Diseases of the Nervous System

1. Diseases of the Nervous System Casey Conway & Jeannie Stall, R.V.T. Credits: Clip Art graphics Alleice Summers-Common Dz’s of Companion Animals

2. Nervous System CNS: brain and spinal cord PNS: cranial nerves and peripheral nerves that connect outside world to the brain Neuron: transmit electrical impulses to/from the brain Pathology anywhere within transmission system results in interruption of messages Clinical neurologic symptoms

3. Brain Trauma Primary event: direct injury to the nervous system Secondary event: ICP, edema, hypoxia, seizures Clinical signs: Hx trauma; seizures, blood in ears, nose, mouth, ocular hemorrhage, loss of cons, shock Dx: Hx, PE, labs, rating scale using motor activity, brainstem reflexes & loss of consciousness Tx: Correct metabolic abnormalities, O2, elevate head, mannitol, diuretics, anti-seizure, corticosteroids Some brain damage is irreversible Coma > 48 hrs – generally don’t survive

4. Idiopathic Vestibular Disease Acute disorder in dogs & cats Clin.signs: Incapacitating loss of balance, nystagmus, disorientation, ataxia, vomiting, anorexia Dx: clinical signs, labs, otic exam to rule out Tx: not recommended( but can Rx Antibiotics & steroids), supportive therapy, force feed Usually resolves in 3-6 weeks Owners should be careful with pets to avoid injury while clinical

5. Neoplasia • Usually progressive clinical signs, metastatic, older animals • Clin. signs: signs reflect tumor location, seizure, endocrine abnormality, +/- vestibular signs, tremors, ataxia • Dx: screen for other tumors, labs, x-rays, CSF tap, eye exam, CT, MRI • Tx: Sx. removal of tumor (superficial singular lesions) Radiation or chemotherapy If showing clin. signs: Rx anti-seizure meds, corticosteroids

6. Idiopathic Epilepsy Repeated seizures, no cure Clin.signs: seizures, often occur @ regular intervals, young animal, “normal” b/t seizures Dx: Exclusion-rule out other possibilities via lab tests, x-rays, CT, MRI…. Tx: Primary dz, if found, Tx if sz > 1/mo Rx Phenobarbital (7-10 days to reach concentration) +/- Rx K Br (Potassium Bromide)

7. Status Epilepticus MEDICAL EMERGENCY!!! Prolonged, continual seizure (>5-10 min.) Irreversible coma, death Rx Diazepam IV, Pentobarbital IV, O2, IV cath, labs, temp If Cerebral edema: Rx Mannitol, Pred Maintenance: Rx Phenobarb Epilepsy: incurable, manageable Low threshold seizure patients- No KETAMINE

8. Intervertebral Disk Disease Herniation Type 1: (younger) acute rupture of annulu fibrosus & extrusion of the nucleus pulposus into the spinal canal Herniation Type 2: (older >5yr) lg-breed, the extrusion occurs over longer period, less acute, less severe C/S Severity of spinal cord injury depends on: Speed that disk material is deposited into spinal canal Degree of spinal compression Duration of compression Clin.signs: pain, acute onset, paralysis, decreased reflexes, altered deep pain response

9. IVD Dz Cont’d……. Dx: age, breed, clin. signs, hx, neuro exam, x-rays, myelogram Tx : Type 1: medical tx, strict confinement, corticost., intensive nursing care, surgical tx. Type 2: may improve initially w/ cortisone, sx may fail to improve spinal function Severe spinal cord damage isn’t currently repairable

10. Spinal Cord Trauma Acute injury, HBC, gunshot wounds, fights Clin.signs: Trauma,Schiff-Sherrington signs, lack of panniculus reflex (pin prick) caudal to lesion, paralysis Dx: neuro exam, x-rays (careful), myelogram Tx: corticost., Mannitol, DMSO, surgery?, supportive therapy, strict confinement, extensive post-op/nursing care Questionable prognosis

11. Cervical SpondylomyelopathyWobbler Syndrome Compression as a result of caudal (C5-C7) vertebral malformation In Danes <1yr & Dobes >2yr.(likely hereditary defect) Clin.signs: Hx of progressive pelvic limb ataxia, abnormality, dorsal surface wear of rear paws/nails, swinging, wobbly gait in rear limbs, worse on rising, +/- atrophy of scapular muscles, rigid flexion of neck w/o neck pain Dx: labs, x-rays, myelogram, CT, MRI Tx: cortisone, neck brace, cage confinement. Without tx, prognosis is poor Sx – high potential for complications, morbidity, $$

12. Degenerative Myelopathy G. Shep, mix, Collies, Huskies, Labs, Kerry Blues Cause unknown – suggested autoimmune response to antigen in nervous system Clin. signs: Older animals, progressive ataxia- (5-6mo), paresis in rear limbs, muscle atrophy, “fall down” when attempt BM Dx: Neuro exam, x-rays, CSF – inc. protein Tx: None exists(corticoster. may help symptoms) Not hip dysplasia, consider euthanasia when unable to support weight

13. Discospondylitis (Vertebral Osteomyelitis) Bact. or fungi implanted in bones of vert. column of cat and dog. Large and giant breeds more common Hematogenous routes, wounds, abscess or infx, sx, migrating grass awn Clinical signs: (nonspecific) wt. loss, fever, depression, spinal pain, +/- neuro Dx: x-rays, labs, CSF, myelogram, blood cultures, biopsy (culture everything) Tx: long-term abx based on cultures – 6wks Brucella – neuter/spay, tetracycline or streptomycin ******** ZOONOTIC !!!! ******** Animals are painful! Prognosis usually guarded.

14. Deafness Central origin: damage to CNS & auditory pathways Peripheral origin: cochlear abnormalities Conductive deafness: chronic otitis, rupture of tympanic membrane, damage to middle ear Neural deafness: A normal aging change, drug related, Hereditary or congenital: Bull terr., Dobe, Rott, Pointers, White Blue-eye cats, Dalm, Aust. Heel., Eng. Sett, Catahoula, Aussie Clin.signs: No auditory stimuli response, excessive sleeping, breed Dx: Evaluation difficult, so refer to a specialist Tx: None in most cases (permanent issue), Special training/hearing aids available(most don’t tolerate it)

15. Metabolic Neuropathy Diabetes Mellitus (dogs, cats), hypoadrenocorticism (dogs), hypothyroidism (dogs) Clin. signs: Progressive weakness, muscle atrophy, paresis, paralysis, varied….. Hypothyroid dogs: head tilt, facial paralysis, strabismus(squinting), nystagmus, circling Dx: Determine underlying dz. & r/o other causes Tx: Underlying dz. symptoms, control & prevent neurologic damage

16. Laryngeal Paralysis Hereditary: Bouvier des Flandres, young S. Huskies Acquired: lead poisoning, Rabies, trauma, inflammatory infiltrates of the vagus nerve Idiopathic: middle-age & older , lg.-breed & giant dogs Castrated male dogs & cats more affected Clin.signs: hereditary 4-6 mo, resp. distress, voice change, cyanosis, complete resp. collapse Dx: laryngoscopy will show laryngeal abductor dysfunction, surgical tx Do not breed hereditary animals

17. Megaesophagus Lack of effective peristalsis, dilation of esophagus, regurgitation of undigested food Congenital: G. Danes, G. Shep, I. Sett, Nfndland, SharPei, Greyh – Seen @ weaning age Inherited form: Wire-hair fox terrier, Min Schn – any age Clin.signs: Regurgitation, resp.signs, poor growth, wt. loss Dx: X-rays w/barium meal (Caution: aspiration pneumonia), lab tests to r/o other causes Tx: No cure but can elevate food bowls, liquid diets, feed several small meals w/objective to prevent aspiration pneumonia

18. Tick Paralysis Common dog tick (Dermacentorvariabilis) Rocky Mt. wood tick (Dermacentorandersoni) Clin. signs: Flaccid, afebrile, ascending motor paralysis Cats appear to be resistant Tick’s salivary neurotoxin interferes w/ acetylcholine @ neuro-muscular junction Within 24-72 hrs.– No reflexes, recumbent Sensation remains Death d/t resp. paralysis Recovery @ 1-3 days after all ticks removed Ventilate resp. distressed animals until signs subside

19. Facial Nerve Paralysis Adult dogs & cats >5yr, cause unknown Cockers, Pem.W.Corgi, Boxer, Eng.Setter, DLH Clin.signs: ear droop, lip paralysis, nasal deviation, collection of food in lips, absence of menace Dx: electrodiagnostic test of facial nerves, clin. signs w/o trauma Tx: corticost, art. tears, keep oral cav. clear Usually no recovery, lifelong maintenance

20. Rabies (Horse) ZOONOTIC! Public health issue (Lyssavirus) State laws vary – Should vaccinate annually Animal showing neuro signs (esp w/bite wounds) should be considered a rabies suspect Lyssavirus passes in saliva, migrates & localizes in CNS, may affect cerebrum, brain stem or spinal cord Brain : Extreme behav. change – aggression Brain stem : Subdued, quiet change Spinal cord : Ataxia, paralysis Signs progress rapidly w/ death 5-10 days post-signs Dx: Examine brain tissue Tx: Should euth. exposed animals showing clin. signs

21. Wobbler’s Syndrome Spinal cord is compressed by a narrowing of the vert. canal Young, fast-growing horses Congenital or result of rapid growth & mineral imbalance Clin.signs: ataxia, weakness, stumbling, toe dragging, hind limbs more affected Dx: Clin. signs, Hx, x-ray Tx: Drug therapy, dietary mgmt, sx, euth.

22. EPMEquine Protozoal Myeloencephalitis 1-5 yr, dead-end host, stressful event, ponies appear resistant Sarcocystis neurona – protozoal parasite Ingests food/water contam. w/opossum feces, organisms divide in nervous tissue Clin.signs: ataxia, gait abn, muscular atrophy, head tilt, signs progress – inability to rise Dx: Analyze CSF for parasite Tx: Naviator, Marquis, Daraprim, >1mo Prevent w/mgmt of feed & water Vx. avail. but unsure of effectiveness

23. Tetanus Horses most susceptible, sheep/goats/humans Clostridium tetani releases toxin that prevents the release of GABA GABA inhibits nerve impulse propagation – if no inhibition, then nerves are always firing – constant muscle contraction Clin.signs: muscle stiffness & spasms, sens. to touch, progresses to rigid paralysis & death by asphyxiation (10 days) Dx: Wound hx & clin. signs Tx: Supp. care, *Easier to prevent than to treat Yearly vx. w/ tetanus toxoid, booster if wound is found & horse is current on vaccine

24. Sleeping Sickness Eastern, Western, Venezuelan equine encephalomyelitis Venezuelan: rare Western: least fatal – hot, humid areas Eastern: most deadly Togavirus family – Each has own vaccine Via wild birds & mosquitoes – horses are dead-end host. Clinical signs: weakness, ataxia, can’t rise Dx: Hx, clinical signs, antibody titers, virus isolation from brain tissue and CSF No tx exists – Good supp. care – fatal in most cases Prevent with regular vaccination – biannual vx. recommended in southern states Zoonotic: passes to human via mosquito NOT horse

25. West Nile Encephalitis Similar to sleeping sickness – birds and mosquitoes Mortality rate – 30-40% No specific treatment – Vaccinate!! Clinical signs: ataxia ,depression or apprehension, weakness, partial paralysis, muscle twitching, death Incubation 3-15 days IgM-capture ELISA test currently most reliable 1999 1st discovered in US 1960’s origin- Egypt,France,Uganda- horses & people

26. Hyperkalemic Periodic Paralysis Genetic dz found only in “Impressive” sired Quarter horses Inherited condition that causes abnormality of sodium channels, results in constant muscle cell depolarization Clin. signs: muscle tremors, sweating, rapid breathing, weakness during an episode often brought on by stress, animals remain conscious Dx: clinical signs, labs – hyperkalemia, DNA testing Tx: hand walking, iv fluids (avoid K), dec. K in diet All Impressive horses should be DNA tested, + animals should not be bred – Regulations are changing

27. Scrapie – Sheep and Goats Reportable disease in US: Transmissible Spongiform Encephalopathy Progressive degenerative CNS disorder, Mainly in (Suffolk) sheep & occas. goats Exact cause & transmission is unknown Clin.signs: mild apprehension, fixed gaze, aggression, exercise intolerance, ataxia, intense pruritis, recumbancy, blindness, seizures, death Dx: Difficult antemortem as no specific lesions or lab test results are specific to dz. No effective treatment exists

28. Listeriosis Bacterium: Listeria monocytogenes – sheds in body fluids of sick & unaffected animals Long lived in environment, assoc. w/feeding of silage & grazing wet, boggy pastures Clin. signs: loss of ability to eat, vestibular dz.signs, depression, dysphagia, recumbancy Dx: no specific test for antemortem cases – R/o other dz. via thorough neuro exam Tx: intensive abx therapy min. of 14 days, Nsaids Zoonotic !!

29. Meningeal Worm White-tailed deer parasite - can affect sheep & goats. Oocysts in deer feces, ingested by snails & slugs, grazing ruminants eat Larvae migrate via peripheral nerves to spinal canal, cause inflammation & destruction, neuro deficits Clin.signs: Acute onset of signs Bright & alert w/ progressive hind-limb ataxia Eventual inability to rise Dx: Clin. signs & hx Tx: Ivermectin (high dose) x 5 days & Banamine Routine deworming program in known areas

30. Polioencephalomalacia Lack of thiamine (rumen microbes normally produce enough to meet animal’s needs) Sudden diet change, prolonged anorexia, ingestion of bracken fern Necessary co-factor for glucose metabolism: leads to lack of glucose which is needed for energy & allows brain to maintain proper osmotic gradient (cellular swelling) Clin.signs: central blindness, strabismus, depression, incoordination, head pressing, coma, death Dx: c/s, response to treatment Tx: Thiamine injections

31. Tetanus “Saw-Horse” Stance