Neuro - medicine Flashcards
What happens when an upper motor nerve is damaged?
Reflex arcs not inhibited - more excitable
Reduced movement (paresis)
No movement (plegia)
Increased tone
Present/increased reflexes
Disuse atrophy over time
What happens if a lower motor neurone is damaged?
Reflexes are weaker or absent
Reduced movement (paresis)
No movement (plegia)
Severe rapid atrophy
Reduced tone
What are the 3 questions that are the aims of the neuro exam?
1 - is it neurological?
2 - if so, where is it?
3 - What might be causing it?
What cardinal neuro presentations should prompt a neuro exam?
Abnormal gait
Abnormalities of head and face
Apparent blindness/deafness
Abnormal behaviour - particularly episodic behaviour
Exercise intolerance
Incontinence
How do you split up the spine?
C1-C5
C6-T2
T3-L3
L4-S2
What are the different kinds of lameness?
Painful - reduced weight bearing phase
Restrictive - altered swing phase
What is ataxia?
Lack of regulation of limbs in space
What is plegia?
Inability to make a movement
What is paresis?
Reduced ability to make a movement
What is weakness?
Cannot generate force in movement
How do you tell the difference between lameness and ataxia?
Lameness - same mistake each time
Ataxia - variable mistake in paw placement each time
What do proprioceptive responses require? What do they tell you?
Responses involve the FOREBRAIN (reflexes do not)
They act as a screening test - wont tell you where a lesion is in the nervous system, just that there is a neurological problem
What two tests assess proprioceptive responses?
Hopping
Paw placement
What do spinal reflexes tell you?
DO NOT involve the forebrain
Test well defined sections of PNS and CNS so can localise lesion
What reflex test will test the pudendal nerve and S1-3 spinal cord?
Perineal reflex - pinch will constrict anus and drop tail
What reflex test will test the sciatic nerve and L6-S2 spinal cord?
Pelvic limb withdrawal - pinch toe, all joints will flex
Tend to lose hock and digit flexion first - less mass/innervation here than hip or stifle
What reflex test will test the femoral nerve and L4-L6 spinal cord?
Patella reflex - stifle extends if strike patella tendon
Can be consciously inhibited though - test dependent limb too
What reflex test tests segmental nerve, lateral thoracic nerve and spinal cord up to T1?
Cutaneous trunci reflex - pinch skin, will contract on both sides
What reflex test tests median and ulnar nerves?
Thoracic limb withdrawal - pinch toes and all joints flex
If abnormal then their kick their leg back caudally instead of not retracting
Not that accurate - lots of nerves in brachial plexus not tested
A lesion in what region causes goose-stepping/floating gait?
C1-C5 typical gait - limbs protracted and extended fully before making contact with ground
A lesion in what region causes short strides in thoracic limbs and longer ataxic strides in pelvic limbs
C6-T2
What is spinal shock?
Temporary reduction in spinal reflexes caudal to an acute spinal cord injury occurring cranially usually to the affected reflex arcs
What does spinal shock mean in practice?
Means its easy to mistake a focal T3/L3 lesion for multifocal or diffuse disease - affects neuro exam results
What 4 areas of the brain are we looking to differentiate between on neurolocalisation?
Forebrain
Brainstem
Cerebellum
Cranial nerves
What are the 3 important tests of forebrain function?
Behavioural responses
Proprioceptive responses
The menace response
Where can lethargy/obtundation come from in the brain?
Either brainstem or forebrain sign
Where can mania come from in the brain?
ONLY the forebrain
What part of the brain causes seizures?
Forebrain disease
What part of the brain regulates proprioceptive responses?
The CONTRALATERAL forebrain
What does the menace response screen function in?
Eye
Optic tract
Forebrain
Cerebellum
Brainstem
Facial nerve
Which cranial nerves cant be tested reliably?
I - olfactory
IV - trochlear
XI - accessory spinal
How should you always look for a head tilt?
Look when the dog is walking towards you
What nerves do you test for when just observing head and face?
Vestibulocochlear nerve
Trigeminal nerve
Facial nerve
What is tested by looking at the palpebral fissure narrowing?
Sympathetic denervation
What is miosis? What is the opposite?
Inappropriate constriction
Mydriasis - inappropriate dilation
What is the route of the sympathetic eye supply?
Down spinal cord through brachial plexus then back up vago-sympathetic trunk
What are the key differentials for miosis?
Horners
Uveitis
Reflex constriction with corneal pain
What nerves are tested in the palpebral reflex?
Tap medial canthus - maxillary trigeminal (more reliable)
Tap cornea - ophthalmic trigeminal
Facial
Brainstem
What does it mean if there is no blink on palpebral reflex?
Facial, brainstem or trigeminal lesion
How does a brainstem lesion affect facial and trigeminal function?
Can affect both - cant feel or cant move
What nerves are tested in menace response?
Optic nerve (II) - sensory
Forebrain
Cerebellum
Brainstem
Facial nerve (VII) - motor
What sides of the brain could the lesion be in that are tested in the menace response?
Contralateral forebrain
Ipsilateral cerebellum
How do you do the menace response?
Hold head, cover contralateral eye
tap face - make sure they blink and are looking at you
Small movement from far away - no air movement
How do you test if they can see? What nerves does it test?
Visual fixation - tests retina, optic tract or forebrain
What is the test to see if the eyes respond to light?
The pupillary light reflex - shine bright light to see if there is bilateral pupillary constriction
What causes neither pupil to restrict from the bright light in pupillary light reflex?
If there is a retinal lesion
What causes only other eye to constrict when shining light into eye during pupillary light reflex?
Oculomotor not working
Or iris not working
What does abnormal nystagmus indicate?
If there is cerebellar disease or vestibular system disease
What is positional nystagmus?
When nystagmus is only visible when animals are in an abnormal position
Must test if disease of cerebellum or vestibular system is possible
What nerves are tested when assessing swallowing and barking?
Glossopharyngeal (IX)
Vagus (X)
Hypoglossal (XII)
How do you do the gag reflex?
Open their mouth and try to touch larynx - should push fingers out of mouth
What other test of eating/barking can you do?
Owner assessment - more reliable than the gag reflex
What are the features seen in forebrain lesions?
Altered behaviour
Proprioceptive deficits
Reduced menace response
What are the features seen in brainstem lesions?
Altered behaviour
Proprioceptive deficits
Other cranial nerve disease
What are the features seen in cerebellar lesions?
Abnormal movement in all 4 limbs
Head tilt/nystagmus
Absent menace with normal vision
What are the features seen in cranial nerve lesions?
Cranial nerve test dysfunction
No other neuro deficits
What is the five finger rule for prioritising clinical information?
Signalment
Onset
Progression
Symmetry
Pain
Localisation
What disease groups can young animals get?
Degenerative (only young and old get these)
Anolamous (eg. congenital abnormality)
Toxic
Traumatic
What disease groups can older dogs get?
Degenerative
Neoplastic
Metabolic
Vascular
What disease groups can you rule out if the dog is middle aged?
Degenerative
Anomalous (congenital)
What disease groups are fast onset?
Toxic
Neoplastic
Inflammatory
Traumatic
Vascular
What is the difference between onset and progression?
Onset - how long it took to go from normal to their worst (eg. peracute, acute, insidious)
Progression - whether the most severe signs have already been reached
What disease groups have strong asymmetry?
Vascular disease
Neoplastic disease
What disease groups have strong symmetry?
Bloodborne diseases - toxic, metabolic
Genetic diseases
Where does pain arise from in the CNS?
No nociceptors in brain or spinal cord
But adjacent structures do - meninges, muscles, connective tissue etc.
What disease groups are non painful?
Degenerative
Anomalous
Metabolic
Toxic
Vascular
What disease groups are painful?
Traumatic
Neoplastic
Inflammatory
How do you tell the difference between a central (brainstem) vs peripheral (nerve) cranial neuropathy?
Central likely if obtunded or paretic
Peripheral likely if all signs can be explained by one nerve not working
Multiple nerves affected could be central or peripheral
What are the different fibres in the spinal cord that help when assessing spinal cord injury severity? Where are they?
Proprioceptive fibres - dorsal, superficial
Motor fibres
Nociceptive fibres - deepest
What is the worst prognosis when assessing spinal cord injury severity?
If cant move, cant feel, no pain perception
Nociceptive fibres deepest so if these damaged then very damaged spinal cord
No pain reaction = ‘deep pain negative’
How do you tell pain perception?
Behavioural response - moving head, lip licking
Cant tell just from withdrawing leg as this is a reflex
What assesses brain injury severity?
Modified Glasgow coma score - evaluates movement, reflexes and consciousness
What are the signs of raised intracranial pressure in a dog?
The Cushing’s reflex:
Increased blood pressure with decreased heart rate
In a comatose dog
What is the intervertebral disc made up of?
Anulus fibrosis - outside, holds disc together
Nucleus pulposis - fluid filled, allows flexible back
What are the features of normal disc ageing?
Fibrous metaplasia - less fluid filled, nucleus replaced with collagen
Some tearing and healing of anulus
Enthesiophyte formation - spondylosis
What is spondylosis? What is it a sign of?
New bone formation ventral to vertebral column
Is a NORMAL sign of aging, not an indicator of spinal disease
What are the 3 main types of disc disease?
Non-compressive nucleus pulposis extrusion (traumatic)
Disc extrusion (hansen type 1)
Disc protrusion (hansen type 2)
What is Non-compressive nucleus pulposis extrusion?
Normal segment subjected to supramaximal force
small fragment of nucleus herniates and contuses cord with no compression (bruises)
What is Disc extrusion (hansen type 1)?
Nucleus pulposis undergoes chondroid degeneration
The hard calcified nucleus of the disc extrudes of out anulus under everyday pressure and causes compression and contusion
What is disc protrusion (hansen type 2)?
Continued progressive fibroid degeneration - normal
But the anulus ligament degenerates and hypertrophies over time, causing progressive compression
What are the 3 conservative treatments of thoracolumber disc disease management?
Rest
Medication - Non steroidals (steroids dont work for acute spinal cord injury)
Time - long recovery times
What is the surgical treatment for thoracolumbar disc disease?
If ventrolateral compression (most common) - mini-hemilaminectomy (window into ventral bone)
Also known as ventral slot
What indicates dogs dont need surgery for disc extrusions?
If the dog can walk with disc disease it is likely to get better without surgery
How quickly do disc protrusions need surgery?
Urgent but not an emergency - not critically time dependent as long as more disc doesnt come out
How often do dogs with disc extrusions relapse?
7% with surgery
18% without surgery
When is surgery indicated for disc protrusions?
For progressive cases
What age dogs get disc extrusions?
Always over 2 years old
What type of disc disease is typically asymmetrical?
Disc extrusion
What is a ‘wobbler’?
Any cervical spine disease that causes ataxia
(slightly different to horse wobblers)
What are the two types of wobbler?
Disc protrusions
Degenerative hyperplasia - articular facet hypertrophy (more bone put down to stabilise)
What degenerative changes are associated with disc protrusions?
Flaval ligament hypertrophy
Dorsal ligament hypertrophy
Disc prolapse
What are the two treatments for wobblers disease in small animals?
Decompression - ventral slot
Distraction fusion - implant to fix bones
What is myelomalacia? When does it occur?
Progressive spinal cord death - softening
Fatal, untreatable and irreversible
Occurs 1-5 days after any spinal cord injury in 20% of pain negative dogs
What are the signs of myelomalacia?
Agitation/lethargy
Hyper/hypothermia
Ascending cutaneous trunci reflex cut off
What is the main cause of ischaemic myelopathy?
Usually a fibrocartilaginous embolism in the ventral artery
What disease does ischaemic myelopathy behave almost identically to?
Acute non-compressive nucleus pulposis extrusions
What is the clinical presentation of ischaemic myelopathy (and acute non-compressive nucleus extrusions)?
Signalment - any dog (non-chondrodystrophic)
Onset - acute (hours)
Progression - non progressive
Symmetry - asymmetrical
Pain - none
Localisation - any spine
How do you treat ischaemic myelopathy and acute non-compressive nucleus extrusions?
Currently no surgical treatment for either condition
Most will be able to walk and not have incontinence depending on severity
50% of no pain sensation dogs will recover walking ability
What most commonly causes haemorrhagic myelopathy?
Angistrongylus vasorum
What is the clinical presentation of haemorrhagic myelopathy?
Acute onset
Not painful
Non progressive
MULTIfocal
What tends to cause spinal fractures?
Need significant trauma eg. RTA
Not just from exercise
So what are the 3 conditions of acute onset, non progressive myelopathies?
Acute, non-compressive nucleus extrusion
Ischaemic myelopathy
Spinal fracture
What are 5 conditions causing progressive myelopathies?
Degenerative myelopathy (like motor neurone disease in humans)
Arachnoid fibrosis
Vertebral malformations
Neoplasia
Myelitis/meningomyelitis
What is degenerative myelopathy?
Non-painful, progressive neuronal death of the spinal cord
Asymmetrical
In older dogs
What is the most common risk factor for degenerative myelopathy?
Genetics - SOD1 mutation
What is arachnoid fibrosis?
Non painful, progressive obstruction to CSF flow around spinal cord
Often caused faecal incontinence - atypical for ambulatory animals
What tends to cause arachnoid fibrosis?
Meningeal injury or developmental anomaly
What is the clinical presentation of neoplasia affecting the spinal cord?
Older than 6 years
Insidious but often acute worsening after bleed/fracture
Strongly asymmetrical
Painful (but not always)
Any spine region
What are the main causes of myelitis/meningomyelitis?
Autoimmune - dogs
FIP - cats
Toxoplasma/neopsora
What is steroid responsive meningitis/arteritis?
Immune mediated inflammation of the meninges and small arteries
What is the clinical presentation of steroid responsive meningitis/arteritis?
Neck pain - NO NEURO DEFICITS (only affects meninges)
Always less than 2 years old
Acute
Strongly waxin and waning
Symmetrical
Very painful
How do you diagnose steroid responsive meningitis/arteritis?
Fever
Cisternal spinal fluid analysis - lots of neutrophils
What is the prognosis for steroid responsive meningitis/arteritis?
Tend to relapse but very good for eventual remission
What causes atlantoaxial subluxation?
Failure of dens to form properly or traumatic fracture
What is the clinical presentation of atlantoaxial subluxation?
Toy breed dogs - less than 6 months at first episode
Acute
Progressive - wax and wane
Symmetrical
Very painful
What is discospondylitis?
Haematogenous spread of bacteria/fungus to vertebrae allowing local invasion into discs
Causes slow abcess development in disc, spreading to end plates and vertebrae
What is the clinical presentation of discospondylitis?
Multisystemic localisation, systemic disease
Any dog
Insidious onset
Progressive - may wax and wane
Symmetrical
Moderate to marked pain - more pain than neuro deficits
What disease can cause discospondylitis in imported dogs?
Brucella
So what are the neck pain differential diagnoses depending on age?
Under 2yo - steroid responsive meningitis/arteritis or atlantoaxial subluxation
Over 2yo - disc disease, discospondylitis or tumour
What is lumbosacral disease?
When the cauda equina is compressed by a combination of degenerative vertebral changes and traumatic damage from disc extrusion
What does lumbosacral disease cause?
Very painful
Inflammation
Tail flaccidity
Incontinence
What is the treatment for lumbosacral disease?
Rest
Epidural steroids
Surgical stabilisation and/or decompression
