Seizures (Holgar) Flashcards
Define seizures
- transient involuntary change in behaviour or neurological status d/t abnormal activity of populations of CNS neurons
- hypersynchronous firing of neurons
- d/t imbalance of excition and inhibition
- specific seizures are named after their lcinical signs
How are seziures classified? How should they not be classified in vet?
- classify by clinical sign
- NOT petit-mal grand-mal (petit mal = focal absent seizure in humans, grand-mal = generalised tonic clonic)
Are seizures in thems in themselve sharmful to the brain? 1* dmaage?
NO unless >30mins (then focal and general both harmful) 1* damage is very little 2* dmaage more important - hypoxia - hypercarbia - hyperthermia - others...
What types of MRI can be used for looking at the brain?
T1W fat is white
T2W fat and water is white
Flair flowing structures/liquid (not visable or white??!)
How can seizures be classified?
> focal
- simple focal (no loss of conciousness)
- complex focal (impaired conciousness)
- focal seizure with 2* generalisation
generalised seizures
- Convulsive
- Non-convulsive
status epilepticus
- prolonged seizuring
- >30 mins according to basic science -> damage
- clinical >5mins seizuring = unlikely to be self limiting
If limbic structures are involved in seizure activity is this easy or hard to tx? What else can affect ease of tx?
- hard
- length of seizure - longer they go on, more difficult they are to tx
Define epilepsy
> 2 seizures
>48hrs apart
What are the stages of tx classified as?
> prodrome
- behaviour changes that occour hours/days before the seizure
aura
- sensory/focal onset seizures may start with sensory experience eg. smell or feeling of deja vu.
- hard to prove in animals but behaviour change often seen minutes before ictus
ictus
- sezire
post-ictal
- neuro alterations hourse/days after ictus
- cf. vestibular/syncope (??) causes with no post-ictal phase
How else may seizures be classified?
> Self limiting
- focal (sensory/motor/automatisms most common orofacial “chewing gum fits”)
- generalised (tonic-clonic/clonic/myoclonic/atonic)
Clustered or continuous (status epilecpticus)
- focal (motor: epileptia partialis continua; sensory: auro continua (hard to dx animals)
- generalised
reflexive
- precipitating stimuli eg. loud bang
What things may be seen with seizures? (random notes!)
- Hypersalivation
- loss of proprioception -> rearing up backwars etc.
- vocalisation in cats
Are seizures conciously perceived?
Focal yes, generalised not concious no
When do seizures often occour?
- when asleep
Does a focal motor seizure involve the cortex? Eg. leg twitch
No
Ddx for seizures (what can mimic seizure like behaviour?)
> syncope
- partial/complete loss of consciousness
- lack of motor activity
- no post ictal signs
- shorter duration
narcolepsy
- v rare
- stimulated by excitement, food or pharmacologically
pain
vestibular syndrome
movement disorders
- scotty cramp (excercise in/dependent, no salivation, concious)
- CKS tetany, hypertonicity and deer-stalking
- norwich terriers
- Boxers paroxysmal dystonic choreoathetosis
- Bichon frise similar to boxers
How does position of disk extrusion in the spine alter clinical severity>
Cervical spine majority of disk can be extruded before myelopathy seen in neck
Typical history with seizures
- last ~1min
- several stages
- often at rest or asleep
- clonic movement (rhythmical muscle contraction) common in partial and generalised seizure
- MOST recurrent seizures respond at least partially to AEDs
- EEG?
Can anyone seziure?
Yes just different thresholds
How can seizures be classfiied by aetiology?
1. type of seizure > symptomatic/2* seizure - structural brain dz - assymmetric > reactive seizure - metabolic/ toxic cause - remove 1* cause and will stop > idiopathic/1* epilepsy - genetic cause - generlised seizures > possible symptomatic/cryptogenic seizure - R/o only via PME - PE abnormlaities but imaging normal 2. branching diagram > intra v extra cranial - Intra = functional (idiopathic) or structural (possible symptomatic epilepsy) - extra = intrinsic (metabolic reactive seizures) or extrinsic (toxic reactive seizures) + further subdivisions!!
What are the subdivisions of extracranial epilepsy Ddx?
> electrolyte imbalance - hypernatraemia - hyponatraemia - hypocalcaemia > energry deprivation - thiamine deficiency - hypoglycaemia > organ dysfunction - uraemic encephalopathy - hepatic encepalopathy
WHat are the subdivisions of intra-cranial epilepsy ddx?
> Cryptogenic (eg. head trauma years earlier, normal imaging)
Symptomatic
- Anomalous (hydrancephaly, lissencephaly, arachnoid cyst)
- Neoplastic (meningioma, astrocytoma, oligodendroglioma, ependymoma, choroid plexus tumour)
- Infectious (Viral, bacterial, parasitic, fungal, rickettsial, protozoal)
- Inflammatory (Granulomatous meningo-encephalomyelitis, eosinophilic meningoencephalitis, other meningoencephalitides eg. pug encephalitis)
- traumatic
- Vascular (ischaemia, haemorrage d/t coagulopthy or hypertension)
Idiopathic
- ion channel mutation
- other genetic mutations
Typical signs associated with idiopathic epilepsy
> dogs
- 6month - 6 years
- generalised seizures (beagles, GSD, lab/ret, gold ret, bermese mountain, belgain tervuerens, keeshonds, irish wolfhounds)
- some breeds mainly partial seizures +- 2* generalisation (vizlas, english springer spaniels, danish labradors, lagotta romagnolo, standard poodles, finnish spitz)
Any pdf in horses for epilepsy/seizures?
- congenital in arab foals (will grow out of it)
- perinatal asphyxia (neonatal maladjustment syndrome) foals
- adults often d/t structual or metabolic brain dz. eg. migrating parasites, previous trauma OR intra-carotid injection
How can signalment help refine ddx?
> 6 months - 6 yrs - idiopathic epilepsy - inflam/infectious - metabolic ~neoplasia, toxin, trauma > >6yrs - neoplasia - idiopathic late onset - inflam/infectious - ~metabolic (HE, hypoglycaemia 2* to insulinoma) ~ toxic/trauma
How can disease onset and progression help narrow down ddx?
- inflam/infectious/neoplasia and generative dz. worsens over time
- metabolic is fluctuating
- trauma and vascular improves over time
How can inter-ictal exam findings narrow down Ddx?
> Normal - idiopathic - metabolic - neoplasia in silent area of brain or early dz -toxic > abnormal symetircal - metabolic - toxic - hydrocephalus - degenerative dz - midline structural eg. pituitary neoplasia - ?!cave - post ictal?! no idea waht this means > abnormal ASYMMETRICAL [laterialising] = intracranial - neoplasia - inflam/infectious - anomalies
How can lateralising (asymetircal) v symmetrical seizures narrow Ddx?
> symetrical generalised onset - idiopathic - metabolic - toxic - degenerative - hydrocephalus - trauma - midline structural > asymetirical focal onset - inflam/infectious - neoplasia - anomalies - trauma -cryptogenic and idiopathic
Extra cranial further diagnostics
> minimum database - CBC and cytology - biochem -+ amonia - resting BA or dynamic BA in smallies - urinalysis (not common horses) - BP (esp cats - cardiac work up) > further diagnostics - depending on signament, hx and PE - infectious agents specific
Intracranial further diagnostics
> imaging
- MRI
- CT
clinical pathology
- CSF (WBC count, differential cell count, protein content)
- positive brain imaging/inflammatory CSF
- infectious agent testing
