approach to eq neuro

History

·    How long been going on?

·    What neurological signs have they seen?

o  Seizures?

o  Compressive walking, ataxia, head pressing – hepatic encephalopathy

o  muscle

·    Are they up to date with worming/vaccinations? Up to date with tetanus?

·    Any gait abnormalities noticed? – when walking backwards = shivers, exaggerated flexion of HLs = string halt, FL muscle tremors = rye grass staggers

·    Any other clinical signs seen?

o  Respiratory signs – herpes

o  Repro signs – abortion/sick foals = herpes

·    Any recent diet/management changes?

·    Possible access to toxins? Ragwort on pasture?

·    Do they seem otherwise well in themselves? – obtunded, depressed = hepatic encephalopathy, reduced mentation = viral encephalomyelitis (APHA)

·    If seizuring: how long? How often? Any progression?

·    History of trauma?

Investigation

·    Full clinical exam

o  TPR – pyrexic = herpes

o  Examine eyes – mydriasis, slow PLR = botulism, prolapsing nictitans membrane = tetanus

o  Look at head – fixed extended neck = tetanus

o  Look at back end – elevated tail head = tetanus

·    Neurological exam

o  CN tests

o  Spinal reflexes – cutaneous trunchi twitch (in response to skin stimuli), a nal reflex, patella reflex, tail tone

o  Assess gait at a walk, circle, can blindfold, use different surfaces/obstacles

·    Haematology – identify infectious/inflammatory cause – incr. WBC, APP (SAA, fibrinogen) = abscess, viral/bacterial/protozoal cause, osteomyelitis

·    Biochemistry – look at ammonia levels – increased ammonia = hepatic encephalopathy

·    CSF analysis (normal = clear) – yellow = xanthochromia (RBC destruction – due to trauma or infection)

o  Is neutrophilia present? Protein level?

·    Radiography

o  Head/skull – assess sinuses, gas within cranium, look at skull structure

o  Cervical region – vertebral body abnormalities, spinal cord compression

·    CT/MRI of head/neck – useful in seizure cases

·    GP endoscopy if CN deficits – CN 9, 10, 11, 12 pass through GP

·    Suspect botulism – feed challenge test – eats slowly = botulism

Neurological signs + gait abnormalities

·    Shivers

o  See gait abnormalities when walking backwards, abnormalities when lifting HLs, tail tremors

o  No treatment

·    String halt

o  See exaggerated flexion of HLs during swing phase, unilateral (due to toxin, trauma), bilateral (pasture associate)

o  Treatment depends on cause: remove from pasture, treat OA, splints, etc.

·    Rye grass staggers (fungi)

o  See muscle tremors on FL, wide based stance, truncal sway, jerky HL movement

o  Treatment: remove from pasture (signs should resolve), quiet environment, support feed and hydration, burn pasture

Clostridial causes

·    Botulism – nutritional support, clean wound, abx if infected (not penicillin or metronidazole)

·    Tetanus – tetanus antitoxin (+ vaccine), ACP (muscle relaxant), clean wound, systemic metronidazole, keep in low light with ear buds

Hepatic encephalopathy

·    Support liver and neurone function

o  IVFT + dextrose

o  Oral lactulose – prevent further ammonia uptake in GIT

o  Plasma transfusion if prolonged clotting time

·    Treat clinical signs

o  Xylazine – stop compulsive walking

o  Phenobarbital – seizure treatment

Seizures

·    Initial treatment: phenobarbital, diazepam, midazolam

·    Maintenance: phenobarbital, levetiracetam

·    Length: foals treat for 3m then taper for 2m, adults treat until 6m seizure free then taper for 4w

Viral encephalomyelitis

·    West Nile virus – NOTIFIABLE

o  See reduced mentation, shifting lameness, ataxia

o  Vaccine to prevent

·    Eastern/western equine encephalitis virus – NOTIFIABLE

o  See fever, reduced mentation, ataxia, CN deficits

o  Vaccine to prevent

·    Borna virus

o  See reduced mentation, central blindness

·    Rabies – NOTIFIABLE

o  See reduced mentation, seizures, recumbency

o  Vaccine to prevent

Ataxia

Spinal ataxia:

·    See crossing, abduction, knuckling (ascending pathways) and foot dragging, stumbling (descending pathways) – see proprioceptive deficits

·    Causes:

o  Cervical vertebral compressive myelopathy

§ Treatment: NSAIDs +/- steroids, intra-articular joint injections, or surgery

o  Equine herpes virus-1

§ See respiratory signs (cough, nasal discharge), repro signs (abortion, sick foals), neuro signs (ataxia, dog sitting, urinary incontinence) and pyrexia

§ Treatment: quarantine and isolate, valacyclovir, NSAIDs/steroids to tx resp. dz

o  Vit E related – equine degenerative myeloencephalopathy, equine motoneuron disease

§ Risk factors: excess Cu in diet, no access to green forage

§ Diagnosis: low vit E in serum

§ Treatment: vit E supplementation

o  Equine protozoal myeloencephalopathy (sarcocystis, Neospora)

§ Treatment: pyrimethamine and sulphadiazine

o  Cervical trauma, e.g. kicks, falls

Vestibular ataxia:

·    See head tilt, wide based stance, leaning/falling to one side

Cerebellar ataxia:

·    Wide based stance, dysmetria (loss of coordination) but NO proprioceptive deficits