Neurology Flashcards
how do seizures occur?
due to an altered balance between excitatory and inhibitory input
leading to hypersynchronisation of neurons
what is a seizure?
an abnormal, uncontrollable, hypersynchronous electrical activation of a large group of neurons
what are the types of seizure?
isolated seizure
cluster seizure
status epilepticus
what is an isolated seizure?
a seizure lasting less than 5 minutes
what is a cluster seizure?
2 or more seizures within a 24 hour period with complete recovery in-between
what is status epilepticus?
seizure lasting longer than 5 minutes
OR
2 seizures without complete recovery in-between
what type of seizure is an emergency?
status epilepticus
what are partial/focal seizures?
asymmetric - one part of the brain is affected
what are the signs of a partial/focal seizure?
facial twitching
hypersalivation
behavioural changes
consciousness maintained
what type of seizure produces no change in mentation?
simple
what type of seizure produces a change in mentation?
complex
what is a generalised (tonic/clonic) seizure?
a seizure with bilateral cerebral hemisphere involvement
what are the signs of a generalised (tonic/clonic) seizure?
autonomic signs (U/D)
loss of consciousness
identifiable pre-ictal, ictal and post-ictal phases
what is the pre-ictal phase? how can it be identified?
phase before seizure onset
may see behavioural changes, altered mentation, attention-seeking behaviour
what is the ictal phase? how can it be identified?
active seizure phase - loss of consciousness, muscle contraction, U/D, salivation
what is the post-ictal phase? how can it be identified?
minutes to days post-seizure - mainly see abnormal neurological signs and behavioural changes but will vary greatly between patients
what are the 2 main types of extracranial seizure triggers/causes?
toxins and metabolic factors
which toxins can lead to seizures?
methaldehyde (slug bait) ethylene glycol (antifreeze) permethrin in cats pesticides ivermectin (collie breeds) human drugs
what metabolic factors can lead to seizures?
portosystemic shunt (blood toxins)
hypoglycaemia
hypocalcaemia
what are the types of intracranial factors which can cause seizures?
structural - brain tumour, inflammation, hydrocephalus
functional - idiopathic epilepsy
what is the most common cause of seizures?
idiopathic epilepsy
what age dogs are more commonly diagnosed with idiopathic epilepsy?
6 months - 6 years
how is a diagnosis of idiopathic epilepsy concluded?
normal inter-ictal neurological exam
normal metabolic investigation
normal MRI scan of brain
normal CSF
what diagnostics should be performed if a patient is experiencing seizures?
thorough history
blood tests MRI scan (IV gadolinium contrast) CSF analysis videos monitoring and recording
retinal exam and blood pressure measurement
if possible
which blood tests are performed when investigating seizures?
haematology biochemistry fasted blood glucose pre- and post-prandial bile acids possibly ammonia
which other conditions/disorders can mimic seizures?
narcolepsy/cataplexy fly-catching movement disorder syncope 3rd degree AV block canine epileptoid cramping syndrome peripheral vestibular disease
what is narcolepsy/cataplexy? how does it present?
a sleep-wake disorder with flaccid collapses
loss of muscle tone but no autonomic signs
what is fly catching and how does it present?
unknown cause - dog appears to be chasing/trying to catch imaginary flies (mins-hours)
normal mentation, no autonomic signs
what is movement disorder? how does it present?
an episodic disorder - patient remains conscious and performs involuntary movements that are spontaneous and uncontrolled
neurologically normal between episodes
what is syncope? how does it present?
temporary loss of consciousness (‘fainting’) due to reduced oxygenation to the brain
what can cause syncope?
cardiac-related (most common)
neurological
hypoglycaemia
hypocalcaemia
how does 3rd degree AV block present?
prolonged hypoxic event with partial seizure-like episodes
what is canine epileptoid cramping syndrome? how does it present?
movement disorder affecting mostly border terriers
patient conscious and responsive with no autonomic signs and normal mentation
what is involved in emergency management of seizures?
oxygen therapy place IV catheter (if possible) administer diazepam assess circulation and temperature intubate if required active cooling if hyperthermic mannitol if seizure >15 mins or suspected cerebral oedema collect full bloods
how do you triage a seizuring patient (over the phone)?
stay calm and reassure owner
enquire into previous history, toxin exposure, head trauma
establish how long patient has been seizuring and how many times
ask if patient is conscious and responsive
any U/D
advise to travel when safe to do so
what kennel considerations should be made with seizure patients?
minimise noise and light in kennel
bottom kennel/easily accessible
seizure plan on kennel with doses calculated/medication drawn up
sign on door to limit staff numbers/traffic
what steps should you take if a patient seizures?
stay calm and note the time, call clinician in charge for help
remove any dangers
dim lights and reduce noise as much as possible
limit handling
monitor vital signs
follow seizure plan if one in place
do not put hands in/near patients mouth!!
what steps should you take when the patient comes into the practice after seizuring?
reassure the owner triage - ABC provide oxygen therapy obtain IV access ASAP administer anticonvulsants check temperature and actively cool if required consider mannitol consider intubation and CRI if frequent/extended seizures
what is the first line treatment for managing seizures?
Phenobarbital (epiphen) tablets
how does phenobarbital work?
acts on GABA receptors in the brain to increase frequency of synaptic inhibition and reduce neuronal excitability
what are the advantages of phenobarbital?
high efficacy and safety, low cost
what are the disadvantages of phenobarbital?
takes ~2 weeks for steady state plasma concentration to be reached
requires regular blood tests
many side effects
what are the side effects of phenobarbital?
hepatotoxicity in high doses sedation polyuria/polydipsia polyphagia ataxia
what else can be used in first line management of seizures?
potassium bromide (libromide) - can be used alone or in conjunction with another antiepileptic drug
what are the disadvantages of potassium bromide?
side effects
takes ~ 4 months to achieve steady state plasma concentration
renally excreted - not good for px with renal compromise
regular blood rests required
causes lung issues in cats
what are the side effects of potassium bromide?
gastric irritation nausea polydipsia/polyuria sedation pancreatitis (rare)
what is levetiracetam (keppra)?
used as an adjunct to other AEDs - unknown method of action
what are the advantages of levetiracetam?
primarily excreted unchanged in urine
excellent oral bioavailability
well-tolerated
what are the side effects of levetiracetam?
ataxia
vomiting
sedation
which drug is licensed specifically for idiopathic epilepsy?
imepitoin (pexion)
which dogs cannot take imepitoin?
those with seizures caused by anything other than idiopathic epilepsy
dogs with impaired hepatic/renal/cardiovascular function
what are the side effects of imepitoin?
ataxia
vomiting
polyphagia
what home care considerations are relevant for patients that seizure?
family situation
financial situation
type of property dog is living in
good communication
what kind of disease is polyradiculoneuritis?
immune-mediated musculoskeletal disease
how does polyradiculoneuritis present?
short-strided gait that progresses to tetraparesis
patient can be ambulatory or non-ambulatory
dysphonia
how long does it take to recover from polyradiculoneuritis?
within 1-4 months once signs stabilise
how is polyradiculoneuritis diagnosed?
accurate patient history
physical and neurological exam
EMG, NCV
muscle and nerve biopsies
how is polyradiculoneuritis treated?
intensive nursing care and physiotherapy
what is myasthenia gravis?
disease of neuromuscular transmission affecting the NMJ
what causes myasthenia gravis?
can be congenital or acquired
how does myasthenia gravis present?
muscle weakness and fatigue (more obvious when patient is exercising)
focal, generalised or acute
regurgitation commonly seen due to oesophageal weakness
how is myasthenia gravis diagnosed?
presumptive based on history and presentation
thoracic radiographs (megaoesophagus)
tensilon test
how is myasthenia gravis treated?
anticholinesterase therapy plus corticosteroids at immunosuppressive doses
intensive nursing care and support
what is polymyositis?
immune-mediated inflammatory myopathy
what causes polymyositis?
idiopathic but can be associated with systemic disease
how does polymyositis present?
exercise intolerance and stiffened gait
muscle weakness and atrophy
dysphonia, dysphagia, regurgitation
signs often wax and wane in initial period
how is polymyositis diagnosed?
criteria not well defined - diagnosis of exclusion
main diagnostics are clinical history, biochemistry, electrodiagnostic testing and muscle biopsy
how is polymyositis treated?
corticosteroids at immunosuppressive doses
intensive nursing care and support
azothrioprine can be used alongside steroids
what are the clinical signs of aspiration pneumonia?
coughing
tachypnoea
harsh lung sounds
crackles on auscultation
which neuromuscular diseases carry the most risk of aspiration pneumonia?
myasthenia gravis
polymyositis
which neuromuscular disease carries the most risk of pressure sores?
polyradiculoneuritis
which neuromuscular disease carries the most risk of contracture?
polyradiculoneuritis (esp in young)
how can you prevent severe aspiration pneumonia?
careful and close monitoring of patients
early administration of antibiotics
IV fluids + oxygen therapy
walking/turning patients regularly very important
feeding balls of food from a height
severe cases may require mechanical ventilation
how do pressure sores form?
recumbency leads to increased pressure over bony prominences, which then leads to ischaemia and necrosis
how can you prevent pressure sores?
thick padded bedding turn every 2-4 hours donut bandages physiotherapy monitor patients closely
how does muscle contracture occur?
recumbency and immobilisation
–> leads to adaptive shortening of the muscle and soft tissues, and inelasticity of the soft tissues
how is contracture treated?
massage
PROM
proprioceptive exercises
neuromuscular stimulation
what is ataxia?
uncoordinated gait
what does -paresis/-paretic mean?
weakness, decreased voluntary movement
what does -paralysis/-plegic mean?
no voluntary movement?
what does mono- mean in regards to gait?
one limb affected
what does hemi- mean in regards to gait?
both limbs on one side affected
what does para- mean in regards to gait?
both pelvic limbs affected
what does quadra/tetra- mean in regards to gait?
all 4 limbs affected
when would you perform a neurological exam on a patient?
seizures
behavioural changes
gait abnormalities
change in posture/positioning
why might you perform a neurological exam?
identify if nervous system involvement
identify specific location/localisation
aid diagnosis and prognosis
continuous assessment of condition/comparisons
what do the upper motor neurons do?
send signals to the lower motor neurons
what do the lower motor neurons do?
connect the CNS to the effector organ (muscle) and send a signal to make them contract
what factors should you assess during a neurological examination?
mentation
gait and posture
cranial nerve function
postural reactions
spinal reflexes
sensory evaluation
palpitation of head/spine/limbs