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What is epilepsy? 

What is 1o/idiopathic epilepsy?

What is 2o/symptomatic epilepsy?

  • Epilepsy = condition with recurrent partial or generalized seizures (vs. provoked seizures)
    • Not a diagnosis; a condition (like anemia)
  • Primary = unknown cause, no treatment
    • Can only give anti-seizure drugs
  • Secondary = intra/extracranial disease
    • Some kind of pathology in the brain that is causing symptomatic epilepsy (tumor, parasites, etc.)
    • Can get rid of underlying cause-->treat the seizures


What are the 2 categories of seizures?

  • Partial--disrupts function in area of cerebrum where they occur
    • Often indicate symptomatic epilepsy
    • Signs depend on area
  • Partial motor seizures--episodes of abnormal movement
    • Contralateral limb jerking, chewing gum fits, flexing, head turning


Head bobbing

  • Boxers, bulldogs, labs, etc.
    • Boxers/bulldogs side to side
    • Dobermans up and down
  • Intermittent--starts/stops spontaneously or if distracted
  • Cause?
    • Focal seizure
    • Basal nucleus discharge--dyskinesia
    • Proprioception abnormality
  • Diagnosis--clinical--N lab, MRI, CSF
  • No treatment


Partial seizures causing abnormal behavior--dogs

Aggressive, salivation, licking/chewing, sudden ingestion, run/vocal/trembling


Partial sensory seizures

Sensory cortex

Dogs--'fly biting,' 'tail chasing'

Put on phenobarb and will cease


Generalized seizures

  • Widespread disorder--not one area
    • Animal can't be conscious
  • EEG--abnormal activity over entire cortex
  • Generalied tonic-clonic "Grand mal"
    • Most seizures in dogs
    • Tonic seizures--tetanus; stiff
    • Clonic seizures--muscles contract-->relax over and over
    • Atonic seizures--loss of muscle tone but conscious
    • Absence seizures--loss of consciousness but no tonic-clonic
    • Incomplete--e.g. aura only


What are the 3 phases of a typical generalized tonic seizure?

  1. Preictal phase
  2. Ictal phase (ictus)
  3. Postictal period


What occurs during the preictal phase of generalized tonic seizures?

  • Aura/prodromal phase
  • Subtle behavior changes--clingy, anxious
  • Few minutes - hour = aura
  • Days = prodromal


What occurs during the ictal phase of generalized tonic seizures?

  • Unconsciousness (all neurons firing)--animal falls into natural recumbency
  • Tonic phase
    • 10-30s sustained muscle contraction--limbs rigid/extended, opisthotonos, apnea
    • Looks like dog has tetanuus
  • Clonic phase
    • Running/paddling/chewing
    • Autonomic--pupils dilate, salivation, defecation, urination
  • Maybe further tonic contract--lasts 1-2 min


What does the postictal phase of generalized tonic seizures consist of?

  • Increased conscious, depression, fatigue, fright, pacing, thirst, hunger, neuro deficits
    • Usually fairly rapid 
    • Animal behaves abnormally for awhile
  • Lasts ~5 hours (not dependent on severity/duration)


Clusters of seizures vs. status epilepticus

  • Clusters = animal regains consciousness between seizures
    • Can be bad; treat immediately
  • Status epilepticus = animal doesn't regain consciousness
    • Finishes tonic/clonic phase, then another seizure immediately occurs
    • Emergency


How do you differentiate between sleep seizures and REM behavior disorder?

  • Normally brain shuts off motor system during sleep--become paralyzed
  • REM disorder = brain doesn't suppress motor system during sleep
    • Extensive motor activity during sleep
    • Completely normal upon waking up
  • Sleep seizure--animal won't be normal when woken up


What is the diagnostic approach for determining seizure type?

  • Differentiate primary/secondary--treatment
  • Signalment
    • Idiopathic: 1-5 yrs
      • Genetic basis in goldens, labs, poodles, border collie, GSD vs dobes, sight hounds
      • < 1yr =  toxic, congenital, infectious
      • > 5yr = 35% idio, neoplasia, metabolic disease
      • Idiopathic not too common in dobes
  • History
    • Seizures? Signs?
      • Episodic weakness? Syncopy, narcolepsy, etc.


History of neurological abnormalities indicates what?

What are the precipitating factors?


  • Intracranial disease
  • Precipitating factors
    • Hypoglycemia
    • High protein meals
    • Head trauma
    • Estrus, vets, lawn, ace (no known factors)
  • Treatment
    • Need seizure diary
    • Phenobarb doesn't cure seizures--works in ~90% of dogs but only eliminates 50% (other 50% just decrease in frequency)


When evaluating a patient for seizures, what is checked on the physical exam? Neuro exam? Specialty exams?

  • PE
    • Heart, neoplasms, systemic infection--retina, skull (trauma, hydrocephalus)
    • Heart beats very fast--> doesn't have time to fill --> CO decreases --> not enough blood to brain --> syncope
  • Neuro exam--essential
    • Abnormal findings--secondary
    • Interpretation in post-ictal period?
    • 45% with normal neuro (>5 yr) had abnormal CSF or MRI
    • PPV = 80%
    • NPV = 55%
  • Special exam
    • FBC, biochem, UA--normal with primary
    • CT/MRI-scanning (esp. if suspect intracranial lesion
      • Ex: 2yr doberman who presents for seizures


What are CSF findings in dogs w/ seizures? EEG findings?

  • CSF
    • In all cases of 1o CSF is normal
    • Increased protein + white cells = inflammation
    • Increased protein = neoplasia
    • Blood/xanthochromia
    • Neoplastic cells
  • EEG (electroencephalography)
    • Confirm epilepsy--dd partial/generalized
    • Find the focus


What therapy is recommended for seizure patients?

  • Old = delay--mirror foci/kindling
    • Just because neurons on one side get excited/stimulated doesn't mean the neurons on the other side will as well
  • Balance toxic and side effects
    • Ex: if animal only has 1 seizure per year it shouldn't be put on daily phenobarb
  • Frequency/pattern--assess pre-treatment
    • 40% completely controlled
    • 50% reduction in seizures
    • Need seizure diary
    • Worry abt animals w/ long-lasting seizures


When do you treat an animal presenting for seizures?

  • < 6-8 wks
  • Clusters/prolonged/status epilepticus
  • Untreatable CNS disease
  • Owner insists


Treatment of seizures--drug therapy

  • Start with monotherapy, then polytherapy
    • 1 drug--phenobarb
    • If phenobarb alone doesn't work add KBr (longer-lasting)
  • 5.5 half-lives; loading doses--sedation
    • Takes couple of weeks to become effective--give loading dose so the blood level for therapeutic effects is reached
  • Blood levels needed when:
    • Steady state, then q 6-12 mo
    • Autoinduction
    • Uncontrolled seizures
    • Toxicity
  • Slow withdrawal--never suddenly stop (will get very severe seizures)


Phenobarbital and seizures

  • Drug of choice
  • Enhances GABA; increases seizure threshold
    • Makes it harder for impulses to occur in the brain
  • Don't use with liver disease
  • PU/PD/PP, sedation, hyperactive, hepatopathy (destroys liver w/ high dose for long time)
  • Lipemia, ALP, ALT, T4--not bile acids, bili, US
    • ALP/ALT useless when detecting hepatopathy--use bile acids (will be normal until hepatopathy)
    • Competes w/ albumin--binds it and knocks down level of bound T4-->will look like dog has hypothyroidism
  • Maintenance or loading dose IV
  • Follow up


Potassium bromide (KBr/NaBr)--seizure therapy

  • Cl channels--dietary salt
  • Add-on drug (70% respond; 20% off pheno)
  • Adverse effects
    • PP (25%), PU/PD, personaliy, GI upset, sedation
    • Bromism--ataxia, paresis, hyporeflexia, tremors
    • Pancreatitis (?)/megaesophagus (?)
      • No liver/thyroid changes
    • Too much bromide in system--> can increase salt in diet to compete w/ bromine and decrease blood levels
      • Will show up as hyperchloric on clin path panels 


What are the contra-indications with using KBr?

  • Renal insufficiency--check BUN, Cr, UA
    • Cl will rise
    • Excreted in kidney--don't use if dog has kidney problems
  • Maintenance-- t1/2 3-6 wks
  • Loading doses--vomiting and GI upset
    • Have to give over days
  • Follow ups
    • 3 wks (50% therapeutic)
    • 3 mo (renal)
    • q 6-12 mo



low-affinity partial benzodiazepine agonist of the GABAA-receptor

Will most likely be used more frequently in the future


What are the common anti-seizure drugs and which is preferred?


What are possible causes of therapeutic failures when treating seizures? Can anti-seizure drugs be withdrawn?

  • Failures
    • Owner compliance
    • Weight
    • Hepatic induction
      • Phenobarb dose will need to be inc.
    • Genes, wrong diagnosis--new diseases, etc.
  • Drugs can be withdrawn
    • Seizure-free for a year


What are some alternative therapies for seizure treatments?

  • Surgery--focus
    • Corpus callosum
      • Joins hemispheres together--if severed, seizure can be localized to left side only--> won't fall unconscious, etc.
  • Vagal nerve stimulation
    • Pressure on vagal nerve--> seizure aborted
  • Acupuncture
  • Ketogenic diets
  • Hypoallergenic diets


Juvenile epilepsy

  • Generalized tonic-clonic seizures in clinically normal puppies up to 4 months of age
  • Lab results are normal
  • Good response to phenobarb
    • 5 mg/kg q 12hrs--100-200µmol/L
  • Wean if seizure-free after 6 mo
  • Etiology? Prob. multifactorial
  • Prognosis good once seizures are controlled


What breed is highly associated with juvenile epilepsy?

Lagotto Romagnolo

Very high rate of juvenile epilepsy--> new gene assoc. w/ epilepsy


Seizures in cats (signs, most common type)

  • Signs more variable--hyperesthesia/violent
    • 50% have non-convulsive seizures (mild generalized or partial seizures, complex focal seizures)
  • Idiopathic epilepsy
    • Cats 1-5 yrs 50% vs 80% are primary/idiopathic
    • Extensive work-up needed
      • FIP, cryptococcus, thyroid, shunts, lymphosarcoma, FIV, FeLV, HCM, etc.


Which idiopathic epilepsy is most commonly seen? What seizures are more common in general practice?

  • Intracranial pathology most common (dogs and cats)
  • Reaction seizures are more common in general practice