LAM: Exam 3 (DONE)

Neurological Localization of PNS and Spinal Cord Disease

• Spinal cord: gait deficits, paresis, ataxia, 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

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

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

Localization of Brain Disease

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

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

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

  • motion, vestibular input

• Cerebellum: Dysmetria/hypermetria, Truncal sway, Intention tremor of head, Loss of menace response, Dysequilibrium 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)

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: ncontrolled synchronous discharge of cerebral cortical neurons

  • 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: 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: Padding, Diazepam (short), Phenobarbital (Long) Levetiracetam (Keppra), Bromides, Gaba

Seizure Disorders in Foals

• Juvenile Idiopathic Epilepsy

  • Sig: arabian, <6m 

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

  • Tx: Diazepam, phenobarbital for 1y, self limiting with age, dont breed

• Lavender Foal Syndrome

  • Et: Autosomal recessive, lethal

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

  • Cs: inability to stand, seizures, death

  • Tx: Euthanasia

• Cerebellar Abiotrophy

  • Et: Autosomal recessive

  • Sig: Arabians, 6m

  • Cs: hypermetria, dysmetria, truncal sway, intention tremor, absent menace

  • Dt: genetic testing

  • Tx: euthanasia

Cranial Trauma

• Et: edema, ↑ ICP, herniation

• Cs: Depression, stupor, coma, vestibular signs, blood/CSF from ears/nose, abnormal pupils

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

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

  • Poll injuries: hyperextension,  basilar fractures, guttural pouch hemorrhage, blindness

• Dt: rads, CT, MRI, endoscopy

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

Metabolic and Hepatic Encephalopathy

• Et: hepatic failure, hyperammonemia, renal failure, glucose/Na/Ca imbalance, hypercalcemia, Theiler’s dz, hyperlipemia, PA toxicity, cholangiohepatitis, chronic hepatitis

• Cs: behavior changes, seizures

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

Neuro toxins

• Nigropallidal encephalomalacia

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

    • necrosis of substantia nigra & globus pallidus

  • Cs: facial dystonia, “sardonic grin,” inability to eat/swallow

  • Tx: Euthanasia 

• Locoism

  • Et: Oxytropis/Astragalus spp 

    • Swainsonine causes lysosomal storage dz

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

  • Px: permanent deficits, ill thrift

• Leukoencephalomalacia

  • Et: Fusarium verticilloides (fumonisin B1), Moldy Corn Poisoning

    • liquefactive necrosis of cerebral hemispheres and liver damage

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

  • Dt: toxin in feed

  • Tx: Euthanasia 

• Sorghum Toxicosis

  • 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:

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

  • Cs: depression, circling, blindness, seizures, CN deficits

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

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

  • 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

Sleeping sickness

• Et: Mosquito-borne, seasonal, viral

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

  • WEE: western US, rare

  • VEE: FAD, South/Central America, zoonotic

    • horses = amplifiers

• Cs: fever, rapid encephalopathy, recumbence

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

• Tx: supportive, core vax

West Nile Virus

• Et: Endemic, polioencephalomyelitis

  • gray matter of brainstem, spinal cord

• Cs: weakness, stumbling, recumbence, muscle fasciculations, CN deficits

• Dt: IgM ELISA

• Tx: supportive, sling support, core vax

• Px: 30% mortality, worse if recumbent

Rabies

• Et: zoonotic, raccoon, skunk, fox, bat

  • bite causes virus ascends nerves, long incubation

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

• Dt: DFA on brain postmortem

  • no antemortem test

• Tx: Euthanasia, core vax

Equine Protozoal Myeloencephalitis

• Et: Sarcocystis neurona, opossum

  • sporocysts in contaminated feed

  • focal/multifocal gray + white lesions

• Cs: asymmetrical ataxia, muscle atrophy, facial paralysis, dysphagia, LMN signs

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

• Tx: ponazuril, diclazuril, sulfadiazine/pyrimethamine

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

Verminous Encephalomyelitis

• Et: Aberrant larval migration

  • Parelaphostrongylus, Helicocephalobus, Strongylus

• Cs: asymmetrical signs

• Dt: difficult, rule-outs, suppurative CSF

• Tx: anthelmintics + supportive care

• Px: poor

Spinal Cord Trauma

• Et: edema, vertebral fracture, cord impingement

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

• Cs: Crepitus, ataxia

  • Stable = standing Unstable= down 

• Tx: DMSO, corticosteroids, NSAIDs, stall rest, Sx

Cervical Stenotic Myelopathy (Wobbler Syndrome)

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

  • Most common non-infectious neuro dz of horses

• Types:

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

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

• Cs: Clumsy, stumbling, falling, poor performance, UMN + spastic tetraparesis, hindlib ataxia

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

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

Occipito-Atlanto-Axial Malformations

• Et: Congenital defect 

  • Cord compression at birth

• Sig: Arabians, QH, Drafts

• Cs: spastic tetraparesis, ataxia, limited cervical ROM (cannot extend neck)

• Dt: imaging

• Tx: euth

Equine Neuroaxonal Dystrophy and Equine Degenerative Myelopathy

• Et: Dev degenerative dz of spinal proprioceptive tracts

  • Vit E deficiency (mare or foal)

• Sig: 6-24m, QH

• Cs: Symmetric ataxia

• Dt: histopath postmortem

  • Normal vitals, labs, CSF, cervical imaging

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

Equine Herpesvirus-1 Myeloencephalopathy

• Et: Neurotropic EHV-1 strains

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

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

• Sig: Adults >3y, event outbreaks

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

• Dx: ↑ protein, pleocytosis, xanthochromia (CSF tap); PCR/VI, paired sera (4x titer rise), IHC

• Tx: NSAIDs, steroids, DMSO, antivirals (valacyclovir), 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

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

  • Central: medulla, pons, cerebellum

  • Peripheral: CN VIII; common in horses

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

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

  • Signs ipsilateral 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

  • Pathologic fracture: acute vestibular signs + facial paralysis

• Dt: endoscopy, radios, CT

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

Otitis Media–Interna

• Cs: vestibular dz, facial paralysis, osteomyelitis, subdural abscess, meningitis

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

• Tx: aggressive antibiotics, anti-inflam

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), 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

  • 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

• Cs: head shaking, sneezing, rubbing, snorting

  • progressive

• Tx: Nose nets, UV masks, cyproheptadine, carbamazepine, euthanasia

Polyneuritis Equi (Cauda Equina Neuritis)

• Et: IM

  • 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, catheterization, manual rectal emptying, nursing care, euthanasia

Stringhalt

• Et: peripheral axonal degeneration of peroneal nerve

  • Sporadic: usually unilateral, often after hock injury

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

• Cs: spasmodic hyperflexion of hindlimbs

• Tx: tenectomy of lateral digital extensor, remove from pasture

Dysautonomia (Equine Grass Sickness)

• Et: enteric nervous system, ANS ganglia degen

  • 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: halter injury, anesthesia compression

  • 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: 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

  • degen 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: contaminated feed, silage, carcasses

  • Wound: rare

  • Toxoinfectious: foals ingest spores and toxin produced in gut

    • Shaker foal

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

• Dt: toxin ID (mouse bioassay)

• Tx: Antitoxin, toxoid vax

Tetanus

• 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: 1025–1060

  • Isosthenuria = 1008–1017

• pH: alkaline 

  • 75–9

• Absent: glucose, protein, bacteria, casts

Acute Renal Failure

• Et: >70–80% nephron loss 

  • Pre-renal: ↓ renal perfusion from hypovolemia, 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

• Cs: Depression, edema, encephalopathy

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

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

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

  • Goal: convert oliguria → polyuria

Chronic Kidney Disease

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

  • Congenital: agenesis, dysplasia, polycystic kidney

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

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

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

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

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

• 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 

  • R equi, strangles, lepto

  • Uncommon

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

• Dt: leukocytosis, ↑ fibrinogen, UA, culture, US, endoscopy, lepto PCR

• Tx: antibiotics

Cystitis (Lower UTI)

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

• Cs: stranguria, pollakiuria, incontinence, hematuria

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

• Tx: TMS, ampicillin, ceftiofur, penicillin

Urolithiasis

• Types:

  • Ca carbonate: #1, yellow spiculated

  • Ca phosphate: Grey-white, smooth

• Sites: kidney, ureter, bladder, urethra

• Sig: males

• Cs: pain, hematuria, obstruction, CKD

• Dt: US, rectal, endoscopy

• Tx: lithotripsy, cystotomy, nephrectomy if unilateral, ↑ water, add salt, avoid alfalfa

Control of Bladder Micturition

• Pontine micturition center controls:

  • Filling: inhibits detrusor, closes sphincters

  • Voiding: contracts detrusor, relaxes sphincters

Neurogenic Bladder

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

  • UMN bladder: lesion above sacral segments 

    • Cs: spastic bladder, dysynergia

  • LMN bladder: lesion in sacral cord/nerves 

    • Cs: flaccid, distended bladder, overflow incontinence

• 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

Detrusor Atony & Idiopathic Sabulous Cystitis

• Et: neuro dysfunction, pain, idiopathic in geldings

• Cs: Flaccid bladder

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

• Px: fair, chronic

Uroperitoneum

• Et: 

  • Foals: Ruptured bladder, urachal tear, ureter

  • Adults: trauma, dystocia, obx

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

• Tx: 09% NaCl + dextrose/bicarb, Sx

  • avoid K fluids

Omphalitis

• Et: FPT, ascending infection through urachus, arteries, vein

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

• Dt: palpation + US

• Tx: antibiotics, Sx removal of infected remnants

Parturient & Urethral Injuries

• Et: bladder rupture, urethral incompetence/laceration, detrusor injury, bladder prolapse

• Sig: Mares

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

Male Dorsal Urethral Hemorrhage

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

• Cs: hemospermia, post-urination bleeding

• Tx: perineal urethrotomy

  • heals by 2° intention

Polyuria & Polydipsia

• Et: renal failure, PPID, psychogenic, corticosteroids, α2 agonists, diuretics

• Cs: 

  • PU: >25 L/day urine

  • PD: >50 L/day water

• Dt: water deprivation test (psychogenic)

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

Ectopic Ureter

• Et: Congenital, ureter opens into vagina/vestibule 

• Cs: incontinence from birth

• Dt: endoscopy, contrast imaging, US

• Tx: unilateral nephrectomy, Sx

Castration Surgical Planning Considerations

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

• When: 1–2 years

  • Sx at 15–2 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: 

  • Tetanus Vax: Must be current 

    • Give tetanus toxoid if uncertain

  • Confirm two testes in scrotum; no inguinal hernia

  • Rx: ± Penicillin, flunixin

• Op: 

  • Closed: Young with small cords

  • Open: Most common

  • Recombinant: 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: 

  • 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

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

  • Prolonged = dystocia and birth asphyxia risk

• Stage 3: <3 hrs

  • Expulsion of fetal membranes

Neonatal Behavior and Vitals

• Behavior: precocious

  • 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

• 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

  • 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 

  • Prenatal: placental insufficiency

  • Parturient: birth asphyxia 

  • Postnatal: immature lungs, aspiration, rib fractures

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

  • dummy foals

• 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

  • 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

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

• 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