LAM: Exam 3

Neurological Localization of PNS and Spinal Cord Disease

• Spinal cord: Gait abnormalities w/ absence of intracranial signs

  • gait deficits, spastic paresis, ataxia, Flaccid paresis & muscle atrophy, proprioceptive deficits

• Cervical: Head normal, both fore & hindlimbs abnormal

• Below T2: Head/neck/forelimbs normal, hindlimbs abnormal

  • If tetraparesis w/o brain signs → lesion localizes to C1–T2

• White matter lesions (long tracts): spastic paresis, ataxia caudal to lesion

  • sensory information from the body to the brain (ascending tracts) and motor commands from the brain to the muscles and glands (descending tracts). 

• Gray matter lesions (LMN): flaccid paresis, muscle atrophy (focal/segmental)

• Peripheral n.: flaccid paresis, focal atrophy, sensory loss in one limb

Motor unit

• consisting of a single motor neuron (nerve cell) and all the individual skeletal muscle fibers it innervates

Localization of Brain Disease

• Cerebrum- Forebrain: depression, disorientation, nervousness, hyperexcitability, compulsive walking/circling, head pressing, maniacal behavior, seizures, cortical blindness

  • Consciousness, awareness, behavior change, intellect, voluntary motor control (UMN)

• Brainstem: Alterations in consciousness & arousal - no brain signs

  • obtunded, stupor, coma, cranial nerve deficits, head tilt, leaning/listing, resting nystagmus, spastic paresis, ataxia, vestibular ataxia

    • motion, vestibular input

• Cerebellum: attention tremor, coordination & motor activity(rate/range/speed/force)

  • Dysmetria/hypermetria(all 4 legs), Truncal sway, Intention tremor of head, Loss of menace response, Disequilibrium or paradoxical vestibular syndrome

    • motor activity, arousal (RAS), aranial nerve nuclei, vestibular & somatic motor integration

• Cranial N.: Head abnormal, limbs/trunk normal

• Diffuse Brain: Head + limbs abnormal

Cerebrospinal Fluid Analysis

• Collection sites:

  • Lumbosacral: Standing horse

    • Needle enters ventral subarachnoid space through conus medullaris (S4–S5)

    • Collect from dorsal subarachnoid space

  • Atlanto-occipital: Recumbent under GA

    • Midline insertion between atlas wings and nuchal crest

  • Atlanto-axial: Standing, lateral approach

• Evaluation:

  • Colour: Clear, colorless

  • WBC: 0–4, mononuclear

    • IgG index = (CSF IgG / serum IgG) × (serum albumin / CSF albumin) → intrathecal IgG production

  • Total protein: < 90 mg/dL

    • Albumin quotient = (CSF albumin / serum albumin) × 100 → BBB integrity

  • Ab testing: 

    • Viral: EHV-1, WNV, EEV, WEV

    • Protozoal: EPM

Diagnostic Imaging of the Nervous System

• Radiography/myelography: vertebral alignment, compression

• CT/MRI: brain, cervical spine

• Electromyography: LMN dz vs myopathy

• Electroencephalography: cerebral electrical activity

• Auditory brainstem evoked response: hearing & brainstem lesions

  • Cell bodies: ventral gray horn (spinal cord) or brainstem nuclei

  • Axons: form ventral spinal roots & motor cranial nerves

  • Why: directly cause muscle contraction (motor unit)

what are the clinical signs of peripheral nerve injuries or neuropathies in a horse?

• lameness, poor coordination (ataxia), and weakness, which can be severe enough to prevent weight bearing.

• muscle wasting (atrophy), drooping or paralysis of facial features like the lip or ear, gait abnormalities like goose-stepping or toe-dragging, and a lack of sensation in affected areas. 

Cranial Nerves

• I Olfactory: Smell (sensory)

• II Optic: Vision (sensory)

• III Oculomotor: Eye movement, parasympathetic to ciliary muscle

• IV Trochlear: Dorsal oblique muscle

• V Trigeminal: Mastication, facial sensation

• VI Abducens: Lateral rectus & retractor bulbi

• VII Facial: Facial expression, salivation, lacrimation, taste

• VIII Vestibulocochlear: Balance & hearing, head position

• IX Glossopharyngeal: Pharynx, salivation, taste

• X Vagus: Pharynx, larynx, parasympathetic to thorax & abdomen

• XI Spinal Accessory: Neck & pharyngeal muscles

• XII Hypoglossal: Tongue movement

Adult Seizures

• Et: Uncontrolled synchronous discharge of cerebral cortical neurons

  • CS Specific to cerebral cortex

• Types:

  • Primary: trauma, infection, toxins, developmental

  • Secondary: hepatic/renal, glucose/Na/Ca disturbances, hyperthermia, hypoxia/ischemia

  • Idiopathic: Sporadic adult idiopathic epilepsy (all breeds)

• Cs: 

  • Focal(partial/localized/absence): facial/limb twitching, compulsive circling, self-mutilation

  • Gen: loss of consciousness, recumbency, tonic-clonic activity, post-ictal blindness/depression

  • Epilepsy: recurrent seizures, non-progressive cerebral cortical disease

• Tx: Diagnosis & treatment of underlying dz #1!!! protect the head, Padding, Diazepam (short/ER), Phenobarbital (Long term) Levetiracetam (Keppra), Bromides, Gaba

  • Management: Loading dose, maintenance dose, daily dose for recurrent seizures

Juvenile Idiopathic Epilepsy

• inheritable

• Sig: Arabian foal syndrome, start ~ <6m

• Cs: post-ictal depression: most common, disorientation, blindness, trauma

• Dx: CS, history and breeding

• Tx: Diazepam acutely, phenobarbital 1y (maintenance), supportive care, self limiting with age, don’t breed

Lavender Foal Syndrome

• coat color dilution lethal

• Et: Autosomal recessive, lethal

• Sig: Egyptian Arabians w/ color dilution (lavender/pink/purple)

• Cs: inability to stand @ birth, seizures,  CNS signs, death

• Tx: Euthanasia

Cerebellar Abiotrophy

• inheritable

• Et: Autosomal recessive

• Sig: Arabians, 6m

• Cs: symmetric hypermetria/dysmetria(4 limbs), spasticity, truncal sway, intention tremor, absent menace

• Dt: genetic testing

• Tx: euthanasia, no treatment

Seizure Disorders in Foals

• Neonatal encephalopathy; due to perinatal oxygen

  deprivation = most common!!!!

  • metabolite/electrolyte disturbances, bacterial meningitis, congenital defects(Arabians), older foals: trauma

• Cerebellar Abiotrophy, Lavender Foal Syndrome,Juvenile Idiopathic Epilepsy

Cranial Trauma

• Common injury: direct impact

• Et: edema #1!!**, ↑ ICP, herniation

  • severe/uncontrolled edema: cerebral and/or cerebellar herniation

• Cs: Depression, recumbency w/ stupor or coma, vestibular signs, blood/CSF from ears/nose = fracture, abnormal pupils, head tilt

  • Frontal/parietal/orbital: concussion, contusion, hemorrhage, brain parenchyma disruption

  • Petrous temporal/occipital: very common - young by flipping over backwards

    • vestibular dysfunction, facial paralysis, bleeding from ears, optic nerve damage

  • Poll injuries: hyperextension of neck,  basilar fractures = fractures/b-sphenoid & b-occipital bone separation = intracranial hemorrhage & severe brain injury, guttural pouch hemorrhage, tearing optic nerve: blindness

    • Rupture/avulsion of ventral straight mm &/or fracture at base of brain

• Dt: rads, CT, MRI, endoscopy

• Tx: Stabilize airway / padding, IV catheter, Mannitol/furosemide (not w/ hemorrhage), hypertonic saline, hyperventilation (foals), Sx for fragments, monitor BP

  • poor prognosis → hemorrhage in CSF, recumbence, seizures, coma, fixed pupils, erratic breathing

Metabolic and Hepatic Encephalopathy

• Very common!

• Et: hepatic failure, hyperammonemia, renal failure, uremia(head pressing), glucose/Na/Ca imbalance, hypercalcemia, Theiler’s dz, hyperlipemia, Plant Alkaloids toxicity, cholangiohepatitis, chronic hepatitis, mycotoxins

• Cs: behavior changes, seizures

• Tx: dextrose fluids, dietary modifications, lactulose, neomycin, metronidazole

Nigropallidal encephalomalacia

• Neuro toxins

• Et: Repin toxin in Yellow Star Thistle & Russian Knapweed

  • necrosis of substantia nigra & globus pallidus: UMN → throat, tongue

  • Cs: facial dystonia, “sardonic grin,” inability to eat/swallow, dunks head into bucket for water

    • necropsy: neuronal cell bodies in midbrain

  • Tx: Euthanasia 

Locoism: acquired polysaccharide storage disease

• Neuro toxins

• Et: Oxytropis/Astragalus spp 

  • endophytic fungus produces → Swainsonine causes lysosomal storage dz

    • Intracytoplasmic vacuolization of cells

• Cs: ataxia, alternating somnolence/excitability, intention tremor, flaccid lips, dysphagia

  • young, herd problem

• Px: permanent deficits, ill thrift

Leukoencephalomalacia: mycotoxin Moldy Corn Poisoning

• Neuro toxins

• Et: Fusarium verticilloides (fumonisin B1),

  • liquefactive necrosis of cerebral hemispheres and liver damage

  • Cs: rapid progressive signs, ataxia, blindness, seizures, agitation, death

  • Dt: toxin in feed

  • Tx: Euthanasia 

Sorghum Toxicosis

• Neuro toxins

• Et: Sudan/Johnson grasses, sorghum hybrids

  • cyanide compounds or lathyrogens

  • Axonal degeneration in spinal tracts, dorsal roots, cerebellar peduncles

  • Cs: Hindlimb ataxia, urinary retention, cystitis

    • Often outbreaks/herd problem

  • Tx: remove source, manage bladder/cystitis

Bacterial Infections of the Nervous System

• Brain Abscess: young horses

  • Et: head trauma, hematogenous spread (S equi zooepidemicus/equi), extension from sinus/middle ear & tooth abscess

  • Cs: brain signs, depression, circling, blindness, seizures, CN deficits, head pressing

  • Dt: inflammlatory leukogram, CSF (↑ neutrophils, protein), imaging

  • Tx: high-dose antibiotics (penicillin, sulfa), NSAIDs, DMSO, drain, seizure (phenobarbital)

  • Px: guarded-poor

• Spinal Abscess:

  • Et: Strangles (Strep equi), septicemia in foals

    • extradural, vertebral body

  • Cs: spinal cord compression, progressive paresis/ataxia

• Meningitis

  • Et: rare complication of neonatal septicemia or local extension

    • neuroborelliosis(lyme)

Sleeping sickness

• Alpha Virus Encephalidities

• Et: Mosquito-borne→birds, seasonal, viral

• Horses dead end host

  • EEE: SE US, severe, high mortality, poor Px

    • very common

  • WEE: western US, rare

    • less common

  • VEE: FAD→regulated, South/Central America, zoonotic, severe

    • horses = major amplifiers

• Cs: high fever, rapid progressive encephalopathy→ recumbence

  • incubation 1-3w

• Dt: IgM ELISA (MAC-ELISA), CSF neutrophilia

• Tx: supportive, core vax → prevention

  • x3 in 1st year, then annually 

  • Combo w/ tetanus

West Nile Virus

• mosquito-borne encephalomyelitis virus, seasonal

• Et: Endemic in north america, polioencephalomyelitis

  • gray matter of brainstem, spinal cord

• Cs: weakness, stumbling, recumbence, muscle fasciculations, CN deficits, blinking, twitching muzzle

• Dt: IgM ELISA

• Tx: supportive, sling support, core inactivated vax: protective

• Px: 30% mortality, worse if recumbent

Rabies

• fatal viral encephalomyelitis → saliva

• DDX MUST be considered for any undiagnosed encephalopathy

• Et: zoonotic, raccoon(#1), skunk, fox, bat

  • bite causes virus ascends nerves, varies from days to long incubation

    • typical bites: muzzle/face/distal limbs

• Cs: paralytic (ascending paraparesis), encephalopathic (“furious/dumb”), terminal hyperesthesia, self-mutilation, recumbency → death

• Dt: DFA on brain postmortem(brainstem & cerebellum), limit exposure: gloves/wash hands

  • no antemortem test

  • NOTIFY PUBLIC HEALTH OFFICALS!!

• Tx: Euthanasia, core killed vax → x2 @ 6/7m & annual

  • prevention is key!

Equine Protozoal Myeloencephalitis (EPM)

• The most common infectious equine CNS disease

  • brainstem & spinal cord most common

• Et: Sarcocystis neurona, opossum** → horse dead end host

  • sporocysts in contaminated feed/water

  • focal/multifocal gray + white lesions → hemorrhage, and necrosis

• Cs: asymmetrical ataxia(side of lesion), focal muscle atrophy w/ ±  cranial nerve defects: facial paralysis, dysphagia, LMN signs(spastic hind limbs), CN 5(facial paralysis)

• Dt: rule-outs, serology, CSF ELISA, necropsy (definitive)

  • + serum titer = exposure

  • S neurona antibodies in serum & CSF: both positive = EPM

• Tx: ponazuril, diclazuril, sulfadiazine/pyrimethamine(cheap)

  • best outcome when tx early!

• Px: 60% improve, 20% full recovery, relapses common

Spinal Cord Trauma

• White matter (long tracts): spastic paresis & ataxia behind lesion

• Gray matter (LMNs): flaccid paresis & atrophy, focal/segmental

• Et: edema, vertebral fracture, cord impingement

  • cervical spine from young horses → flipping over, pulling back

    • dens/atlas & thoracolumbar fractures: young

• Cs: paresis, ataxia(disrupts long tracts)*, hypalgesia: diminished sensitivity or response to normally painful stimuli

• Stable = standing Unstable= down 

• no brain signs, tetraparesis localizes to C1-T2

• Tx: Non fracture/stable: DMSO, corticosteroids, NSAIDs, stall rest, Sx(unstable fractures)

Cervical Stenotic Myelopathy (CSM)

• “Wobbler Syndrome” → young, rapidly growing foals

  • OC: Developmental disease of growing cartilage

• Et: Abnormal vertebral growth/development (osteochondrosis OC), Instability/malformation with cord compression

  • Most common non-infectious neuro dz of horses!!

    • Abnormal growth & development = cervical cord compression & tetraparesis & spastic ataxia

  • cervical: Osteochondritis dissecans (OCD) of facet joints &/or Physeal dysplasia

• Types:

  • Type I (Dynamic instability/high): C3-C6, intermittent, young horses

  • Type II (Static compression/low): C5-T1, constant, older horses

    • present @ 2-5 yrs

• Cs: young Clumsy → BAR, stumbling, falling, poor performance, UMN + proprioception defects, spastic tetraparesis, hindlib ataxia(more severe)

• Dt: rads, sagittal ratios, myelography, CT/MRI

• Tx: reduce growth rate, Vit E supp, steroids, DMSO, Interbody fusion Sx “bagby”(type I), Dorsal laminectomy (type II)

Occipito-Atlanto-Axial Malformations (OAAM)

• Stenosis/cervical spinal cord compression!

• Et: Congenital defect 

  • Cord compression at birth

• Sig: Arabians, QH, Drafts

• Cs: spastic tetraparesis & ataxia: from birth some a bit older, limited cervical ROM (cannot extend neck)

• Dt: imaging(cervical), history, PE

• Tx: euthanasia 

Equine Neuroaxonal Dystrophy (eNAD) and Equine Degenerative Myelopathy (EDM)

• Et: Dev degenerative dz of spinal proprioceptive tracts( ALL 4 limbs)

  • Vit E deficiency (mare or foal)

    • had no access to green grass/quality hay

• Sig: 6-24m, QH

• Cs: Symmetric ataxia @ 6-24m , clumsy young horse

  • Generally no CS(eNAD), CS showing (EDM)

• Dt: exclusion, history of Vit. E deficiency, histopathology postmortem

  • Normal vitals, labs, CSF, cervical imaging

• Tx: Vit E supp (prevents progression, not reversal)

Equine Herpesvirus-1 Myeloencephalopathy (EHM)

• Herpes, reportable!, effects white matter

• Et: Neurotropic EHV-1 strains → acute ataxia & sacral signs & abortion

  • Latent virus: resp dz, cell-associated viremia in CNS, endothelial infection

    • Vasculitis in thoracolumbar & sacral cord: edema, hemorrhage, infarction

• Sig: Adults >3y, event/comingling/stress outbreaks

• Cs: Acute onset hindlimb ataxia, urinary retention, bladder paralysis, tail/anal tone loss, penile prolapse, fever

  • RARE: encephalopathy/brainstem/CN signs

• Dx: ↑ protein, pleocytosis, xanthochromia-yellow (CSF tap); PCR(nasal/blood), paired sera (4x titer rise), IHC(necropsy)

• Tx: NSAIDs, steroids, DMSO, antivirals (valacyclovir @ risk), biosecurity, quarantine, vax (resp only; not protective for CNS dz)

• Px: 40% mortality, residual deficits

Post-Anesthetic Myelomalacia

• Et: dorsal recumbent anesthesia

  • ischemic injury to lumbosacral spinal cord gray matter

• Sig: young draft horses after Sx

• Cs: Fail to rise, bilateral hindlimb paresis, paralysis

• Ddx: Type I PSSM (draft breeds), Post-anesthetic myopathies/neuropathies (treatable)

• Px: poor, don’t recover

 Vestibular Disease

• Vest. system: Maintain posture, muscle tone & equilibrium, Orientation of head

• Et: trauma, infection, petrosal fractures, temporohyoid osteoarthropathy, otitis media-interna

  • Central: medulla, pons, cerebellum

  • Peripheral: CN VIII; common in horses → temporal bone

    • CN VII & VIII run close together, lesions may effect both

      • Facial paralysis very common

• Cs: Head tilt, leaning, falling, rolling, resting horizontal fast nystagmus

  • Signs ipsilateral(same side) to lesion

Temporohyoid Osteoarthropathy

• Et: otitis media, guttural pouch dz, cribbing, idiopathic degen

  • Bony proliferation, sclerosis, fusion of temporohyoid articulation

  • Stenosis of ear canal, obliteration of tympanic bulla

• Cs: mastication pain, head rubbing, head shaking

  • spontaneous fracture(due to fusion): acute vestibular signs + facial paralysis

• Dt: endoscopy, radios, CT

• Tx: anti-inflam, antibiotics, protect cornea, ceratohyoidectomy Sx→ prevent fracture 

Otitis Media–Interna

• Cs: vestibular dz, facial paralysis,

  • Extension beyond inner ear: osteomyelitis calivrium, subdural abscess, meningitis → lead to CNS signs

• Dt: tympanocentesis, cytology/culture, rads/CT/MRI

• Tx: aggressive antibiotics, anti-inflammation → less severe

Pharyngeal & Laryngeal Neuropathies

• Pharyngeal:

  • Et: guttural pouch mycosis, trauma (surgery, fractures), neoplasia

  • Cs: dysphagia, feed in nostrils, weight loss

• Laryngeal:

  • Et: Idiopathic left laryngeal hemiplegia, recurrent laryngeal nerve injury: (perivascular injection of NSAIDS) or lead poisoning (polyneuritis)

  • Cs: abnormal whinny, inspiratory noise, obx

Horner Syndrome

• Et: cranial trauma, guttural pouch disease, cervical injections, SC injury, brachial plexus injury, thoracic trauma/mass

  • disruption of Sympathetic pathway dz to head/neck

• Cs: Ptosis, enophthalmos, 3rd eyelid prolapse, miosis, focal sweating (distribution helps localize lesion)

Neuropathic (Photic) Head Shaking

• Et: trigeminal (CN V ophthalmic branch) hyperesthesia

  • exposure to light or environmental stimuli

• Cs: head shaking, sneezing, rubbing, snorting

  • progressive

• Dx: r/o other head shaking issues

• Tx: Nose nets, UV masks, cyproheptadine, carbamazepine, euthanasia(many cases are debilitating)

Polyneuritis Equi (Cauda Equina Neuritis)

• Et: Immune-mediated

  • chronic granulomatous inflam, fibrosis of cauda equina nerve roots

• Cs: hyperesthesia around rump/tail, tail rubbing!!, flaccid bladder (overflow incontinence), urine scald, fecal retention, tail paralysis/atrophy, perineal anesthesia, penile prolapse/anesthesia

• Tx: no cure, corticosteroids(temp effect), catheterization, manual rectal emptying, nursing care, euthanasia

Stringhalt

• characteristic gait abnormality spasmodic hyper-flexion of one or both hind limbs!

• Et: peripheral axonal degeneration of peroneal nerve

  • Sporadic: usually unilateral, often after hock injury

  • Epidemic: herd outbreaks, bilateral, Plant tox: flatweed, false dandelion, cheeseweed

• Cs: spasmodic hyperflexion of hindlimbs

• Tx: tenectomy of lateral digital extensor → sporadic

  • remove from pasture → epidemic 

Dysautonomia (Equine Grass Sickness)

• generalized GI motility disorder

• Et: enteric nervous system, ANS ganglia degeneration

  • idiopathic, C botulinum type C toxin

• Sig: pastured horses, UK

• Cs: Dysphagia, gastric dilation, reflux, impaction, SI ileus, colonic impaction, death

• Px: fatal

Traumatic Peripheral Nerve Injuries

• Et:

  • Facial nerve: base of ear or halter injury under anesthesia

  • Suprascapular nerve: harness/collar injury

    • Sweeney

  • Radial nerve: trauma, fracture, anesthesia

  • Brachial plexus: root avulsion, limb paralysis

  • Femoral nerve: anesthesia, pelvic/femur fracture

  • Obturator nerve: dystocia, pelvic fracture

  • Sciatic/peroneal nerve: IM injection in foals, pelvic trauma, anesthesia

• Tx: Sx, time, anti-inflam, corticosteroids, slings/splints, hydrotherapy, eye care (lubricants, tarsorrhaphy)

Equine Motor Neuron Disease

• Et: Vit E deficiency, poor hay, no pasture, stabled

  • degeneration of LMNs in cord & brainstem

• Cs: weakness, trembling, recumbency, weight loss, muscle atrophy, base-narrow stance, dropped head, elevated tailhead

• Dt: low serum Vit E, muscle biopsy (sacrocaudalis), retinal lesions

• Tx: Vit E supp, pasture access

• Px: guarded

Botulism

• Et: C botulinum toxin (types B, A, C) blocks NMJ

  • Forage: ingested contaminated feed, silage, carcasses

    • many horses effected/herd issue

  • Wound: rare

  • Toxoinfectious: foals ingest spores and toxin produced in gut

    • “Shaker foal” → endemic areas

• Cs: weakness, dysphagia, generalized paresis, recumbency, resp failure, flaccid paralysis!

  • signs occur 1-17d after ingestion/exposure!!

• Dt: toxin ID (mouse bioassay on feed/poop)

• Tx: Antitoxin, toxoid vax → prevention

  • good if remain standing 

Tetanus

• Clostridium tetani in wounds/conditions that favor anaerobic growth

  • spinal cord and brainstem, UMN w/ renshaw cells

  • CS: generalized muscle rigidity, vague stiffness, muscle spasms “sawhorse”, prolapsed 3rd eyelid, sensitive to touch/sound

    • End stage: respiratory failure

  • TX: wound debridement & antibiotics, antitoxin, acepromazine, quite place w/ low light, supportive care

    • Core vax: tetanus, revaccinate w/ injury or sx if vaccine was >6m ago

      • give toxoid and antitoxin together

UA

• Looks like Beer

• Consistency: Turbid/viscous 

  • Ca carbonate & mucus

• Colour: Yellow–brown color

  • Pigments: hemoglobin, myoglobin, bilirubin, plant pigments, drugs

  • Bld: kidney, bladder, urethra

  • Dz: NSAID injury, neoplasia, cystitis, idiopathic hemorrhage

• USG: 1.025–1.060

  • Isosthenuria = 1.008–1.017

• pH: alkaline 

  • 7.5–9

• Absent: glucose, protein, bacteria, casts

Acute Renal Failure

• Et: >70–80% nephron loss & Isosthenuria in the face of azotemia!!

  • Pre-renal: ↓ renal perfusion from hypovolemia/fluid defect, shock, dehydration

    • Physiologic oliguria, reversible

  • Renal (intrinsic): ischemic injury =Hypoxia, toxic injury 

    • Commonly acute tubular nephrosis

    • shock, SIRS/endotoxemia, sepsis, NSAIDs, aminoglycosides, tetracyclines, myoglobin (rhabdomyolysis), hemoglobin, cantharidin (blister beetles), vit D/K3, acorns, heavy metals

    • renal ischemia is a major predisposition for

      toxic injury

• Cs: Depression, edema, encephalopathy

• Dt: azotemia, ↓ Na, ↓ Cl, ↑ K, isosthenuria, aciduria, ↑ GGT:Cr, casts

• Tx: Fluids!! (until Cr stabilizes), diuretics (furosemide) until CK drop

  • Monitor: urine output, lytes, creatinine, PU/PD will persist during recovery

  • Goal: convert oliguria → polyuria

• can’t concentrate urine, &/or creatinine

  remains elevated, there is chronic renal disease

Chronic Kidney Disease

• Irreversible, progressive

• Et: >70–80% nephron loss = renal failure and compensatory hypertrophy, reduced nephrotic mass

  • Congenital: agenesis, dysplasia, polycystic kidney

    • Sig: Young horses (1–5 yrs) @ birth, poor BCS, rough coat

  • Acquired: chronic interstitial nephritis (#1), infiltrative diseases (LSA, neoplasia), glomerulonephropathy →  hypoalbuminemia and edema

• Cs: Gradual weight loss, poor appetite, rough coat, PU/PD, edema, dental tartar

• Dt: azotemia, isosthenuria,↓ Na, ↓ Cl, ↑ K, metabolic acidosis, small fibrotic kidneys, ± ↑ Ca

• Tx: Hydration, salt, grass hay (↓ Ca), palatable concentrate, add fat, lyte balance, tx acidosis

• Px: poor

Renal Tubular Acidosis

• Et: Tubular dysfunction → bicarb loss → hyperchloremic metabolic acidosis

• Cs: depression, weakness, inappetence

  • No azotemia 

• Tx: bicarb + KCl

Pyelonephritis

• Et: ascending or hematogenous: Uncommon

  • R equi, strangles, lepto, septic foals

• Cs: fever, depression, pyuria, bacteriuria, hematuria

• Dt: leukocytosis, ↑ fibrinogen,

  • UA, culture, US, endoscopy, lepto PCR

• Tx: antibiotics based on culture

Cystitis (Lower UTI)

• Et: secondary to bladder stones, paralysis, incompetent sphincter (mares), catheter, abnormal flow

  • mares more prone, iatrogenic w/ catheters

• Cs: stranguria, pollakiuria, incontinence, hematuria

• Dt: >10 WBC/hpf or >20 bacteria/hpf, culture, endoscopy

• Tx: based on culture: TMS, ampicillin, ceftiofur, penicillin

Urolithiasis

• Types:

  • Ca carbonate: #1, yellow spiculated

  • Ca phosphate: Grey-white, smooth

• Sites: kidney, ureter, bladder, urethra

  • some: spontaneous develop in bladder, CKD

  • Renal Calculi: originates from renal pelvis → hydronephrosis, abdominal pain

• Sig: males > females

• Cs: pain, hematuria, obstruction, CKD

• Dt: US, rectal, endoscopy

• Tx: lithotripsy, cystotomy, nephrectomy if unilateral,

  • ↑ water, add salt, avoid alfalfa, reduce calcium intake

Control of Bladder Micturition

• Pontine micturition center in brainstem controls:

  • Filling/storage: inhibits detrusor, parasympathetic LMNs, closes sphincters

  • Voiding: contracts detrusor, relaxes sphincters

• Ascending: sensory

• Descending: UMN

Neurogenic Bladder

• Et: Polyneuritis equi, EHV-1, sorghum toxicity, EPM, neoplasia, spinal trauma

  • UMN spastic bladder long tracts: lesion above sacral segments 

    • Cs: spastic bladder, open internal sphincter, and spastic urethralis → dysynergia(detrussor & urethralis), intermittent incontinence 

  • LMN Flaccid bladder: lesion in sacral cord/nerves 

    • Cs: flaccid, distended bladder, overflow incontinence,  loss of perineal reflex

• Tx: Manual evacuation, catheter, Bethanechol (stimulate detrusor), Phenoxybenzamine (relax sphincter), Dantrolene (relax urethralis), Phenazopyridine (mucosal analgesic)

• Px: risk of sabulous cystitis from Ca carbonate buildup

  • sabulous cystitis: accumulation of sediment in floor of bladder

Detrusor Atony & Idiopathic Sabulous Cystitis

• Mares, idiopathic 

  • retention of urine & accumulation of sabulous debris = ultimately resulting in detrussor atony

  Et: neuro dysfunction, pain = urine retention , idiopathic in geldings w/ sabulous cystitis

• Cs: Flaccid bladder

• Tx: flush bladder, antibiotics, Bethanechol (stimulate detrusor), Phenoxybenzamine (relax sphincter)

• Px: fair, chronic

Uroperitoneum

• Et: 

  • Foals: Ruptured bladder(most common), urachal tear(dorsal), ureter, hospital aquirred

  • Adults RARE: trauma, dystocia, obstruction(males)

    • Sm: dorsal tears: medically managed, LG: SX repair

• Dt: azotemia, ↓ Na, ↓ Cl, ↑ K, met. acidosis, peritoneal Cr > serum Cr, US, abdominocentesis

• Tx: 09% NaCl + dextrose/bicarb (#1), Sx→ stabilize first

  • avoid K fluids

Omphalitis

• infection of the umbilical stump, the remnant of the umbilical cord left after birth

• Et: failure passive transfer, ascending infection through urachus, arteries, vein

• Cs: umbilical inflam, patent urachus, abscess, uroperitoneum

• Dt: palpation + US for signs of infection!

• Tx: antibiotics, Sx removal of infected/leaky remnants

Parturient & Urethral Injuries

• Et: bladder rupture, urethral incompetence/laceration, detrusor injury, bladder prolapse→ urethra or cervical tear

• Sig: Mares

• Tx: catheter, Sx, Bethanechol (stimulate detrusor),

Male Dorsal Urethral Hemorrhage

• Et: Defect in dorsal urethral mucosa communicating with corpus spongiosum

• Cs: hemospermia &/or expulsion of blood at end of urination

  • blood staining on canon/pasterns

• Tx: perineal urethrotomy/transect bulbospongiosum

  • heals by 2° intention, relieves pressure 

Polyuria & Polydipsia

• Et: renal failure, PPID(cushings), psychogenic(wet stall), corticosteroids, α2 agonists, diuretics

• Cs: r/o renal issues 1st

  • PU: >25 L/day urine

  • PD: >50 L/day water

• Dt: water deprivation test (psychogenic: primary) very common

Urinary Neoplasia

• Et: 

  • Kidney: renal cell carcinoma (old), nephroblastoma (young)

  • Bladder: SCC, TCC, adenoma

  • Urethra/external genitalia: SCC, sarcoid, melanoma

• Dt: rectal exam, US, biopsy

• Tx: nephrectomy if unilateral

Castration Surgical Planning Considerations

• Why: Stop stud behaviour, genetic soft cull, Dz of testis or spermatic cord

• When: 1.5–2 years

  • Sx at 1.5–2 years allows MS dev under testosterone

  • Older stallions have learned behaviour persists + more complications

• Risks: Hemorrhage, preputial/scrotal swelling, septic funiculitis, schirrhous cord, septic peritonitis, hydrocele, omental prolapse, visceration or eventration

Pre and Post Op Considerations for Castration

• Pre-Op: make sure you have the RIGHT horse

  • Tetanus Vax: Must be current 

    • Give tetanus toxoid if uncertain

  • Confirm two testes in scrotum; no inguinal hernia

  • Rx: ± Penicillin(clostridial), flunixin

• Ventral scrotum incision, no ligatures

  • Nut to nut : emasculators 

• Op: 

  • Closed: Young with small cords

  • Open: Most common

  • Recombinant R lateral: xylazine (sedation), ketamine (induction)

    • Better control, safety, hemostasis BUT risk & $$ of GA

  • Standing: alpha-2 + butorphanol (sedation), local to testicles & cords

    • Avoids GA, cheaper BUT bad for movement, bleeding, poor behaviour, ponies, donkeys, mules, small testes

• Post-Op: 

  • Incisions left open for drainage

  • Confine 24 hrs, then exercise twice daily for 2w

    • reduce edema and promote drainage

Routine Castration

• Position: 

  • R Lateral recumbency: upper hindlimb pulled forward & secured

    • Remove halter, pad, cover eyes

  • Standing: Wrap tail

• Insise: 

  • Compress testes into scrotum

  • 10 cm incision over each testis, parallel to median raphe, 2 cm from midline

• Exteriorize: via ventral scrotal incisions

  • Closed: Tunic not opened and strip fascia around cord proximally

  • Open: Open vaginal tunic, split mesorchium

• Cut: Apply emasculator “nut to nut”

  • Open: Crush vessels, then vas deferens, cremaster, tunic separately

• Close: Incisions left open for drainage 

  • second intention healing

Testicular Descent

• Normally occurs by 1m 

• Testis initially behind kidneys

• Gubernaculum testis: connects testis to scrotum

• Testis enlarges → regresses → descends via inguinal canal

• Gubernaculum contracts, pulling testis into scrotum

• Inguinal extension of GT

  • becomes proper lig of testis, lig of tail of epididymis, scrotal lig

Cryptorchidism

• Et: Failure of, one > both, testicles to descend into scrotum

  • Inguinal: testis in inguinal canal

  • Incomplete abdominal: epididymis in canal, testis just inside internal ring

  • Complete abdominal: both epididymis & testis retained in abdomen

• Sig: Percherons, Saddlebreds, QH

  • TB are RARE

• Cs: late descent at 2-3y, absent testes, stallion-like behavior, unclear castration history

  • produce testosterone, no sperm from retained testes

• Dt: Palpation, US, high testosterone/estrogen, hCG stim, Laparoscopy (definitive)

• Tx: castration: inguinal (most common)

Cryptorchid Castration

• Inguinal approach (#1):

  • GA, dorsal recumbency

  • Incise over superficial ring

  • Locate inverted vaginal process and exteriorize

• Para-inguinal: incomplete abdominal retention

  • Considered safer than inguinal

• Abdominal: complete abdominal retention

• Laparoscopic: Minimally invasive option

Parturition in Mares

• Gestation: 320-365 days 

  • avg 340, generally are constant year to year

  • premature if <320d

• Stage 1: 4-24h

  • Discomfort, restlessness 

• Stage 2: delivery within 20 min

  • Rupture of chorioallantois (water breaks)

  • Prolonged = dystocia and birth asphyxia risk

• Stage 3: <3 hrs

  • Expulsion of fetal membranes

Neonatal Behavior and Vitals

• Behavior: precocious, BAR, teat seeking

  • Sternal in 10 min

    • Abnormal = Not sternal by 10 min

  • Standing by 1 hr

    • Abnormal = Not attempting to rise by 20 min or standing by 1 hr

  • Suckling by 2 hrs

    • Abnormal = Weak suckle reflex at 10 min

  • Sleep ~50% of time, stretches then teat seeks

• HR: 80–120

• RR: 40–60

  • Abnormal = not breathing in 30 sec

• Temp: 99–102°F

• Diet: Consume 25%+ BW in milk/day

• Feces: Pass meconium at 12–24 hrs

Neonatal Septicemia

• Et: FPT → bacterial dissemination

  • Bacti enter umbilicus, MM, GIT, lack of colostrum

• Cs: neonatal weakness, organ failure, sepsis, dropped ears, fever Prolonged CRT, weak pilse, cold limbs 

  • major cause of neonatal death

• Tx: Correct FPT, Antibiotics, Resp Support, Cardio Support, Nutrition, Seizure Management, Umbilical Care, Enviro Management 

  • Treat ASAP

• Px:Poor

Peripartum Asphyxia (Hypoxic-Ischemic Encephalopathy)

• Et: oxygen deprivation “dummy foals”

  • Prenatal: placental insufficiency, fescue tox, bacterial, torsion

  • Parturient: birth asphyxia 

  • Postnatal: immature lungs, aspiration, rib fractures

• Cs: neonatal weakness, disoriented, no suckle reflex, seizures, coma, brain edema

• Tx: Correct FPT, Antibiotics, Resp Support, Cardio Support, Nutrition, Seizure Management, Umbilical Care, Enviro Management 

• Px: Good if full-term

Prematurity/Dysmaturity

• Et: Placental insufficiency, placentitis, fescue toxicosis late pregnancy(placenta edema), late abortion

  • Premature: < 320 days

  • Dysmature: signs of immaturity despite normal gestation

• Cs: neonatal weakness, abnormal ossification (carpal/cuboidal bones), tendon laxity, respiratory issues, domed head, floppy ears, silky hair coat

• Tx: Correct FPT, Antibiotics, Resp Support, Cardio Support, Nutrition, Seizure Management, Umbilical Care, Enviro Management 

• Px: Fair to Poor

Placentitis

• Ascending bacterial infection in 3rd trimester

  • Mare not very sick

• CS: Vaginal discharge, premature udder development, premature lactation(colostrum lost)

  • death, abortion, premature, Premature placental detachment, prenatal septicemia

• Foals hypoxemic in utero, high rish for asphyxia : small weak foals

• high risk for FPT

Fescue toxicosis

• Mares ingest tall fescue pasture in late pregnancy 

  • Ergots Alkaloids induce the endocrine dysfunction and negative effects on preg/lactation

• CS: placental edema and insufficiency, hypogalactia(low milk supply) & lack of udder development!

• Take mare off pasture >30d before gestation 

Supportive & Intensive Care for Neonates

• Correcting FPT: colostrum within 12hrs (15–2L in divided feedings), plasma transfusion after 12hrs (gut closure)

  • Goal is IgG >800 mg/dL by 24 hrs

  • Measure plasma IgG w/in 24h, test colostrum

• Antibiotics: Ceftiofur (mild), beta-lactam + aminoglycoside (severe)

  • Broad spectrum (G-) for E coli, streptococci, anaerobes

• Resp Support: insufflation (septic/recumbent), continuous (premature/asphyxiated) 

• Cardiovascular Support: use arterial blood gas analysis 

  • Fluids: boluses (20 ml/kg), maintenance 100 ml/kg/day

    • Correct electrolytes & glucose

  • Pressors (dopamine/dobutamine): hypotensive

• Nutrition: Mare’s milk (#1), goat’s milk, replacer, pan feed, NG tube, TPN

  • Goal is 15–25% BW milk/day, gain 1–3 lbs/day

  • Dextrose, AA, lipids 

• Seizure Management: diazepam/midazolam, phenobarbital, mannitol/furosemide (cerebral edema)

• Umbilical Care: palpate, US; daily antibiotics or Sx removal

  • Omphalitis/omphalophlebitis common in weak foals

• Enviro: padded stall, keep sternal and rotate hourly, ophthalmic care to prevent corneal ulcers