Neuro

Question 1

Relationship between equine herpesvirus-1 viremia and abortion or equine herpesvirus myeloencephalopathy in domesticated horses: A systematic review

Answer 1

Viremia as a Prerequisite
• Viremia consistently identified as a prerequisite for both abortion and EHM.
• The duration of viremia may influence risk, especially for neurological disease (EHM), but the magnitude of viremia had inconsistent associations with outcomes.

Neurological Disease (EHM)
• Inconsistent findings across studies regarding the relationship between the level of viremia and EHM:
• Some studies linked longer viremia duration to increased risk of ataxia.
• Others found no significant differences in viremia levels between horses with or without neurological signs.
• Peak viremia levels did not reliably predict EHM development, although viremic horses with neurological signs had higher viral loads than asymptomatic viremic horses in some studies.

Abortion
• Abortion rates were variable among studies and not consistently linked to the magnitude or duration of viremia.
• Pregnant mares with longer viremia durations appeared more likely to abort in some studies, but findings were inconclusive.

Methodological Challenges
• Heterogeneity in Study Design: Variability in virus strains, doses, challenge protocols, and diagnostic methods (e.g., PCR vs. plaque assays). Different methods of quantifying viremia (e.g., gene copies, cycle thresholds, TCID50) complicated comparisons.
• Reporting Gaps: Lack of raw individual horse data prevented robust statistical comparisons. Limited access to data on viremia duration and peak levels for both EHM and abortion outcomes.
• Small Sample Sizes: Low statistical power in many studies hindered conclusive analyses.
• Bias: Many studies lacked blinding of treatment groups or assessors, increasing the risk of bias.

• Monitoring viremia is essential for understanding EHV-1 pathogenesis and predicting disease outcomes, though current tools lack precision.
• Reducing viremia duration (e.g., via antiviral treatments) could theoretically lower risks of EHM and abortion.

Question 2

Equine grass sickness is associated with major abnormalities in
the ultrastructure of skeletal neuromuscular junctions

Answer 2

EGS: Findings dissimilar to botulism. Evidence of accelerated SV exocytosis and depletion, acumulation of neurfilament like matierial and termial bouton degeneration in ICM and diaphragm. Consistent with an excitatory neurotoxin or reuptake inhibitor.

Question 3

Sidewinder gait in horses

Answer 3

Neurologic Findings:
• leaning toward the affected side with contralateral pelvic limb abduction.
• Compressive Myelopathy: Caused by trauma, instability, or intervertebral disc disease.
• EPM: Confirmed in two cases and presumed in others; characterized by spinal cord or brainstem lesions.
• Ischemic Injury: Rare vascular events such as thrombosis, affecting motor and sensory tracts.
• Gliosis and Perivascular Cuffing: Suggestive of potential viral or inflammatory etiologies.

Musculoskeletal Findings:
• Advanced coxofemoral osteoarthritis.
• Multiple pelvic fractures.
• Severe myonecrosis of pelvic limb muscles (rare).
• Horses with musculoskeletal causes leaned contralateral to the most affected limb due to pain or mechanical limitations.

•Electromyography (EMG) was effective in distinguishing neurologic from non-neurologic causes and in localizing spinal cord lesions.
•Cerebrospinal fluid (CSF) centesis near the lesion site increased diagnostic yield but was not feasible in all cases.

• Supportive treatments included NSAIDs, antiprotozoals (e.g., ponazuril for EPM), and antioxidants, with minimal success in resolving the gait abnormality.
• Overall prognosis for recovery of function and quality of life is poor, with a high case fatality rate (79%).
• Remaining live horses showed persistent gait abnormalities despite treatment, precluding return to physical activity

Question 4

Wobbler surgery: What is the evidence?

Answer 4

Comparison of Treatment Modalities:
• Surgical treatment offers better long-term outcomes compared to conservative methods in most cases.
• Conservative management may be effective for mild cases in young horses.
• Surgical correction is more reliable for addressing static or severe compressions, especially in older horses.
• requires strict selection criteria: >/=50% narrowing of the dorsal myelo- graphic contrast column, grades 1–4 neurological horses of ages from 6 months to 24 years of age

•horses <1 year of age with evidence of kyphosis and/or stenosis of the cervical foramen require surgical fusion for a successful outcome

APJ pathology:
• Following intra-articular corticosteroid medication, 32% of horses have improved performance although in 50% of the improved cases the effect lasted only 1–6 months
• Older ataxic horses had a 60% improvement with an average 2 grades improvement of ataxia that was effective for 1–8 years (average 2 years)
• Horses with milder grades of ataxia (less than grade 3), normal MSD ratios and moderate APJ changes (grade 3a–4b) are good candidates for medication

Question 5

Serum and cerebrospinal fluid phosphorylated neurofilament heavy protein concentrations in equine neurodegenerative diseases

Answer 5

Evaluated serum and CSF phosphorylated neurofilament heavy protein (pNfH) concentrations as biomarkers for neurodegenerative diseases in horses.
Diseases studied: equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM), cervical vertebral compressive myelopathy (CVCM), and Shivers.

• Serum pNfH concentrations >1 ng/mL were highly specific (99%) for eNAD/EDM but had poor sensitivity (12%).
• CSF pNfH concentrations >3 ng/mL were significantly associated with CVCM (P = .0002), but sensitivity was moderate (50%).
• Shivers did not show significant elevations in serum or CSF pNfH concentrations.
• Younger horses (<5 years) with eNAD/EDM or CVCM exhibited higher CSF pNfH concentrations, correlating with more severe axonal degeneration in early stages.
• Older horses with these conditions often had unremarkable CSF pNfH levels, potentially due to disease stabilisation or progression differences.

Disease-Specific Findings:
• Elevated CSF pNfH in CVCM likely reflects the severity of spinal cord compression.
• Serum pNfH >1 ng/mL indicated axonal damage in eNAD/EDM, but many cases fell below this threshold, limiting sensitivity.
• Shivers pathophysiology, limited to Purkinje cell axons in the cerebellum, does not significantly elevate pNfH levels.

• Serum and CSF pNfH combined offer higher diagnostic value for eNAD/EDM (AUC = 0.82).
• Elevated levels indicate axonal degeneration but are not disease-specific.

Question 6

Computed tomographic findings in 101 horses presented for the investigation of headshaking

Answer 6

CT under standing sedation provided diagnoses in 3 of 101 horses, with a likely diagnosis in one additional case. Enabled detection of mild periapical infections and a paracondylar process fracture, which were not evident in clinical examinations or standard radiographs.
• Despite its low diagnostic yield, CT remains a valuable tool for identifying alternative causes of headshaking, especially when other diagnostic modalities are inconclusive.
• Standard radiography has moderate sensitivity (52–76%).
• no association between IOC compression and headshaking.

Question 7

Optimisation and validation of immunohistochemical axonal markers for morphological and functional characterisation of equine peripheral nerves

Answer 7

• FFPE tissue with optimised protocols provided unambiguous detection of motor, sensory, and sympathetic axons.

RLN:
• Composed of large-diameter myelinated fibres (ChAT-positive motor axons) and unmyelinated fibres (predominantly sympathetic TH-positive and occasionally sensory CGRP-positive).
• Presence of ChAT-negative myelinated axons raises questions about their motor or sensory origin. ? Loss of ChAT expression could be an early indicator of motor neuron degeneration in RLN.
• Future studies on diseased horses could clarify if RLN selectively affects large-diameter motor axons or also involves sensory and unmyelinated fibres.

Phrenic Nerve Findings:
• Similar composition to RLN, containing myelinated motor axons, unmyelinated sympathetic, and sensory fibres.
• Extensive clustering of sympathetic fibres (TH-positive) within fascicles. Suggests that sympathetic fibres run parallel along the phrenic nerve, branching distally.
• Highlights the potential role of sympathetic fibres in regulating skeletal muscle blood vessel tonicity and intrafusal muscle spindle receptors.

Plantar Digital Nerve Observations:
• Did not contain myelinated motor axons (ChAT-negative).
• Myelinated fibres presumed to be sensory, while unmyelinated fibres were TH-positive (sympathetic) and CGRP-positive (sensory).
• CGRP-positive fibres likely contribute to vasodilation effects on digital arteries and veins.

Question 8

Cellular distribution of cannabinoid-related receptors in equine cervical dorsal root ganglia

Answer 8

Investigated cannabinoid-related receptors (TRPV1, PPARγ, GPR55, and GPR3) in equine cervical dorsal root ganglia (DRG).

• TRPV1: Widely expressed in sensory neurons and satellite glial cells (SGCs) of the DRG. desensitisated by cannabinoids like CBD
• PPARγ: Expressed in the nuclei of neurons, SGCs, and interneuronal cells. PPARγ ligands are known for anti-inflammatory and neuroprotective effects.
• GPR55: Found in neurons, SGCs, and macrophages in the DRG. Associated with inflammatory pain modulation and macrophage activity. CBD acts as a GPR55 antagonist,
• GPR3: Expressed in sensory neurons but absent in nerve fibres. Linked to neuropathic pain modulation and neuroprotection. Though CBD shows low potency at GPR3, it may contribute to pain relief in pathological conditions.
• Strong evidence of cannabinoid receptor-mediated interactions between neurons and SGCs. SGCs play a crucial role in pain modulation by releasing neurotransmitters and inflammatory mediators, influencing nociceptive pathways.
• Neuron-Glia-Macrophage Triad: GPR55 expression in macrophages highlights their role in inflammatory responses and pain hypersensitivity. Suggests a significant role for the neuron-glia-macrophage complex in managing nerve injuries and pain.

• Cannabinoids may regulate nociception, inflammation, and neuroprotection via TRPV1, PPARγ, and GPR55 receptors.

Question 9

Vitamin E depletion is associated with subclinical axonal degeneration in juvenile horses

Answer 9

• Investigated the relationship between vitamin E deficiency and subclinical axonal degeneration in juvenile horses using phosphorylated neurofilament heavy (pNfH) as a biomarker. Up to 6 months of age. QH only. no histo
• Vitamin E depletion was associated with elevated cerebrospinal fluid (CSF) pNfH concentrations in otherwise healthy foals, indicating subclinical axonal damage.
• In eNAD-affected foals, CSF pNfH showed variability but ultimately increased by 6 months.
• Axonal damage occurred in foals without overt neurological symptoms, suggesting early subclinical degeneration due to vitamin E deficiency.
• Vitamin E supplementation mitigated the increase in CSF pNfH concentrations observed in vitamin E-depleted foals.

Diagnostic Implications:
• CSF pNfH could aid in diagnosing eNAD but should be interpreted alongside vitamin E levels to account for subclinical effects.
• Serum pNfH concentrations were unreliable due to detection limitations and potential interference, emphasizing CSF as the preferred diagnostic medium.
• CSF pNfH concentrations increased with age in vitamin E-depleted foals but remained stable in supplemented foals.

Question 10

History, Rest and Exercise Score (HRE-S) for assessment of disease severity in horses with trigeminal-mediated headshaking

Answer 10

• The study validated the History, Rest and Exercise Score (HRE-S) for assessing the severity of trigeminal-mediated headshaking (TMHS) in horses.
• Addressed limitations of existing scoring systems by creating a tool that evaluates TMHS comprehensively, including history, resting signs, and exercise-related signs.

Advantages Over Existing Systems:
• Improves on subjective grading systems by integrating specific, measurable parameters.
• Includes chronicity and triggering environmental factors, which existing scores often overlook.
• Expresses results as percentages, increasing precision over categorical grades.

Key Findings:
• Excellent inter- and intraobserver reliability, even across observers with differing expertise levels. Reliability was highest for extreme scores (low or high severity).
• Strong convergent validity with Talbot’s score for exercise signs, though rest signs were not directly comparable.
• Discriminant validity confirmed by differentiating severity levels assessed by expert observers.
• Practicability: Generally rated as “easy” or “fast” to use, though more time-consuming than subjective scoring systems. Observers found it particularly effective in identifying subtle changes in clinical severity.
• Indicators of Disease Severity: Presence of “pain face” and “electric shock-like jerking” were strongly correlated with higher scores, highlighting their significance in TMHS evaluation.
• The HRE-S detected variability in severity between rest and exercise, underscoring the need for context-specific assessments.

History score: weater, activity, location, seasonality, duration
Resting score: vertical, horizontal, rotating, vertical head and neck, ear shaking, other, lip/ tongue movement, pain face- and duration up to >3min
Exercise score- the same as rest, defined as number/ round.

Question 11

The prevalence of headshaking in horses with primary and secondary dental sinusitis and computed tomographic evidence of infraorbital canal pathology

Answer 11

headshaking may be casued by IOC pathology but not all IOC pathology causes headshaking

• IOC pathology was common in horses with dental sinusitis (65 out of 66 cases) but did not consistently correlate with headshaking.
• Only 5 out of 48 horses with follow-up exhibited headshaking behaviour, despite widespread IOC abnormalities.
• Most IOC changes included hyperostosis, periosteal proliferation, and osteolysis, yet these were present in both headshaking and non-headshaking horses.

Significance of IOC Pathology:
• Hyperostosis was the most frequent abnormality, often involving both the IOC and supporting bone structures.
• In 43 cases, hyperostosis extended to surrounding structures, yet only 5 showed clinical headshaking, indicating hyperostosis may be incidental in many cases.
• In horses exhibiting headshaking, the behaviours often coincided with advanced IOC pathology or ongoing dental inflammatory processes (e.g., oroantral fistulas or periapical osteitis).
• Resolution of inflammatory conditions (e.g., fistula debridement) reduced or eliminated headshaking in some cases.

Question 12

Detection of equine herpesvirus-1 (EHV-1) in urine samples during outbreaks of equine herpesvirus myeloencephalopathy

Answer 12

• Confirmed the presence of EHV-1 DNA in urine, particularly during later stages of viraemia, suggesting a diagnostic role for urine samples.
• EHV-1 DNA persisted longer in urine compared to blood (buffy coat, BC) and had similar duration but lower concentrations compared to nasal swabs (NS).

Clinical Implications:
• Urine sampling offers a less invasive diagnostic alternative
• potential use in monitoring EHV-1 infection and ensuring biosecurity measures during outbreaks.

Differences in Detection Patterns:
• In the 2021 outbreak: BC samples were positive for shorter periods (up to 13 days post-onset of fever) compared to urine (up to 18 days). Urine samples showed higher EHV-1 DNA concentrations than BC towards the end of viraemia.
• In the 2023 outbreak: NS samples had higher positivity rates and DNA concentrations compared to urine. Urine samples were positive for shorter periods (up to 8 days).

Significance of Findings:
• The urinary bladder may serve as a site for EHV-1 persistence or replication, although further studies are needed to confirm this.
• Urinary shedding of EHV-1 could potentially contribute to viral transmission, though this requires investigation.

Question 13

Equine herpesvirus-1 genotype did not significantly affect clinical signs and disease outcome in 65 horses diagnosed with equine herpesvirus-1 myeloencephalopathy

Answer 13

• No significant difference in clinical signs (fever, lethargy, ataxia) or disease outcomes (survival vs. non-survival) between horses infected with D752 and N752 genotypes.
• Urinary incontinence was significantly more common in horses infected with the D752 genotype (P = 0.04).
• The distribution of EHV-1 genotypes among horses with EHM (46% N752, 54% D752) showed no genotype frequency bias.

Clinical Observations:
• Ataxia was the most common clinical sign (97%), with similar severity levels across genotypes.
• Urinary incontinence, linked to D752, may reflect neuroanatomical tropism or severity of EHV-1-mediated vasculitis in the central nervous system.
• The study findings challenge earlier research suggesting D752 is more commonly associated with severe clinical signs.

Question 14

Computed tomography findings in horses presented with signs of head-shaking

Answer 14

• Found CT to be useful, identifying abnormalities in 94 out of 103 cases (91.3%).
• In 22 cases (21.4%), treatable conditions were identified, leading to resolution of head-shaking.
• Trigeminal nerve-mediated head-shaking (TNMH): Most common diagnosis (60.2%, 62 horses). Diagnosis was by exclusion when no CT abnormalities accounted for clinical signs or when structural abnormalities were treated unsuccessfully.

Primary Treatable Conditions:
• Dental fractures, sinusitis, temporomandibular joint (TMJ) arthritis, and otitis externa were among the conditions leading to resolution of head-shaking after treatment.
• Less common findings included nuchal bursitis, musculoskeletal pathologies, infraorbital nerve mass, and basisphenoid bone fracture.
Incidental Findings:
• Common incidental findings included gas within the infundibula, nuchal ligament enthesopathy, and minor infraorbital canal changes.

•Limitation: Difficulty in distinguishing incidental findings from clinically significant abnormalities.

Question 15

Genome-wide association study for host genetic factors associated with equine herpesvirus type-1 induced myeloencephalopathy

Answer 15

• No significant SNPs, haplotypes, or runs of homozygosity (ROH) were identified as associated with the development of EHM.
• The study did not confirm a previously reported association of a specific SNP (BIEC2-946397 on chromosome 6) with EHM.
• Findings exclude the involvement of a recessive genetic factor in susceptibility to EHM but could not rule out other genetic contributions, such as dominant, additive, or complex inheritance patterns.

Limitations:
•Small number of cases (27) and controls (67) limited the statistical power to detect associations, particularly for complex traits.
•The inclusion of diverse breeds may have introduced variability, complicating the detection of breed-specific genetic influences.
•The phenotype used (development of EHM) likely encompasses a variety of genetic and environmental factors, reducing the likelihood of identifying simple genetic markers.

Question 16

Computed tomographic myelography for assessment of the cervical spinal cord in ataxic warmblood horses

Answer 16

• CTM effectively identified sites and causes of spinal cord compression, quantified compression severity, and detailed the direction of compression.
• No association was found between AP joint size and degree of compression, suggesting other factors contribute to compression severity.

Question 17

Partial ceratohyoidectomy as surgical treatment for horses with temporohyoid osteoarthropathy: 10 cases (2010-2021)

Answer 17

• Similar clinical outcomes compared to complete ceratohyoidectomy were observed.
• Two horses experienced complete resolution of clinical signs.
• Nine out of ten horses returned to their previous work level, indicating a high success rate for functional recovery.
• Minimal complications in planned partial ceratohyoidectomy cases, with no instances of intraoperative hemorrhage or postoperative neuropathy.
• Complications were more frequent when surgeries were transitioned from planned complete ceratohyoidectomy to partial due to complications during dissection (e.g., hemorrhage, tongue mobility issues).
• All complications resolved before discharge, with no long-term adverse effects.

• Partial ceratohyoidectomy had fewer intraoperative complications compared to complete ceratohyoidectomy, likely due to avoiding deep dissection near neurovascular structures.
• Return-to-performance rates (90% in this study) were comparable or better than previous reports of complete ceratohyoidectomy.

Other Sx options include sytlohyoidectomy/ full ceratohyoidectomy

Question 18

Caudal cervical vertebral morphological variation is not associated with clinical signs in Warmblood horses

Answer 18

• Morphologic variation of C6 and C7 was detected in 28.6% of horses, consistent with previous studies.
• Variations were more frequently found in control horses (38%) compared to case horses with clinical signs (23.7%).
• Morphologic variation did not correlate with clinical signs such as ataxia, cervical pain, or lameness, suggesting no direct pathological impact.
• Multivariate analysis confirmed the lack of association between morphologic variations and clinical signs, even after adjusting for age and breed.

• The presence of morphologic variations should not be assumed to indicate clinical relevance or pathology in Warmblood horses.
• Contradicts earlier hypotheses suggesting variations could predispose to pain or dysfunction due to altered biomechanics.

Question 19

The safety and efficacy of neuromodulation using percutaneous electrical nerve stimulation for the management of trigeminal-mediated headshaking in 168 horses

Answer 19

• Approximately 53% of horses experienced remission after the initial three-procedure course.
• Median remission duration was 9.5 weeks, with a range of 2 days to 156 weeks (ongoing).
• Follow-up revealed that horses with longer remission periods (>56 weeks) often remained in remission for years.
• Horses were more likely to achieve remission by the third procedure if they responded to the first and/or second procedure.
• Horses that relapsed often regained remission after additional procedures, with subsequent remission durations generally increasing.
• Complication rate was 8.8% across 530 procedures, mostly mild and transient (e.g., suspected neuritis, haematomas, minor compliance issues).

• No placebo or control group; reliance on owner-reported outcomes introduces a potential bias,

Question 20

Accuracy of transcranial magnetic stimulation and a Bayesian latent class model for diagnosis of spinal cord dysfunction in horses

Answer 20

• TMS (Magnetic Motor Evoked Potentials, MMEP): Highest specificity (97.4%) and strong sensitivity (87.5%).
-Best diagnostic performance using the minimum latency time of pelvic limb responses (Youden’s Index: 0.85).
-Mean latency time of pelvic limbs showed high sensitivity but slightly reduced specificity.
• Neurological Examination: Highest sensitivity (97.6%) but lower specificity (74.7%).
-Second-best overall diagnostic performance (Youden’s Index: 0.80 for pelvic limb latency).
-Observations of ataxia were subject to interobserver variability, particularly in mild cases.
•Cervical Radiography: Lowest sensitivity (43%) and moderate specificity (77.3%).
-Performed poorly across all metrics (Youden’s Index: 0.18–0.31).
-Unable to detect soft tissue compression or subtle spinal cord abnormalities.

TMS-MMEP emerged as the most reliable test, offering superior specificity for confirming spinal cord dysfunction.
• Accuracy varied with different criteria:
-Minimum latency times were more accurate for confirmation.
-Mean latency times were better for screening (higher sensitivity).
-Decision criteria involving pelvic limbs outperformed those using thoracic limb measurements.

TMS limitations:
• Focused on motor dysfunction; sensory deficits were not evaluated.
• In cases with significant sensory dysfunction, TMS performance may decline.

Suggested diagnostic strategy:
• Use neurological examination as an initial screening tool (high sensitivity).
• Confirm findings with TMS-MMEP (high specificity).

Question 21

Comparison of 2 collection methods for cerebrospinal fluid analysis from standing, sedate adult horses

Answer 21

• Protein Concentration: Slightly lower at C1-C2 compared to LS; statistically significant but not clinically relevant (P = 0.03).
• RBC Count: Lower contamination at C1-C2 (6 cells/μL) versus LS (33 cells/μL; P = 0.02).
• Blood contamination (>50 RBC/μL) was more frequent at LS (50%) compared to C1-C2 (13%).
• WBC Count and Cytology:No significant differences between sites (P = 0.17).
• Ease of Collection: Median collection time not statistically significant. Operator experience reduced collection time at C1-C2 over the study.
• Horse Response: C1-C2: Better tolerated; 16/24 horses had no reaction. LS: More unpredictable reactions, often during dura penetration. Severe reactions (score 4/4) observed in one normal horse.

Safety and Post-Procedure Observations
• C1-C2 Site:
-Post-procedure swelling or soreness in 4 horses, resolving within 48 hours.
-Necropsy: Mild to moderate hemorrhage in cervical musculature, epidural tissues, or subarachnoid space in 7/11 horses.
-One case of spinal cord penetration with focal hemorrhage, attributed to horse temperament and refractory sedation.
• LS Site:
-Necropsy revealed mild hemorrhage in dorsal soft tissues or epidural fat but no subarachnoid hemorrhage.

• Operator experience is crucial for minimizing risks, particularly for C1-C2 centesis.
• Horse temperament should guide the choice of method; reactive horses may not be suitable for C1-C2 collection.

Question 22

Facial nerve paralysis in 64 equids: Clinical variables, diagnosis, and outcome

Answer 22

Primary Causes of FNP
• Trauma (31%): Most common cause. Frequently involved auricular or auriculopalpebral nerve branches, sparing buccal branches. Associated with lip droop or muzzle deviation.
• Central Nervous System (CNS) Diseases (25%): Included equine protozoal myeloencephalitis (EPM, 16%), neuroborreliosis (8%), and West Nile virus (WNV, 1 case). Strongly associated with additional neurological signs such as ataxia (OR: 32.09) and head tilt (OR: 6.33).
• Idiopathic FNP (19%): 6% classified as “true idiopathic” after thorough diagnostics. Often presented with corneal ulcers, increasing likelihood of diagnosis (OR: 7.44).
• Temporohyoid Osteoarthropathy (THO, 16%): Positively associated with ear droop (OR: 6.81), inability to blink (OR: 7.08), and ocular pathology (OR: 17.69). Quarter Horses (OR: 8.14) and ponies (OR: 40.71) overrepresented.

Outcome Associations
• Full Resolution (53%): More likely in younger equids (OR: 0.89 per year of age). Associated with acute onset (OR: 7) and targeted neurological drug treatment (OR: 3.12). Less likely with ptosis (OR: 0.35).
• Partial Improvement (11%): Linked to idiopathic FNP (OR: 5.21).
• Unchanged/Worsened (11%): Associated with corneal ulcers (OR: 8.81).
• Euthanasia (25%): Linked to generalized weakness/malaise (OR: 8.56), abnormal mentation (OR: 4.8), ataxia (OR: 8.01), and neuroborreliosis (OR: 14.14).

Question 23

A pilot study of optical neuronavigation-guided brain biopsy in the horse using anatomic landmarks and fiducial arrays for patient registration

Answer 23

• The Brainsight Vet 2 neuronavigation system was compatible for use with the equine skull using both fiducial arrays and anatomic landmarks.
No significant difference in accuracy between fiducial arrays (median distance to target: 5.75 mm) and anatomic landmarks (median distance: 3.76 mm; P = 0.52).
Experienced surgeons achieved significantly greater accuracy (median: 2.52 mm) compared to novices (median: 6.55 mm; P = 0.001).

Both methods successfully used for brain biopsy simulation in cadaver heads.
• Fiducial arrays required minor surgical placement but offered slightly more consistent accuracy for small lesions.
• Anatomic landmarks eliminated the need for additional anaesthesia or surgical procedures, reducing patient risk.

Question 24

Postmortem diagnoses of spinal ataxia in 316 horses in California

Answer 24

Prevalence
• CVCM: Most common cause (29.1%). Includes:
-Type 1 (dynamic, younger horses, C1–C6): 47%.
-Type 2 (static, older horses, C5–T1): 36%.
-Mixed type: 17%.
• eNAD-EDM: Second most common (14.3%); increased diagnoses post-2008.
• Trauma: 9.4%, often involving fractures or hemorrhage.
• Unknown Origin: 17.7%, highlighting diagnostic gaps.
• Less frequent causes: neoplasia, THO, silicate-associated osteoporosis, intervertebral disk disease.

Breed Associations
• CVCM: More common in Thoroughbreds (OR: 2.54) and warmbloods; less likely in “other” breeds.
• eNAD-EDM: Common in AQHs (OR: 2.95); less frequent in Thoroughbreds (OR: 0.11).
• Trauma: Associated with “other” breeds (OR: 2.65).

Age Patterns
• Younger Horses (< 5 years): Higher odds of eNAD-EDM (OR: 6.17) and Type 1 CVCM (OR: 2.82).
• Older Horses (≥ 5 years): More likely to have trauma, neoplasia, or THO.

Sex
• Males overrepresented (64.9%), though no strong link to specific conditions.

Question 25

Head tossing behaviour in six horses: Trigeminalmediated head shaking or musculoskeletal pain?

Answer 25

All six horses were found to have musculoskeletal pain that contributed to head-tossing behaviour:
• Diagnoses included proximal suspensory desmopathy (PSD), sacroiliac pain, foot pain (e.g., navicular disease, osseous cyst-like lesions), and spinous process impingement.
• Behaviour resolved in five horses after musculoskeletal pain was addressed with diagnostic analgesia.
• In one horse, head-tossing improved but did not fully resolve, suggesting a potential component of trigeminal-mediated head-shaking.

Trigeminal-mediated head-shaking typically presents with:
• Clinical signs at rest and during exercise, often worsening with sunlight or wind exposure.
• Features like nasal irritation, sneezing, or rubbing the nose, none of which were observed in this study.
• Seasonality of clinical signs, which was absent in these horses.

Head-tossing due to musculoskeletal pain in this study was:
• Only present during ridden exercise (except for one horse with occasional signs at rest).
• Associated with other pain behaviours (e.g., tail swishing, reluctance to move forward).

Question 26

Quantitative sensory testing of the equine face

Answer 26

Tactile Sensory Threshold:
• Increased with age (0.90 g/year; P = .001).
• No significant effect of sex or shaving.
• Most consistent results at the nostril stimulation site.

Mechanical Nociceptive Threshold:
• Increased with age (0.25 N/year; P < .01).
• No significant effect of sex or shaving.
• Temporomandibular joint was the most reliable site for testing.

Thermal Nociceptive Threshold:
• Increased with age (0.2°C/year; P = .008).
• No significant effect of sex or shaving.
• Supraorbital foramen yielded the most consistent thresholds.

Effects of Stimulation Site
• Stimulation sites influenced tactile and mechanical nociceptive thresholds significantly, but not thermal nociceptive thresholds.
• Locations with less soft tissue (e.g., supraorbital foramen) had higher mechanical and tactile thresholds.
• Shaving had no statistically significant effect on any thresholds, though subjectively shaved areas appeared less sensitive.

This study is underpowered for most comparisons

Question 27

Increased α-tocopherol metabolism in horses with equine neuroaxonal dystrophy

Answer 27

eNAD/EDM-affected horses exhibited significantly increased α-TOH metabolism compared to controls.

Proof-of-Concept (POC) Study:
• Higher α-metabolic ratios (metabolites α-CEHC and α-CMBHC) in eNAD/EDM horses (P = .0013).
• Post-supplementation, α-metabolic ratios were elevated at 6, 12, and 24 hours in eNAD/EDM horses.

Validation Study:
• Increased α-metabolic ratios confirmed (P = .03) in eNAD/EDM horses, particularly within 18-24 hours post-supplementation.
•CYP4F2 Expression increased 1.63-fold in liver. No differences in CYP4F2 gene copy number between eNAD/EDM and control horses, indicating expression changes likely result from secondary mechanisms.

Vitamin E Metabolites in Serum and Urine
• Serum:
-α-TOH concentrations increased with supplementation in all groups, but metabolism was faster in eNAD/EDM-affected horses.
-γ-TOH metabolic ratios were not significantly different between groups.
•Urine:
-Unconjugated α-CEHC metabolites were higher in eNAD/EDM-affected horses within 24 hours (P = .004).
-Conjugated γ-CEHC metabolites were lower in eNAD/EDM horses over 56 days (P = .04).

Diagnostic Potential
•Increased α-metabolic ratio provides a potential biomarker for eNAD/EDM but overlaps with controls reduce diagnostic specificity.
• Metabolic profiling post-supplementation may improve sensitivity, especially with fasting protocols.

Pathophysiology
• Increased α-TOH metabolism in eNAD/EDM suggests a compensatory mechanism linked to genetic or environmental factors.
• Elevated CYP4F2 expression mirrors findings in human ataxia with vitamin E deficiency (AVED), highlighting potential shared pathways.

Question 28

The effect of prior thecal puncture on cerebrospinal fluid analytes in normal adult horses

Answer 28

• No significant differences in CSF analytes between initial (day 0) and repeat (day 14) collections for either cervical (C1-C2) or lumbosacral (LS) sites.

Analytes tested:
• Protein Concentration: Minor, non-significant increase observed at both sites
• Total Nucleated Cell Count (TNCC): No significant changes; small increases were not clinically relevant.
• Red Blood Cell (RBC) Count: Slightly higher median counts after repeat LS puncture but not statistically significant.

• Repeat thecal punctures 14 days apart are unlikely to significantly alter CSF analytes, supporting their diagnostic reliability in follow-up evaluations. Clinicians can perform repeat CSF collections for monitoring or research without risk of false-positive changes in TNCC, protein, or EPM titer due to prior sampling.
• Serum:CSF ratios should be interpreted cautiously in cases with visible blood contamination or elevated protein levels.

Question 29

Computed tomographic cervical myelography in horses: Technique and findings in 51 clinical cases

Answer 29

• CT myelography identified SCC in 61% of cases (31/51 horses).
• Compression types: lateral/dorsolateral (81%), dorsoventral (35%), circumferential (19%).
• CT myelography detected DJD in 98% of horses (50/51), primarily affecting the articular process joints (APJs).
• Radiographic myelography underperformed in detecting lateral and circumferential compression compared to CT.

• CT myelography findings align with studies identifying C5-C6 and C6-C7 as primary sites for SCC and DJD in horses.
• Agreement with radiographic myelography was highest for dorsoventral compression but low for lateral and circumferential compressions.
• Dynamic assessments (e.g., flexed CT) were not possible due to gantry size limitations.

Technique:
• withdraw 50 mL of CSF timed over 150 seconds. Immediately after withdrawal of the CSF
• 20 mL of iohexol was injected into the subarachnoid space followed by a 60 mL of a 50:50 dilution of iohexol and serile hartmann’s (total 80ml)- aim to reduce ventral pooling effect.
• CSF then used to flush the remaining contrast in
• elevate head for 5 mins

Question 30

Juvenile idiopathic epilepsy in Egyptian Arabian foals: A potential animal model for self-limited epilepsy in children

Answer 30

• Seizures originated focally at the central vertex (Cz) with rapid spread to other cortical regions.
• Most JIE foals experienced generalized tonic-clonic seizures (91%) characterized by violent body movements, facial motor involvement, and loss of consciousness.
• Focal seizures (9%) involved facial, oral, and tongue motor alterations (e.g., trismus, chewing, tongue protrusion).
• Postictal signs included cortical blindness, disorientation, ataxia, and dysphagia.

Electroencephalographic Insights
• Interictal epileptic discharges (ED) were detected in 95% of JIE foals, predominantly during sleep (100% of cases).
• Focal discharges were most common, originating at Cz and spreading to centroparietal regions.
• Generalized spread from focal origins occurred in 40% of foals.

Photic stimulation (PS):
• Triggered epileptic discharges in 62% of JIE foals.
• Reproducible and time-locked responses with no clinical manifestations.
• Auditory stimulation and hyperventilation did not induce ED.
•Activation procedures like PS enhance diagnostic yield for ED but should be interpreted cautiously as PD responses may also occur in healthy foals.

Genetic Inheritance
• Likely autosomal dominant inheritance with incomplete penetrance.
• Presence of ED in asymptomatic siblings suggests genetic susceptibility without phenotypic manifestation.

Therapeutic Considerations
• Most JIE foals respond well to antiseizure medication, primarily phenobarbital and levetiracetam.
• Monitoring and early treatment reduce risks of trauma, aspiration pneumonia, and other complications.

Only had ictal recordings in 2

Question 31

Clinical and histopathological features in horses with neuroaxonal degeneration: 100 cases (2017-2021)

Answer 31

Signalment and History
• Median age: 8 years (range, 1–22 years), differing from earlier studies that primarily reported eNAD/EDM in younger horses (weanlings and yearlings).
• Predominantly Warmbloods (72% of cases), suggesting breed predisposition.
• Overrepresentation of geldings (80%) likely due to sampling bias from equestrian disciplines favoring geldings.

Primary complaints:
• Behavioral changes (68% of cases), including spooking, hypervigilance, and aggression.
• Ataxia (73%), mild to moderate (median grade: 2/5), often underrecognized by owners.
• Poor performance, lameness, and other behavioral abnormalities (e.g., bolting, rearing).
• Behavioral abnormalities may reflect functional, not structural, brain changes; neurotransmitter imbalance (e.g., altered glutamate metabolism) is a possible cause.

Diagnostic Imaging and Pathology
• 57% of horses had cervical vertebral abnormalities on radiographs, including osteoarthritis and stenosis.

Histological findings:
• Symmetrical axonal degeneration in brainstem and spinal cord gray matter (lateral and medial cuneate nuclei most affected).
• White matter degeneration in 24% of cases, typical of EDM.
• Despite imaging findings of stenosis, histologic evidence of spinal cord compression was absent in most cases.

Vitamin E and Oxidative Stress
• 90% of tested horses had normal serum vitamin E levels, but early-life deficiencies or altered metabolism may play a role.

Etiology and Contributing Factors
• Genetic predisposition suspected but not confirmed; incomplete penetrance may explain variable presentations.
• Environmental factors (e.g., poor-quality forage, limited pasture access) may contribute.
• Potential exposure to toxins (e.g., insecticides, neurotoxic chemicals) has been noted anecdotally.

Question 32

Cerebrospinal fluid and serum proteomic profiles accurately distinguish neuroaxonal dystrophy from cervical vertebral compressive myelopathy in horses

Answer 32

Of 368 proteins analyzed:
• CSF: 84 proteins detected, 18 significantly different among groups.
• Serum: 146 proteins detected, 30 significantly different.

A two-protein CSF model (R-spondin 1 [RSPO1] and neurofilament-light [NEFL]) achieved:
• 87.2% accuracy for normal horses.
• 84.6% accuracy for CVCM.
• 73.5% accuracy for eNAD/EDM.
• A combined CSF/serum model incorporating RSPO1, NEFL, and Dickkopf-1 (DKK1) showed similar diagnostic accuracy.

Key Biomarkers
•RSPO1: Highest-ranked CSF biomarker. Decreased in CVCM and eNAD/EDM compared to normal horses, suggesting a protective role in neurodegeneration.
• NEFL: Elevated in CVCM, distinguishing it from eNAD/EDM and normal horses. Known as a marker of neurodegeneration in humans; this study represents its first evaluation in horses.
• DKK1: Serum biomarker involved in Wnt signaling, relevant in neuroinflammation and neurodegeneration.

•Proposes a novel, minimally invasive method to improve antemortem diagnosis of equine spinal ataxias.
• Neurofilament-heavy (pNfH) protein, used previously, lacks specificity between CVCM and eNAD/EDM.
• Random forest and conditional inference models efficiently identified small, diagnostically relevant biomarker sets

Question 33

Opioid-free sedation for atlantoaxial cerebrospinal fluid collection in adult horses

Answer 33

• Procedure times were lower in horses sedated with DX or DM, compared to D0
• Procedure reaction scores were lower in horses sedated with DX, or DM compared to DO
• Reactions to dura mater puncture were recorded in 3 of 6 horses in D0 and DD groups, and 0 of 6 horses in DX and DM groups.
• Positive associations were observed between reaction score vs total distance or farthest excursion distance from baseline- good correlation

n=6, neurologically normal only

Question 34

Neurological disease suspected to be caused by tick-borne encephalitis virus infection in 6 horses in Switzerland

Answer 34

• All horses exhibited acute neurological signs, including ataxia, proprioceptive deficits, and in some cases, cranial nerve abnormalities and skin hypersensitivity.
Diagnoses were supported by:
• Positive TBEV-specific IgM antibody results in 5 horses (suggesting acute infection).
• Virus neutralisation test (VNT) results confirming TBEV exposure.
• Exclusion of other common neurologic diseases (e.g., West Nile virus [WNV], equine herpesvirus-1 [EHV-1], Borna disease virus [BDV]).
• In one horse with borderline IgM levels, findings were interpreted as a transition from acute to chronic infection.

• All horses were located in endemic areas where human TBEV cases were reported.
• TBEV prevalence in equine populations may be underestimated; these symptomatic cases likely represent a fraction of total infections.
• In the euthanised case (horse 5), histopathology revealed mild to moderate non-purulent meningitis and encephalitis.
• Negative immunohistochemistry (IHC) results for TBEV highlight the difficulty of detecting the virus during later disease stages.
•Sentinel Role of Horses- Horses could serve as sentinel species for TBEV surveillance due to their shared environment with humans and susceptibility to tick exposure.
• Routine serological testing in horses could aid in mapping TBEV risk areas.

Question 35

Effect of time and autologous serum addition on the analysis of cerebrospinal fluid in horses

Answer 35

Control Samples (unaltered CSF):
• Significant deterioration in cell morphology scores at 48 hours (median: 2), 72 hours (median: 2), and 96 hours (median: 3) compared to baseline (T0, median: 1).
• Morphological degradation impacted cytological interpretation, with increasing cellular unrecognizability over time.
Serum-Stabilised Samples:
• Morphology scores remained unchanged across all timepoints (up to 96 hours).
• Addition of autologous serum (2 drops per mL of CSF) effectively prevented cellular degeneration.

• TNCC was stable over time in both serum-stabilised and control groups.
• Protein concentration remained stable in control samples between T0 and T96.

Clinical Implications
• Autologous serum addition allows accurate cytological evaluation of CSF up to 96 hours post-collection, critical for field and referral diagnostic situations.
• Unaltered CSF is suitable for determining TNCC and protein concentration, but cytological interpretation deteriorates beyond 24 hours.
• Recommend splitting CSF samples into two aliquots: Serum-stabilised aliquot for cytological analysis. Unaltered aliquot for biochemical and antibody-based diagnostics (e.g., EPM serology).
• Both aliquots should be refrigerated at 4°C to maintain sample integrity.

Question 36

Cerebellar axonopathy in Shivers horses identified by spatial transcriptomic and proteomic analyses

Answer 36

Spatial transcriptomics revealed:
• Significant differential gene expression (455 genes) in axon-rich white matter, but no differences in Purkinje cell (PC) somas.
• Downregulation of genes linked to axonal structure (e.g., neurofilaments), ion channel function, and myelin integrity.
• Upregulation of the Toll-like receptor 4 (TLR4) cascade, indicative of neuroinflammation.

Proteomic analysis identified:
• Decreased expression of axonal proteins: Neurofilaments (NEFL, NEFM, NEFH). Myelin-associated proteins (MBP, CNP). Ion channel proteins (e.g., sodium-potassium ATPase).
• Increased expression of proteins associated with: Axonal regeneration (e.g., vimentin, talin). Neuroinflammation and oxidative stress (e.g., annexin A2, sirtuin 2, heat shock proteins).

Histopathology
• Axonal degeneration was localized to PC axons in the cerebellar white matter.
• No major changes observed in PC somas, consistent with the unique response of PC to axonal injury.

Implications
• Shivers is associated with selective axonal degeneration, sparing the PC soma.
• Neuroinflammation, mediated by TLR4 activation, may contribute to axonal injury.
• Altered calcium signaling and reduced neurofilament expression impair axonal stability and function.
Functional Consequences
• Axonal degeneration disrupts cerebellar motor coordination without producing classic ataxia.
• Specific targeting of PC axonal networks explains the unique motor phenotype in Shivers horses.
Potential Regeneration
• Upregulation of axonal regeneration markers suggests a compensatory response, but the presence of glial scar-associated proteins (e.g., proteoglycans) may hinder effective regeneration.

Question 37

Evaluation of real-time polymerase chain reaction for the diagnosis of protozoal myeloencephalitis in horses using cerebrospinal fluid

Answer 37

• rtPCR failed to detect S. neurona DNA in all 52 EPM-positive cases, including: 23 necropsy-confirmed EPM cases. 29 clinically diagnosed EPM cases (based on serum:CSF titer ratios <50).
• One false-positive result was identified in the EPM-negative group (out of 47 samples).
Sensitivity: 0%.
Specificity: High but undermined by the single false-positive result.
• Intracellular nature of S. neurona likely explains poor DNA presence in CSF, as the parasite primarily resides in brain and spinal cord parenchyma.

Discrepancy with earlier research reporting 38 rtPCR-positive results (without necropsy confirmation) from a cohort of suspected EPM cases:
• Likely attributable to methodological differences (e.g., CSF sample handling, patient populations).
• Prior studies lacked diagnostic rigor, raising concerns about false-positive findings.

Established Diagnostic Methods
• Immunodiagnostic tests (e.g., SnSAG2/4/3 ELISA with serum:CSF ratios) remain more reliable:
• High specificity (98.8%) when using stringent ratio cutoffs (<50).
• Confirmatory testing still requires necropsy for definitive diagnosis.

Question 38

Genetic polymorphisms in vitamin E transport genes as determinants for risk of equine neuroaxonal dystrophy

Answer 38

Significant Polymorphisms:
• Two intronic SNPs in CD36 (chr4) were significantly associated with eNAD/EDM in both clinical and postmortem-confirmed cases.
• A third SNP in ABCG1 (chr26) was associated with clinical cases but not with postmortem-confirmed cases.

• Low allele frequencies for CD36 variants in QHs (0.22–0.26) and even lower in public databases (0.06–0.10 across breeds).
• The association was possibly biased by the QH population substructure, as other breeds with higher allele frequencies (e.g., Warmbloods, Thoroughbreds) show lower eNAD/EDM prevalence.
•Many postmortem-confirmed cases were wild-type for the associated CD36 SNPs, suggesting:
-Genetic heterogeneity in eNAD/EDM.
-A possible false-positive association due to population stratification in QHs.

Functional Insights
•CD36: Involved in fatty acid and oxidized LDL uptake and indirectly regulated by α-tocopherol. SNPs were intronic, with low Genomic Evolutionary Rate Profiling (GERP) scores (<2), suggesting limited functional significance.
• ABCG1: Associated with cellular vitamin E efflux and metabolic regulation. The clinical-only association weakens its role as a major risk factor.

Question 39

Measurement of 8-hydroxy-20 -deoxyguanosine in serum and cerebrospinal fluid of horses with neuroaxonal degeneration and other causes of proprioceptive ataxia

Answer 39

No significant differences in 8-OHdG concentrations in CSF or serum among the four groups:
• NAD/DM: CSF median 169.9 pg/mL; serum median 130 pg/mL.
• CVSM: CSF median 157.1 pg/mL; serum median 125.8 pg/mL.
• EPM: CSF median 131.4 pg/mL; serum median 120.6 pg/mL.
• Control: CSF median 149.8 pg/mL; serum median 157.6 pg/mL.
• No correlation was found between CSF and serum 8-OHdG levels or between biomarker concentrations and disease status.
• suggesting no ongoing oxidative DNA damage at the time of sample collection.
• Findings imply that oxidative stress may play a role early in the disease or as an initiating event but not as a persistent factor in NAD/DM progression.

Question 40

Equine neuroaxonal dystrophy/degenerative myeloencephalopathy in Gypsy Vanner horses

Answer 40

Pre-supplementation:
• 94% of GVs had serum vitamin E concentrations ≤2.0 µg/mL (median: 1.0 µg/mL).
Post-supplementation:
• After 28 days of oral α-tocopherol (10 IU/kg daily), 73% of horses normalized vitamin E concentrations (≥3.0 µg/mL).
• Younger horses (<2 years) were less likely to normalize, suggesting age-dependent differences in vitamin E metabolism.
• Median post-supplementation value: 3.39 µg/mL (range: 1.23–13.87 µg/mL).
Neurological Findings
• 5 of 26 horses (19%) were “suspect” or confirmed for eNAD/EDM with ataxia grades ≥2.
• Ataxic horses showed symmetric proprioceptive deficits and wide-based stances.
Pathologic evaluations confirmed eNAD/EDM in 4 horses:
• Lesions included axonal degeneration, neuronal chromatolysis, and spheroids in the brainstem and spinal cord.
Genetic Predisposition
• Pedigree analysis indicated a genetic component:
• Affected horses were frequently related, with one sire (GV1) linked to multiple ataxic or equivocal offspring.

Question 41

Clinicopathological and pedigree investigation of a novel spinocerebellar neurological disease in juvenile Quarter Horses in North America

Answer 41

• Described Equine Juvenile Spinocerebellar Ataxia (EJSCA), a novel, likely autosomal recessive neurological disease in Quarter Horse (QH) foals in North America.
• Differentiated EJSCA from similar conditions such as eNAD/EDM and explored its inheritance patterns.

Clinical and Pathological Features
• Affected foals (n = 12) displayed acute-onset neurological signs within the first month of life:
• Severe pelvic limb ataxia (grade 4–5/5), thoracic limb ataxia (grade 1–3/5), and paraparesis.
• Rapid progression to recumbency (median: 3 days).

Histologic evaluation showed:
• Dilated myelin sheaths and digestion chambers in the dorsal spinocerebellar tract.
• Axonal spheroids and glial cell proliferation.
• No lesions in the cerebellum, brainstem, or cerebrum, distinguishing EJSCA from eNAD/EDM.
• Alpha-tocopherol (vitamin E) concentrations were normal or elevated, excluding vitamin E deficiency as a contributing factor.

Clinical Outcome
• Uniformly fatal disease course: 92% of foals euthanized due to severe neurological impairment. The remaining foal found dead; no necropsy performed.
• Pedigrees revealed affected foals shared common ancestors on both sire and dam sides within 4–6 generations.
• Proposed autosomal recessive inheritance based on: Equal male and female representation. Healthy parents producing affected offspring.

EJSCA vs. eNAD/EDM:
• EJSCA: Asymmetrical pelvic limb deficits, rapid progression, and dorsal spinocerebellar tract lesions.
• eNAD/EDM: Symmetrical ataxia, slower progression, and lesions in brainstem nuclei and spinal cord.
• Normal vitamin E levels in EJSCA exclude vitamin E metabolism issues seen in eNAD/EDM.
EJSCA vs. ruminant neurodegenerative disorders:
• Similarities to Tyrolean Grey cattle and sheep axonopathies.
• Earlier onset and more rapid progression in EJSCA compared to ruminant diseases.

Question 42

Electroencephalographic evaluation under standing sedation using sublingual detomidine hydrochloride in Egyptian Arabian foals for investigation of epilepsy

Answer 42

• Sublingual detomidine provided effective sedation for electrode placement and EEG recording without requiring redosing.
• Induced slow wave sleep (SWS), facilitating the identification of epileptic discharges (ED).
• Foals remained standing and did not exhibit oversedation or complications during recovery.

EEG Results
• Epileptic Foals (10):
-ED detected in 9 of 10 foals, including focal, multifocal, and generalized spike-and-wave discharges.
-Central vertex (Cz) was the primary site of ED, with secondary diffusion to parietal and frontal regions.
-Photic stimulation triggered ED in 7 foals but not in controls, aiding diagnosis.
•Control Foals (9):
-Normal EEG background during wakefulness and sleep.
-Photic stimulation elicited normal photic driving responses without ED.

Clinical Relevance
• EEG confirmed interictal abnormalities in 90% of epileptic foals, higher than typical diagnostic yields reported in human epilepsy studies (30–40%).
• Photic stimulation enhanced diagnostic accuracy, demonstrating its utility as an activation procedure.
• Sound stimulation did not elicit ED, suggesting limited relevance for diagnosing epilepsy in foals.

Question 43

Long-term performance of show-jumping horses and relationship with severity of ataxia and complications associated with myeloencephalopathy caused by equine herpesvirus-1

Answer 43

Performance Outcomes
• 68% of horses returned to exercise.
• 52.9% achieved similar or improved levels of competition.
• Horses with ataxia grade ≥4/5 had only a 10% chance of regaining previous performance levels.

Negative Prognostic Indicators
• Grade ≥4/5 at admission was strongly associated with poor outcomes. These horses had a 60% fatality rate, with only 10% returning to preoutbreak levels.
• Complications: Development of both systemic vasculitis and urinary complications was associated with the worst outcomes. No horses with these combined complications returned to their previous performance level.
• Vaccination Status: Vaccinated horses had higher fatality rates (71.4%) compared to unvaccinated horses (10.5%), suggesting vaccine protocols or timing may influence disease outcomes.

Long-Term Recovery
• Recovery times varied: 12% returned to training within 6 months. Majority returned between 6–12 months. Full recovery took up to 24 months in some cases.
• Two horses retired due to residual ataxia and were used for breeding.

Question 44

Shapes of cervical articular process joints and association with histological evidence of osteochondrosis in Warmblood foals

Answer 44

APJ Shape Variability
• Substantial variation in APJ shape observed, contradicting the expectation that oval and flat surfaces are predominant.
• Most prevalent combinations:
-Oval and bevelled: 24%.
-Oval and flat: 23%.
-These combinations may both be considered normal in young Warmblood foals.
• Abnormal lateral view shapes included concave, convex, folded edge, and raised edge configurations.

Certain APJ shapes significantly associated with OC:
• Oval and folded edge (odds ratio [OR]: 2.5–3.5, p < 0.01).
• Oval and flat + additional shapes (OR: 2.8–3.9, p < 0.01).
• Shapes like convex or bevelled had lower odds of OC.
• The presence of OC lesions was more frequent in cranial cervical APJs than caudal cervical or cranial thoracic regions.

Shape and Location
• Abnormal shapes were more prevalent cranially on vertebrae and in the cranial cervical region, suggesting localized biomechanical stress.
• Caudal articular surfaces had significantly higher shape grades (moderate-to-severe abnormalities) than cranial surfaces.

Question 45

Computed tomographic examination of the articular process joints of the cervical spine in warmblood horses

Answer 45

CT effectively identified abnormalities of the cervical APJs, including:
• Narrowing of the intervertebral foramen (NIF): Present in 85.7% of cases, most often due to AP enlargement.
• Degenerative changes: Found in 57.1% of cases, including bony proliferation, subchondral irregularities, and joint collapse.
• Periarticular osteolysis: Identified in 52.9% of cases, particularly at C6-C7.
• Cyst-like lesions: Detected in 27.3% of cases, often localized at C6-C7.
• Fragmentation: Present in 28.6% of cases, commonly affecting C7-T1.

NIF, periarticular osteolysis, and high articular process-to-vertebral body ratios (APBR > 1.5) were significantly associated with:
• Forelimb lameness.
• Cervical pain or stiffness.
• Fragmentation was primarily associated with ataxia.
• No significant association found between cyst-like lesions and specific clinical signs.

Regional Variability
• Abnormalities were most frequent in the caudal cervical spine (C5-T1):
• NIF and periarticular osteolysis were common at C6-C7.
• Degenerative changes were more frequent at C3-C5.
• Fragmentation most often affected C7-T1.

Specific Findings
• Enlarged APJs without degenerative changes suggest developmental or congenital origins, such as dysplasia or osteochondrosis.
• NIF due to AP enlargement may indicate potential nerve impingement but requires further investigation (e.g., myelography or MRI).

Question 46

Comparison of blind, ultrasound‐ and neurostimulator-guided methods of percutaneous inferior alveolar nerve block

Answer 46

• Higher success rates with caudal blind (87.5%) and ultrasound-guided (85.7%) methods compared to ventral blind (50%) and neurostimulator-guided (57%).
• However, differences were not statistically significant (p = 0.1), likely due to sample size limitations.

Needle Placement Accuracy
• Ultrasound-guided method resulted in the closest needle placement to the mandibular foramen (median: 12.5 mm).
• Caudal blind method also achieved good proximity (median: 17.5 mm).
• Neurostimulator-guided method had the largest range in distances, with statistically significant differences from the ultrasound (p = 0.005) and caudal blind (p = 0.02) groups.
Staining of the Lingual Nerve
• Similar frequency across all groups (50%–75%), with no significant differences.

Question 47

Distribution of West Nile virus cases in horses reveals different spatiotemporal patterns in eastern and western Canada

Answer 47

Western Canada (Prairies): High recurrence of cases in specific census divisions (CDs), particularly southern Alberta and Saskatchewan.
Six significant high-risk clusters were identified:
• Three clusters in British Columbia and Alberta (2016–2018).
• Clusters in Saskatchewan, Manitoba, and Ontario occurred between 2012 and 2018.
• Most clusters were located near the US border, reflecting shared ecological conditions and vector habitats.

Recurrence of cases in specific regions likely driven by:
• Overwintering of Culex spp. mosquitoes and local environmental factors (e.g., climate, land use).
• High seroprevalence in endemic areas (up to 76%) indicates dynamic shifts in susceptible populations.
Role of Vaccination
• Unvaccinated horses accounted for 96% of cases, emphasizing vaccination gaps in certain regions.
• Vaccination rates varied significantly between provinces, potentially influencing case distributions.

Use of Horse Data in Surveillance
• Horses are reliable sentinels for WNV due to their overlapping risk with humans, especially in low-density human populations.
• Data on equine cases aid in targeting vaccination and mosquito control measures in at-risk areas.

Question 48

Use of a novel helical fan beam imaging system for computed tomography of the head and neck in sedated standing horses

Answer 48

The system is effective and safe for routine head and neck imaging in horses.
Caudal cervical imaging limited to C4-C5 due to horse anatomy and scanner dimensions.
High-resolution soft tissue imaging was adequate but could be further improved with MRI in select cases.