objectives

To describe the use of endoscopic guided, esophageal balloon dilatation in horses for cervical and thoracic esophageal strictures and administration of intralesional corticosteroids at the time of dilatation.

Animals

Nine horses from the hospital population with benign esophageal strictures.

Methods

Retrospective study: Medical records were reviewed from horses presented to the William R. Pritchard, Veterinary Medical Teaching Hospital at UC Davis from 2002 to 2013. Records were searched using the key words: equine, horse, balloon dilatation, bougienage, and esophageal stricture.

Results

Nine horses with esophageal strictures were treated with esophageal balloon dilatation. Five horses survived (survival at writing ranged from 2 to 11 years after discharge) and all nonsurvivors were <1 year of age and presented with concurrent problems or developed complications including megaesophagus, unresolved esophageal obstruction requiring esophagostomy, or severe aspiration pneumonia. Four horses were treated with intralesional corticosteroids with no adverse effects noted in the survivors (n = 3). Four horses available for long‐term follow up were alive at 2, 5, 6, and 11 years after presentation and 3 of these horses were being fed a hay‐based diet.

Conclusions

Resolution of esophageal strictures in the horse can be performed successfully, safely, and under standing sedation using balloon dilatation. Intralesional corticosteroids might reduce the incidence of recurrent strictures.

Cerebral and brainstem electrophysiologic activity during euthanasia with pentobarbital sodium in horses

Background

An overdose of pentobarbital sodium administered IV is the most commonly used method of euthanasia in veterinary medicine. Determining death after the infusion relies on the observation of physical variables. However, it is unknown when cortical electrical activity and brainstem function are lost in a sequence of events before death.

Hypothesis/Objectives

To examine changes in the electrical activity of the cerebral cortex and brainstem during an overdose of pentobarbital sodium solution for euthanasia. Our testing hypothesis is that isoelectric pattern of the brain in support of brain death occurs before absence of electrocardiogram (ECG) activity.

Animals

Fifteen horses requiring euthanasia.

Methods

Prospective observational study. Horses with neurologic, orthopedic, and cardiac illnesses were selected and instrumented for recording of electroencephalogram, electrooculogram, brainstem auditory evoked response (BAER), and ECG. Physical and neurologic (brainstem reflexes) variables were monitored.

Results

Loss of cortical electrical activity occurred during or within 52 seconds after the infusion of euthanasia solution. Cessation of brainstem function as evidenced by a lack of brainstem reflexes and disappearance of the BAER happened subsequently. Despite undetectable heart sounds, palpable arterial pulse, and mean arterial pressure, recordable ECG was the last variable to be lost after the infusion (5.5–16 minutes after end of the infusion).

Conclusions and Clinical Importance

Overdose of pentobarbital sodium solution administered IV is an effective, fast, and humane method of euthanasia. Brain death occurs within 73–261 seconds of the infusion. Although absence of ECG activity takes longer to occur, brain death has already occurred.

Electrophysiologic confirmation of heterogenous motor polyneuropathy in young cats

Background

Reports of motor polyneuropathies in young cats are scarce. Further, in‐depth electrophysiologic evaluation to confirm a motor polyneuropathy in young cats of various breeds other than 2 Bengal cats is lacking.

Hypothesis/Objectives

To confirm a motor polyneuropathy in young cats of various breeds.

Animals

Five young cats with heterogenous chronic or relapsing episodes of weakness.

Methods

Retrospective case series. Cats were presented for evaluation of generalized neuromuscular disease and underwent electrophysiologic examination including electromyography, nerve conduction, and repetitive nerve stimulation. Minimum database and muscle and nerve biopsy analyses were carried out. Descriptive statistics were performed.

Results

Disease onset was at 3 months to 1 year of age and in 5 breeds. The most common clinical sign (5 of 5 cats) was weakness. Additional neurologic deficits consisted of palmigrade and plantigrade posture (4/4), low carriage of the head and tail (4/4), and variable segmental reflex deficits (5/5). Motor nerve conduction studies were abnormal for the ulnar (4/4), peroneal (5/5), and tibial (2/2) nerves (increased latencies, reduced amplitudes, slow velocities). A marked decrement was observed on repetitive nerve stimulation of the peroneal nerve in 3 cats for which autoimmune myasthenia gravis was ruled out. All sensory nerve conduction studies were normal. Histologic evaluation of muscle and nerve biopsies supported heterogenous alterations consistent with motor polyneuropathy with distal nerve fiber loss.

Conclusions and Clinical Importance

Heterogenous motor polyneuropathies should be considered in young cats of any breed and sex that are presented with relapsing or progressive generalized neuromuscular disease.

Brainstem auditory evoked responses in an equine patient population: part I--adult horses

Background

Brainstem auditory evoked response has been an underused diagnostic modality in horses as evidenced by few reports on the subject.

Hypothesis/Objectives

To describe BAER findings, common clinical signs, and causes of hearing loss in adult horses.

Animals

Study group, 76 horses; control group, 8 horses.

Methods

Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Horses were grouped under disease categories. Descriptive statistics and a posthoc Bonferroni test were performed.

Results

Fifty‐seven of 76 horses had BAER deficits. There was no breed or sex predisposition, with the exception of American Paint horses diagnosed with congenital sensorineural deafness. Eighty‐six percent (n = 49/57) of the horses were younger than 16 years of age. The most common causes of BAER abnormalities were temporohyoid osteoarthropathy (THO, n = 20/20; abnormalities/total), congenital sensorineural deafness in Paint horses (17/17), multifocal brain disease (13/16), and otitis media/interna (4/4). Auditory loss was bilateral and unilateral in 74% (n = 42/57) and 26% (n = 15/57) of the horses, respectively. The most common causes of bilateral auditory loss were sensorineural deafness, THO, and multifocal brain disease whereas THO and otitis were the most common causes of unilateral deficits.

Conclusions and Clinical Importance

Auditory deficits should be investigated in horses with altered behavior, THO, multifocal brain disease, otitis, and in horses with certain coat and eye color patterns. BAER testing is an objective and noninvasive diagnostic modality to assess auditory function in horses.

Brainstem auditory evoked responses in an equine patient population. Part II: foals

Background

Reports of the use of brainstem auditory evoked response (BAER) as a diagnostic modality in foals have been limited.

Hypothesis/Objectives

To describe BAER findings and associated causes of hearing loss in foals.

Animals

Study group 18 foals (15 neonatal, 3 nonneonatal), control group (5 neonatal foals).

Methods

Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Clinical data were extracted from the medical records. Foals were grouped under disease categories. Descriptive statistics were performed.

Results

Ten neonatal foals had complete absence of BAER bilaterally and 5 had findings within reference range. Abnormalities were associated with common neonatal disorders such as sepsis, neonatal encephalopathy, neonatal isoerythrolysis, and prematurity. BAER loss also was observed in foals with specific coat color patterns such as completely or mostly white with blue irides or lavender with pale yellow irides. An American Miniature foal with marked facial deformation also lacked BAER bilaterally. One nonneonatal foal with an intracranial abscess had no detectable BAER peaks bilaterally, and 2 older foals, 1 with presumed equine protozoal myeloencephalitis and the other with progressive scoliosis and ataxia, had BAER within normal limits.

Conclusions and Clinical Importance

In neonatal foals, BAER deficits commonly are complete and bilateral, and associated with common neonatal disorders and certain coat and eye color patterns. Sepsis, hypoxia, bilirubin toxicity, and prematurity should be investigated as potential causes of auditory loss in neonatal foals.

Factors associated with survival in 148 recumbent horses

REASONS FOR PERFORMING STUDY

There are currently few data available on the prognosis and outcome of recumbent horses.

OBJECTIVES

To investigate the outcome of hospitalised horses that had been recumbent in the field or hospital and factors affecting their survival within the first 3 days of hospitalisation and survival after 3 days to hospital discharge.

STUDY DESIGN

Retrospective analysis of clinical records.

METHODS

Records of 148 horses admitted to the William R. Pritchard Veterinary Medical Teaching Hospital, University of California Davis from January 1995 to December 2010 with a history of recumbency or horses that became recumbent while hospitalised were evaluated. Exact logistic regression was used to assess the association between clinical parameters and survival within the first 3 days of hospitalisation and survival to hospital discharge after 3 days.

RESULTS

There were 109 nonsurvivors and 39 survivors. Multivariate analysis showed variables associated with an increased odds of death within the first 3 days of hospitalisation included duration of clinical signs prior to presentation, with horses showing clinical signs for over 24 h having increased odds of death (P = 0.043, odds ratio [OR] 4.16, 95% confidence interval [95% CI] 1.04-16.59), the presence of band neutrophils (P = 0.02, OR 7.94, 95% CI 1.39-45.46), the horse not using the sling (P = 0.031, OR 4.22, 95% confidence interval 1.14-15.68) and horses that were unable to stand after treatment (P<0.0001, OR 231.15, 95% CI 22.82-2341.33). Increasing cost was associated with lower odds of death (P = 0.017, OR 0.96, for each additional $100 billed, 95% CI 0.93-0.99).

CONCLUSIONS

This study demonstrates that the duration of clinical signs, response to treatment and the ability of horses to use a sling are associated with survival to hospital discharge for recumbent horses.

Sensory nerve conduction and somatosensory evoked potentials of the trigeminal nerve in horses with idiopathic headshaking

BACKGROUND

Idiopathic headshaking (HSK) in horses is a distressing disorder in which the etiology and pathophysiology are unknown.

HYPOTHESIS

Differences in sensory function of the trigeminal nerve exist between healthy and affected horses.

ANIMALS

Six healthy mature geldings and 6 mature geldings with idiopathic HSK.

METHODS

Prospective study. Sensory nerve action and somatosensory evoked potentials studies were performed. The stimulus site comprised the gingival mucosa dorsal to the maxillary canine. A pair of recording electrodes was placed along the sensory pathway of the trigeminal complex at the infraorbital nerve (R1), maxillary nerve (R2), spinal tract of trigeminal (R3), and somatosensory cortex (R4). Sensory nerve action potential latency (ms), amplitude (μV), duration (ms), area under the curve (μVms), and conduction velocity (m/s) were calculated.

RESULTS

Threshold for activation of the infraorbital branch of the trigeminal nerve was significantly different between 5 affected (≤ 5 mA) and 6 control horses (≥ 10 mA). After initiation of an action potential, there were no differences in all parameters measured and no differences between left and right sides. A horse with seasonal HSK tested during a time of no clinical manifestations showed a threshold for activation similar to control horses.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study confirms involvement of the trigeminal nerve hyperexcitability in the pathophysiology of disease. Further, results might support a functional rather than a structural alteration in the sensory pathway of the trigeminal complex that can be seasonal. The horse could serve as a natural animal model for humans with idiopathic trigeminal neuralgia.

Abnormal plasma neuroactive progestagen derivatives in ill, neonatal foals presented to the neonatal intensive care unit

REASONS FOR PERFORMING THE STUDY

Increased levels of pregnanes have been reported in foals with neonatal maladjustment syndrome (NMS). These steroids may cross the blood-brain barrier and have depressive effects in the central nervous system leading to behavioural abnormalities and altered states of consciousness in affected foals.

OBJECTIVES

The aim of this study was to determine the pregnane profile of foals with NMS and compare it with that of healthy controls and sick, non-NMS foals.

STUDY DESIGN

Prospective-clinical study.

METHODS

Thirty-two foals with a clinical diagnosis of NMS, 12 foals with other neonatal disorders and 10 healthy control foals were selected for the study. Heparinised blood samples were collected from each group of foals and pregnane and androgen concentrations determined using liquid chromatography mass spectrometry at 0, 24 and 48 h of age.

RESULTS

Healthy foals showed a significant decrease in pregnane concentrations over the first 48 h of life (P<0.01). Foals with NMS and sick, non-NMS foals had significantly increased progesterone, pregnenolone, androstenedione, dehydroepiandrosterone and epitestosterone concentrations compared with healthy foals (P<0.05). Progesterone and pregnenolone concentrations of sick, non-NMS foals decreased significantly over 48 h (P<0.05), whereas concentrations in NMS foals remained increased.

CONCLUSIONS AND POTENTIAL RELEVANCE

Pregnane concentrations of ill, neonatal foals remain increased following birth, reflecting a delayed, or interrupted, transition from intra- to extra-uterine life. Serial progesterone and pregnenolone measurement may be useful in aiding diagnosis of NMS.

Pathological evidence of pancreatitis in 43 horses (1986-2011)

REASONS FOR PERFORMING STUDY

Definitive ante mortem diagnosis of pancreatitis in horses is difficult. Reports summarising the most common clinical signs, clinicopathological features and concurrent disorders in horses with a definitive diagnosis of pancreatitis that may aid in the recognition of disease are lacking.

OBJECTIVES

To describe case details, clinical signs, clinicopathological data and necropsy findings in horses with a definitive diagnosis of pancreatitis.

METHODS

This was a retrospective study (1986-2011) and inclusion criteria consisted of horses with a definitive diagnosis of pancreatitis. A medical records database search was performed and data extracted included case details, clinical signs, clinical laboratory data and post mortem findings. Pancreatitis was defined as acute, active chronic or chronic and presumed primary or secondary, based on postmortem findings.

RESULTS

Pancreatitis was diagnosed in 43 horses (acute pancreatitis in 34, active chronic in 4 and chronic in 5). A presumed diagnosis of primary pancreatitis was made in 6 horses. Pancreatitis was associated with gastrointestinal disorders in 28 horses (14 large colon, 10 small intestine and 4 gastric ruptures) and primary hepatic disease in 3 horses. Six horses had pancreatitis associated with other disorders: multiple endocrine neoplasia syndrome (one horse), strychnine toxicosis (one horse) and compromised immune system (4 horses).

CONCLUSION

Pancreatitis is an uncommon disorder that can occur as a primary problem or secondary to gastrointestinal, hepatic or immunocompromising disorders, and when it occurs it affects adult horses more commonly.

POTENTIAL RELEVANCE

Unexplained abdominal pain, gastric dilation or rupture, peritonitis and/or the presence of white fibrinous plaques and fat necrosis in the peritoneum and mesentery or mass-like structures in the root of the mesentery during an exploratory celiotomy should raise a suspicious of pancreatitis.

Pedigree analysis and exclusion of alpha-tocopherol transfer protein (TTPA) as a candidate gene for neuroaxonal dystrophy in the American Quarter Horse

BACKGROUND

Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (NAD/EDM) is a neurodegenerative disorder affecting young horses of various breeds that resembles ataxia with vitamin E deficiency in humans, an inherited disorder caused by mutations in the alpha-tocopherol transfer protein gene (TTPA). To evaluate variants found upon sequencing TTPA in the horse, the mode of inheritance for NAD/EDM had to be established.

HYPOTHESIS

NAD/EDM in the American Quarter Horse (QH) is caused by a mutation in TTPA.

ANIMALS

88 clinically phenotyped (35 affected [ataxia score ≥2], 53 unaffected) QHs with a diagnosis of NAD/EDM with 6 affected and 4 unaffected cases confirmed at postmortem examination.

PROCEDURES

Pedigrees and genotypes across 54,000 single nucleotide polymorphism (SNP) markers were assessed to determine heritability and mode of inheritance of NAD/EDM. TTPA sequence of exon/intron boundaries was evaluated in 2 affected and 2 control horses. An association analysis was performed by 71 SNPs surrounding TTPA and 8 SNPs within TTPA that were discovered by sequencing. RT-PCR for TTPA was performed on mRNA from the liver of 4 affected and 4 control horses.

RESULTS

Equine NAD/EDM appears to be inherited as a polygenic trait and, within this family of QHs, demonstrates high heritability. Sequencing of TTPA identified 12 variants. No significant association was found using the 79 available variants in and surrounding TTPA. RT-PCR yielded PCR products of equivalent sizes between affected cases and controls.

CONCLUSIONS AND CLINICAL IMPORTANCE

NAD/EDM demonstrates heritability in this family of QHs. Variants in TTPA are not responsible for NAD/EDM in this study population.

Allopregnanolone infusion induced neurobehavioural alterations in a neonatal foal: is this a clue to the pathogenesis of neonatal maladjustment syndrome?

REASONS FOR PERFORMING THE STUDY

Increased plasma progestagen concentrations have been reported in foals with neonatal maladjustment syndrome (NMS). These steroids may cross the blood-brain barrier and have dampening effects in the central nervous system.

OBJECTIVES

To evaluate if the infusion of a progesterone derivative (allopregnanolone) in a healthy neonatal foal would induce clinical signs compatible with NMS.

METHODS

A healthy neonatal foal from a healthy mare with a normal gestation (length, no complications), birth and placenta was infused with allopregnanolone to observe its neurobehavioural effects. Heparinised blood samples were collected pre- and post infusion to determine various progestagen concentrations using liquid chromatography mass spectrometry. A second healthy neonatal foal was infused with ethanol and saline for comparison of clinical observations.

RESULTS

Infusion of allopregnanolone resulted in obtundation, lack of affinity for the mare and decreased response to external stimuli. These effects were short-lasting and associated with measurable concentrations of progestagens.

CONCLUSIONS AND POTENTIAL RELEVANCE

Infusion of a steroid metabolite to a healthy neonatal foal resulted in neurobehavioural alterations compatible with those observed in foals with NMS. These findings suggest that increased progestagen concentrations may be responsible for some of the behavioural changes observed in foals with NMS.

Equine degenerative myeloencephalopathy in Lusitano horses

BACKGROUND

Equine degenerative myeloencephalopathy (EDM) is a neurodegenerative disorder that has been previously associated with low vitamin E concentrations.

OBJECTIVE

To describe the clinical, electrophysiologic, and pathologic features of EDM in a group of related Lusitano horses.

ANIMALS

Fifteen Lusitano horses.

PROCEDURES

Neurologic examinations were conducted, and serum vitamin E concentrations were measured. Three neurologically abnormal horses were further evaluated by ophthalmologic examination, electroretinography, electroencephalography, muscle and nerve biopsies, and post-mortem examination.

RESULTS

Six horses appeared neurologically normal, 6 were neurologically abnormal, and 3 had equivocal gait abnormalities. Abnormal horses demonstrated ataxia and paresis. An inconsistent menace response was noted in 4 neurologically abnormal horses and in 1 horse with equivocal findings. All horses had low serum vitamin E concentrations (<1.5 ppm). Ophthalmologic examinations, electroretinograms, electroencephalograms, and muscle and peripheral nerve biopsies were unremarkable in 3 neurologically abnormal horses. At necropsy, major neuropathological findings in these horses were bilaterally symmetric, severe, neuro axonal degeneration in the gracilis, cuneatus medialis, cuneatus lateralis, and thoracicus nuclei and bilaterally symmetric axonal loss and demyelination mainly in the dorsolateral and ventromedial tracts of the spinal cord. A diagnosis of EDM was made based on these findings. Pedigree analysis identified 2 sires among the affected horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Equine degenerative myeloencephalopathy is a neurodegenerative disorder that causes ataxia and, in severe cases, paresis, in young Lusitano horses. The disease appears to have a genetic basis, and although vitamin E deficiency is a common finding, low serum vitamin E concentrations also may occur in apparently unaffected related individuals.

Latent equine herpesvirus-1 in trigeminal ganglia and equine idiopathic headshaking

BACKGROUND

Trigeminal neuralgia or neuropathic pain has been regarded as a putative cause of idiopathic headshaking in horses. Equine herpesvirus-1 (EHV-1) infection and resultant postherpetic pain have been suggested as a possible cause of such neuropathic pain.

HYPOTHESIS/OBJECTIVES

To determine the presence of EHV-1 in the trigeminal ganglia of horses with idiopathic headshaking.

ANIMALS

Nineteen horses: control (n = 11, 9 geldings, 2 mares, median age 11 years) and headshaking (n = 8, all geldings, median age 11.5 years) horses were sourced from the equine research herd and caseload at the Veterinary Medical Teaching Hospital.

METHODS

Prospective study to determine the presence of EHV-1 latency in trigeminal ganglia of horses with idiopathic headshaking by real-time PCR detection of the glycoprotein B (gB) gene and the DNA polymerase (ORF 30) gene of EHV-1 in the absence of detectable late structural protein gene (gB gene) mRNA. Control horses were used for comparison. A house keeping gene (equine GAPDH) and positive and negative samples for EHV-1 were used for quality control.

RESULTS

All samples from control horses and 7 of 8 headshaking horses were negative for EHV-1. One headshaking horse tested positive for a single copy of EHV-1 gene.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study does not support a role for EHV-1 infection and presumed postherpetic pain in the etiopathogenesis of equine headshaking.

Effect of lipopolysaccharide infusion on gene expression of inflammatory cytokines in normal horses in vivo

Horses are exquisitely sensitive to bacterial endotoxin and endotoxaemia is common in colic cases. In this study, gene expression of inflammatory cytokines was characterised in the blood of healthy horses following i.v. administration of lipopolysaccharide (LPS). Six horses received an LPS infusion and 6 controls received an equivalent volume of saline. Gene expression of genes encoding interleukin (IL)-1alpha, IL-1beta, IL-6, IL-8, and tumour necrosis factor-alpha (TNF-alpha) was quantified by real-time PCR. Gene expression of all inflammatory cytokines was upregulated following administration of LPS. Interleukin-1alpha, IL-1beta, IL-8 and TNF-alpha gene expression peaked at 60 min, while IL-6 expression peaked at 90 min post LPS infusion. Interleukin-1beta and IL-6 messenger RNA expression levels were above the baseline values 3 h post LPS infusion, whereas IL-1alpha, IL-8 and TNF-alpha expression levels returned to baseline values by 3 h after LPS infusion. It was concluded that LPS infusion upregulated gene expression of inflammatory cytokines in the blood of healthy horses.